I'd like to see what a Wideband says. Your injector duty doesn't seem to be quite right on the RPM climb. The whole harmonics thing does hold true to some extent but I don't know if it could cause these kinds of issues. Being that it's a new(er?) crate LS1 I'm inclined to blame it on the harness. I had all sorts of crazy issues when I swapped my LS1 into the FD. Given the frequency and voltage of the wires to the coils packs a break up of some sort seems likely.

 

is it pulling timing? like a knock sensor picking up on the vibration/harmonics from the pulley

 

I gotcha.....good luck with it. At least its somewhat predictable so that should help as you try to track it down.

 

We didn't have the wideband logging this time at the dyno, but in the past, it's just gone a little rich.

Not pulling timing. HPTuners doesn't show it pulling timing and we also put a mark on the pulley and watched it with a timing light through several pulls to make absolutely sure that timing wasn't changing when it broke up. It wasn't.

I still have absolutely no explanation for why Orion's known-good coil packs cause my engine to break up like crazy... and that's bothering me.

 

Did you do the crank angle sensor relearn procedure after you replaced the part?

 

We did not do the relearn. What's involved in that?

 

We haven't had time to put an oscilloscope on the car, but I went back and looked at some hpt logs. We logged 'cam signal hi to lo', 'cam signal lo to hi', and 'crank sensor current cyl'. Does it make sense that 'crank sensor current cyl starts' to count down around the start of the pull (TPS 100%, MAP 100 kpa) and the cam signal transitions stop counting around 4100 rpm and doesn't come back till after the pull? This was on a dynapack with the starting rpm set to 3000.

I attached one of the logs. There are other points where this stuff happens and it looks somewhat correlated with throttle input.

 

WOW weird problem. Hope you figure it out soon. I hate litte **** like this

 

Breaking News!!!

Because the problem is really exhibiting the symptoms of early valve float and because these other guys have demonstrated that cheapo U/D pulleys can cause the issue, I went ahead and pulled my front pulley so I could replace it with Orion4096's pulley straight off his crate LS6. Well guess what????



Which of these is not like the other? That's right, I have either a:

- truck pulley or something designed for another application OR
- a cheapo Chinese knock-off

You can see the casting texture on the (current) pulley on the left. The one on the right, off the LS6, is significantly lighter and has a MUCH larger rubber ring between the inner and outer sections.

I'm still holding my breath, but I think we might have a winner! I won't get to test it on the track for almost two weeks, but I'm totally fired up to find something suspect with the pulley.

Cheers,

 

It was the pulley! I haven't had the car to the dyno to be 100% sure, but I had the car at the track this weekend and it pulled cleanly right up through 6000 rpms after I put on the RIGHT harmonic damper/pulley. Damn. Who would have thought it would be that "simple"?

Thanks for all the help, guys, and I'll be sure to post back once I get it to the dyno and confirm that the HP plots look good and the problem is completely solved.

Cheers,

Dean

 

Good to hear it's fixed.

Seems lots of guys having trouble with high rpm break up using UD or different crank pulleys.

 

Awesome, That is great to hear! I am happy for you man. Little stuff like that can drive you crazy. I know how you felt.