propane for high performance
propane for high performance
(OP)
I'm about to convert my car over to propane using standard Impco parts. I have a 360 Mopar engine that will be running 11.5 to 1 compression. The heads have stainless valves, bronze guides and hardened seats. Everything internally is pretty much new, as is the machining. I have chosen a Weiand 2x4 tunnel ram, and will be using 2 425 mixers, 2 vaporizors(model E), and 2 fuel lock offs. Are there any additional parts that would optimize this set-up? And I was thinking of fabricating my own mixer adapters and removing the current top plenum of the intake(to help a bit with hood scoop issues. Is this going to cause any problems if there is no front to back balance tube between the intake runners, like the top plenum provides? Thanks in advance.
Tom
Tom





RE: propane for high performance
One area you did not cover is the ignition, it should be top-line. The OEM ignition is barely adequate as it is. Try initial of around 8 degrees, and all in by about 3000, somewhere around 32 degrees.
Since propane vapor displaces about 5 to 8% of the incoming air, anything you can do to improve airflow is a benefit, but remember that larger ports and runners will hurt low speed perforamance, so a trade-off is in store.
Personally, unless this is an all out performance application, you may not like the way it runs at low to moderate speeds, but once the throttle is opened. . . .
Franz
RE: propane for high performance
Tom
RE: propane for high performance
The same company that owns MSD also owns Dualcurve, and provides closed loop fuel control systems for LPG vehicle. With a little adaptation, one could be installed on this engine.
The closed loop devices take engine RPM, Oxygen sensor output, and either manifold vacuum or throttle position to determine engine demands, and adjust the fuel mixture accordingly.
There are basically two types of closed loop controls for a mechanical LPG-CNG carburetor system:
By controlling the pressure at the regulator/vaporizer, thus changing the delivery pressure/volume to the carb.
By controlling the volume of the gas output to the mixer/carburetor. This device uses a vacuum operated restrictor in the vapor line. There are some electric models that work very well too.
Both have advantages over the other in certain applications, but both have drawbacks too. The pressure type can be a little slow to respond to rapid throttle openings and may lead to intake backfires, where the the volume type allows fast response but may be a bit difficult to initially tune. The same electronics can be used on each. The pressure type is the one most used here in the US, where the rest of the world uses the volume type. Sounds like a good article for my webpage.
Using dual vaporizers should not be too difficult to plumb.
Franz
RE: propane for high performance
Tom
RE: propane for high performance
As for if your engine could benefit from closed loop, it all depends on what the final application will be. If its straight competition, then no, it would be of no benefit. If its street use, your entire engine setup seems a bit radical for comfortable use, but it would help some, but personally, I wouldn't recommend it. You will find throttle lag unacceptable, and a bit more aggravated with closed loop.
Closed loop works best with a single plane manifold where the mixer is close coupled, meaning less plenum volume to control.
The 425 offers 3 gas valves for mixture tuning, and you may have to experiment to obtain the best ones. You should also run a balance line between the two. When it is running, I would try to locate a gas analyzer, or install an O2 sensor in the exhaust for tuning. If you run open exhaust, tuning can be difficult due to air pulses.
Franz
RE: propane for high performance
you seem to know your stuff. i have done a lot of tuning on aftermarket computers and find almost universally engines seem to like 15 to 20 degrees at idle. My own runs 24 degrees and 30 total. I was wondering why why has this not caught on with the traditional tuners? I can run the engines at a much cleaner idle with this sort of advance, especially big cammed cars which seem to just love it, and the engine that responded most impressively to this treatment was a 351 windsor with a single plane manifold. It had 38 degrees advance at light load at 2000 rpm (but still only 32 total)( both arrived at by tuning for maximum torque). I know the 20 degress advance might be a bit radical if you are still using mech advance distributor without the benefits of a totally programmable 3D map.
Was just wondering as I still come across people that underestimate the benefits of ignition and ignition control.
I agree with you that especially on LPG a top quality ignition system is crucial.
