Twincharging - calling Warpspeed!
Twincharging - calling Warpspeed!
(OP)
thread71-174690: twincharging estimated results
Hi guys, i subscribed to this forum because i found the thread (referenced above) on twincharging while doing a Google search for information on this subject.
I have to say, the thread and contributions from forum users was very good and informative, which gave me a direction to follow for my own twincharger build.
Some background on this: I have a 1997 Mitsubishi Lancer Evolution 5 which i've used for sprints and hillclimbs in Scotland for a few years now. The state of tune of the car is such that we were producing around 650hp, but with the big turbo at 2.6bar, lag was always an issue. Twincharging seemed the most sensible option for the car to eliminate the lag and hopefully produce a torque curve with spool much lower in the rev range.
I'm using a Harrop HTV 1320 blower and the existing turbo which is a hybrid T04Z with 0.82 housing. This is the turbo that gave us 650hp previously, but on a 0,63 housing. The system is compound compression with the turbo feeding the blower. The blower has a 75mm pulley and the crank 150mm pulley so a ratio of 2:1.
I have the blower mounted and all pipework finished and finally had her on the rolling road a few days ago. We saw some impressive torque figures but had to cut the session short due to belt slip on the blower pulley when the turbo reached 1.5bar. The system i have uses a 32mm toothed belt but the length of the belt seems to be an issue as it's stretching and allowing it to jump over the pulley when the turbo spools up. We also had issues with controlling the turbo boost and decided i need to install another wastegate to allow better control of the boost. I'll have that done by next week RR session so we have control of the turbo boost and can carry on mapping.
It seems the belt starts to jump when the turbo reaches 1.5bar and the drive simply cannot cope with the power needed to increase boost by a factor of 2. I have a larger pulley (100mm) which i'll be fitting over the weekend and hope the longer wrap around of the belt on the larger pulley and the reduction of the drive ratio should sort out the issue of the drive. If it doesn't then i have another modification i can do to run a shorter belt on the blower and split the ancilliaries onto 2 separate belts but i'd like to try this again with the reduction in drive frst before i go to the trouble of a re-design of the belt drive. Space is at a premium so 32mm is the widest i can go and still have a chassis leg...
We never went above 4000rpm. Despite this, we saw 460ft/lbs torque and 360hp at 4000 and 2.9bar which confirms there's definatley power to be made! Obvously slowing down the blower will mean the turbo will need to be producing more to reach our goal of 2.5bar total. The outlet temp of 80c from the turbo at 1.5bar was logged, which is about the limit of the blower seals. I hope to keep the turbo around 1.5 bar so the outlet temps don't fry the blower seals. The combined air then goes through a very good intercooler and reduces the final temps to 16c (this is Scotland remember....!) at the plenum.
I think we're almost there and hope to have it mapped on the larger pulley with the extra wastegate fitted for turbo control. Looking at the RR graphs and data we collected the other day, we monitored the pressure from the turbo and combined total and can clearly see a multiply of the turbo by the blower very close to 2:1 from 1800rpm to 4000rpm but we couldn't control the turbo and it looked like it would have carried on climbing which would have killed the engine or the blower.
Because the engine already had the big turbo and supporting mods to make good power, we hope to see some good figures once the issues are ironed out. The engine itself is built to produce 1000hp 'reliably'.
I would like to hear any views and comments on my findings so far. I had considered swapping the turbo and blower order to reduce the power needed to drive the turbo but i felt the extra restriction on the exhaust (because the turbo would be working harder than it used to) would likely end up making less power, as the exhaust back pressure would then be much higher. It would certainly reduce the power needed by the blower
Thanks for posting the useful information, it really was a huge help and if you have anything to add that could help us, i'm all ears!
Donald
Hi guys, i subscribed to this forum because i found the thread (referenced above) on twincharging while doing a Google search for information on this subject.
I have to say, the thread and contributions from forum users was very good and informative, which gave me a direction to follow for my own twincharger build.
Some background on this: I have a 1997 Mitsubishi Lancer Evolution 5 which i've used for sprints and hillclimbs in Scotland for a few years now. The state of tune of the car is such that we were producing around 650hp, but with the big turbo at 2.6bar, lag was always an issue. Twincharging seemed the most sensible option for the car to eliminate the lag and hopefully produce a torque curve with spool much lower in the rev range.
I'm using a Harrop HTV 1320 blower and the existing turbo which is a hybrid T04Z with 0.82 housing. This is the turbo that gave us 650hp previously, but on a 0,63 housing. The system is compound compression with the turbo feeding the blower. The blower has a 75mm pulley and the crank 150mm pulley so a ratio of 2:1.
I have the blower mounted and all pipework finished and finally had her on the rolling road a few days ago. We saw some impressive torque figures but had to cut the session short due to belt slip on the blower pulley when the turbo reached 1.5bar. The system i have uses a 32mm toothed belt but the length of the belt seems to be an issue as it's stretching and allowing it to jump over the pulley when the turbo spools up. We also had issues with controlling the turbo boost and decided i need to install another wastegate to allow better control of the boost. I'll have that done by next week RR session so we have control of the turbo boost and can carry on mapping.
It seems the belt starts to jump when the turbo reaches 1.5bar and the drive simply cannot cope with the power needed to increase boost by a factor of 2. I have a larger pulley (100mm) which i'll be fitting over the weekend and hope the longer wrap around of the belt on the larger pulley and the reduction of the drive ratio should sort out the issue of the drive. If it doesn't then i have another modification i can do to run a shorter belt on the blower and split the ancilliaries onto 2 separate belts but i'd like to try this again with the reduction in drive frst before i go to the trouble of a re-design of the belt drive. Space is at a premium so 32mm is the widest i can go and still have a chassis leg...
We never went above 4000rpm. Despite this, we saw 460ft/lbs torque and 360hp at 4000 and 2.9bar which confirms there's definatley power to be made! Obvously slowing down the blower will mean the turbo will need to be producing more to reach our goal of 2.5bar total. The outlet temp of 80c from the turbo at 1.5bar was logged, which is about the limit of the blower seals. I hope to keep the turbo around 1.5 bar so the outlet temps don't fry the blower seals. The combined air then goes through a very good intercooler and reduces the final temps to 16c (this is Scotland remember....!) at the plenum.
I think we're almost there and hope to have it mapped on the larger pulley with the extra wastegate fitted for turbo control. Looking at the RR graphs and data we collected the other day, we monitored the pressure from the turbo and combined total and can clearly see a multiply of the turbo by the blower very close to 2:1 from 1800rpm to 4000rpm but we couldn't control the turbo and it looked like it would have carried on climbing which would have killed the engine or the blower.
Because the engine already had the big turbo and supporting mods to make good power, we hope to see some good figures once the issues are ironed out. The engine itself is built to produce 1000hp 'reliably'.
I would like to hear any views and comments on my findings so far. I had considered swapping the turbo and blower order to reduce the power needed to drive the turbo but i felt the extra restriction on the exhaust (because the turbo would be working harder than it used to) would likely end up making less power, as the exhaust back pressure would then be much higher. It would certainly reduce the power needed by the blower
Thanks for posting the useful information, it really was a huge help and if you have anything to add that could help us, i'm all ears!
Donald





RE: Twincharging - calling Warpspeed!
A simple test would be to inject some water into the air duct just before the blower to cool the rotors.
If cooling the rotors fixes the problem, setting up the blower with slightly wider clearances should fix it. Harrop may also be able to advise on rotor clearances.
Can you get a better belt design or quality.
Regards
Pat
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RE: Twincharging - calling Warpspeed!
I've had a look inside the blower and can't see any evidence of the rotors touching anywhere. Also, the belt slips as soon as the inlet pressure reaches 1.5bar. if it was a clearance issue, would it not take a few seconds for the rotors to heat and expand?
I have a better belt drive in production now which should hopefully transmit the power without jumping. nce i have it finished i'll update with findings
Donald
RE: Twincharging - calling Warpspeed!
Out of interest, do you have any sort of bypass around the SC at all currently? Or is this what you mean by the additional wastegate? What about during idle? Is the SC clutched?
Have you got any data with a measurement of the exhaust pressure?
RE: Twincharging - calling Warpspeed!
We tried the single wastegate without any spring in it to start with to see if it was physically big enough to bypass the turbo. It didn't take long to deduce another wastegate was needed....
No clutch on the blower - direct drive
Sorry, no exhaust pressure data
Back on the rollers on Tuesday eve :)
RE: Twincharging - calling Warpspeed!
If the main design objective is to reduce lag, have you considered only using the SC to bolster the bottom end and then bypass it with a diverter valve at higher rpm, allowing the turbo to provide the total boost?
RE: Twincharging - calling Warpspeed!
We considered all options and did a lot of homework before starting this project. Using a diverter valve to bypass the blower would have meant we would only have seen the bottom end torque rise and the turbo producing top end power on its own. To me this wasn't an option as i want as much top end and low down torque as i can get. Economy isn't a consideration on this one... The turbo was running out of puff at the top end which limits the engine to around 650hp. The compound system seemed the best way to go - the turbo working at half it's designed pressure then have the blower multiply to have a much higher inlet pressure than the exhaust and therefore fill the cylinders more. I think it was covered in the previous thread about valve overlap and duration too. I could probably run more duration with this setup but cams for the 4G63 engine are designed to be used with a turbo only so i'm searching for cams with certain characteristics now. It may be that we have to design these and get a set ground to spec to get the best from the setup.
