Supercharged V8 fueled by LPG
Supercharged V8 fueled by LPG
(OP)
i am about to build a supercharged 308 and was going to dedicate it to LPG. The super charger will be a blow through setup so the LPG setup will be after it. I am using twin small roots blowers blowers from a toyota MR2. information i have found goes both ways some say supercahrgers can't be used on LPG some say they can. ANY help in this area would be much appreciated





RE: Supercharged V8 fueled by LPG
LPG usually flows into an engine under low pressure. You will have to figure out out how to make it flow correctly regardless of intake boost pressure. Since you are going for much more power than usual, A/F ratio will also be more critical. It might be better to inject liquid instead of gas.
Why not LPG through the blower?
RE: Supercharged V8 fueled by LPG
Ken
RE: Supercharged V8 fueled by LPG
A blow through system is not as easy to configure than a pull through, but on a Rootes system, a pull through works well. Also, there is no turbo lag.
Configuring a liquid injection system is a real engineering challenge and way out of bounds for a self built system.
Franz
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RE: Supercharged V8 fueled by LPG
I guarantee that an aftermarket controller could be easily configured to allow some rudimentary control of the system and all without the associcated headaches mentioned above. Infact I am quite convinced that it would make the whole job a lot easier & more elegant.
MS
RE: Supercharged V8 fueled by LPG
MAP compensated SEFI would work great, just source the injectors, controller, pressure reducers, program the pcm for the varying fuel densities and temps, calculate the corresponding ignition timing at NA/boost.
It is do-able, just takes some homework and a fresh mindset on different SI combustion principals than liquid fuel applications.
Franz
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Supercharged V8 fueled by LPG
The first thing I would say is that you will have a problem with spark timing whatever system you use, it will never be optimum. Having said that, LPG is pretty knock resistant so you should be safe to play around a bit.
Find yourself an injector & setup that you can install before the compressors and ensure that it is specced for your application. ie LPG at atmospheric conditions. I am sure you can get a fuel system/regulator to deal with that, LPG isnt exactly an exotic fuel...
Obtain an aftermarket ecu/pcm that will operate with an SPI setup (should be millions about) and wire the thing up.
Guess at the spark tables, LPG is pretty safe so dont worry to much at part load, just be conservative at WOT points. To ensure safety fit & monitor a thermocouple in the exhaust manifold.
Try and get a wideband O2 sensor from somewhere to properly map the fuel tables.
Drive and map, drive & tweak until happy - using the above.
Your saving grace will be lack of knock sensitivity of LPG and also the fact that the rich misfire equivalency ratio is higher than gasoline.
As always, any questions then let me know.
MS
RE: Supercharged V8 fueled by LPG
I GUESS the 308 is an Australian Holden V8, even though the OP does not indicate that.
So I GUESS the information below might be of interest
Garry Willmington has some experience with suck through LPG conversions on Australian V8s and roots blowers.
As far as I know, he is in Luddenham near Sydney
Regards
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RE: Supercharged V8 fueled by LPG
No resistance, just trying to put it in perspective. You wouldnt believe how many people have contacted me at my real, bill paying job, asking if they can use gasoline injectors for LPG, run LPG liquid through gasoline fuel lines and rails and so on.
Sourcing an LPG capable injector can be a challenge but there has been some good development there and a greater supply then ever before. Keihn and Siemens are good sources, and suppliers in Italy always seem to be ahead of the rest of us in this field.
Using LPG as a fuel in the injected state requires a different mindset than with gasoline, plugging things in like injector lead-time, pulsewidth, doublehits, lean and rich modes under boost, cold start enrichment, and so on.
In almost all cases, its not a simple plug and play, but with very careful matching of injector flow rates and pressures, an OEM PCM can work well. I like the Ford EEC-5 with the TWEECER, but have used the Motec, Electromotive, and other industrial controllers in the lab.
Franz
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: Supercharged V8 fueled by LPG
RE: Supercharged V8 fueled by LPG
RE: Supercharged V8 fueled by LPG
for high end performance. I would suggest using a fully tunable DFI controller such as:
http://force-efi.com/dfi.htm its not the best but it is very user freindly and has enough flexability for your purpose, First find an injector/injectors that will meet your needs.
I would also recommend using liqiud injection after the supercharger to take advantage of the evaporation cooling effect.