Ref the fuel setting as Iggu and JustCharlie have already said a lower fuel setting means your car will be running a richer AFR and a higher fuel setting means your car will be running a leaner AFR.
For those that don't know AFR = Air Fuel Ratio. If you log block 31 with VCDS you will see the lambada sensor value which can be multiplied by 14.7 to give you your actual and specified AFR. When
not boosting and
not running at WOT (Wide Open Throttle) your car will always try to maintain an AFR of 14.7:1 When running WOT and boosting the AFR will be richer - anything from about 12.2:1 to 11.5:1 at the redline depending on what you have the fuel setting at (with REVO).
The reason the AFR is especially important in turbo charged cars is because:
- The leaner the AFR is the higher EGTs (Exhaust Gas Temperature) are going to be. High EGTs are the number one killer of cats and turbos. Having less fuel in the cylinder per combustion stroke will create a hotter burn. However REVO owners don't worry! Running a fuel setting of 9 is perfectly safe and well withing the limits of what our K04 turbos can handle.
The reasons why you might want to turn down the fuel setting and hence run a richer AFR:
- Running a richer AFR will bring down EGTs and cylinder temperatures as more fuel per combustion stroke means a cooler burn. The reduction in temperatures means you should be able to advance timing a little more and hence produce some more power.
Stage 1 and Stage 2 cars really do not have much scope to adjust the fuel setting if you want to be able to maintain a decent level of boost like for example B6 with REVO. This is because the standard HPFP will struggle to keep up with the requested fuel pressure and running too low a fuel setting could lead to fuel cuts. On my stage 1 S3 I run F8 and would not go any lower until I get a HPFP.
As always before playing around with any settings you should always log thoroughly with VCDS the pre and post results. If you don't know what you are doing or understand the ramifications of the changes you are making then it would be better not make these changes yourself and go to your local tuner or local friendly forum member