Wierd HP curve . . . ideas?

[1BADAIR]

do not use hardened push rods with stock valve springs

[balz2dwall]

The valvetrain is bone stock . . .
I use high octane fuel and always have . . .
I've used octance boosters and even unleaded 100 and I still get detonation in the higher RPMs . . .

Also, it is bonafide detonation and not knock (i.e. rod knock) and its not piston slap? (or something like that) . . . The guy who was gonna tune the SS put new plugs in and showed me the tiny pieces of piston that had clung to the old plugs caused by detonation . . . and now that I think of it, if he had noticed what cylider the fouled plug had come from . . . *sigh*

What ticks me off is I've practically got the whole suspension rebuilt and I put in the 12-bolt last year when the stock POS rearend broke and I've been ready for some hard launches at the track (I got to race it at Infineon Raceway (Sears Point) back home once before the rear end started to go and never got to test out the new 12-bolt and new drag radials). It's been a depressing couple of years.

[balz2dwall]

Ok, some more info on A/F ratio . . .

Apparently, the stock A/F ratio @ 5100 RPM is supposed to be 12.3, which the table shows. However, the table just simply shows what the PCM is set to run @ 5100 RPM. The A/F ratio at 5100 was actually running between 12.8 and 13.0 on three seperate pulls on the dyno shown by the dyno's air sensor and computer . . .

So, the PCM thinks everything is perfect, but somehow the engine is leaning out and its not being picked up by the PCM . . .

[1BADAIR]

the 02's aren't used at WOT so the computer doesn't care whats actually happening.

wot tuning is usually 12.8-13.0 so your car isn't lean.
Your PE tables probably say 12.3 but many things can affect it. 12.3 commanded and 12.8-13.0 actual is about right.
A wideband O2 on a dyno is much more accurate than the cars 02's.
The narrow band o2's are only accurate right at 14.7


Does the car use oil? Oil cause's bad detonation.
You had EFI live, whats the timing tables look like?

Does the car loose more and more power the longer you drive it? I have seen clogged cats cause detonation

[balz2dwall]

the 02's aren't used at WOT so the computer doesn't care whats actually happening.

wot tuning is usually 12.8-13.0 so your car isn't lean.
Your PE tables probably say 12.3 but many things can affect it. 12.3 commanded and 12.8-13.0 actual is about right.
A wideband O2 on a dyno is much more accurate than the cars 02's.
The narrow band o2's are only accurate right at 14.7


Does the car use oil? Oil cause's bad detonation.
You had EFI live, whats the timing tables look like?

Does the car loose more and more power the longer you drive it? I have seen clogged cats cause detonation

Yeah, it uses oil . . . I never really measured how much, but I probably add about 1/2 to 1 quart between oil changes . . . The last time I took it in to the the shop was because it was throwing a code . . . bad cat on one side . . . I had them replace both cats and rear O2 sensors, those are about a year old now. It does seem to be loosing power as time progresses. The detonation is also worsening (bad plugs again, maybe?) . . . I need to take it in for a tune-up anyhow . . . maybe I'll just have them check the outer valvetrain for any problems while they're at it. I would love it if I still had EFI Live . . . I traded it to a co-worker back in California for a set of GM chrome 10-spokes rims with only 3000 miles on them and a half worn set of Nitto drag radials.

[SS4Matt]

it's an easy task to pull the coil packs/bracket, pull the valve covers, take the rockers off, take all the pushrods out and check them out along with the springs,

i think i clogged cat would make the car act sluggish all the time rather then just at a certain RPM, however, since your in MI now, take those effers off anyways! an air hammer to the cats inners does wonders, or hell do the "my cats are bad so i must need long tubes now" excuse...

sucks your on the other side of the state, as one of our sponsors Sean@C.A.R.S. coulda fix your problem and tune your car in a day

[balz2dwall]

sucks your on the other side of the state, as one of our sponsors Sean@C.A.R.S. coulda fix your problem and tune your car in a day

Back home I used to drive almost 2 hours to get the car worked on . . . and since it only takes 2 hours to cross Michigan . . .

[kammi10]

seriously take it to sean at cars. he is awesome when it comes to these cars

[wasjo6431]

it could be lots of things.
monitor your Fuel Pressure when you go to high revs. make sure you dont have a clogged cat. your TB is clean.

and do a tune up.