RE: Twincharging - calling Warpspeed!
Would it be daft to suggest a larger compressor, and to transition between the efficient SC region into the efficient TC compressor region at a pre-set point? Of course this requires alot more complex control, and may not give the same throttle response, but the SC will see lot lower temps and the actual energy used to compress the intake air will be lower. Of course if fuel efficiency is not a problem then you can just burn more to get to the same air setpoint, but you will then have to deal with a hell of alot more heat.
Does the SC spec come with a rating for max intake pressure?
RE: Twincharging - calling Warpspeed!
Until we see some further data, i can't say how we'll end up setting up the relationship between the blower and the turbo. With the bigger blower pulley, the ratio is now 3:2 instead of 2:1 so we expect the turbo to be producing no more than 1.5bar and the blower then multiplying it to around 2.4 bar - pretty much where we want it to be. I suspect a pulley in between the 2 sizes would be ideal as we can then reduce the turbo pressure and therefore the charge temperature the blower is fed with.
Harrop say 50c is the design inlet temp Eaton specify for reliability but we could go to around 70-80c however that will reduce seal life. We saw 80c at the blower inlet when the turbo was producing 1.5 bar. Ideally i'd like to get this down to 1.2bar and have the blower supply the rest.
Fitting a larger blower isn't an option now. It took a while to get hold of this one from Australia then manifolds and brackets needed made. It sits behind the engine and only just fits in the space. A larger blower would mean a complete re-design of the whole system again. I think the pulley we're away to try is about right to keep the blower within a good range of efficiency to do the job we want it to do.
I guess it's a compromise, as most things like this are. Some minor changes to blower drive pulley may be needed but at the moment i think we're not too far off the mark to see some good results. Obviously with unlimited time and money we could perfect this, but at the moment we're going to keep going with this setup now that the drive has been modified.
Thanks for the input. None of this is set in stone and needs to be tried/played with to get the best from it.
RE: Twincharging - calling Warpspeed!
Best of luck with the next test, it's a very interesting project and would be the first real 'current' account ` regarding compound charging on this site if you can post again afterwards. It would be great to see if the correct matching of drive ratios (TC and SC) will actually allow you to have a decent overall efficiency (i.e. temps are in check).
RE: Twincharging - calling Warpspeed!
I'll keep the thread updated as we progress and share the results as and when we have them. Next dyno session is Tuesday evening and i have a test day organised at a local kart track for the Thursday, so hopefully we'll have it mapped and safe to run, even if it's not quite finished.
My first Hillclimb is Doune on 17th April so i'm cutting it a bit fine!
RE: Twincharging - calling Warpspeed!
You're sure you don't want to bypass the blower once the turbo has spooled? And just accept the increase in power under the curve, rather than try to use a blower to help keep your turbo on the charts at higher flows?
RE: Twincharging - calling Warpspeed!
I'm also relying on the difference between cylinder inlet and exhaust pressures to make some real top end power as well - having the turbo do all the work at the top end loses that advantage as the exhaust pressure increases as the turbo takes over.
Definately food for thought tho. I really don't know if we'll finish the mapping next week but i'm confident that if it holds together, we'll see some interesting results! If the earlier power/torque figures are anything to go by, this engine will pull like a large capacity V8 from 1500rpm.
RE: Twincharging - calling Warpspeed!
All those advising that do a site search using the google feature. You will find that topic has been covered in detail several times already.
The main thought process should involve mass air flow and density, not volume.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
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RE: Twincharging - calling Warpspeed!
One thing i can't remember if i mentioned - the throttle butterfly is in its original place, on the plenum so the blower would compress against this it idle and cruise if there was no bypass. My previous supercharged engine build had the butterfly before the blower as the whole lot was mounted on the 'V' of the engine and the most sensible place to have this was right at the blower entry.
On this compound charged engine, the induction length is too long to have the butterfly before the blower as response would have been slow due to the mass of air to be moved through the pipework and intercooler.
RE: Twincharging - calling Warpspeed!
Thanks for the tip on the google search...
RE: Twincharging - calling Warpspeed!
It will still create some amount of boost as the small internal bypass then acts as an orifice from outlet to inlet. An M90 that usually creates 12 psig would still create 3-4 psig at full throttle with the internal bypass open, for example.
The bypass is a small butterfly valve, so that bore could be sleeved or partially filled to reduce the orifice size and increase the pressure developed when bypass is open at high RPM's. But still allow sufficient bypass at low RPM's.
This may allow you to use a higher drive ratio for better low end response, without excessive parasitic loss or pressure ratio of the blower, once the turbo is spooled.
I guess I am asking, have you tried opening the internal bypass once the blower sees a few psi of pressure on it's inlet (indicating that the turbo is ready to "take over"?)
RE: Twincharging - calling Warpspeed!
I like your idea to restrict the bypass if we need to allow bypass on boost. i hadn't really given that much thought before. The blower is a fair task to remove from the engine bay and the bypass is cast into the body so i think that would be quite tricky to do. I had thought the bypass was already too small for the amount of air we're pumping into the blower as it is!
Because the car is purely used for 30 - 70 second blasts up a tarmac hill, i'm prepared to live with minor gremlins in the search for massive torque and power over the widest range possible. As long as it's smooth between on/off power and the throttle response is sharp then i think i'll be happy. No doubt over the season i can iron out gremlins to continually improve the setup.
Just a few more adjustments to the belt drive and we're good to head for the rollers and see what it's capable of! All the info you guys have put forward has been really helpful. Thanks!
I'll keep the thread updated as we go.
RE: Twincharging - calling Warpspeed!
We had wheelspin problems so couldn't get any power readings but she's now mapped and safe to drive in anger. We're on the largest blower pulley i had, so i was aware that the blower could hardly be contributing to the overall pressure. Over 5000rpm there was only 2psi difference between the turbo and blower and turbo outlet temps went quite high during the runs so we tried an inertia run to keep the runs short. That halved the turbo temps and would mimic real world driving so i'm happy to leave to where is is for the moment. Total boost is 1.8bar although our target is 2.5bar. The pressures we logged show very similar trends to those seen when we had the 2:1 pulley on - just a lot less total boost so ultimately i want to get the blower back to 2:1 or even 2.1:1 as soon as i can get a break in the season
To change pulleys now will involve a re-make of the whole drive to accomodate available belts so i'll leave that for during the summer.
Driving it on the road, the low end torque is immense, turbo spools quickly and is at full spool by 2800rpm. At 4500rpm the cams come in and all hell breaks loose! Definately a lot quicker than last year (with 635hp), all i need to do now is learn to drive it again!
Thanks for all the help - we've got the basis of a good system to build on now so i'll post back again when changes are made
Donald
RE: Twincharging - calling Warpspeed!
Which hillclimbs will you be doing? Will you be at Harewood at all?
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
At what power was the max boost pressure achieved with the TC alone? How do you feel that the response time/lag has been improved? Have you noticed any greater oil loss from the TC compressor seal into the intake tract?
Sorry if this sounds like a repetition, but you would see alot lower intake temps and lose none of the anti-lag properties if you could bypass the SC at higher rpm, and use a slightly bigger TURBOcharger compressor. The control is simply a boost operated butterfly/flap valve. There are suitable valves used on most series connected twin turbo arrangements.
If you still intend to pass the whole boost through the SC when aiming for higher total Pr, then why not try fitting a valve next time its in the workshop when you are changing the pulley? Do a back-to-back run with it closed and with it opening just after max SC-only boost is reached to see the temp/efficiency differences. You will see higher power output due to recovering the SC drive power and lowering intake temps. Never mind exhaust pressure upstream of the turbine, if the turbine is correctly matched should have a positive drive ratio anyway at max boost, supplementing this with inefficiently produced SC boost will not win the war.
Although Warpspeeds very useful, insightful and obviously experienced posts are very positively written, the whole 'twincharging' story is not written there....
By the way, thanks for proving that a throttle ahead of a positive-displacement blower is not dangerous, even at those high Pr's. Also thanks to VW for proving that with their 2006/2009 engines of the year!!
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Interestingly, the intercooler i have is an awesome piece of kit. When the turbo was running alone, the IC took temps down from 212c to 21c so this is why we have the combined charge being cooled through the IC. Last time on the dyno the plenum temp was down to 6c with ambient air at 5c (cold night!)
No noticeable oil loss from the blower. looking inside it shows no oil leaking around the seals - so far so good.
Being honest, i've not really had many chances to drive it yet. The most i've done was a 6 mile 'stage' round the block. Throttle response is good, the turbo is at full spool at 3000rpm (ish) so she's very torquey to drive. I'm still wanting to try the new pulley ratios before i decide on any bypass. Going by the initial results, i don't think a bypass is required and we'll be keeping the compound effect throughout the rev range. It's most defiantely a development in progress so i'm not discounting a bypass in the future - i just want to try this before any decision is made.
