Thinking about twin-charging w/ remote turbo, Good idea or utter fail?

[TexasAceTA]

Ok, I am a bit out of my league with this one and this is the only place I have found that seems to have people that really know what they are talking about.

Quick rundown of my setup. I have a 2000 Toyota 4runner 4wd with a 5vz 3.4l DOHC engine. Right now it has an eaton MP-62 TRD supercharger on it running about 10.5psi of boost making ~250-260whp if I had to guess. I am using methanol injection as it is and plan to use more with the turbo, I figure around ~2000cc all said and done (need the fuel since the stock injectors are maxed out).

I want more power out of it mainly because I can.

I have pretty much decided on doing a remote mount turbo setup (planning on a 6262 turbo). These trucks have no options for turbo manifolds up front and getting a custom one made will cost more then this whole remote setup.

At first I was just going to remove the supercharger and run the turbo alone but then started thinking about twin-charging it.

I have put a lot of thought into this and I am just not sure if it is a good idea in the long run or not.

First off the 5vz motor I am working with while pretty strong does have a limit of around 400hp on stock internals before the rods become a weak link. I plan to get as close to that as possible and want room to grow later when I build the motor but till this one blows thats about the limit.

The supercharger uses power to make power and as such would put more stress on the motor for a given power output then the turbos.

Next up is the supercharger adding a LOT more heat to the air charge then the turbo and no ability to intercool it after the supercharger on my setup.

These were my reasons for ditching the SC in the first place.

I then got to thinking about the by-pass valve. What if I took control of it and opened it once the turbo is spooled. Would that basically render the supercharger as doing nothing?

My theory (no idea if it is correct, thats why i am here) is the supercharger will not know the turbo is doing anything before it and the by-pass valve should still vent off any extra boost from the supercharger allowing the turbo to produce all the boost.

Thus giving me the fast spool of the supercharger and the top end power of the turbo.

I am sure there are flaws in this plan as I have never done or even seen a twin-charged setup myself and there is remarkably little info on these setups.

Is it practical to open the by-pass valve once the turbo is spooled to stop the supercharger from working? Or will the by-pass valve turn the supercharger into a heat pump?

Should I just nix the supercharger and run the turbo alone?

Is a 6262 (62mm) turbo about right? Any larger would be pretty laggy if the twin-charging doesn't work so I didn't really want to go bigger in case I decided to ditch the supercharger afterall. Without the supercharger I expect the turbo to spool around 3500-3750rpm which is about perfect with my 5500 redline.

I already ordered the turbo but the order won't go through till tomorrow so could use a response quick. Thanks

Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[MikeHalloran]

First, read _all_ of this:

http://www.eng-tips.com/viewthread.cfm?qid=267889

and all of the referenced material.
Then, get back to us.


Mike Halloran
Pembroke Pines, FL, USA

 

[patprimmer]

6262 is plenty big enough.

By methanol injection I presume you mean an add on kit that adds water/alcohol or a mix as manifold pressure builds. That is a dangerous way to add extra fuel with maxed out injectors. You really need fuel pump, injectors fuel lines etc to cope with your fuel requirements.

The easiest way would be to use the blower as is and just feed boost into it via the blower inlet. Leave bypass etc alone.

I think remote turbo setups are pure junk due to the losses between the turbo and the engine. The blower might help offset the extreme lag they have, but you will still end up with all the complexities of a twin charger but still with lag.

Blowers take power to make power. SO DO TURBOS. It's just normally not quite so much and not nearly so obvious where the power is taken from. A bad turbo will leach of just as much or more power to drive it as a good blower will. An Eaton is a good basic design and should be reasonably efficient if sized and installed correctly.

I think your truck should have plenty of room under the bonnet (hood) for the turbo to go in the engine compartment, close to a front mount inter cooler.

Don't put water/alcohol into the system before the inter cooler and especially before the turbo. In my opinion it is best added just before the blower to cool, lubricate and seal the rotors. I would run 50/50 water alcohol at most. The alcohol can be methanol or ethanol, depending on what's available at what cost. Methanol has more potential to increase power, but is a lot more problematic to handle due to corrosion, attack on plastics and toxicity.

There have been several previous in depth twincharger threads on here. You would do well to read them.

If your looking for power, 5500 is a really stupid low redline unless your a diesel, 1960s technology with flimsy rods, crank and block and long heavy flexible push rods, or have about a 6" stroke.


Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[TexasAceTA]

Mike, yep I read that and all the other threads on twin charging I could find and learned a TON. My question was asked in that thread but not answered. The biggest thing I could never find though was using the by-pass valve to turn the supercharger off once the turbo spooled.

Pat, Yes, I have a coolingmist meth injection kit. While not commonly recommended or common for that matter. I have been running this way for over a year on this truck with no issues and GREAT results. Also ran my MR2 this way before with 2000cc pumping into it and know of a lot of other guys doing the same thing.

It is quite common to make 100whp over the stock injectors. With the right failsafes in place it is very reliable as well.

I have played with everything from pure water to pure methanol and with nozzles from 5gph to 2x 14gph on this truck. The best results have always been on pure methanol or almost pure and with as much of it as I can pump in without going overly rich. Same for all my other cars.

Right now I have about 1000cc being injected just before the SC and AFR's stay in the 12:1 range and it runs better then ever.

Meth injection systems is something I have spent a lot of time with myself. I run it on all my cars.

I agree with you on the remote mount setup, it is far from my first choice. It comes down to cost. I can put together the whole remote mount setup for well under $1000 excluding turbo cost. A manifold to mount it under the hood would cost $2000-$2500 alone and take weeks to have it fabbed up. Just can't afford that.

If there was a manifold for these I would run it for sure and a 6766 turbo since it would spool nice. Not even worry about twincharging either. But got to work with what you got, or in this case can afford.

Another note is I have an automatic transmission with a high stall ~3500rpm converter. So lag is not as big of a deal as it would otherwise be. My powerband is 3500-5500.

You are right that the turbo robs power to make power as well but the turbo uses power be reducing exhaust efficient and thus VE, the engine is not actually working any harder, just not working as efficient. This will not cause the rods to let go any earlier.

The supercharger is using power the engine has already made thus putting more stress on internal components so the rods will let go at a lower HP level then with a turbo.

Thats where the by-pass valve comes into play. If i can "disable" the supercharger once the turbo comes online so as to lesson the strain on internal parts and let the turbo do the work then I get the best of both worlds.

I just can't find an answer as to what will happen with the by-pass open or if it is a good idea. Controlling the by-pass is easy, my piggyback can take care of that no problem.

I agree the redline is low but I am on the stock ECU and stock valve springs. Even if I could raise the redline the valve springs need to be upgraded for that. When I build the motor it will be able to rev to ~8k-9k but that is out of the budget for a long while.

Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[patprimmer]

I have no first hand experience, but from what I understand, the bypass helps at high manifold vacuum and saves fuel by reducing load on the blower by reducing its pumping losses.

At full boost you still get an advantage from the boost multiplication in the blower. This helps by increasing boost, but also by increasing pressure in the inlet relative to the exhaust and so giving better exhaust scavenging than a turbo engine gets. This helps cool exhaust valves and reduces charge dilution with hot exhaust gas and makes more power with less inclination to detonation at the same boost.

I don't know your engine and I don't know your access to welding, but $2500 sounds like a hell of a lot of money for a simple manifold. Turbo manifolds do not need to be long runner or equal length or any of that. They can be a basic log design, they just need to be beefy re wall thickness and flange thickness. A stock cast iron manifold can often be adapted with moderate skill with an electric welder and the right rods or a simple adaptor plate made with hand tools. Your local exhaust man should be able to make the dump pipe and a good cat back system.

Regards
Pat
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[TexasAceTA]

You are right on what the by-pass valve does under normal circumstances. What I don't know is how it will react with the turbo pumping boost into the supercharger and it is open. The roots style supercharger is uniquely setup to take advantage of it if it works like i hope.

I don't want the boost multiplication. Getting enough boost is not my problem, I am limited to mid-high teens for boost anyways before I am making too much power for the rods. The only thing I want the supercharger to do is spool the turbo.

The engine is a 3.4l V6 in a truck. No call for a manifold for it. I have already got a few quotes for the manifold and all were in the $2k+ range.

You are right that the stock cast manifolds can be used but are FAR from ideal and would still cost a fair amount to have a custom setup to make a turbo work due to the tight space for the crossover.

