Hi all,

I'm hoping someone can help me understand the function of the spark advance by temp and map/spark advance by rpm and map tables. Specifically, why they don't match the main advance table and seemingly just add 20° at a certain point?

Keep in mind this is on the old CCC system. I'm attempting to modify the tables to better suite a 350 with vortec heads and a pretty healthy cam (gm #12677151). The biggest issue is I need to run 12° of initial timing at idle.

Thanks in advance.

 

I suspect you have a "Base Temp. Correction Table Bias" of 20.04* somewhere in your scalars. It has to be subtracted from the "SA by Temp and MAP" values. Ex: 29.88* = 9.88*, 15.12* = -4.92*.

Same logic would apply to "SA by RPM/MAP Unlocked TCC". Over 1600 RPM it's zero. I don't know where this value is used in the final SA calculation. But it looks like it's pulling timing under 1600 rpm and over 90 MAP.

I believe, but I am not proficient in the CCC system, that your final SA (the SA you read at the balancer with timing light) is your MAIN SA table + "SA by Temp and MAP". Ex: with CT 115, RPM 1600 and MAP 50 = 28.12* - 4.92* = 23.2*

You should have a scalar for initial SA. It should be changed to 12* if it's what you will set it at.

Does the CCC system have a PE SA adder?

 

I didn't see a power enrichment in tunerpro but I can screenshot what I do have after work (it might be called something else for the ccc system). I know there's an initial spark advance and maximum spark advance scaler - does changing the initial advance scaler basically offset what the computer will add?

Finally, if I wanted to change my spark map to match an LT1 would I need to change more than just the main advance table?

Thanks for the help.

 

Yes, final SA is what you see on data logger. ECM will reduce final SA by the initial SA. It’s called reference SA. So if SA table is 29*, ecm will advance 29* minus initial SA.

Yes. LT1 has a more complex SA tune. Not sure you can just copy and paste.

 

FYI here's a screenshot of the ECU source. There appears to be a "Final SA" function in the ECM.

 

Why do you need 12* initial advance? Take that recommendation and forget about it. That number is for use with the specific GMPP HEI that has a mechanical and vacuum advance curve to it. Your car uses the computer instead. Set your Initial timing to the factory value for the CCC setup on your car. My guess is the spec is somewhere between TDC to 6*. Set the distributor to the specified value. Then you can tune your timing values in the prom.

The Main Spark Advance table needs help badly. Spark advance should decrease with additional load and increase with RPM. There are places in your map that have more timing with more load than the lower load area next to it.

 

I'd rather have the initial set manually where I want it but that's easy to change in the prom. Anyways, I get the point. Spark advance does look weird - especially for a "performance chip" made by Chevy. Should I just try adjusting the main spark table first and see how it behaves? I found an L69 table and interestingly it adds more timing with cooler temps.

 

Careful now. The more recent $6E and $8D for TPI have a cold SA feature. Under a certain CT threshold, the ecm will set SA using the Main SA table’s last column.

The CCC might not have this feature. I don’t know if the L69 had it.

 

Note that there is nothing wrong with putting a timing light on the damper. Look at the reported SA (ALDL), look at the expected SA, and see what the damper is showing. Can't argue with that reading. Be sure that the engine CTS is taken into account.

RBob.

 

I found a vortec spark table online and tried to replicate it. The car idled fine but acceleration was horrible. I'd love to get some opinions.