I have my first event this weekend so i'll be back to post results at the start of the week
Donald
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Had a good weekend, i got to within 0.6 of a second of my best ever time up the hill and set a new class record. Overall a successful 2 events as i beat the other competitors in the modifieds division to take maximum division points on each day along with 2 class wins and an extra point for breaking the record.
The car performed well, didn't break and had no issues over the weekend. I was taking it easy as the suspension geometry has changed so much to try and get rid of the understeer the car has always had. Took time to get to grips with this new setup on the Saturday. It rained all day sunday so i couldn't push hard and essentially just drove it smoothly up the hill! Looking back at the videos from last year and now this year the difference in low end torque is very noticeable. I think i had it over 8000rpm once but generally was short-shifting at 6000rpm and playing with the new torque while i learned the handling again.
Last years launches were around 2.3s to 64ft due to having to spin the wheels off the line to stop the turbo stalling. With the compound system i was regularly doing 2.09s with a 2.04s my best due to the torque.
While checking the car over the other night i discovered a crack in the bellhousing where the front stabiliser mount bolts on so it's in bits again! The box was stripped down to weld the crack and bracing added. I have it ready to go back together but waiting for my clutch plates to be re-lined since i was in there anyway as it was looking pretty worn. While it's apart i've decided to do the new pulleys to take the blower to 2:1 ratio so hoping these will be here by this weekend coming. I have the dyno booked for Tuesday evening to get it mapped with the higher boost level.
Hopefully we'll see some good gains and be ready for the next hillclimb on 8th/9th may at my local track- Fintray
I'll keep you posted
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Nick
RE: Twincharging - calling Warpspeed!
So how did the new mapping session go? Did you keep all temps in check with that HUGE intercooler? Did the belt manage to withstand the forces this time?
RE: Twincharging - calling Warpspeed!
The blower is actually very quiet and can't be heard when driving. Some spectators say they can hear it but others say they can't. There is a whine from the belt drive though. The new pulleys will be here today so over the weekend i'll build it back up with the 2:1 ratio in advance of the dyno session on Tuesday. Hopefully we'll be able to turn the turbo boost down a bit, reduce the temps into the blower and see the full compound charge effect of cylinder filling. If it stays together i'm predicting some good gains in spool, torque and power.
Intercooler is impressive! I haven't seen any other IC get close to this one in terms of flow and cooling. Every time we've had it on the dyno, it cools the inlet down to only a few degrees above ambient, even when the turbo was producing 212 degrees. The drive belt handled the bigger pulley (this was the one we were using at Doune last weekend). Whether the belt can handle the power needed with the 2:1 ratio remains to be seen!
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
We've come to the conclusion something had fallen into the turbo outlet during the latest pulley change and sat there until the turbo started producing boost - firing it into the blower. An expensive one! We first thought a turbo blade had broken off but the turbo looks in A1 condition on stripdown.
I've bought a water/air chargecooler, small radiator and a 12v pump to make up a small cooling system for the turbo outlet. Hoping this would also minimise any risk to the blower if the turbo ever came apart as i've always been aware this could happen. Having cooler charge entering the blower will also prolong its life and allow us to go slightly higher on the turbo boost.
I'll update once we're back on the rollers
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Sorry to hear about the demise of your blower, but these things happen to a great many of us sometimes.
A supercharger bypass is not required for performance, but if fuel economy, heat buildup in the blower, or noise and vibration is an issue in a civilized everyday road car, a supercharger bypass is well worth the effort.
If it is strictly for full throttle off road competition, you can do very nicely without a supercharger bypass.
Working up a trouble free supercharger drive is not as easy as it first appears. As the air density going into the blower increases, so does the required blower drive torque increase. There are several things to be on the alert for.
No doubt all the pulleys are dead in line, and parallel with the crank. Absolute rigidity of the blower mounting can be an issue.
It is not just absolute strength of the mounting points, but rigidity, and freedom from resonant vibrations. Belt stretch under load is sometimes another difficulty with a high mounted supercharger with wide pulley spacing. And lastly belt flap.
Where the belt feeds onto the crank pulley will always be under tension. But where the belt feeds back onto the blower pulley is the "slack" side.
The belt can start flapping and lead to it jumping or destroying itself. The solution is to fit an idler pulley on the outside of the belt a few inches ahead of where the belt feeds back onto the blower pulley. A flat slightly crowned pulley, or one with side cheeks will centre and damp the worst of the belt contortions, and feed the belt centrally onto the blower pulley with far fewer belt under tension dramas.
Looking forward to hearing much more about this exciting project.
RE: Twincharging - calling Warpspeed!
Will keep you updated :)
RE: Twincharging - calling Warpspeed!
I have the chargecooler installed and went on to the dyno a couple of weeks back. The belt drive held up great - no issues we can see and the belt is reliably spinning the blower at a ratio of 2:1 now.
Turbo is putting out 1.2bar with the blower multiplying that to 2.2bar combined. Power: well we couldn't get grip on the rollers so the best figures i have are that it's making 591 wheel horsepower at 5000rpm, then the cams start working and we couldn't hold it back!
looking at coast-down losses from previous runs, we've deduced the engine to be making around 690-700hp at 5000rpm. The dyno couldn't give us coast down losses due to the wheelspin so we've had to interpret power approximately. On the road there's no lag that's noticeable at all and the torque and power delivery is very smooth. No 'whoosh-bang' from the turbo as it used to be like as all the power came in within 1000rpm with turbo only! We reckon it's somewhere between 750 and 850hp with torque not far behind.
We did find out why the first SC failed. We had been monitoring the turbo outlet temp ans pressure, and also the plenum temp/pressure. We never thought to measure these parameters within the pipe from the SC to the plenum. It would appear that at 'cruise' (exactly where we were setting up the dyno when the failure happened) the bypass valve can't flow enough at the 2:1 ratio and pressure starts building up against the throttle butterfly. This in turn allows the air to go past the partially open throttle and lowers the vacuum in the plenum. At this point the bypass valve closes - we think about halfway, and the air is bypassed between inlet and outlet thousands of times, heating up more each pass. This caused the blower to overheat very quickly and expanded the rotors until they contacted the rear face of the casing.
We measured the pressure in the pipe from the SC to the throttle butterfly and saw 2.5bar pressure in there at cruise throttle! 2% movement of the throttle is enough to stop this but it seems over time, cruising would kill another SC. For the moment i've fitted a BOV just before the throttle to stop pressure building up. It seems to work very well so far. I'd removed that BOV as we couldn't keep it closed on previous attempts.
If you've read all my posts, this now goes back to our first dyno session where i was seeing the BOV in that position opening at cruise. Now it all makes sense! We never thought to measure what was going on in that pipe as we were taking readings from the plenum and at full throttle, the pressures/temps would have been the same...
I'm just back from Shelsley Walsh hillclimb having never been there before. car performed 'almost' faultlessley! For some reason the idle when hot is very lumpy. Other than that, a successful weekend with me finishing just over a second away from the class record. Very much a power hill and the Evo drove every bit as well as i'd expected. The reliability was 100% and i took it home in one piece which is always a bonus!
It's blowing a bit of oil and we suspected the oil rings have been on their way out for a while. This engine is tired now but still producing the goods. I hope to build another engine to suit the charging system when coin allows.
Here's the car performing:http://www.youtube.com/watch?v=FkXLKZLPNmw
And in-car:http://www.youtube.com/watch?v=hrLsnR8gNiA
I touched the gearlever before i wanted to change into 2nd off the line and this kicked in the flatshift, so the first changes sound rough!
Enjoy!
RE: Twincharging - calling Warpspeed!
Jay Maechtlen
http://www.laserpubs.com/techcomm
RE: Twincharging - calling Warpspeed!
The bypass does not need a very large flow area, as long as the up stream pressure from the supercharger does not rise all that high against the just open throttle.
But the same air will be flowing round and round in an endless loop heating up slightly on each pass.
A larger flow area bypass may help slightly, by unloading the blower more completely, but a much more effective solution is to bypass the air from the supercharger after the intercooler.
The supercharger heat input will not that high, because the pressure differential the blower is working against is low. But the total temperature rise can build up to become alarmingly high.
The intercooler will easily handle the low total heat input, especially at the high road speeds that always go with this condition.
It will result in a far cooler running blower casing, rotors, and all induction pipework. And then when you nail it.... that will initially absorb much heat too. So you will be a bit ahead there as well. Doing it that way can also reduce the acoustic rotor noise level coming from the open air bypass. It is all a step in the right direction.
RE: Twincharging - calling Warpspeed!
Having the BOV just before the butterfly works fine and although it doesn't stop the air circulating through the bypass valve, it does give it somewhere to leave the pipework stopping the heat building up & allowing cold air to feed the blower from the chargecooler
I'm having talks with the blower manufacturer about fitting the bypass from their larger model into the unit they have back for repair. They reckon this can be done easily enough so i might get that done before it's sent back to me.
RE: Twincharging - calling Warpspeed!
Regards
Pat
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RE: Twincharging - calling Warpspeed!
I'm giving this some serious thought however!
RE: Twincharging - calling Warpspeed!
