Does anyone know what might be going on here? The car is a 97 Z, fresh built 383, mild ported heads, mild cam, A4 with a TCI 3500 converter and a STS turbo. Boost gauge shows 5~6 psi. I'm tuning it and am pretty convinced that the problem is not in the tune. The car just starts breaking up around 5200 rpm. I originally thought it was a MAF maxing out problem, but after getting the car on the dyno, I don't think it is now as the furling still looks pretty good when it happens. We are thinking it may be the spark blowing out. It does have a MSD Opti and a MSD coil, but no MSD box. I'm not entirely convinced it's a spark issue. Any ideas or seen something like this before?

 

Looks like blowing ut the spark to me. Mine did the same thing, had to go with different plugs and an msd box and it fixed it.
What r your plugs gapped at?

 

They are TR6s gapped at .030. I've seen those weird squigley graphs before on N/A auto cars with high stall converters and was wondering if it is somehow this has something to do with it being an auto with the turbo. Only other STS cars I've dealt with have meen M6s.

 

My graph looked like that when it was blowing spark out. I switched to the same plugs you have now. I also have a high stall. Stalls around 3800rpm. I also had the msd coil at the time. I installed a msd 6al and it cleared it up. You could try that and see if it works.

 

My vote is spark blowing out. Been there, done that. MDS or Crane box cured it. An auto with a converter doesn't cause that.

 

Hmm, a stock 96-97 ignition system should be able to easily support that much power.

Try graphing the run by power/none/speed instead of power/torque/engine rpm.

Sometimes you can lose some information graphing it vs torque/engine rpm if the inductive lead has any interference.

 

i donno bout it blowing the spark out, you should me making more power across the graph period. timing on? fuel pressure good? what size injectors? with my stock motor with sts on 3-4lbs i made close to 400RWHP but due to injectors it leaned out around the same spot yours did. i doubt you are maxing the MAF on 5lbs.

 

Here it is by power/none/speed. You can hear the car breaking up when it does it. It is not the dyno losing the tach signal.

 

The car owner said he has driven the car with a FP gauge at WOT and FP was 43.5 or better. The car has a MSD boost-a-pump. Injectors are 44 lb. I don't think it's a fuel issue as the A/F would respond to changes I would make in the program. Timing was at 26* when no KR would occur. Some pulls had 4* KR when we would start the pull and ramp down to 1 or less by the end of the pull. We are waiting until the car quits breaking up to turn the boost up and pull to higher rpms where the power should go way up. Car has meth injection too but was only armed on the last pull to see if it would make any difference and it didn't. A MSD 6AL box is being installed probably going to try a different plug too. If that doesn't fix it I'm out of ideas.

 

ok that makes more sense now..... umm is the knock false knock? i doubt that is the reason but my timing was around 35 if i remember right with no knocks but i do have a bad memory. thats defently a tricky problem for sure. wounder what would happen if you were to dyno with no boost? sorry im unabel to help but when you figure it out could you let us know? when i get back home il be putting in my 383 with the sts kit...

 

Just an update. I spoke to the car owner today and he said when he went to change the plugs, he realized he had put in TR6 Iridium plugs. He installed a set of regular TR6 plugs gapped at .030 and now the car pulls fine up to the rev limiter. What can I say, I'm just the tuner. I'll update again when he brings the car back to re-dyno it.