finally got a good dyno tune (thanks to D'agostino racing in fort lauderdale!) and there is a strange dip from 5400-5700rpm where power drops a bit then picks back up to fall off around 6200.
car did not hesitate or any other noticable symptom at that spot, but it shows up on the graph.
A/F was right on perfect throughout that whole range, so i dont think its that.

2 issues they noticed

wide open throttle, should there be vacuum in the intake???
the tuner said he noticed a bit and that it might indicate that my air intake is causing a restriction (slp dual tube cai, possibly a bit dirty but not real bad)
is that cai known to flow less than others?

one sides valve train sounded louder than the other, possibly need to make sure its all adjusted properly?? the car did sit for about 1.5 years from when i assembled the engine, just had short 20-30 mins runs once a month to keep it lubed up.


im pretty happy with the torgue curve, it starts low and strong and keeps goin!
pull was on a very humid hot evening.

dyno graph

 

Valve spring harmonics?

 

how much vacuum are you measuring? does oil pressure do anything weird at the point of the dip?

 

Here are the SAE #'s with the a/f, found it on a local f-body site.

so you can see the a/f is fine. Was there any knock retard on any of the pulls?

 

lol, what site was it on, i didnt even know about it? (cant see the pic, work firewall filters it out)

there was false knock when they started tuning but he said he tuned that out, its not happening up top and its not pulling timing that i know of.

 

dunno, i didnt ask what the measurment was.

oil was fine if i remember, next time i do a full pull ill watch the guage.

 

well i think the air restriction was a seperate problem, if that is happening it would be hurting performance across the entire band, so the dip would still be there from something else.

 

Are you running an Auto or M6? If an auto, can it be the converter locking up?

 

its an m6

 

It depends how much vacuum you are pulling, any street car is going to show some vacuum in the intake manifold, and Nory is obsessed with the vacuum thing, he seems to think K&N filters are a huge restriction. My friend with a 93 hotcamed camaro took off his SLP intake at the track (speed density so no MAF) and was just running an open throttle body and didn't gain anything.

 

Oh yeah its posted on www.sffba.net

 

clutch slip?

 

mmm, good thinking..........its possible.........its a brand new Spec Stage 4, and it was broken in 500miles atleast, so i really hope not.

if it was clutch slip tho, it probably wouldnt pick back up with higher power. my experiences with clutch slip, once it starts slipping up top it just drops.

 

That looks like a timing issue. You need to make sure you aren't getting any false knock or real knock. If you aren't getting any knock retard, make sure the timing curve is smooth through that area. Did you make more than one dyno pull? If so, was that dip there in the same spot on every pull?

 

Looks like valvesprings to me.