Why ProPain works.

[1badTTA]

I am posting this as an informative post and also a question/open for debate.

In what I have experienced, read, researched, etc.. The reason propane injection has as much effect as it does on our turbocharged gasoline engines as it does is due to 2 reasons.

1) An octane ratine of 108-112 (seen different ratings posted all over the internet)

2) The fact it is a gas and not a liquid.


I believe that the 2 combined also play a mojor role in the combustion process. Since propane is a high octane gas completely mixed with the air in the cylinder, any lean spots will effectively have a higher octane than rich spots. The definition of octane is essentially "the resistance to detonation" and a lean mixture will detonate easier than a rich mixture so therefore if the lean spots have a higher average octane than the rich spots you will be less prone to detonation and also able to make more power than by simply running straight high octane gasoline. Basically since you are injecting about 90% gasoline (91-94 octane) and 10% propane (108-112 octane) you really only have a true octane rating of 92.7-95.8, but actual results show more around 105-110 octane performance.

If anybody disagrees with this or has anything to add to it, feel free as I would like to learn as much as possible about the subject.

 

[HurstGN]

To add to the reasons it works:
Gasoline atomized and mixed with air creates the basic fuel for the combustion process. But gasoline is only so efficient when burned in the combustion chamber. There is still more potential to be had, but this potential is typically expelled via the exhaust. Hence the factory EGR, Catalytic Converter, and other EPA stuff we turbo owners don't like. Plainly said, the internal combustion engine just isn't efficient at burning the gasoline.

By adding propane to the mixture, we get the benefits mentioned above, but we also release some of the unused potential of the gasoline we usually lose out the exhaust. I would suspect this would explain the "actual results" octane that 1badTTA has noted.
So, bottom line is you burn the gasoline more completely and make more power.

Dan

 

[S10xGN]

Have ya'll thought about having a chip burned specifically for propane? My O2's at full throttle are ~815 mv or so... wonder how much fuel would need to be pulled to get that down a bit? Or would it be better to lean the whole curve by dropping fuel rail pressure?

 

[1badTTA]

Originally posted by S10xGN
Have ya'll thought about having a chip burned specifically for propane? My O2's at full throttle are ~815 mv or so... wonder how much fuel would need to be pulled to get that down a bit? Or would it be better to lean the whole curve by dropping fuel rail pressure?

Yea mine too. I think any chip with a BLM lock for WOT would allow us to tune it easier. I will probably end up with a new chip eventually (money willing) and that will definately be a feature of it. My problem is that part throttle blasts keep screwing with the last BLM and then it is rich under full throttle passes. I'm not really complaining since I have stock injectors running over 100% on just gas so the propane is acting like a 7th injector also and might actually make my goal of 11's with stock combo on 91octane a reality if it takes the small injectors out of the equation.