Gen2 CTSV falling on it's face

[camarochevy1970]

Folks, working on a V that at about 4300 RPM falls on it's face every time. On the dyno chart, it actually has almost a straight line drop of about 60 hp/tq, and then the curve rides out to the end of the pull, however isn't nearly as smooth as it should be. I have attached a tune and a log from one of the pulls. I can't see what is happening.

It pulls real well up to that point, making 588 ft lb and the hp is on pace to hit 600

Mods are:

2.5 upper pulley
heat exchanger
cat delete pipes
btr stage 3 cam and valve train
airaid cai
ngk tr7ix plugs
msd wires

[SultanHassanMasTuning]

^your a little on the rich side, i would like away 5% past 9000 MAF hz and up.

also as your going up in RPM your dropping in timing not the right way

also under speedo limiter change from GMLAN to Calibration. I believe your throttle body is closing as your commanded shift is set to 6500 but your power is killed at 6200 rpm.


report back after

[camarochevy1970]

ok will try those adjustments. That is basically the stock timing table, as I haven't been able to make a clean pull to really do anything. My power is actually getting killed at 4300 rpm according to the dyno though, I am lifting out around 6000 for the pull

[DSteck]

I'd bet on a mechanical issue with the drivetrain. That's based on not seeing the log though.

[camarochevy1970]

What mechanical issue would cause it to fall on it's face and drop hp/tq like that at the same rpm every time though?

[DSteck]

Valve float has done it on stuff for me in the past.

[camarochevy1970]

yeah I kinda thought about that. I was hoping the BTR springs were good enough to prevent that (.660) lift, but have never seen it on a log or dyno screen to know what it looks like

[KLR CADI]

What injectors are you running? There is a weird spike in clyair and MAF at 4300, but nothing throttle/MAP wise to suggest why. Your MAF curve is pretty rough an can use some work, but looks fat enough up top. That cam should be plenty of top end pull and really coming alive @4300 and springs should be good since its not monster lift. What does dyno look like?

[camarochevy1970]

Injectors are Siemens 63lb

Maf curve isn't fully dialed in yet, as I havent finished tuning due to this issue.

I will see if the dyno operator can post a picture of the graph, but basically it is a nice line for both tq and hp right to 4300, then it straight line drops 60hp/tq in about 100 rpm, and then the curves flatten out again, although not as smooth

[camarochevy1970]

Any other thoughts guys? Sultan suggested maybe I am hitting the p0068 limit. Other then adjusting that and his other items in the tune, anything else give clues to why power would cliff dive at 4300 rpm?

[DSteck]

I don't think this has anything to do with the tune.

[camarochevy1970]

Dave, outside of valve springs, anything else you can think of mechanical that would cause it?

[basa]

I'm a big noob at hptuners still but comparing your file to mine it looks like your code P0068 is still enabled. I had to raise mine.
Just a random pic I found online of what I'm talking about.