RE: propane for high performance
Tom
RE: propane for high performance
As for the timing issue, 99%+ of the engines with LPG are not performance oriented, and smooth idle and low emissions are mandatory. Although I personally like more aggressive timing profile for crisp throttle response and a bit more power, emissions take precedent.
I did a study at a major research lab in the early 90's with timing and we found a huge difference in emission production with not so much an improvement in power (LPG only, not so true with NG). I also did a timing map on an engine dyno and came up with some numbers, but all this is out the window when working with non-stock compression ratios and more aggressive cam profiles, as it would with any fueled engine.
Increasing base timing in the regions you describe increases the cylinder pressure at BTDC, which may indicate some deficiencies in other areas of the engine, and also increases NOx production. Ideally, you want maximum combustion pressure just after TDC, and before the 90 degree mark.
No argument that a good effective 3D ignition map is necessary, along with a corresponding fuel map. This is only possible with a good engine management system. Someone with a VERY good mechanical system can get close, but it's not adaptable.
Franz
RE: propane for high performance
Can't really comment on the hood clearance issue, but I strongly recommend against removing the plenum, unless you plan on using 8 individual carbs. Going to a lower profile dual plane intake is far superior to removing the plenum. There are plenty of autos running VERY well on a "X" type single plane intake with a single carb, gasoline or propane.
I think you are placing too much emphasis on runner length and plenum volume, which only provides minimal gains anyway, and then only in certain rpm ranges.
In the "old days" I had a small street engine (292 cid) with an early small single plane manifold and 700 Holley that outperformed the replacement engine (350, large single plane with 850 Holley) by a big margin. Just because its larger, doesnt mean its better (grin). There are plenty of posts on Eng-Tips dealing with pipe sizes and harmonics.
Franz
RE: propane for high performance
Tom
RE: propane for high performance
This ought to work ok. My guess is that this engine will see primarily high rpm use, so any transition from idle to mid range is not particularly important.
You should insure that the plenum volume is the same for each side.
The plenum volume may help with additional homogization, something the tunnel ram with individual port runners will not have.
Franz
RE: propane for high performance
RE: propane for high performance
A lot depends on what type of carburetion you are using. This engine seems like its pretty warm. I would recommend installing an oxygen sensor in the header collector to test for fuel mixtures. I suspect you will find the problem there, assuming you have enough air-flow.
Franz
RE: propane for high performance
I am about to start building a Mopar 360, which will be put in an '89 Ramcharger 4x4. I will not be doing any sort of competitions for speed that I can forsee, except maybe drag with other trucks here and there, due to the fact that this era of Dodge trucks were designed with the aerodynamics of a cinderblock. Anyway, what I will need is low RPM power for occasional offroading, but this will mainly be my daily driver, and I'm looking to save some cash on gas in the longrun (since propane is still a lot cheaper than gas here), and do my part for the environment. At this point, I am leaning heavily toward going with propane, but I am concerned with a few things.
First and foremost is the lower energy content of propane. I will most likely be using an Edelbrock dual-plane 4bbl intake, because dual-planes are better for the low powerband. Tunnel-rams and single plane intakes were mentioned above as better for propane power, but that was for high-rpm/horsepower applications - their low rpm power is almost non-existant.. How well will a dual-plane work?
The stock 360 uses I believe 8.5:1 compression. From what I've gathered from the net, propane works better with higher (10:1 or better) compression due to the higher octane rating. What kind of gains can I expect going with a 10:1 over stock using propane?
Im not going to be using a radical cam, - just an RV cam made for power.. (don't have the specs here in front of me, but it's very close to stock)
I'm interested in a Closed Loop system, but I can't seem to find any real info on them.. MSD's website only shows their new Diesel Digital Propane systems, which wouldn't work with my application.. Can you point me in the right direction??
Thant's all I have for now.. Any advise would be appreciated. Thanks..