I have a feeling my headers running to the remote mount turbo will preform about as good as that setup would, they would have about the same amount of piping before the turbo all said and done, which is why I decided to go remote. Not to mention the nightmare dealing with the manifolds is due to space.

Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[1gibson]

Do you have the coolingmist kit with the PWM valve that takes a signal from the injectors? All things considered that is a pretty accurate way of supplementing a fuel system.

If you did want to open the bypass (my opinion is that you should*) once the turbo spools, just rig your bypass solenoid to a pressure switch (hobbs switch) on the blower inlet. 5 psi from turbo = open the bypass.

* = Because of you specific concern about losing CRANK HP to drive the blower. That's an important distinction between blower and turbo losses. There's a few considerations.

1) Look at the Eaton blower charts, any parasitic loss you see with increase directly based on the incoming air density. Leaving the bypass closed, the blower has to do more work to add pressure to higher density air.

2) When you open the bypass, the blower will still make a small amount of boost (bypass acts as an orifice at high RPM, at idle it pretty well can keep up with the recirc flow 100%). Not completely sure how the supercharger's boost with bypass open will be affected with pressure on the inlet, but a detailed orifice calculation should be enlightening.

 

[TexasAceTA]

I actually have a fairly unique injection setup, why more don't do this I am not sure, it works SO darn good.

I have the coolingmist progressive CMGS controller, just the normal one that can inject off boost or a 0-5v signal.

I then use a piggyback (right now using the coolingmist "smart controller" but moving to an AEM FIC shortly) to create a map based on RPM and boost.

I then tune that map like any other fuel map through the RPM range. The controller outputs a 0-5v signal to the CMGS which then controls the methanol flow rate based on the signal. Works GREAT, keeps AFR's nice and steady when tuned right. It's only weakness is that it can't turn the flow down to less then ~50% of the overall nozzle flowrate but thats not a problem for me.

Been running it this way for over a year with GREAT results. The timing control/knock detection on the stock ECU is very good so that takes care of itself. It actually can run more timing with the supercharger and meth injection then it did stock with 87oct.



Now onto the by-pass valve. I have already figured out how to control the by-pass valve real simply. I have a spare solenoid laying around that I will hook up to an output on the piggyback so I can set it to open the bypass anytime I want, under any conditions.

The valve is vacuum activated so I will need to add a vacuum resivor but thats easy and no big deal. The setup I have planed will have the valve working normally until the noid trips and opens it manually.

I have spent a lot of time looking at those charts actually and If the supercharger reacts like I think then everything should fall into place real nice.

I am going to copy/paste a post I made on another board on this subject that should give you a few more pieces to the puzzle. I tried running the supercharger with the by-pass open as it is and these were the results:

Today I did an experiment by zip-tieing the by-pass valve open to see what would happen. With my 2.0 pulley (10.5psi with the bypass closed stock is 2.37 (~6psi with the bypass closed), I am technically overspinning the SC with this one to ~17,000).

With the valve tied open I found 2 things. First off this thing is SLOW without boost. I had forgot how slow it was!

Next it will still build ~2.5-3psi of boost with the valve open.

With the stock pulley used instead of the 2.0 pulley I am guessing that it will only make ~.5-1psi of boost. I think I tried it before with the stock pulley and that is about what it was many years ago.

Looking at these graphs It looks like with the by-pass open and it making ~1-2psi to be on the safe side it will be using ~5-10hp to drive the supercharger. It will also be adding ~30-75 degrees to the air temp.

I found some underdrive pulleys as well that will lesson the boost more if needed. Down to ~3psi if I need it.

So looks reasonable to try it. The meth injection (estimate ~2000cc-2500cc total split between pre-turbo and pre-SC will be needed for the fuel) should net me ~ambient air temps going into the supercharger from the turbo. It will then hit another nozzle at that point which should equal out any temp gain from the supercharger netting me ~ambient air intake temps if all goes to plan.

From experience on my MR2, 2000cc of methanol was enough to bring 160 degree+ intake temps down to ~20 degrees below ambient.

The 5-10hp loss from the supercharger are acceptable if spool gains are worth it.

Overall, I am thinking the twincharge might work and it will be an interesting project for sure. I can also pickup a stock intake manifold to swap out without much hassle to test the differences back to back. Maybe even back to back dynos.

I am still looking for a second opinion on my earlier predictions on how the by-pass will work under these conditions.

