Tuning forced induction for road race, ls1 383ci, D1-SC, bad tip-in problem

[Rudolph]

Hello guys,
Good day.
My car is a 99 Z28, with a 9.5:1 static compression ratio and forged 383ci, FAST 90/90, Headers 1 3/4 steped 1 7/8, AFR heads 66cc, and 10 psig of boost and all the coolers of course. One thing that is a importante factor, that I live at 8,000 feat over sea level. I am not an experienced PCM tuner, btw.

I have a problem with my car, which is driven /raced at the race track (road racing), and for that reason I have to be really carefull with the tune, due to the fact that at the track temps with FI get really high and detonation is a matter ot time if you are not carefull with the fuel and timing (as for sure, all of you know). I have a good friend that help me out, at the beginning, with a soft tune of the PCM where WOT races did not matter at all, because there was not knock retard at all... The problem came up, once I was at the "esses" where KR at 19% of the throttle was in minus 6 degrees, which tells you that mid throttle was not tuned properly, and there is where I am having problems.

I can tune up the car really nice once the PE mode gets in after 21% of the TB is engage. I tought that maybe lowering the PE mode to 14% might be a good call, but I drive my car to the race tracks (100 to 150 miles away), so I do not think that could be such a great idea. I have been reading that one with option is to tune up the MAF, which btw is scaled down, due to a suggestion of my tuner friend, but now, as I told you before, I am the one doing the work. I would like to have a good tip-in on the car, but unless I lower the PE mode engage, it sends KR that last from 2 to 3 seconds and ranges from 2 to 4 degrees. I have been trying to fix the car's problem and it dying coming to completed stop after high reving, even with the Throttle Follower function, and it does not work really well. Between the awful tip-in and dying after high revs and to complet stop, it is being a nightmare... Tip in mostly.

Guys, is there a way to richen up the fuel withouth the PE mode? Do I have to edit the MAF to do so? Engine dying after high revs and complete stop, how to?

Any help is going to be greatly appreciated.

Thanks in advance.
Rodolfo Lara P

[blownbluez06]

Dial your MAF and VE tables in properly. Your fuel trims are all over the place. In deceleration, they max out and then you touch the gas pedal and they have to try and move. I also see the trims going high positive. You've got a real mess on your hands. Turn your LTFT's off. Is your fuel system boost referenced? If it is, make sure the fuel pressure is following the vacuum or change your IFR table to have the proper slope. Increasing throttle follower can be a problem because the idle routine won't begin until it's fully decayed, so it's often better to have it decay sooner and let your adaptives take over rather than trying to slow it down. Get your idle airflow set properly. I get the impression although you didn't log the IAC that it's not right. Set your throttle blade to where your IAC counts are reasonable and then do the TPS relearn procedure. Make sure with the engine warm your throttle is 0% at idle. So many things need attention. Your That should keep you busy for a while.

[Rudolph]

Dial your MAF and VE tables in properly. Your fuel trims are all over the place. In deceleration, they max out and then you touch the gas pedal and they have to try and move. I also see the trims going high positive. You've got a real mess on your hands. Turn your LTFT's off. Is your fuel system boost referenced? If it is, make sure the fuel pressure is following the vacuum or change your IFR table to have the proper slope. Increasing throttle follower can be a problem because the idle routine won't begin until it's fully decayed, so it's often better to have it decay sooner and let your adaptives take over rather than trying to slow it down. Get your idle airflow set properly. I get the impression although you didn't log the IAC that it's not right. Set your throttle blade to where your IAC counts are reasonable and then do the TPS relearn procedure. Make sure with the engine warm your throttle is 0% at idle. So many things need attention. Your That should keep you busy for a while.

Thank you very much for the quick replay! I appreciate your comments and help, big time.

I have been Reading about the proper way to dial in the MAF, and many posts mention that you have to increase the flow base on the given amount of Hertz, and I did, I got more KR on tip in, which freaked me up. I guess I have been just trying to avoid the KR, instead of properly tune up. BTW, my tune is not boost referenced

I will look for an improvement, and post results.

Thank you very much.

Rodolfo Lara P