Idle underspeed timing advance not working on 2009 ZR1

I'm tuning an '09 ZR1 with a fairly large cam (unknown specs), 2.35 pulley i believe, and headers. When it idles, the car would surge badly and the afr would fluctuate a lot whether it be in closed loop or open. The car is MAF only for now and I plan to keep it that way if possible. I got the fuel under control just by making all the cells in the MAF curve have the same value. With the rough cam and unstable idle it was hitting about 10 different cells while at idle. I know this probably isn't the right thing to do but it worked.

This cleaned up the fuel a lot, and for the most part I'd say the car idles pretty good. However I have noticed that the timing at idle will never go over the commanded timing in the idle spark table. When the rpms dip a bit under the desired idle speed the timing will just flatline at 22 degrees and never go over that value to bring the rpms in check. The adaptive idle spark tables are all set to stock, and it works fine when timing needs to be pulled to slow the rpm down a bit. With it not going over 22 degrees ever, the rpm still has a very slight surge. If i set the timing higher in the idle spark table it will show up...but it will still not go over the value commanded.

The afr/fuel trims look pretty horrible in this log at startup...partly just because the commanded is lower at the cold start temps however they aren't too bad when warmed up. They are still a bit to the positive even when warm....so I guess I can richen it up in the maf curve maybe 10% or so which should help the trims all around but any other suggestions to improve this would be appreciated as well.

Any ideas on why the adaptive idle underspeed spark advance doesn't seem to work? Is there something tune related I'm overlooking or maybe just a bad pcm? A previous tuner couldn't get the car to idle worth a crap to be honest...they even drilled a giant hole in the tb butterfly lol. The problem isn't idle airflow related and fixing the adaptive spark will fix the issues completely.Attachment 38716Attachment 38717

Hi, I am new to tuning. But, I am pretty sure the reason it will only go to 22 degrees is that is what you have set in your main spark table. It will never advance the timing more than the main table. You will have to up the timing in the main table and lower the timing in the idle tables. That way you will have a fair amount of advance to catch the falling idle.

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Originally Posted by openwheel25

Hi, I am new to tuning. But, I am pretty sure the reason it will only go to 22 degrees is that is what you have set in your main spark table. It will never advance the timing more than the main table. You will have to up the timing in the main table and lower the timing in the idle tables. That way you will have a fair amount of advance to catch the falling idle.

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Thanks! I matched the two tables because I have had surging / cam bucking issues in the past and matched the tables up so that there was no large transition from one table to the other if it were to switch tables while coasting along... I bet I have done that on 2 dozen cars now and this is the first one that showed up like it did. Thanks again, the timing is working just as it should now. :)

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Originally Posted by openwheel25

Hi, I am new to tuning. But, I am pretty sure the reason it will only go to 22 degrees is that is what you have set in your main spark table. It will never advance the timing more than the main table. You will have to up the timing in the main table and lower the timing in the idle tables. That way you will have a fair amount of advance to catch the falling idle.

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agree to what he said ... plus due to unknown cam you have .. sometimes need to play with the timing abit til you find sweet spot ..couple of degree above stock value otherwise it will keep hunting up and down with too much timing ..

you can use VCM scanner and reduce the timing and see how it behave ..( its shame that in GEN3 u can play with the timing up and down but not in GEN4)

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Originally Posted by 4evervette

agree to what he said ... plus due to unknown cam you have .. sometimes need to play with the timing abit til you find sweet spot ..couple of degree above stock value otherwise it will keep hunting up and down with too much timing ..

you can use VCM scanner and reduce the timing and see how it behave ..( its shame that in GEN3 u can play with the timing up and down but not in GEN4)

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Hey, I just moved to Dubai early this year, with a monster ZR1 (heavily tuned in Europe).

I see you are based here? What is your shop name? I would love to come by with my car. Even if it is only to chat with other car lovers.

Have you tuned C6 ZR1 's ?

The fuel here is abysmal (first hand experience, shocking); so I've gotten the tuning redone; but its nowhere near what I want it to be.

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Originally Posted by RedBaron

Hey, I just moved to Dubai early this year, with a monster ZR1 (heavily tuned in Europe).

I see you are based here? What is your shop name? I would love to come by with my car. Even if it is only to chat with other car lovers.

Have you tuned C6 ZR1 's ?

The fuel here is abysmal (first hand experience, shocking); so I've gotten the tuning redone; but its nowhere near what I want it to be.

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Hi agree with u about the fuel,here ..check ur inbox pm sent