10" Pulley Tuning Help

[evonschu]

Hey all. Been working with a great shop in town and got some mods on my 2013 ZL1. Put on kooks no cat headers, 10" LPE pulley, id850 injectors, and tuned. Already have RotoFab CAI, and CMAX ported TB, and extra reservoir for coolant.

Been having some issues where when I go to accelerate sometimes the car chugs a few times before launching. It's been a process getting the tune hammered out, specifically in this transient area of acceleration. I believe what the tuner at the shop was saying was that the pulley is pushing out so much air in that less than 50RPM range when I punch it, its pulling timing or something along those lines. Gone with him on several rides with his computer and HPTuners. Tried adjusting lots of different values, mainly centered around this small area when I accelerate hard from a cruising speed. Some things have helped but still continue to have this issue.

Got new plugs in and that helped a ton with IAT2 temps, but didn't solve. If I'm already at higher RPM and then punch it I've never had the issue. But If I'm cruising at about 1-2k in any gear and step on it, it'll usually happen. It also seems worse if I downshift and rev match, then floor it a second later in the lower gear. Or similar situation, I rev the engine and then punch it while cruising. The weird thing is it doesn't happen every time. Sometimes I punch it and it feels ok. I'd say about 1 out of every 4 times it'll chug like this prior.

For those of you guys running 10" pulleys with stock size SC pulley any advice on what might be causing this? The shop I've been working with is very good and we've both been confused as to why this continues to crop up.

Thanks for any info. I've attached the dyno results too if that helps. It will never happen while on dyno though, just street driving.

[m1key1111]

Email me your tune and a log file and I'll take a look at it for you.

Mb3689@gmail.com

Thanks,

Mike Brown

[2013 ZL1 #7860]

How did your plugs help with IAT?

[Candr3535]

I've had no problems with this. Just sometimes it doesn't rev to life after a hot restart. Starts no problem. Just not a vroom style start like if I just started after sitting for a day or so.

[ZO6 Bryan]

It is 100 % being caused by burst knock. Lower the values down so burst knock can't exceed 4 deg. Stock values will allow more than 20deg to be pulled. That will put your actual advance into the negative numbers. Hence the bog you feel.

[jayno20]

Originally Posted by ZO6 Bryan

It is 100 % being caused by burst knock. Lower the values down so burst knock can't exceed 4 deg. Stock values will allow more than 20deg to be pulled. That will put your actual advance into the negative numbers. Hence the bog you feel.

The more you post the more I want you to tune my car!

[evonschu]

Originally Posted by 2013 ZL1 #7860

How did your plugs help with IAT?

Massively!! Like 1 pull before was 190-225 degrees IAT2. After, I haven't even seen it go above 130 after several pulls.

[evonschu]

Originally Posted by ZO6 Bryan

It is 100 % being caused by burst knock. Lower the values down so burst knock can't exceed 4 deg. Stock values will allow more than 20deg to be pulled. That will put your actual advance into the negative numbers. Hence the bog you feel.

Thanks. I'll relay this info on to the shop. I think he might have mentioned this and that tuning that down is kind of an easy way out that might increase the chances of damage to the engine. I don't know for sure if this is what he was referring to specifically though. Did you have this same problem with your setup initially?

[m1key1111]

Originally Posted by Candr3535

I've had no problems with this. Just sometimes it doesn't rev to life after a hot restart. Starts no problem. Just not a vroom style start like if I just started after sitting for a day or so.

I had this same issue and I worked around it in the tune by adding some startup airflow (fired up fast every time, even after a hot start) however I knew it was a workaround.

I read some threads about hot start issues and leaking ID injectors and I swapped my injectors out and it fixed the problem 100%! It ended up being a leaking injector dripping fuel when the motor was hot (which acted like it was semi-flooded and fumbled during a hot start) but cranked up fine after sitting a day or two (when it cooled down).

[2013 ZL1 #7860]

Originally Posted by evonschu

Massively!! Like 1 pull before was 190-225 degrees IAT2. After, I haven't even seen it go above 130 after several pulls.

I think your data is flawed. That is not how "colder" plugs work...

Perhaps your pump wasnt on for the higher IAT pull?

[evonschu]

Originally Posted by 2013 ZL1 #7860

I think your data is flawed. That is not how "colder" plugs work...

Perhaps your pump wasnt on for the higher IAT pull?

Don't think my data is flawed. I read the data off normal and hard accel driving on my scan gauge II for about 2 weeks before and 2 weeks after.

Other adjustments on the tune might have been made too when they changed the plugs, but I was told they were minor and not enough to make this much of a difference.

What do you normally expect to see with better plugs in?

[ZL1Kid_AL]

I just don't see how changing anything within the ingnition process is going to drop iat2 temps by 70+ degrees.

[Candr3535]

Originally Posted by m1key1111

I had this same issue and I worked around it in the tune by adding some startup airflow (fired up fast every time, even after a hot start) however I knew it was a workaround.

I read some threads about hot start issues and leaking ID injectors and I swapped my injectors out and it fixed the problem 100%! It ended up being a leaking injector dripping fuel when the motor was hot (which acted like it was semi-flooded and fumbled during a hot start) but cranked up fine after sitting a day or two (when it cooled down).

Thanks for the info. Will be sure to check it out. Thanks again

[evonschu]

So I talked to my tuner today and while I was out with him on some test runs on the street he had already tried turning burst knock way down and it didn't make a difference so that's not it...