It can work pretty well on a Vee engine, and that is very fortunate, because there is not really any other choice.
The more air volume you have between throttle and intake valves, the worse the throttle response will be.
Especially when you close the throttle.
While that is not such a big issue with an automatic transmission, it can be a real obstacle to quickly shifting a manual box.
It also causes the supercharger to act like a vacuum pump at very small (high rpm) throttle openings, which can consume a surprising amount of crank power.
If you are running an EFI engine of any description, you would be well advised to leave the throttle in the original position, if at all possible.
The best way to completely unload a roots blower at light throttle, is with a direct opening air bypass around the blower. If you do this, a clutch is not required, and the effect is almost the same.
My own testing of various bypass systems, has repeatedly produced around a ten percent fuel economy improvement on a typically mildly driven road car. That is probably why every factory roots supercharged car that I know of, uses a blower bypass of some description.
A blower bypass is not required for serious off road competition, where light throttle fuel economy is of absolutely no concern.
RE: Twincharging - calling Warpspeed!
I'm not sure if it would make a difference but next time i'm on the dyno i'll try swapping over the position of the actuator pipe into the plenum to the other end. It may be that where we have it connected close to the throttle butterfly that the air being pushed past the butterfly is creating a venturi effect within the plenum. Perhaps a long shot but worth a try for all the time it would take. There's fittings all over the manifold for various pressure/vacuum feeds so simple enough to move some of the pipes around.
Can i attach photos to the thread?
RE: Twincharging - calling Warpspeed!
I can recommend an external turbocharger wastegate, fitted with a suitably light spring for this application. There is another thread here at Eng-Tips where I go into how to do this in some depth. The details are all in the last two posts of this thread :
http://www.eng-tips.com/viewthread.cfm?qid=174690
Give this a try, I think it will bring a smile to your face.
RE: Twincharging - calling Warpspeed!
The actuator itself is double-ended, similar to an external wastegate with one outlet above and one below the diaphragm. I've only plumbed up the vacuum side but it has the port for pressure too. I spoke with the manufacturer who advised me the port for pressure is only there because they use a generic actuator which has this already. They didn't think i could plumb it in using both ports to any advantage. Thinking about it now, the bypass shaft has a small spring similar to the kind found on throttle butterflies so perhaps i could use the existing setup ?
The butterfly is mounted in such a way it would close on pressure out of the SC even if the spring and actuator failed.
I'm guessing there would be a way to plumb this up using both vacuum and pressure and pretty much do the job of a wastegate but without the extra plumbing work? After all, it's very similar in function and being internal to the SC is also out of sight and keeps it simple.
This would be my preferred route for the moment so any suggestions on making this work would be welcome
RE: Twincharging - calling Warpspeed!
Earlier it was mentioned that a larger bypass was being fitted while the blower was being rebuilt, so I assume the whole bypass assembly is external to the actual blower casing itself.
If the pressure intake to the bypass can be plumbed after the intercooler, instead of right at the blower discharge, it should solve the temperature buildup problem.
I suggest you try using both ports on the actuator, and plumb it directly across the throttle body. Success will depend on the relationship between diaphragm area and the internal spring.
I have in the past encountered difficulties using butterfly throttles as air bypasses. The problem is the grossly non linear relationship between opening angle and flow area. They can also be prone to flutter under some conditions. A poppet valve is far more linear in flow versus actuation pressure, and they work just as smoothly in the supercharger air bypass role, as a more normal turbo exhaust turbine exhaust bypass.
Anyhow, it is all very well to speculate, but trying out a few ideas on the road under actual driving conditions will quickly tell you how drivable the beast is, when transitioning from small throttle high vacuum to full throttle max boost (in both directions). When done right it will be absolutely seamless, and drive like a factory car.
RE: Twincharging - calling Warpspeed!
I think i'll try the actuator ports on each side of the throttle and see how it goes. I can always fit an adjustable restrictor in each line to the actuator to slow the bypass valve movement to fine tune it. The manufacturer edvises me they have seen this done with great success I seem to remember a fundamental reason why using both ports wouldn't work but i can't think what it was now....!
I'll be speaking to the manufacturer again tonight as it's the only time i can get hold of them due to the time difference
RE: Twincharging - calling Warpspeed!
Just a quick update. The car has been running fine as it is, although the blower is damaged and hasn't been replaced yet due to not having coin in the bank. I've done another 4 events since i last posted and have to say the setup is proving reliable in daily use. We've identified the reason for the blower overheating and added a BOV to act as a safeguard. The ratio between the turbo and blower pressures has altered slightly due to the blower slowly dying but the combined boost remains the same. This only gives a problem with turbo outlet temps for the short term. I built a tank to hold iced water and can pump that around the chargecooler for the short runs we do on the hills. This copes quite well and we're experimenting with anti-freeze/water at -18c from the freezer to run the chargecooler. So far so good.
Also just installed a temperature monitering system to keep an eye on 6 different temps throughout the system. I haven't yet used the car since installation so i can't comment on actual temps until after this weekend, which is my next event.
So far though the car has set aother 2 records and taken it's second FTD (fastest time of the day) since i last posted on here! Once we get a new blower back on, fit a bigger exhaust housing on the turbo and a larger throttle body, we should see some real horsepower. The map that's been done is also only a safe map and overfuelling so more power to be found there once the final bits are fitted and it's mapped for power
Will let you know how it goes
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
1. Because the blower limits the top end airflow, it can be geared to deliver much higher boost at low rpm than the alternative setup.
2. At the top end, the blower will be adding power to the crankshaft courtesy of the low pressure between the blower and the turbo. This power is sourced from the exhaust turbine so efficiency will benefit on this count as well as the higher compression efficiency compared to a roots operating at high boost.
3. Boost control is much simpler although the turbo pressure ratio would need to be monitored during initial setup, to avoid overspeed.
On another note. There have been several mentions of using a valve to bypass the blower at high boost levels. Of course this will flow backwards when open although some posters seem to indicate it would flow toward the engine. What's important of course, is that it would unload the blower by equalising the pressure above and below. It would probably also eliminate the need for the second wastegate by increasing the PR and therefore the load of the turbo compressor.
RE: Twincharging - calling Warpspeed!
The simplest way is to run two fuel pressures, each pressure referenced to the intake pressure of the space they are spraying into eg: fuel flows to higher pressure injectors first (post-blower) then pressure reg #1 (with reference hose connected to manifold post-blower), then to rail #2 feeding injectors pre-blower, then pressure reg #2 (with reference hose connected to manifold post-blower). The two regs could have the same pressure setting if desired, the actual fuel pressures will differ by whatever the pressure increase across the blower happens to be.
RE: Twincharging - calling Warpspeed!
I settled on building mine the way i did to keep the exhaust pressure lower than the intake to allow a fuller cylinder charge, after all, that's where the power is made. Running a turbo after the blower will result in high exhaust manifold pressures as the turbo has to work harder. For the kind of power i'm wanting, i have to bear in mind the exhaust valve temps so filling the cylinders more with fresh charge will help with valve cooling and reliability of the engine.
I guess preference on plumbing will depend on the final use of the car. In my case, i just want torque and power - and fuel consumption isn't a consideration!
Modern fuel injectors are able to flow higher rates than only a few years ago and still keep a decent spray pattern at idle so twin injector setups shouldn't be needed (on my build anyway). On V-Power fuel, we're getting away with 1600cc injectors in their original position - so far we're only at 75% duty cycle although i expect that to rise once we get round to doing the final changes. I may yet start using E85 and would expect to then need 2200cc injectors
RE: Twincharging - calling Warpspeed!
An added bonus is the high top end airflow that only a centrifugal type of compressor can provide. It all adds up to a wonderfully drivable package, with excellent reliability, high detonation resistance, and long engine life. In other words, power that lasts.
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
I've replaced the damaged SC and been back to the dyno. This is the first time the system has been in good health since it was first put together so as far as figures go, we didn't know how it would perform - or stay together
Result was just over 700ft/lbs torque at 5500rpm, no lag at all and a very healthy spread of torque from 2500rpm up to 7800rpm. Power at the flywheel estimated at 700hp. Estimated because the dyno only gave wheel figures and wasn't setup for coast-down losses. Going by the previous visits to a different dyno, we have estimated 100+ hp and torque losses through the 4wd system.
It's incredible to drive now. From 2000rpm it pulls hard even in 5th and picks up a fair pace very quickly! Overall i think a very worthwhile modification as the car is very very quick on the hillclimb tracks. No waiting for the turbo to spool on the exit of the hairpins, it's instant torque at any revs and speed!
The last few events i've suffered clitch slip so a triple plate Superclutch has been fitted. There's also been the odd transmission breakage due to fatigue. I stripped first gear on the line and then twisted the centre diff output shaft at Doune. Both breakeages have evidence of classic fatigue and had reached the end of their life.
Here's an in-car run of Doune Hillclimb with 700ft/lbs torque: http://www.youtube.com/watch?v=uGyLHvqifgU
I'm not having to rev the engine above 6500. The shift lights are set to start at 5500rpm although i was learning the car all over again. It's not been the same at each event!
