i made 420rwhp 396rwtq last time at the dyno since then ive added a flowtech 3" cutout and a shaner s3 tbody and i went to the dyno and only made 407rwhp 382rwtq......my a/f looks a little weird at the beginning of the graph 2500rpms the a/f is like 14:1(which i know is lean) and its a steady angle down to about 12.8:1 at 6600rpms last time i went to the dyno it was pretty flat across the line at 13.2:1 or so......cutout closed it only made 399rwhp so thats down 20rwhp.....what the hell any ideas?

 

Any vaccum leaks?

Tired valve springs?

 

Was it the same dyno, is fuel pressure ok?
I would look into the A/F ratio, lean can ruin alot more than your dyno run.

 

987 valve springs w approx 5k miles on them.....were you speaking of exhaust vacuum leaks?.....graph indated not gettin any valve float.....i guess it would be easier to post a pic of the dyno sheet

 

did you happen to dyno at the TEA dyno day ? on the 31st??

 

nope we had a local dyno day.....ive always used this dyno so there is no dyno difference just different day....different correction factor

 

oh yea when i did 420 i had factory ws6 wheels with 275 40's on it, this time was with 18x9.5 z06 wheels with 285 35s on it......i know i didn't lose that much through the wheels and i was hoping that the cutout and tbody would at least soak up the loss for the wheels....regaurdless my a/f still looked a little funny...ill try to get a pic up soon, and ill be heading to the dyno for further tuning but before then i think i might give the lsx intake and a FMS cam a try then tune

 

I was thinking vaccum leaks on the intake side maybe with the new TB and that might be what was effecting the A/F.

 

what size cam? Fatigue on the 987s maybe?

 

X-ER 224 581 112+2 comp cam.....heads were at TEA approx 1500miles ago spring pressure was good.....and no valve float on the dyno....ill check for leaks in the intake area....where is a common place to find leaks(be specific)

 

I had the exact same thing happen with me (dynoing lower). I re-flashed the PCM right on the dyno with LS1_Edit and immediately picked up ~12-15 RWHP......no explanation!