The bypass will always be feeding air out of the plenum and it is impossible to actually bypass the supercharger?

The supercharger and by-pass will not know the difference with the turbo pumping boost into it. The supercharger should still do the same work which as I showed above should be in the 1-2psi range with the bypass open.

That all sound right so far? If all of that is a go then it is almost time to start picking out parts to make this work.

Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[patprimmer]

I have never done it, but from what I understand, the problem is how to control the bypass so it does not have an adverse effect on throttle control.

In my experience with turbo cars, the biggest problem is the time related changing relationship between pedal movement and power delivered. The bypass flipping open or closed after the throttle might give time delayed surges if it;s not carefully tuned.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[TexasAceTA]

I am not worried about that. With the piggyback controlling the by-pass valve I have a LOT of control over when it opens and can tune it to work just right. It will only open when the turbo is making over X psi of boost, the TPS is over X % and any other parameters I end up needing. I love having things electronically controlled, makes dialing in things like this FAR FAR FAR easier.

The biggest thing I am wanting to know is how it will act with the by-pass open. Will it just turn the supercharger into a heat pump circulating hot air round and round? Will it still draw off more then the ~1-2psi worth of power that should? Will it add more heat then the 1-2psi should add? Will it really unload the supercharger?

Any other issues with having it open under WOT with the turbo making the boost? What are the downsides?

Can't find an answer to those for anything, I know SOMEONE out there has done it or know what will happen. If I knew for a fact that with the by-pass open it would work like I hope, I would get a larger 6766 turbo (the turbo I really wanted to get in the first place).

Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[Lou Scannon]

You will tend to have difficulties with independent control systems that are trying to control or are affecting the same dependent variables. Especially if they have similar response times. A word to the wise.
Another, related axiom of control systems: when a control system is trying to control a parameter that it does not have control over, the result usually is not very pretty.

 

[patprimmer]

I know people have sorted out the bypass control, but it was not easy, even with microprocessors.

I would start with a straight blow through, get that sorted then maybe play with the bypass. I think you are over thinking the parasytic power and heat thing.

Where the heat really matters is in the chamber and turbos scavenge the last remaining bits of hot exhaust gas very poorly due to back pressure created by the small orifice at the end of the scroll. Belt driven blowers scavenge very well, often to well and waste boost. The combination can work very well.

Even with a bypass open you still turn the blower and create friction and heat from friction and shear. How much is hard to say and I would expect quite variable from case to case.

I would drive the blower relativly slow to just give a bit more power when the turbo is out of boost, but to also create extra exhaust gas to spool the turbo faster. The roots blower has a double whammy effect and does not need to pump very hard. By not pumping hard it does not consume so much power.

I think an Eaton maxes out at about 60% efficient and a turbo at about 70% efficient.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[TexasAceTA]

Hemi, If you are talking about the piggyback, I am not a fan of them either but in this case it is not doing anything that would cause any problems. The only thing it will be doing is adjusting the O2 sensor voltage to adjust AFR's in light boost and then controlling the meth kit. Otherwise it is mainly going to be used for logging.

Pat, True I am sure I will have some issues getting the by-pass just right but I drive 500whp++ cars on the street with twin plate clutches on a regular basis. Needless to say I am not real worried about a small hickup as it comes onto power long as it doesn't hurt the motor.

The problem with running it in compound mode is that the turbo will be making virtually no boost at all. I plan to start off around ~12psi for boost and in compound mode the turbo may be making 3psi. Not really worth it IMO.

The heat is a pretty big problem. I see intake temps right now DEEP into the 300 degree range without methanol. With methanol I am guessing intake temps are still ~200 degrees with the supercharger alone. Add a turbo on top of that and intake temps will get even higher.

Another problem with this line of thinking is the belt drive system for the supercharger. The belt is MAXED out as it is, I am getting belt slip right now and I have done every trick in the book to get rid of it. A 4 rib belt just is not big enough.

Try to pump compound boost through the supercharger and the belt will scream.

I don't mind a little power and heat being used/added with the by-pass open. The idea is to take the ~40hp+ it is using now down to 5-10hp and the 225+ degrees of heat added to the intake temps down to a more manageable 20-40 degrees.

This supercharger is real undersized for this motor, so it is already out of it's efficiency zone in stock form. It really should have been an M90 instead of an MP62.