I've attached the torque graph but not sure if it will show up on the thread. The dyno software had trouble matching speed to revs on the graph but the dyno operator assures me the readings are correct, just the scale has been affected for some reason
Happy to say Twincharging the engine has been a success!
RE: Twincharging - calling Warpspeed!
Those are some pretty impressive figures, from what is in reality a rather small capacity engine by most standards.
Unless you have ever had the personal experience of driving something like this, you would never believe how smoothly and willingly it pulls at low rpm in the higher higher gears around town.
And unlike many other highly tuned very high output engines, it will still be going strong for many many tens of thousands of road miles.
RE: Twincharging - calling Warpspeed!
To five you an idea of how quick the car is now - it does a standing 0-100mph in 4.6 seconds, not bad for a 2.2l 4-pot engine. The engine is now almost 5 seasons old and is showing signs of wear. It's probably only covered 5000 miles in that time, but they have been very hard miles. I intend to either freshen it up over the winter or build a new engine. Having the required funds will decide which route i go there.
One thing i wanted to ask - all through the year of development, the engine has produced quite a lot of black smoke on boost. We had this down to the damaged SC and balance being out from the original mapping we did but now the new SC is fitted and the map has been corrected, the fuelling is at 12.4:1 on boost so we know it's as lean as it can be and still be safe. One theory we're looking at is the smoke is being produced because unburnt fuel is going straight out the exhaust and burning in the manifold. This would then indicate the 272 cams i have may have too much overlap. We had originally thought we should try a pair of 282 cams but if i'm right in my assumptions of why the black smoke is so prominent, 282's would make the problem worse. Going to a set of 260 degree cams seems like a retrospective step for torque and power however.
Do you have any views on this?
Cheers
RE: Twincharging - calling Warpspeed!
The sudden heat gets a lot further down the exhaust pipe, and a lot of soot and crap can be blasted out.
This can create quite an impressive black haze in the rear view mirror if you normally drive around at legal speeds, and suddenly call upon a bit of real acceleration.
With boost pressure normally quite a bit higher than exhaust manifold pressure, (and a good four valve head), a little valve overlap goes a VERY long way.
The docility and tractability of twincharging (or supercharging) can easily mask excessive valve overlap.
It is not like a cranky highly tuned high compression n/a engine with bulk exhaust reversion at low rpm.
Another way to attack this problem might be to set the injector opening time to be after exhaust valve closing.
This works, until you start getting up to very high injector duty cycles, where the injectors might be spraying almost constantly flat out. Larger injectors will fix that.
Blowing a bit of cold air over the exhaust valves cannot be all bad, but blowing fuel out can be a financial hazard.
RE: Twincharging - calling Warpspeed!
It's not a problem really, just unusual to see it now the mapping has been done.
I hope to post some out of car videos soon. My season is almost over and then we'll be into the winter rebuild in advance of the new season starting in April next year.
Mr Warpspeed, where are you based?
RE: Twincharging - calling Warpspeed!
Melbourne Australia.
RE: Twincharging - calling Warpspeed!
Good luck with the sprinting, hopefully I will be able to see your beast in real life sometime soon...
RE: Twincharging - calling Warpspeed!
NB. If you need to reduce overlap, before you change cams, why not try opening up the lobe centres by retarding the inlet cam and/or advancing the exhaust cam a smidge?
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Between 4,000 and 7,000 there is 500 to 600 ft/Lb, only a 20% change.
That is rather a lot of torque !
But one thing that is rather less obvious, (but Donald will probably confirm), the acceleration potential, especially in the lower gears will now be far more fierce than it was originally with just the straight TO4-Z. It is not JUST the Hp and torque, but the ability of the engine to very quickly gain rpm under load in the lower gears.
There is a lot more to the responsiveness of twincharging, and how it actually feels to drive, than just eyeballing the dyno sheets may suggest.
Difficult to put into words really, it is something you have to experience yourself, but Don will know what I am trying to say.
RE: Twincharging - calling Warpspeed!
With a turbo it needs both rpm and time to spool.
It is not the least bit surprising that a twin charger gives instant response and huge top end without sacrificing bottom end. That to me is the original driving force behind such a project.
What I had not considered (although once mentioned seems so obvious) was the extra pressure multiplication from the roots blower increases exhaust scavenging to such an extent.
On considering this, the cam strategy at overlap should be similar to that if only a roots blower where used. OK if only a roots blower with a somewhat restrictive exhaust where used.
If it where a SBC and presuming duration is measured at 0.050" I would say with 280 deg duration it needs about 114 deg lobe centres.
Being a 4 valve engine with smaller valves but bigger total curtain at the same lift and no shrouding between the valves at small lift, I would think 0.050 is a bigger %age of total lift and flow at lower lift is relatively better than a 2 valve engine at the same lift. Bottom line is significantly better scavenging, so even wider lobe centres might help. Some top fuel guys run 116 deg lobe centres, but they also run 300 deg or more duration.
With twin cam and adjustable cam gears I would open the lobe centres a stupidly big amount just to see, providing piston to valve allows it.
I agree with sequential timed EFI you are probably losing more air than fuel during scavenging.
It is my understanding that unburned air in the exhaust shows lean not rich or average as the O2 sensor senses the O2 but not the HCs, but black smoke indicates only partly burned fuel discharging from the exhaust.
Open the lobe centres but keep a close eye on exhaust valve tappet clearance to look for valve stretch. If valve stretch is even hinted at, close the lobe centres 2 degrees again.
Sorry if the post is a bit random as I typed as I thought and did not edit it for logical progression and concise structure.
Regards
Pat
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RE: Twincharging - calling Warpspeed!
If only one could get decent bearings and rotors for the Toyota SC14. They are dirt cheap and fairly compact and big enough I think for a D16 Honda even bored and stroked to 1.8 litre.
Hmmmm
If it could be turned over so the inlet port becomes the outlet it would not need the drive direction to be changed.
Sorry I will cease with the thread jack and start a new thread if I don't come to my senses.
Regards
Pat
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RE: Twincharging - calling Warpspeed!
Slightly less duration with wider lobe centres would definitely be the way forward for a more general purpose type of twincharged vehicle.
But then again, Donald is not the least bit concerned with fuel economy, just winning.
And the cooling effect of both extra air and extra fuel, with over scavenging, will add to power production, detonation resistance, and greatly aid thermal management.
A higher EGT would certainly benefit the turbo, but the blower more than makes up for that with the extra mass flow.
No doubt more tuning and more development lies ahead, but it is probably not such a bad thing to start out with it the way it is.
There is a very great reliability benefit in having a high detonation margin, and keeping peak EGTs down.
RE: Twincharging - calling Warpspeed!
But on a Ford Laser 4WD, I fitted an SC14 down beside the gearbox, ditched the SC14 blower clutch, and ran a long jack shaft, coupled to the SC14 input with a small chain coupler.
That ran along the side of the sump and left plenty of clearance for all the existing belt driven engine accessories, none of which needed to be moved.
It is the only space it would reasonably fit.
It also left plenty of room for a large turbo, mounted in the usual location.
RE: Twincharging - calling Warpspeed!
I will start a new thread
Regards
Pat
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RE: Twincharging - calling Warpspeed!
Opening lobe centres will improve piston to valve clearance (as I'm sure you know). Agree with everything else you said.
Warpspeed. Regardless of the vehicle purpose, I think it should run fairly wide lobe centres if it isn't already. Duration is probably OK as it is.
[i]It is my understanding that unburned air in the exhaust shows lean not rich or average as the O2 sensor senses the O2 but not the HCs, but black smoke indicates only partly burned fuel discharging from the exhaust.[i/]
Unburned scavenged air is 100% lean so the "average" or overall AFR in the exhaust stream looks leaner than the portion that was in the cylinder during combustion. (I am/was talking about unburned air with no HCs). Result = WB lambda reads 12.4, cylinder sees a lower-number/richer-mix.
Black smoke is predominantly carbon particles. Available oxygen reacts easily with the outer hydrogen atoms leaving carbons with no oxygen left to burn them.
RE: Twincharging - calling Warpspeed!
I'm just back from Loton Park Hillclimb near Shrewsbury which saw 100% reliability and the car performing faultlessly all weekend. This is a track i've only been to once, and the first time i was driving a Hayabusa engined Wesfield as the Evo was missing a SC at the time. My best time in the Westie was a 59.4s - this time i got the Evo to within 0.09s of the class record to finish with the class win and a personal best time of 54.80s (the class record being 54.71s set by Roger Banks in the mighty Audi A4 V8 twin turbo in 2007) To get that close without knowing the track well shows the car is very quick as it is.
I have a pair of S2 cams with duration of 272. These are timed to the manufacturers settings 117.5 degrees but to date, we haven't had a chance to play with the timing yet. The car is away to be stripped and lose another 100Kg over the winter although i still hope to keep it road legal! I have plans for building a new engine before next year as this one really is tired after 5 seasons of racing. I had always thought it best to use this old engine as a test bed for the compound charge system in case it went horribly wrong!
Food for thought on the cam timing tho. I'll pay attention to this during the spec and build of the new engine and hopefully we can have time to play with the cams at the pre-season dyno session next year. From the recent results at the hillclimbs, i have every confidence that the car is more than capable of taking most of the class records next year providing reliability remains.