Matt
RE: propane for high performance
Franz
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RE: propane for high performance
I have a turbocharged 265 CI Australian "Hemi 6cyl", running 10psi, straight LPG, fully mappable ECU with 6 coils off a Nissan RB30 ignitor, 9.2:1CR, 270deg 520/520 valve lift cam 114 centre, 1.64 2.02 valves in flowed head, individual runner manifold inlet and exhaust, intercooler,2000RPM stall auto, 3.23 diff, 1650KG vehicle weight.
What would be an ideal ignition curve?
Hope you can help.
Thanks,
Joe
RE: propane for high performance
That would be like recommending a favorite cut of steak as the only acceptable cut there is.
There are too many factors to consider here, more than what you plugged in, even though, I hesitate recommending a spark curve across the board.
Your ECU should have the capability of including a knock sensor which I recommend with what you have set up. Propane will indeed detonate under the right (wrong) conditions, and with your engine setup, a slight almost or barely audible detonation may result in blown pistons or head gaskets.
Your ECU may have the capability of mapping via snapshot your knock sensor output based on inlet pressure, current timing, air temp, coolant temp, etc. This is what the OEM's use. A rolling road (chassis dyno) is invaluable here, otherwise, a good road trip is needed along with a good helper. Either way, this engine combination sounds like a real runner.
Franz
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RE: propane for high performance
It was a fairly generic question I know but any base lines are welcome information as in New Zealand this kind of LPG application may as well be from another planet, and very few people can get their head around it (though the price of petrol may soon change that).
I currently run around 20BTDC at idle and 17BTDC at 10psi boost. Dont know if its right or wrong as I am on my own with this at home, but its a start.
It goes very well with massive torque and completley driveable. As you suggest, a decent day on a DECENT dyno will be invaluable. Again, its getting my knock sensor baselined correctly so the ECU can read whats actually happening.
Injection with LPG is next on the to do list. I replied to another thread about 120psi injectors and mentioned that I have replies from half a dozen companies that can supply kits to sequentially inject LPG up to 500HP. I can email the 3 pages of replies to anyone who is interested.
Thanks for your time.
Joe.
RE: propane for high performance
Please send me a copy to pprimmer@acay.com.au
If you send it, I promise never to cheer if ever we beat the all blacks again.
PS, we did build you that nice hemi 6
Regards
Pat
Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: propane for high performance
http://p20
http://www.hemiperformance.com.au/
My engine is the black one with stainless inlet runners.
Go to "whats new" then "Photographs" on the Hemi perf site for shots of the block.
I will send the file when I next get a minute.
Did you win again? I have been away along time and not been up to speed.
Pine tree meads said it best about the current state of our teams with "there are too many mirrors in the changing rooms"
Cheers,
Joe.
RE: propane for high performance
You may have luck playing with air to fuel ratios when at hard boost. I have leaned the fuel mixture from L=1 to L=1.4 at 20 psig boost, reducing exhaust temps to 900 Deg F.
By the way, VERY VERY NICE engine! Liquid injection has not caught on here in the states, primarily due to the injection pressures. 125 psig is about 1/4 the amount seen in a typical liquid injector (propane saturation pressure + engine absorbed heat + added heat from road and radiation) I have seem pressures in excess of 400 psig! Add in one Texas day of 90 Degrees, plus road absorbed heat, and your tank temperature can reach 125 degrees F. That equates to 250 psig tank pressure. Liquid injection works by circulating propane through the injectors to flush the partially vaporized propane and returns it back to the tank. Usually, dual fuel pumps are used, one for maintaining a circulating pressure, the other for purging. We then add about 50 psig above the saturation pressure to keep the propane in liquid phase (you may have seen that name in marketing material).
Its not as simple as you may think. Supplying fuel for 500 bhp is no problem, but keeping it in liquid state is. One glug of vapor at an injector and its 270 times leaner than it was. Toss in that the fuel mapping program must operate at 270 times more precise/shorter pulse width profiles, and may injectors cannot operate that fast with an injector pressure that high.
Franz
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: propane for high performance
Maybe they have cracked it.
Im gonna find out and let you know.
Thanks very much for your time.
Have a great new year everyone.
Joe.