So, they released a new version of DashCommand yesterday for the Droid. It's still kinda crappy, but they seem to have fixed a few things - like the busted fuel trim issue I've been having. <img src="/forums/images/graemlins/rolleyes.gif" alt="" /> Anyway, I plugged it in for the hell of it to test it out. It was interesting to see how badly the timing is out of whack under light throttle. <img src="/forums/images/graemlins/frown.gif" alt="" />

Brief explanation of WHY this is a problem ...

Engines need timing advance. You can just set the timing to zero so the spark is triggered at top dead center (TDC) of the stroke because of several physics issues. Primarily its because fuel doesn't burn instantaneously. So the mixture has to be ignited slightly BEFORE the piston reaches TDC to get the maximum amount of 'push' on the down stroke.

It's a trade off. Since the combustion process starts BEFORE the piston reaches TDC the engine is 'fighting' against the force of the expanding combustion process as the piston moves upwards to TDC. But, the mixture must be ignited BEFORE it reaches TDC; just not TOO MUCH before.

What's happening in this case is the combustion process is too far along while the piston is still on the upward stroke to TDC. This is causing the engine to fight against the combustion process. In other words, it's like a big hand pushing down on the piston while the crankshaft is still trying to push the piston up. This generates an enormous amount of heat and stress - more than the engine and cooling system are designed to get rid of.

Ignition timing that is advanced too far wastes energy in the combustion cycle trying to push the piston the wrong way.

Edward