I have one more event left this year - a sprint at Boyndie Kart track this weekend coming. This should be interesting as the circuit is so tight that i'd be having to brake for the next corner just as the turbo was spooling previously but now i think the car will hump the class record big time due to the instant response and mid range torque. I'll update with the video from Loton later today
Cheers for all the tips so far, i will of course keep you updated with progress!
RE: Twincharging - calling Warpspeed!
Very good going indeed, well done Donald.
And I am sure you will blitz the field at the cart track too.
The instant response and wide torque band should make your car a lot more drivable on such a really short tight track, than many of the other cars there.
I just wish I could be in Scotland to watch you do it.
RE: Twincharging - calling Warpspeed!
Here's the video from loton park. Running 2 videos side-by-side of this run and another where i make it round the first corner cleanly, i lost 0.3s - more than the margin i missed the record by! Had i not been so late on the brakes at the first left hander, i'd have the record in the bag on that last run
http://www.youtube.com/watch?v=XI1CsX4S7hc
Ce'st la vie!
RE: Twincharging - calling Warpspeed!
Wicked video!! Quick question, how is your SC pulley/belt system set up? You mentioned that you had to redesign a better system to eliminate belt slippage. Are you using a cog belt/pulley similar to this
http
or running the typical multirib belt that comes with most of the SC's?
I have an Audi 5 cyl Coupe Quattro and have a couple SC's I can use for this project. I don't care about belt noise levels as I'm just going to rally/auto cross this car. I just don't want belt slippage.
RE: Twincharging - calling Warpspeed!
I didn't think i should risk the multi-V belt at the start. mainly because i was having pulleys custom made and didn't want to have to remake them if the belt couldn't cope. As it turned out, i had to get more made anyway! Development...
I was thinking that because i have a damaged SC here, i could loan it out to others wanting to do a test fit and see if that is the SC for their project. When i started, i ordered the SC, then while waiting for it to arrive, made a wooden mock-up of the unit to make manifolds and pulleys so when the SC arrived, it bolted straight on.
RE: Twincharging - calling Warpspeed!
You would have to give them drawings for the parts to work from but the quality is very good and the prices are surprisingly cheap.
The best tip i can give you is to find out the lengths of available belts and design your drive around the nearest size.
RE: Twincharging - calling Warpspeed!
Donald is right, use an automotive belt catalog to select a cam belt off a fairly common vehicle, and design your blower drive around that, right from the outset.
They always give tooth count, and the length will be tooth count x 8mm pitch. Curiously there are always an odd number of teeth on automotive belts to even out the wear, which is not a bad thing.
Using a readily available belt will save a lot of pain and frustration later on. The automotive belts are thinner and more flexible than the industrial belts, and are much better suited to small pulley diameters and the very high belt speeds we need.
Aluminium pulleys are ideal for a competition engine, but will show rapid wear in a long mileage street engine.
For the street, stick with steel pulleys, cast iron may be o/k, but mild steel is much safer at very high rpm.
Plastic idlers should be of large diameter, (to keep the idler rpm sane) and placed on the outside of the belt on the slack side, just before the blower pulley.
Working up a reliable blower drive is always one of the major frustrations of installing a custom blower.
RE: Twincharging - calling Warpspeed!
Future plans include having the pulleys hard anodised to reduce wear from the belt. For my application, steel pulleys were not even considered due to weight. The aluminium pulleys will eventually wear out but by then, i will have no doubt refined the design and need a new set made.
I also ended up using the standard sprung tensioner as it had the travel i needed to remove and refit belts easily. I modified it so it would spring into the belt and then i could lock it in place with the centre bolt. The beauty of this is it's so simple and strong and gives me a large range of movement as the belt inevitably stretches. I found that by not locking it in place, the inertia of the SC on the overrun would pull the tensioner open and cause the belt to jump off. The belt drive was one of the biggest challenges of the build - but looks easy now it's working properly!
RE: Twincharging - calling Warpspeed!
Yup, that is always the way.
Usually people doing this for the first time are fairly impatient to get to the initial road test stage, and the blower drive is usually the very first problem that shows up.
Aluminium is perfect for this project, but just cautioning people that aluminium is a less than perfect long term choice for an everyday road car. Hard anodising will help a lot, but that too will eventually flake off.
These pulleys are never cheap to buy new, so just a word of caution on material selection.
RE: Twincharging - calling Warpspeed!
Tony,
BTW, I've acquired a few SC's for my various projects. 3 Whipples and an M90.
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
"I have an Audi 5 cyl Coupe Quattro and have a couple SC's I can use for this project. I don't care about belt noise levels as I'm just going to rally/auto cross this car. I just don't want belt slippage."
Bigjuicesr20,
I was planning something similar on the 5 pot Audi. Where were you thinking of placing the SC? I was thinking under the inlet. Would love to share info and even some development.
Cheers
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Usually wherever the great enormous thing will fit.
They don't usually look that large in photographs, or even the engineering drawings.
But once purchased, and sitting on your work bench, they kind of grow in size.
Sitting loose, and balanced on top of your valve cover, and looking at the available (?) space around the engine, the reality of the true enormity of the thing is going to hit pretty hard.
Almost every blower installation requires several other things to be moved to make room, and that is what complicates things.
RE: Twincharging - calling Warpspeed!
In my installation, i had to cut the flange off the alloy fabricated inlet manifold, tilt the plenum to 15 degrees and weld the flange back on then skim the flange again. This just gave me enough room to fit the SC below the manifold behind the engine. The chassis leg also needed a small section cut away for the drive pulley. The SC now sits less than 1mm from the water pump with the bypass actuator 2mm away from the engine block. This all had to be achieved while still allowing for access to the transfer box top bolts! It's very tight in that space but now looks almost OE fitment. Also think about weight distribution. If you can install it on the opposite side of the engine from the driver, and back as far as possible - this is the racer in me thinking out loud!
Weight is the enemy when it comes to competition which is why i hope to lose some myself soon - i'm not a small guy!
Have a look at this article our local newspaper did on the car a few months back: h
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
PorschaTwin,
Not sure where I'm going to squeeze it in but like Warpspeed and Madmac says the SC looks small in pics but it'll be a challenge to find room in engine bay. I don't need AC so I'm pulling compressor out I don't mind removing OEM intake manifold and making custom one. That small radiator inside engine bay may have to be moved as well. I'm gonna butcher this car to make it fit!! LOL.
RE: Twincharging - calling Warpspeed!
Here in the US the closest one I know of is in New Hampshire on Mount Washington. http://www.climbtotheclouds.com/
A 5 cyl Audi has the record but Travis Pastrana in a built Suby just missed record this year. Bad weather prevented him from 2nd run. even though this Suby is professional sponsored and fully race prepped it can't touch the torque numbers your Evo is putting down. They'd freak if they saw that dyno graph. From 2800rpm to 5500 is just sickness!
If you get some sponsors you need to ship it over here for next years run.
As PorschaTwin asked could you link us to some engine shots of Sc and pulley setup? I like the idea of using a timing belt and tensioner. BTW, how wide is the belt you're using?
RE: Twincharging - calling Warpspeed!
Regards
Pat
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RE: Twincharging - calling Warpspeed!
http://www.usacracing.com/ppihc
There are some tight hairpins with big drops off of them. It is a good drive, but not being a racer, I think it would freak me out to drive that road really fast.
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Anybody tried this calculator from Supercharger Performance?
There is a twincharger calc so I will have a mess about with it!
RE: Twincharging - calling Warpspeed!
http
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
"To the experts on here: If this project was repeated on something very similar (and I am tempted!), what would a good choice of SC and turbo be for 750bhp on a 2.1L motor? Eaton M90 & GT40R?? Should I be thinking of approx half boost from the SC and half from the turbo?"
Any pointers please?
RE: Twincharging - calling Warpspeed!
Take a look at the much newer Eaton TVS range of superchargers. They flow much more air at both ends of the range, and with much higher thermal efficiency everywhere.
The rather special Harrop blower Donald is using is an Australian upgraded version of one of these Eaton TVS blowers. These are still a roots style blower, (not a screw blower) but are designed for the very high airflow required these days on modern high output V8 engines. An M90 simply cannot breathe as well at the top end as a TVS.
Again, a large size GT40R would be a quite reasonable choice for that power range, but the TO4Z would have a considerably wider flow range at both ends.
I guess it depends upon your budget.
The M90 and GT40R would certainly be workable, but Donald's much more expensive combination of blower and turbo would make that top end power range a lot easier to achieve, and also be more responsive down low.
RE: Twincharging - calling Warpspeed!
As for the new Eaton TVS type, are they available from any UK production vehicles or do they need to be purchased from Eaton? Are they still known as M90, M112 etc?
If I need to buy a new one, should I go twin screw with a Whipple? I have a couple of 140AX blowers for another project.....
Thanks again.
RE: Twincharging - calling Warpspeed!
I am from Oz, so remain blissfully unaware of what production vehicles in the UK are using.
The just announced new Australian FPV supercharged Ford V8 uses the Harrop blower.
