[2old]

In our cars or in general?

In our cars the only thing you can change is the cam timing if you bought adjustible cam gears. The objective here is to tune the where the optimum valve overlap occurs to change the torque and HP curves (Currrently our cars timing should be optimized for around 5-6000 RPM... I would need to check the graphs to be sure).

If you are using the car for racing you can change the time the valves overlap to try to maximise HP at high rpms (this reduces your overall torque at low RPM which actually makes your car slower when accerating from a dead stop) but you need a dynometer to do this because unless you have supercomputer to model the flow there is no hard and fast rules about adjusting the cam timing.

In general (IE only apply to SOHC versions of our cars that have distributer or aftermarket modded ignitions) you can adjust the ignition timing to advance it so that the flame front will hit the piston when it reaches just after TDC (Top dead center) which would maximize power. In general you want the flame front to reach AFTER TDC because if it hit before it puts a lot of stress on the crankshaft and robs you of power in a hurry.

Technically Fuel timing is not as critical in gasoline engines as it is sprayed into the pre-chamber and doesn't do anything (except maybe leave deposits) if it is done early. In diesels or cars with direct fuel injection this is more critical as it is used to cool the ignition chamber to prevent pre-detonation so that the engine can be designed with a higher compression ratio.