If the twin-charging doesn't work I will just pull the supercharger off and go with my first plan. I just figured I have a twin-charger setup here, ready and waiting. Why not give it a go.

You can Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[MikeHalloran]

>>>Try to pump compound boost through the supercharger and the belt will scream.<<<

Uh, no, not necessarily. The belt load is proportional to the difference between the pressures upstream and downstream of the supercharger, not to the absolute downstream pressure. So the turbo may even reduce the belt load a bit.




Mike Halloran
Pembroke Pines, FL, USA

 

[pontiacjack]

For the methanol-injection figures mentioned (2,000 cc, etc.)- is that supposed to represent a volume-per-unit-time? If so, is it per minute?

The term "twin charged" is new to me; is it applied to ANY form of two-stage forced induction (two turbochargers, etc.)?

 

[patprimmer]

I have only seen it applied to belt driven and turbo combinations.

Mike is correct re the belt slippage.

Reduce the drive ratio on the blower so it only pumps say 5 psi of boost then blow through it with the turbo and the turbo boost will be increased by 1/3, so 10 psi from the turbo will be 13psi after the blower.

What really counts is mass air flow, so the same boost at lower temperature is still more air. The combined gas laws apply.

There is a big difference between driving with a lot of power and a savage clutch and driving something that feels dead as you squeese the throttle mid corner, then 1/2 second later unleashes a truckload, then as you back of a bit nothing happens, then you ease of a bit more and it just dies, then you give it a bit more, then nothing, then all hell breaks loose again. That can happen with a factory turbo and automatic with a crappy shifter (read Toyota Soarer MZ21). It can only get worse with a bypass that is not spot on.

Anyway it's a pretty easy experiment to put a manual control on it and try it open at certain times and permanently closed.

Regards
Pat
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[TexasAceTA]

Mike, true but I would have to underdrive the supercharger down to ~3psi to have it not be past the limits of the belt traction. From what I have read on this site it seems that compound boost is harder for the supercharged to compress then normal boost.

As it is, ~10psi is the limit for belt slip, 10.5psi on a good day. Without belt slip I should be making ~12psi.

Jack, That is cc/min, same rating system as fuel injectors.

Pat, you are right that the air temp plays a major factor in power which is why I am so concerned with turning the supercharger off. ~ 10psi of boost the supercharger is adding over 200 degrees to the inlet air temps with no way to intercool it.

Right now, normal intake temps with my setup are well into the 300's. Add in the high inlet temps from the turbo before the supercharger and those temps could easily get into the 400+ degree range before the methanol cools it down and even then it could be 200+.

With the turbo alone I know I can get intake temps down to ambient or less with the meth injection for sure. that is a LOT of power gained right there. Using the 10f air temp = 1% power rule that is 10%+ power right there by turning the supercharger off, not to mention a lot safer on the motor.

So 10% power @ the 350whp level = 35hp extra. Then you have the ~35hp savings from not driving the supercharger and there is a total of 70+hp "gained" for free all the while making it easier and safer on the motor.

Thats why I am so worried about turning the supercharger off, it is notoriously bad at making power compared to the turbo. Compound boost would just make the problems worse.

Far as drivability. With proper tuning I am not worried about it, I daily drive all my cars and have yet to experience any of the issues you mention with a proper tune. It is truly all in the tune.

I know lots of 600-1000whp cars that drive like stock.

You can Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[1gibson]

This discussion about belt slippage is not considering the increased air density (increased mass flow, increase in work that the blower performs) when using compressed air at the inlet.

Assuming it has the same differential pressures with or without the turbo, you're getting an increase in mass air flow (increase in work) without drawing more power from the blower...

 

[TexasAceTA]

That was my thinking on the matter and exactly why I said what I did above. I just don't think the belt could even drive the supercharger in full compound mode without a massive underdrive and even then it would be close. At that point I am also at the point of why leave the supercharger on at all if it will only help spool ~100 rpm's.

Being able to turn the supercharger "off" under boost by opening the by-pass would seem to be the best of both worlds. I get the super fast spool of the twin charge and the top end power of the turbo.

You can Call me TA

I carry a gun cause a cop is too heavy.

If guns kill people, then Spoons make people fat.

 

[1gibson]

While you're at it (and because of the piggyback features) have you checked into getting a clutched supercharger pulley? Toyota Previa minivans (mid 90's I think) had them on M45's.