If you google "Eaton TVS" that should get you started with some info, and tracking one down locally.
Buying new opens up quite a few possibilities, and the price differential for the various types and sizes is not that great, so you get to choose exactly what you want.
Buying secondhand limits you to the much older designs, but at a huge cost saving compared to new.
Comparing a Toyota SC14 to a Whipple M90, to a screw blower or a TVS is like chalk and cheese. The technology and performance difference is immense.
Similar to comparing a fifty year old diesel turbo with sleeve bearings and very heavy and crudely designed wheels, to a modern ball bearing turbo.
To the uninitiated they appear to look pretty much outwardly the same, and do the same thing, but they sure are not the same.
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
TIA
RE: Twincharging - calling Warpspeed!
I read today that all the famous turbo aircraft engines (which means mainly the P-38 and P-47) were actually "twin-charged" - the engines kept their in-unit blowers. Presumably the idea here was better engine reponse as with car engines.
RE: Twincharging - calling Warpspeed!
You can imagine how big a turbo would be involved, and turbo technology was not as sophisticated as today. The lag would have been considerable. Less than ideal for maneuvering in a serous close quarters life and death dog fight.
I am told by the fighter jocks, that acceleration is far more important than top speed in getting the jump on the other guy.
The Germans came up with a great idea, a twin prop bomber with THREE piston engines. The third engine sat in the fuselage and just drove an enormous roots blower to boost the other two engines. As I remember, the roots blower was almost as large as the engine driving it.
RE: Twincharging - calling Warpspeed!
http://www.aviation-history.com/republic/p47.html
I think only the P-38 and P-47 were the only turbo fighters made in any real numbers.
RE: Twincharging - calling Warpspeed!
Anyway, back on topic. I've made a few changes to my system and hope to go back to the dyno in the next few weeks. I will update the changes and link to a dyno graph as soon as i can. Suffice to say all these changes should release more of the systems potential and hope to see even more torque and power.
Interesting project and i feel my results are worthy of publishing for all to see so anyone wanting to have a go at compound charging can at least see the benefits of this on their car.
RE: Twincharging - calling Warpspeed!
So far we have seen more power at less boost but we are still a long way from having the mapping complete. The new ECU has had to be mapped from scratch so it's taking a while. Seems the old engine is still hardy and taking the punishment though!
The failure of the actuator won't stop us carrying on mapping as i fitted a BOV that opens at 11psi to bleed off the excess pressure which prevously caused the SC to overheat and fail.
Hopefully have a nice torque and power graph soon!
RE: Twincharging - calling Warpspeed!
It will need to be fitted with a spring that exercises the actuator over its mechanical range with an applied differential pressure varying between about 2psi and 3psi.
HKS wastegates use dual springs, the stiffer outer spring providing most of the force. The much lighter inner spring can be changed to give much smaller force increments. If you just run one of the HKS inner springs by itself, it would be an off the shelf solution to finding a suitable spring for the actuator of your choice.
From memory, there are two springs that cover the range of pressures that are of interest for a supercharger bypass actuator.
RE: Twincharging - calling Warpspeed!
The problem i have is the actuator is only 1mm away from the engine block and the space available is incredibly tight. I'm looking at machining my own one from alloy billet now so i can make it to my own spec. The operation of the internal Harrop bypass works great - it's just the actuator simply isn't strong enough to accept 38psi boost! In terms of driveability and how well it operates as a bypass it does seem to be perfectly setup with the right amount of spring pressure.
Warpspeed, i can't find a manufacturer that makes a wastegate body small enough to fit the space available, although Forge Motorsport had a good selection, only one was setup to pull the rod, and it wasn't designed to have pressure at the opposite side of the piston. Also, as you mention - the travel of these units usually isn't enough to open the bypass fully - it needs 25mm travel.
For the moment i can fit another Harrop actuator but only operate it with vacuum for the duration of the mapping session. Once the engine is out for rebuild next week i can look at the problem more closely and take more time over a solution.
I guess it's just another hurdle to overcome - hopefully the last one and the results should be worth the hours!
RE: Twincharging - calling Warpspeed!
As very high temperatures are not an issue, how about some sort of industrial rolling diapragm such as this:
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RE: Twincharging - calling Warpspeed!
Mike Halloran
Pembroke Pines, FL, USA
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
I took apart the 3 actuators that have failed during the year and all have the diaphragm intact. These have the diaphragm held on the outer circle by the 2 casings that are glued together and this time it's come away internally.
I'm pretty confident i can make a new alloy casing that clamps together and holds the diaphragm in place reliably now. If i use the diaphragm that is designed for the stroke i need, ie the one from the old actuator, then as long as it's strong enough to handle the boost then i'm willing to give it a try.
Update to follow
RE: Twincharging - calling Warpspeed!
I think a flap type valve can do the job, but not sure you have enough room under the bonnet of an Evo . This can directly solve the problems of bypassing and can be use to enhance fuel economy. But your EFI setup must use a map sensor.
RE: Twincharging - calling Warpspeed!
To make the turbo the only compressor at the top end increases exhaust backpressure dramatically and effectively strangles the engine - less power and torque than compounding.
RE: Twincharging - calling Warpspeed!
What camshaft does the engine has finally? It has mentioned a few in previous posts. If you are running compound compression which your intake pressure is always higher than exhaust pressure. Then you never need much overlap. One main reason is that you might have your fresh charged air/fuel mixture directly blowing out to the exhaust manifold. Have you ever notice this effect?
To correct this situation, only need is an adjustable cam spockets for intake side. Advance will make it more overlap, retard will make it less overlap. Retard too much will cause intake charge to flow back to the intake manifold. This is not harmful and will not cause much problem in fuel economy but hurt your VE therefore less power.
RE: Twincharging - calling Warpspeed!
I don't have the pneumatic circuit for your actuator sorted in my head so this may be a stupid question. What is the highest differential pressure seen by the diaphragm - I assume 38 psi? If so - does it need that much, or does full actuation occur at a much lower pressure? If so - why not limit the pressure with a simple regulator? This should protect from the failures you are seeing.
Engineering is the art of creating things you need, from things you can get.
RE: Twincharging - calling Warpspeed!
I have the actuator beefed up and pressure tested now and the car is back at the dyno today for the final mapping session. I plan to make a completely new bespoke alloy actuator before the start of this season
To explain how the actuator is plumbed, it's a simple diaphragm with a port on each side. One port is connected to the plenum so the vacuum at idle and cruise opens the valve, and on boost it keeps the valve tightly closed. This end sees vacuum and boost up to 38psi. The other port is connected to the SC outlet, before the throttle body so that the bypass opens if pressure builds up in the pipe due to the throttle being partly closed. This was the reason we destroyed 2 blowers - at cruise the throttle was only part open but it appeared there wasn't enough vacuum in the plenum to open the bypass and the air still being compressed had nowhere to go. Result of that was superheated air in the blower and rotor growth. The extra port essentially opens the bypass should pressure start to build up before the throttle body, more of a fail-safe than anything. Only a fail-safe if the actuator works....! With the BOV in the pipework now this port only sees 11psi which is what the BOV spring is set at. Differential therefore would be no more than 25psi extreme case.
I had looked at a regulator for limiting the pressure to the actuator but long term i think making a stronger actuator is the best way to go.
Hopefully the mapping will be completed tonight then it's back to tear the engine apart for the rebuild.
The shonky old engine is doing well. Compression test indicates all 4 cylinders are still producing good compression - 13.5bar to be precise
RE: Twincharging - calling Warpspeed!
However, if you can go for electronics, its much more simple and can have a more flexible control strategy base on your parameters. If the control is a simple logic on/off signal, then it can be implemented using simple passive components rather than relying on vacuum which is a bit unreliable when you are driving almost full time partial/full throttle, the system have no chance to accumulate enough vacuum even you have a reservoir.
FYI, there are lots of electrical throttle bodies from wreckers as there are so many cars out there in the past decade moved to electronic throttle. They are very suitable in your application with good flow characteristics.
RE: Twincharging - calling Warpspeed!
You are not seriously suggesting that a couple of pressure transducers, a microcontroller and a stepper motor would be simpler ?
On the other thread you asked if I knew anything about microcontrollers.
Well.......
Almost twenty years ago, I designed and built completely from scratch all the hardware, wrote all the software for my own EFI system and the GUI to go with it, completely by myself.
I am an electronic engineer by profession.
Does that answer your question.
I have been building twincharge systems with blower bypasses also for at least the last twenty years as well.
I just cannot see any need to use a microcontroller for this task.
RE: Twincharging - calling Warpspeed!
I have never even considered using electronics to control this part of the system due to the complexity of setting up the software - let alone building it in the first place.
On another note, i just had my mapper on the phone saying a coil has packed in and he can't continue the mapping. We have a set of Hyperdynamics coils available to use but i suspect i need to look at a better system now. I had hoped this could wait until the engine was rebuilt but now it seems the tuning gods have spoken and are telling me to get it upgraded now...
RE: Twincharging - calling Warpspeed!
Am pretty pleased with the results! We seem to have lost some torque since the last dyno session although it was a different rolling road last time that only measured wheel power.
