This is a question that I really think Mr. Cahill can tackle.

On a 1994 Cavalier 2.2 does the computer adjust (advance or retard) the timing as RPMs increase? I need to change the timing due to a radical cam that I had made but do I slot the timing gear and move it manually or can it be done electronically?

Thanks guys.

are we talking ign timing ... if so then the ecm controls it .... i dont know how changing the timing gears in any way would have a acurate effect on the timing (the ecm uses the cam and crank pos sensor to as well as engine vacum to determen spark ...... and if your talking cam timing the ecm does not control that


but maby im just missing the point and the ?

What we have done is advanced the timing by rotated the timing gear on the cam by re-cutting the keyway slot 4 degrees. This car does not have a cam position sensor so all the ecm knows if what the crank sensor tells it. This opens the valves up sooner that normal so to your point, ignition timing did not change. If this is correct, getting someone to reflash the OBD1 chip to fire at a new position. Does anyone one know who could hook me up?

when you change the cam timing it is not nessesary to change the iginition timing. with a bigger cam you may want a few more degrees of timing at idle to clean the idle up, but usualy total timing doesnt need to change. for optimum performance you may want to add 1-2 degrees total timing, but this may cause detonation with cheap fuel.

Of course the ecm changes timing with rpm. It also changes timing with vacuum, with throttle position, with intake air temp, and with engine coolant temp. Finding someone who can change timing is probably easier than finding someone who can give you the correct timing for your new engine configuration It's like asking for the right tires without describing where you're going to be driving.

As a general rule:

timing increases with increasing rpm and decreases with increasing load. Timing under Power Enrichment (WOT) is usually 2 - 6 degrees greater than timing under closed loop, non PE mode, depending on RPM and temperature.

The best way to get a combination which is good for your car is to get the appropriate tuning tools and do it yourself by trial and error. The next best way is to find someone with the tuning tools and bring your car to them.

hth
-->Slow

The car is a 1994 Cavalier 2.2 5 speed. It is set up for 3/8 mile dirt track racing. WOT all the time.