So I'm working on the timing and have set my base timing at idle 10 btdc with the esc plug unplugged. But when restart with the plug reconnected, my idle timing is around 16 or 18 and is very erratic. With the plug disconnected, the marker is dead on 10 and steady. Is this normal? Also should I time it back a bit so it will run a closer to 10 once the plug is connected. Thanks


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1992 Camaro RS V6 3.1

 

When the ESC is plugged in, the computer will adjust the timing to where it feels it works the best. Base timing is always adjusted with the ESC unplugged to remove the computer control.

Base timing is also adjusted to best suit the camshaft that is installed. Total timing needs to be programmed since increasing the base timing will also increase the total timing which the engine may not want.

10- to 12-degrees of initial timing when the duration of the camshaft is less than 220-degrees @ 0.050” of valve lift
14- to 16-degrees of initial timing with a camshaft duration of less than 240-degrees @ 0.050”
18- to 20-degrees of initial timing when the camshaft duration is less than 260-degrees @ 0.050” of valve lift.
More than 260 degrees @ 0.050" is normally a full race cam and a locked out ignition set to full advance with a start retard is generally used but you can still use a timing curve if you want.

Where your engine wants the total timing is best figured out on a dyno or dragstrip. 32-34* total timing is most common but higher or lower numbers can be used depending on how the engine is built and used. Power adder engines usually want less total timing while NA engines usually want a little more but there are a lot of other factors in there also.

 

This is completely normal. Set the base to 10° BTDC and be done with it. Although it should be set on a warmed up engine. The jumpy timing with the EST/BYPASS connector closed is due to the ECM varying the SA to help hold a decent and steady idle speed.

RBob.

 

Pretty normal, except that usually it will go to 20something advanced once it's plugged in, and maybe jiggle around a bit as the ECM dithers around with it, maybe 4 - 6 degrees or so. But if it only goes to what you say, but runs good, then,,, ... , .. hey, .... ,, ... it runs good.

No you should not do what you said.

If it RUNS good, it IS good. Don't outsmart yourself.

 

I never thought about it because I use timing gears and a crank trigger but timing that jumps around a lot at idle is usually from a worn timing chain set. Even good quality double roller chains don't last forever.

 

Thanks so much for the help. Timing chain is prob good since it is dead on 10 with the cable unplugged, which is good to know, so I'll just let the ECM do its thing with base at 10.