Liquid LPG conversion on small 4 valve motor 1

[patprimmer]

Franz

I have a car I am restoring and I am considering an LPG conversion. We get a government rebate of A$2000 here for the conversion.

I really want one fuel only system and probably liquid injection. Can you recommend a list of possible equipment suppliers. The car is a 1988 Honda CRX and The engine needs a rebuild, so if I go LPG I was wondering what compression ratio I could use with twin cam multi valve engine. My guess was 11:1. Is response to quench area and clearance the same as for liquid fuel.

Do I need to change the ECU. How good are piggybacks.

I would expect to install a more efficient cooling system and oil cooler.

I would expect to change the ignition timing, but I am not sure how best to do it.

I would expect I need a bit better VE on the induction side and I intend porting the head and manifold and maybe bigger valves if available and they will fit.

I would expect I do not need to change the cams or cam timing.

The Aussie model CRX has no pretense of a back seat so there is room for a reasonable sized tank there or maybe in the place now occupied by the petrol tank. That would mean relocating the spare tyre, but I have tackled more than that before.

To investigate further I need a list of available tank sizes with all dimensions. I have not used Mr Google yet, as I only got the car yesterday, but that is my plan for tonight, then tomorrow to do some major strip down in preparation for a complete respray inside and out and repairs to motor, frame, body and suspension, so if the gas conversion happens, now is the time.

The engine is the D series 1600 twin cam.

I am also considering a small turbo, inter cooler and maybe 7:1 and 10# boost or maybe even 15# boost and water/ethanol injection.

I know things can go wrong and burn valves and pistons with gas fuels and rich mixture will not suppress detonation, however I expect the water injection will work as it does for liquid fuel. Is this correct.

I am not sure just what A:F ratio to shoot for to get best power and minimum detonation, and what ignition timing map to shoot for and how to achieve these.

I expect an aftermarket computer and a complete fuel and ignition mapping process will be required.

Does this sound completely nuts. I do like to "bravely go where no man has gone before" and feel pleased when I achieve what others considered to difficult.

Regards
Pat
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[patprimmer]

Google found 2 potential tank suppliers for me and several potential gas phase sequential injector suppliers who claim good results with the cars OEM computer. I have not yet located potential liquid phase injector equipment.

Regards
Pat
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[patprimmer]

Just found this mob

http://www.lpgli.com/features.html

Looks a bit dodgey to me. Oh translation dodgey means untrustworthy or sleezy or slippry or schister or snake oil salesman.

Regards
Pat
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[patprimmer]

Just found this mob

http://www.vialle.nl/home.html?L=1

They seem very credible, and are used for Ford OEM in Aus, but do not list a local distributor.

Regards
Pat
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[MarkoFSB]

hello,

as far as the ECU goes since the car is 1988 the electronic only controll the engine, no ABS , all of those fancy electronic gizmo's. not even shure if the car has A/C.

i would suggest getting a standalone ecu called VEMS

http://www.vems.hu/

its cheap, it can drive any kind of injectors, it has all the specifications of much more expensive ecu's. another benefit is that is capable of running 2 sets of injectors (one for each fuel , petrol and LPG) with diffrent sets of ignition and fueling maps for each type of fuel.
Its even capable of switching fuels at desired load/rpm's/any input signal. the ecu is programable.


piggyback's are used in car that need the standard ecu to run the advanced electrical system's (ABS , TC , Stability programs,brake assist,...etc..).

removing the old wireing loom can help in reduction of wireing( old wireing) issues due to old insulation,fryed wires,DIY projects on the engine...

 

[patprimmer]

I only intend to run one fuel as stated earlier.

I have had excellent results from Microtech ECU, but I am always prepared to investigate something different, so thank you for your advice.

Regards
Pat
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[MarkoFSB]

...forgot to mention , built in EGT, Wideband O2, and dataloger.


you where right to chose to install a standalone ECU because they usualy have lots of AUX input and output channels that can be used to perform tasks like boost controll and water injection as stated in your post above.

and you mentioned that the engine needs a rebuild, it would be smart to get your hands on a workshop manual.

while youre taking the engine apart, you can consider of instaling bronze valve guides and valve seats. Internet is full of aftermarket parts for Honda, and they are cheap and readily available (compared to other cars, for example silicone bronze guides under 80$).

as far as the compression ration on the N/A engine , i dont think that any modification's are required since the octane number is higher than pump fuels.

 

[patprimmer]

Since the octane is higher I can increase compression with new pistons which I need anyway. Higher compression pistond probably cost a bit more but not to much.

Regards
Pat
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[franzh]

One company whose products I really like is ICOM. They are a major player in Europe and reportedly supply at the OEM level to several major players. They have a complete system, fuel tank, internal pump and fuel lines, injectors wiring, support modules in both dedicated and dual fuel applications.

http://www.icomitalia.it/lang1/index.html

Vialle is well recognized and world quality. I am unfamiliar with the other company except to say that their website has been unchanged for a VERY long time. One reference they cite is a college in the US that I provided technical support to during an engineering competition, in 1997.

Franz


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[patprimmer]

Is 11:1 about the highest safe compression for propane butane mix guaranteed at least 100 octane.

Does water injection help.

Does maximising quench help.

Regards
Pat
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[franzh]

Raising compression on a dedicated propane or butane (autogas) fuel blend can be a practical means of regaining some of the lost thermal value seen with gasoline. Realize that with a compression ratio significantly above the stock CR will require ignition timing remapping, not just a retarded timing map.

Water injection and quench work as effectively with a dry gas fuel as it would with a liquid fuel. Liquid propane injection has an additional benefit of cooling the incoming air charge and suppressing detonation by slightly delaying the onset of ignition. The vaporization of the liquid fuel is not instantaneous (visualize tossing water into a red hot frying pan, it sizzles, it doesnt flash to vapor).

Quenching the fuel helps to direct the air-fuel mixture towards the spark plug and works well during lean fuel mixtures.

Franz

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[patprimmer]

Thanks Franz

That is exactly what I needed to confirm ideas and fill a few gaps. I knew you would have the answered I needed to proceed with confidence.

Regards
Pat
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[sydneyACE]

Pat,
How is your project working out? I have great interest in this as I would like to do the same type of thing to my car. I plan on using a supercharger to take advantage of the propane's higher octane. By the way, I used to have a CRX with the 1.6. Great car! I have been lurking around the forum for a few days now, and decided I would like to see how this is working out for you. Hopefully you will still get this post even though this thread is a little old.
Thanks in advance,
Travis

 

[patprimmer]

Travis.

I ran into a bit of trouble with the tax department over a missunderstanding of the requirements of a self managed superanuation fund, so the project is on hold until some funds become available.

Regards
Pat
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