- Joined
- Jun 30, 2012
- Messages
- 14,006
There are 4 things which affect combustion temperatures and knocking - the anti-knock rating of the fuel, the compression ratio, the fuel/air ratio and the ignition timing. The optimum is a balance of those 4 things. Usually your comp. ratio is fixed, and you don't change your fuel - so you end up balancing two things - your mixture and the amount of ignition advance you use to fire it. If you advance your ignition point, it usually has the same effect as leaning-off your mixture. Even if your advance is a few degrees wrong for the fuel you are using, you usually correct by adjusting the mixture. As far as power goes, there is nothing in it. HOWEVER - the needle and needle jet are critical if you are seeking high performance. If you have a range of needles with different tapers and a programmable ignition system and don't change the fuel you use, you might get a bit more out of petrol. You would probably find you would be playing a lot with those two factors at every race meeting. I get around the problem by using methanol fuel. It has unlimited anti-knock and hides-up the tuning errors. I never race using petrol, even in two-strokes methanol is better.