Moderators..I posted this in the tech seciton also...hope you don't mind as I need serious help and need the big brains to see this.

Ok...got the new heads on the car. Went to the dyno yesterday and the dance began. First...as soon as we would hit the throttle the car would go dead lean...so we lifted. started stesting stuff. Adjusted the fpr and make a run..ok...ran good..ran a back up and loaded up and dead lean again(once again lifted after the car loaded up and the A/F went off the scale on the dyno). We changed the FPR..problem fixed. Next problem, Injectors were 100 % and he a/f was all over the chart...very wavy. Put in some delphi 37s..problem solved and a/f had a nice flat curve. Next problem...I was getting this weird pop mid rpm(4400ish) when making a pull. The car would lunge..then recover and it would happen again up top around 5600. This was repeatable from run to run. Tried different msd box, different coil, checked plugs, different tunes, finally changed the opti. Ok...problem fixed..pulles fine right past where the pop was happening..untill..next problem.

Now at 6700 the car starts to studder. The dyno showes that it nose dives and falls...never recovers. In the dyno graph we didn't lift untill after 7000 rpms. The weird thing is that when the studder starts (6700)my tach goes dead..goes right to 0 then when we lift off the throttle it recovers and starts showing correct rpms again. So..since we didn't get to test anything up top we starting replacing things again with the spare parts we used the day before on the first problem. Changed msd box, same thing, changed coil/coil wire, same thing, changed the opti pickup wire(whatever its called..plugs into the top of the opti), no change, changed plugs..which were brand new yesterday when we started this whole thing...and plug wires, no change. We ran a wire from the alternator right to the power distribution block(battery in rear so it gets power from the rear normally)..no change. So...does anyone have any idea what this could be. What about the pcm, I didn't have a spare 6 speed one to try so I couldn't rule that out. Also..when this happens on my logs my right bank O2s go lean bad. The reading are almost uniform between the two banks all the way through the pull untill this starts to happen. We put the wideband in that muffler(I run dual bullets off the headers) and this problem could not be reproduced on the wideband.

I need help guys...the thunder shootout is next weekend and I have to get this thing running.

Here is the dyno chart...Here is my dyno..remember..we let off after 7000 rpms.

 

do you mean that when the line is going down at about 6750 that you are actually still on the gas?

what is the max rpm of the stock pcm? isnt it like 7200 or so? i have never turned one that high so i wouldnt know what the sypmtoms would be if you reached the limit...maybe it just cuts out .

well hell, i just realized that its happening bfore 7000! nevermind...lol

 

yes, we are still in the gas at that point. Its start to studder..the car lunges..My aftermarket tach goes to 0..then picks back up when we lift off the throttle for the decel..the right bank O2 shows very very lean..but we can't reproduce that with the wideband.

 

I have heard stories of the Opti freaking up there but we have never experianced it our selfs. I twist mine to 7,000 with out issues. Hope you get it fixed man! Tired of seeing fast LS1 cars out there! The turbo car ate the pistons this weekend in licencing so he is out

 

what does the MAF GPS look like when it starts to break up ?

 

Tim, does your battery voltage drop (on the guage) when the stutter happens?

Your combo is making some good power for the problems! You went to LT4 heads right? Same cam?

Jason

 

its steady and consistantly climbing through the whole rpm range untill it starts to break up. Then its goes ffrom 425ish down to 370ish..then back to the 400s..then back down to the 370...then the run is over.

 

voltage stays steady

Yea..just changed to lt4 heads/intake. No other change to the motor.