All:

I'm in a debate with a fellow friend that thinks if you tune a car at 91 oct and then put race gas in the car, he thinks your car will immediately gain whp.

I don't think so. I think the car will stay the same performance and maintain it under less-than-ideal conditions (i.e. hot weather) to prevent detonation.

-M

 

Actually if you put in race fuel, without raising boost or changing your tune, ie, more timing leaner afr, etc you usually lose power UNLESS the tune you are on has knock bad enough to pull timing. We put VP109 in a race bike with full exhaust but no tune and the bike was like 7 hp down over stock, it was an 03 R6, which made 93rwhp on the fuel but no tune. He was like 99-100 whp with stock exhaust on same dyno, so he paid for full custom tune on that fuel and wound up at 110 whp after the tune, with more power everywhere.

 

Why though?

This makes no sense and it certainly doesn't mean that it's the case for cars.

-M

 

If you do not raise the boost and/or adjust your tune then no you will more than likely lose power (assuming your pump gas tune was decent to start with).

Me and a friend were tuning my car on pump gas and got the a/f at a nice 11.5. We then put in 110octane and did a few low boost pulls to mix the gas in and the a/f dropped to high 9s/low 10s.

 

leaded race gas has a much higher flash point than unleaded 93/91 pump gas causing it to run richer than pump gas

 

Gotcha!

How about 100 octane (which is what I put in my car)?

-M

 

100octane doesn't affect a/f too much over 93octane, but does offer a bigger window for tuning obviously.

 

Thanks! So I should be good to go then (no power loss or gain)?

-M

 

This is correct. I think the whole thing has to do with the fact that higher octane is harder to burn.

 

100 octane unleaded gas will yeild slightly more power, but you will not notice true gains unless you are tuned for the higher octane.

 

You shouldn't see any negative effects from it, but it's a waste of money if you're not tuned for it.

 

I AGREE it is a waste unless the car is tuned. it will only be an advantage if the timing is advanced and it runs a leaner air fuel ratio.

 

I put the 100 octane in there because I'm headed to the track tommorrow and it will be *HOT*. With consecutive runs down the track, 91 oct will surely start to become unstable. I put it in the car to make sure there is no knock with the heat and thus maintain the whp when it was tuned..

-M

 

youre just wasting money on 100, especially if you are stock boost levels, pretty much like the guys have previously stated

even with higher ambient temperatures, 100 isnt necessary, in fact, could actually hurt your performance

 

If you put 100 octane ras gas in and turn up the boost you can see nice gains even without a retune(if you have been previously tuned).