Are there any thumb rules that one should consider when making a spark table for different cam. There are a lot of tuners that make mail order tunes. How can they make a good tune without having engine near them? They usually ask for cam specs and from that parameters they are able to make at least start-up maps. In my situation, I'm about to step up from #219 cam to CompCams HR-288-10 cam which has much more duration and even tighter lobe separation angle. I had custom tune from PCMforless for my last combo, but now I'd like to try to do my own tune. I allready have WBO2 (LM-1), so I can check fuel tune, bur I'm really concerned about spark tune. Any information about spark tuning would be appreciated!

Check out this (Tuning the Timing) in the prom burning guide.


Does anyone know why my browser wont let me paste anything in the quick reply box? Its firefox, and is up to date.

One area thats different with a cam is the low speed operation. Here, with a lot of overlap and increased valve duration, the cylinder bleeds down. This results in the need for more timing as essentially the dynamic compression is much lower than stock. If you try to use modest timing at low engine speeds/idle, the engine will run poorly, lack power, and be prone to surging. Its also a good idea to use the same spark advance everywhere in the timing table where the engine idles. This will make controlling the engine easier. Set up properly, the motor will still be somewhat responsive when its out of its powerband. Be careful to only add as much timing as necessary to get the engine to run well. Too much can cause overheating and detonation under high load.

Ive attached my SA tables as an example. One is used during closed throttle idle, while the other is used when the throttle is open. Your ECM will be different. You will see that there is more timing at idle and low RPM/high load than you would have with a stock engine. This is to help compensate for the low cylinder pressure. If you have higher compression, you will need less timing as the cylinder pressures will be greater.