The mapper had to gently squeeze the throttle at 1800rpm to stop the car trying to launch off the rollers, so the bottom end of the map isn't at full throttle.
Now finally i can get the tired engine out and rebuilt! I will be changing the cylinder head and cams at the same time so i reckon there's more to come before the season starts.
Can't wait to drive it hehe
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Update, the engine is out and in component form, showing little signs of the hard work it's done for the last 4 years. The pistons and bores are just on their tolerance limits so i've decided to go for a rebore. It's away for a new crank and 86mm pistons, oil pump and seals as well. The rods have been crack tested and are good to re-use. They are rated to 1400hp. The intention is to build the engine to withstand (and hopefully eventually produce) 1000hp reliably. The cylinder head is being ported to suit the induction setup, with higher lift & slightly shorter duration cams with solid lifters.
Could get interesting....!
RE: Twincharging - calling Warpspeed!
Big torque and four wheel drive can be pretty hard on the clutch and transmission. Metal fatigue is going to be your worst enemy.
RE: Twincharging - calling Warpspeed!
Very aware that the drivetrain is the weak point now!
I always load the drivetrain before launch and don't just drop the clutch to avoid the sudden impact through the components. That method has served me well over the years but with this new power and torque, i have concerns! The flatshift is also kinder to the dogbox as opposed to using the clutch to change gear.
I guess i will have to beef up areas of failure as they happen to eventually iron out the weak points. This had to be done with the clutch and i've ended up with a triple-plate 'superclutch' that is showing little signs of wear after 4 events
RE: Twincharging - calling Warpspeed!
The new engine was built, mapped and we started the hillclimb season in April. A few transmission failures have hampered the reliability and although not unexpected, these have been quite costly and stopped me developing the car further. So far the results have been a new class record at Prescott Hillclimb, a 2nd FTD at Fintray and some good times at other events. The weather here has been terrible so most events have been wet/damp and records have been unachievable!
I have a break in the season now so hope to make a seperate exhaust for the 2 wastegates as i think the 3.5" exhaust is restricting the airflow out of the engine (exhaust boxes have expanded and blown out some rivets!). I have space constraints for this additional system though so expect this will take some time to get made.
I have 3 boost settings now, 1.9bar, 2.2bar and 2.6bar. On high boost, the power delivery is simply stunning! Instant response, almost negligable lag and a very quick car on corner exit!
I had to have the turbo seals replaced after Fintray Hillclmb so in the vids there's oil smoke which has now disappeared.
Here's some vids of the season so far: http://www.youtube.com/watch?v=F3O4tyLnDlA
Wet run (hit the embankment which ruined the run): http://www.youtube.com/watch?v=pZaTd8k2krY
This is the record breaking run at Prescott on high boost: http://www.youtube.com/watch?v=-uZMMgn_B20
http://www.youtube.com/watch?v=GIqd1XZHNAA
http://www.youtube.com/watch?v=1zcHx3TGamY
Safe to say when she's not breaking shafts, she's very competitive now. Thanks to all who have contributed here, this wouldn't be half the car it is without the help! She's an animal now and i'm still learning how to drive her in anger!
As this is very much an on-going project, i will update as and when changes are made.
RE: Twincharging - calling Warpspeed!
Mac initially ran 2.5bar total and 1.5bar from the turbo. Does it mean that the supercharger is working at a ratio that produces (2.5+1)/(1.5+1)=1.4bar? So (1.4-1)*14.7=5.88psi read on a boost gauge?
And then only (1.5-1)*14.7=7.35psi wastegate pressure on the turbo?
RE: Twincharging - calling Warpspeed!
for a 1.6l/rev blower, it means that it is plumbing very closely 1.6 litter per revolution if the inlet air pressure is the atmospheric pressure; but what if it is being fed charged air of 2.5 bar (1.5 bar from the turbo plus 1 bar of the atmosphere)? Will it become 1.6*2.5=4l/rev?
And if we were to plot dots on a compressor map, which boost pressure should be used on the turbo map? the blower map? and what about the flow rate for either?
Thanks a lot!
RE: Twincharging - calling Warpspeed!
Update: I have had 6 events in a row where the car and engine has not broken. Over these 6 events i have taken an FTD at Ingliston and set 4 new class records, often mixing with single-seater times lol. To say she's quick is an understatement now. Building the twincharger system is one of the best things i've done to the car in terms of the sport i compete in. The instant response, torque and driveability is just stunning and there is no lag at all on corner exit, or any time i have to lift off to keep traction.
Some more vids here: http://www.youtube.com/user/evomadmac?feature=mhee
Almost at the end of the season for me and hopefully the car will stay reliable for the final round at Doune. Winter plans are to remove some excess weight from the car, but leave the engine and twincharger well alone!
RE: Twincharging - calling Warpspeed!
Mike Halloran
Pembroke Pines, FL, USA
RE: Twincharging - calling Warpspeed!
With a lot of this stuff, raw engineering can only take you so far, the final bit is about tuning, tweaking, and optimization.
RE: Twincharging - calling Warpspeed!
Warpspeed, when i put the twincharger together it was experience with my previous SC project and simply working out what i thought would be the best combo of SC and turbo. No real maths were done at all and surprisingly it worked quite well as it was. Developments such as belt drive and pulley ratios along with the larger turbo housing saw the system come to life in a way i never thought possible and i guess i was lucky the components were well matched at the outset!
Thanks for all your help again. This has been a learning experience like no other for me and i hope that sharing my project on here has helped others with their twincharger builds.
RE: Twincharging - calling Warpspeed!
It's certainly helped me.
I think you short sell yourself by putting it down to a lot of luck.
There have obviously been some sound judgements on this.
Regards
Pat
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RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
Or to quote myself in another forum, when building an engine, if you leave anything to luck, you almost always have bad luck.
Regards
Pat
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RE: Twincharging - calling Warpspeed!
Thanks for the comments guys, i just wish i could take you for a run and let you experience what it feels like to go from 0-100mph in just over 5 seconds! It's very addictive lol
RE: Twincharging - calling Warpspeed!
RE: Twincharging - calling Warpspeed!
The season finished at the end of September at Loton Park with some great overall results. The engine and twincharger system has stayed in great shape for 8 events in a row. The only issue i had was a tensioner for the power steering belt broke away and left me with no power steering at Doune. The result was an mostly undrivable and dangerous car so i just teased her up the hill to get an official time for the event. Going into Doune, i was ahead in the ModProd Division by 2 points and my challenger didn't enter, so all i had to do was record a time for the Division win.
Final results:
Scottish Hillclimb Championship (SHC)
SHC class B3 winner
SHC Modprod Division Winner
SHC 5th overall - a place usually reserved for a single seater!
SHC Class records in B3 at Fintray, Doune and Forrestburn
Not a bad end to the season considering the reliability issues for the first half of the year.
I've been playing with pre-preg carbon parts. I made a complete dashboard that weighs only 1.7Kg as my oven and vac system is now operational and hope to make the complete underfloor in e-glass as the current fibreglass one weighs 40kg. I reckon i can get it down to 10kg including the bumpers.
In all, around 100Kg of weight is easily removable for the car which will make a huge difference to its performance. I'm considering building a spaceframe Evo and use Skyline running gear mated to this engine and twincharger, but that's a huge project that i can't afford to do yet.
RE: Twincharging - calling Warpspeed!
The GTR drive train is not without it's quirks.
The front diff is located in the GTR sump, and is pretty much impossible to adapt to something else (I have attempted this myself) and the available diff gear ratios are limited.
The front prop shaft is also on the same side as you, and the steering, which could get rather crowded in a race car. Much better to have the front diff and prop shaft over on the passenger side. Safer too.
But worse, the GTR's computer controlled wet clutch system that drives the front diff will have some very different characteristics to the much more benign and predictable epicyclic torque splitter you have in the EVO.
How the power is split in the transfer case is critical to vehicle dynamics and handling, and a major design decision that is going to be very difficult to change later on.
Start with a nice beefy epicyclic transfer case, and build everything else around that IMHO.
RE: Twincharging - calling Warpspeed!
One of the biggest considerations is, do i want to move from the Modified Production Division into Sports Libre and be competing directly against single seaters! At the moment the Evo is regularly beating a lot of the single seaters as it is so my point has been proven with the car in it's current guise.
I'll certainly be enjoying her for a few more seasons as she is so any spaceframe project is a few years from beginning.
Here's some of the last videos from the season
Harewood: http:
Fintray 2nd FTD yet backing off before the finish line as the right kink when the car goes light at 80mph is a known car killer after the line! http:
Forrestburn NCR and division win: http:
Loton Park (final round of the season): http:
Loton park in-car: http:
Here's an interesting video of the underbody aero in the wet. Not at any big speeds (max 70mph) but it shows a definate 'rooster tail' behind the car with the wing and venturi working: http:
Will update with any news as it happens. I've been considering changing to a GT42 turbo as the power is now restricted due to the flow capabilities of the To4z hybrid and would expect to see over 1000hp on 98RON pump fuel using a GT42 unit. I'm confident the Harrop SC will deal with the extra flow so that is a natural progression to the project. The only unknown would be whether turbo lag may start coming back into the equation with a compressor that big.