1981 Corvette Timing
09-15-2010, 09:38 AM
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1981 Corvette Timing
I remember a thread discussing the merits of advancing the timing to 12 degrees with I believe the 4 terminal connector disconnected. I checked the Shop Manual and it states "Electronic spark timing is used on all engines, EST uses no direct mechanical control for spark timing. Engine parameters are monitored and these inputs are electronically processed to obtain optimum spark timing."
So, my question is this - does re-timing with the terminal disconnected and then re-connected really adjust the timing curve? My car has great torque at 1/3 to 1/2 throttle, but at WOT seems to fall way off. I'm looking to get a little more juice out of it while keeping the car 100%stock.
So my question is what is the exact procedure for re-timing it and does the computer off-set these changes when the connector is re-attached, or is it a dumb system that you can fake out?
Jon
So, my question is this - does re-timing with the terminal disconnected and then re-connected really adjust the timing curve? My car has great torque at 1/3 to 1/2 throttle, but at WOT seems to fall way off. I'm looking to get a little more juice out of it while keeping the car 100%stock.
So my question is what is the exact procedure for re-timing it and does the computer off-set these changes when the connector is re-attached, or is it a dumb system that you can fake out?
Jon
09-15-2010, 10:24 AM
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The computer does not know what the timing actually is: It is pre-programmed with a map that adjusts the timing from the base setting, and it assumes the base setting is correct. By advancing the base timing to 12 degrees, you advance the entire ignition curve and give the engine a more aggressive timing advance throughout the operating range. It is a "poor-man's performance chip" for the OBD1 system, and actually works pretty good. Keep in mind that advancing the timing will also increase hydrocarbons, so it will affect emissions test results if you have to pass an emissions test.
Lars
Lars
09-15-2010, 10:51 AM
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The computer does not know what the timing actually is: It is pre-programmed with a map that adjusts the timing from the base setting, and it assumes the base setting is correct. By advancing the base timing to 12 degrees, you advance the entire ignition curve and give the engine a more aggressive timing advance throughout the operating range. It is a "poor-man's performance chip" for the OBD1 system, and actually works pretty good. Keep in mind that advancing the timing will also increase hydrocarbons, so it will affect emissions test results if you have to pass an emissions test.
Lars
Lars
Jon
09-15-2010, 04:37 PM
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So I just pull off the 4 wire connector before starting it and then re-time it?
09-16-2010, 03:05 AM
#5
Exactly. Disconnect 4 wire connector, set timing to 12 - 14 degrees advanced then reconnect and your done. You may have to reset your idle as it may idle a bit higher with the advance. If you do adjust your idle then check your tps voltage as it may be off - 0.56 is what you want.
