rosscob

Since my 6.0 swap my truck has been stronger down low, but overall the truck is slower that with my 5.3. I finally got it on a Dyno so I could see where the power was and possible diagnose something.

The torque curve is wierd! It is basically flat 360ft/lb from 2500 - 5000 except for a bump in the curve between 3200 & 4000 where it jumps up to 385ft/lb. Then after 5000rpm it starts to drop off drastically.

Horse power make a nice steady increase across the rpm rage until 5000rpm where it also levels off and takes a dive.

I am running a comp cam 212/218 558/563 115. Since this cam should be good from 2000 - 6500rpm I thought mabye it was degreed incorectly when it was put in the motor. I re-degreed it and got identical dyno charts.

I'm at a little bit of a loss as to what to try next.

My thoughts are:

1. Possilbe Coil Problem. We were getting a wierd read from the DYNO when it was attached to one specific wire. My only problem with this theory is that I would think the PCM would alert us to that.

2. Possilbe Bad PCM? Once again the only reason I would suspect this is...There was some audible knock the other day, but no KR from the PCM.

3. Last but not least. Something wrong with the Cam. Just a bad grind.

Any thoughts and suggestions would be appreciated.

99Silver6.0

iTrader: (1)

You might be having some false knock issues. Have you logged at all to see what your active timing is along with any KR?? I had big time false knock issues till I replaced my PCM with one from an 02.

rosscob

Thanks for the reply. There is zero KR detected anywhere. That's part of the reason I suspect the PCM could be bad. At one point Allen was tuning and there was audible knock, but the PCM did not retard timing at all. the knock sensors didn't do anything.

99Silver6.0

iTrader: (1)

Maybe a newer PCM might be worth a shot.

rosscob

I have an '02 PCM already. I don't think I can go any newer, I might try a different one. The more I think about it the more I think that is where the problem is. Although it's the same PCM that the 5.3 was running great with.

99Silver6.0

iTrader: (1)

Oh. Didnt know you had an 02. But was the onset of this condition gradual or what?

rosscob

This is the way the has run ever since it was put in. Feels great down low, just not up on top.

fox_forma

i take it you did retune the PCM for the 6.0? Sounds odd that its ok down low but not up top.

rosscob

Nelson Performance re-tuned the computer for the 6.0. I'm pretty confident that the tune is correct.

I'm starting to get frustrated. Larger Motor & More boost, but less power than the 5.3L with Z06 cam.

budhayes3

iTrader: (19)

Is it possible that the fuel volume can't keep up with the increased airflow...maybe a bigger fuel pump is in order? just throwin an idea out there...