Converting a legacy GT-B to LPG

[rutland]

Hi has anyone out there had experience of converting either a 2.5se or a legacy GT-B to run on LPG? I have read a few articles but wondered what would be the positive and potentially negative aspects of both. Ie cheaper to run but effects in engine wear etc. All comments welcome. :grin:

[anothernord]

This would be an interesting project to undertake. I am not aware of anyone that has done the conversion, but I'm sure it can be done.

[rutland]

I was wondering if it would harm the Twin Turbo engine in the long run, I've read somewhere that the higher octane could actually give a high boost under a turbo, but the gas temperatures burn hotter so could do some damage ??

[anothernord]

Higher octate will reduce the tendency of the engine to knock or predetonate, so the engine will be able to have a greater timing advance, and therefore have more power.

[Sarra]

Do it! The higher combustion temps shouldn't make a huge difference, except possibly on NOx emissions. Oh well.

All you will need to do is run 30% larger injectors, remove all Cold Start enrichment programming from the computer, Cold Start high idle programming, and convert the fuel tank, run new fuel lines, and put in new fuel rails. Not THAT hard to do. :)

Good luck if you decide to do it. You CAN make a vehicle dual fuel, if you put TGV delete housings on a USDM turbo vehicle with 2 injector ports per cylinder, you could easily run the car on gasoline, then switch over to propane whenever you wanted. ;) EM would be a pain in the ass though.

[anothernord]

Do it! The higher combustion temps shouldn't make a huge difference, except possibly on NOx emissions. Oh well.

All you will need to do is run 30% larger injectors, remove all Cold Start enrichment programming from the computer, Cold Start high idle programming, and convert the fuel tank, run new fuel lines, and put in new fuel rails. Not THAT hard to do. :)

Good luck if you decide to do it. You CAN make a vehicle dual fuel, if you put TGV delete housings on a USDM turbo vehicle with 2 injector ports per cylinder, you could easily run the car on gasoline, then switch over to propane whenever you wanted. ;) EM would be a pain in the ass though.

Exactly. Its all in the tune, and with ECU's that aren't easily flashable with tools such as Accessports and the like, you would almost have to go with a standalone EMS.

[Sarra]

Do it! The higher combustion temps shouldn't make a huge difference, except possibly on NOx emissions. Oh well.

All you will need to do is run 30% larger injectors, remove all Cold Start enrichment programming from the computer, Cold Start high idle programming, and convert the fuel tank, run new fuel lines, and put in new fuel rails. Not THAT hard to do. :)

Good luck if you decide to do it. You CAN make a vehicle dual fuel, if you put TGV delete housings on a USDM turbo vehicle with 2 injector ports per cylinder, you could easily run the car on gasoline, then switch over to propane whenever you wanted. ;) EM would be a pain in the ass though.

Exactly. Its all in the tune, and with ECU's that aren't easily flashable with tools such as Accessports and the like, you would almost have to go with a standalone EMS.

Megasquirt is an option, though not an easy one.

Doing this on a 2002+ WRX, 2004+ STi, or 2005+ any other Subaru would be very easy. Standalone would be your only option on an older vehicle as mentioned.

What is Stoichiometric (ROFL! Stoichiometric was not in the spell checker that Firefox uses and kept messing me up! I finally looked it up on dictionary.com) of propane anyway? Whoop, answered my own question. 14.7:1 is the Air Fuel ratio that is best for emissions for gasoline, and it appears that 15.5:1 is the best ratio for Propane. So you run a little bit leaner on Propane, a stock automotive narroband O2 sensor might not be suited for Propane as well... Not sure how that works.

[rutland]

Thanks for the help guys, it is much appreciated :smt023

[slaytalera]

contact Steinbruchsoldat, he has a LPG conversion on his GT-B

[ouch1011]

GT-B is twin turbo, yeah?

You will want to increase the boost when you do this. Propane has less energy than gasoline and also creates volumetric efficiency problems because it will expand radiply in the engine, reducing the amount of air the engine can injest. On an N/A engine you would increase the compression ratio...a lot. The Civic GX (runs on natural gas, same sort of idea) runs 12.5:1 compression ratio and it still loses a considerable amount of power versus a similar gas engine. On a turbo engine, you can increase the boost. You will still lose a considerable amount of power when below the boost threshold though.

I would not recommend a bi-fuel setup because in order to make the engine run on both LPG and gasoline, you'll end up with an engine that runs poorly on LPG on gas. Better to dedicate it for one fuel or the other. This is the problem with flex fuel gas/e85 vehicles. They wouldn't have such a big problem with fuel efficiency if they increased the compression ratio as much as they easily could if they built it to run only on the 105 octane E85.