JMS4

Is there any benefit to run race gas on track if my car is not chipped?

D all over

I thought that was why the chipped guys did it too???:P

NASA racer

Octane is the measure of a fuel's resistance to pre-ignition. Primary reason the fuel ignites before the spark plug fires is high cylinder temperatures and pressure...ie a turbo engine on a hot day or a high compression ratio engine.

If you are using 91 CA **** gas, you would probably get better performance on an 85 degree day at a track due to the "overkill" of 100 octane resisting preignition (and the consequent cut in timing and reduction of power that the ECU will do to prevent the preignition causing damage). In reality, if you have 93 octane available that would probably suffice to.

But "race gas" does not MAKE power, it only enables the engine to run to it's maximum AVAILABLE power with no fear of preignition.

0700

owie

JMS4

thanks for the info

DarinS4Turbo

Right on.

VonK :: Retired

The S4's stock ECU contains a timing map that sets WOT ignition timing to the advance required for max power using <b>91</b> (spec) octane fuel (It does not automatically advance to the maximum permitted by detonation, except under extraordinary circumstances such as over boost, heat soak, desert heat, inferior fuel, etc.).

The greater resistance to pre-ignition of 100 octane fuel brings with it a slower flame front propagation through the combustion chamber. This "slower burning" would require earlier timing for max power than would be optimum for 91 octane. Therefore a 91 octane optimized timing map (stock S4) running 100 octane fuel would cause later timing, and less power than would be optimum for 100 octane.

As mentioned above, the knock sensor may interfere under extraordinary circumstances like tracking in desert heat on 91 octane. This may cause the knock sensor to delay timing more than would running 100 octane fuel. So, if you can afford it, run 100 octane, or a mixture, just for insurance.