Questions on converting a subaru wrx to cng

[ldscamaross]

hey i am thinking about converting a 06 subaru wrx sti to cng. i am trying to do some research. does anybody have any experience doing anything like this. the engine is a 2.5 liter turbocharged car running around 18 lbs of boost. I know that there will be some power loss with the natural gas but figured that i could switch it back to gas for spirited driving. I am looking to decrease the pain of filling up at the pump for $3+ on premium and geting 15 mpg in the city. what type of power loss would i see. the engine compression is about 8.5:1. I have got a quote from a guy who says he can do it for about 6200 and i am thinking about it. any responce would be gladly appreciated
thanks
andy

[Highmarker]

ldscamaross,

It has been reported that you get about a 15% reduction in power. I read that in an article somewhere. I'll see if I can dig it up. CNG has an optimum compression ratio of about 12-13:1.

[neongreen]

I drive a 2.3liter turbocharged ford ranger and have been looking into the same thing. One thing you should realize with a turbo motor is that while you may experience a power loss in normal driving, the octane rating of cng is anywhere from 120-130. You could run as much boost as any turbo could push and make up for that loss. That is one thing that really appeals to me. I am just having a heck of a time finding any good info on how to actually do it, as i would prefer to do it myself.

[leighroyz]

So nobody on here really knows much about cng on performance applications huh?:confused:;)

[cngmike]

The guys at So-Cal Speed Shop have built a CNG hot rod. Sorry no picts.

[neongreen]

I have heard that an Australian rally team will be running on CNG this coming year. I don't really know any details though.

[cngaz]

They ran on natural gas last year, this year they running it all on biogas.
Sponsored by OMV, its a CNG Mitsubishi, The first rally race is in Austria this coming week.
I have a photo of the car on our blog. http://blog.cngaz.com
LICO Lavanttal Rally, April 4-5

[rtry9a]

My best guess is that a turbocharged engine would do very well with ngas, but you will likely need some way to pump in extra gas under boost conditions. It probably would take some kind of enrichment circuit (probably using an extra injector) regulated by a pressure sensor mounted in your intake manifold. Boost pressure in a turbocharged system is controlled by the level of work done/heat produced in the exhaust- it is independent of any mechanical coupling with the engine.

The problem you need to overcome is that because turbocharger's boost is not rpm dependent like a supercharger, which could use the base programming hardware to provide the needed fuel enrichment. It is dangerous to run any boosted system too lean; detonation is the likely outcome.

I have a twin turbocharged Mustang Cobra that Id love to convert...

[cngaz]

2 of the guys up at FuelMaker in Toronto, Canada converted their Mustangs, but thats Canada.................................

[rtry9a]

Converting the basic Mustang is no problem (could use any kit designed for the F150's). The problem involves tuning the turbochargers tho Im sure it can be done with a wide band O2 sensor and a few "modified" parts.

[neongreen]

If you had a boost referenced Fuel Pressure Regulator like many gasoline motors (turbo and non-turbo) that would not be a problem. As th eboost pressure rises, so does fuel pressure.

[ldscamaross]

hey thanks for all the replies you guys. i hadnt looked here for a while.