- Location
- Atlanta, GA
- Car
- 2007 FX35
For our cars, 91 is fine (and no car requires more than 91 since that's what's mandated in so many areas now). Higher octane doesn't give more power, it just lets you run a more aggressive tune or boost. High octane takes more energy to combust so it's less likely to pre-detonate (knock). It lets you run more aggressive timing or higher boost without knock. If you just pump 105 octane race gas or E85 into a stock car, you're not going to gain any power. You have to have a tune that compensates for the extra octane and is more aggressive.
ie, I leave the piggyback on my 335 to autotune so it basically runs a map appropriate for the gas that's in there based on knock sensors and all that. If I pump E85, it will up the boost and go to a more aggressive map. That is what's making the power, not the gas.
---------- Post added at 08:00 AM ---------- Previous post was at 07:57 AM ----------
With uprev, fuel maps are changed along with timing maps so 91 will work fine. But the VQ already runs on the lean side from the factory so if you run bolt ons and no tune, you're even leaner. If you run bolt ons, no tune and +2 timing, it is much more likely to knock. Knock sensor will just pull timing, but that is going to result in loss of power which defeats the purpose.
ie, I leave the piggyback on my 335 to autotune so it basically runs a map appropriate for the gas that's in there based on knock sensors and all that. If I pump E85, it will up the boost and go to a more aggressive map. That is what's making the power, not the gas.
---------- Post added at 08:00 AM ---------- Previous post was at 07:57 AM ----------
With uprev, fuel maps are changed along with timing maps so 91 will work fine. But the VQ already runs on the lean side from the factory so if you run bolt ons and no tune, you're even leaner. If you run bolt ons, no tune and +2 timing, it is much more likely to knock. Knock sensor will just pull timing, but that is going to result in loss of power which defeats the purpose.
