I have a 2001 C5 with 8,500 miles on it. The stock dyno run was smooth and topped out at 309HP at about 5,500 rpm. I then installed: Vortex Ram Air box; Vortex Power duct; Corsa 3.5 Pro series exhaust; street legal X-pipe. The new dyno run was smooth up to 4,200 RPM and then eratic, droping 15 HP and topped out at 306HP at 5,000 rpm. My parts manufacturer is offering me no explanation of what could be wrong. I got the same dyno results 2 weeks later. Any suggestions?

 

Sounds like the mods caused you to go lean and you are getting KR cutting your timing and power back.

 

You need to see what the PCM is doing. Do you have access to AutoTap or a Tech II scanner? You need to see if you're getting knock retard, running lean, etc. If it's from a lean condition, it would show up on a dyno that has a wideband O2 sensor to show your a/f ratio. Did the dyno have a wideband, and was it hooked up?

 

Air Fuel looked rich on the dyno.
Initial ATAP record showed KR 4 degrees at 5000rpm. Will look at recording -
STerm fuel
LTerm fuel
KR
RPM
O2 sensors pre-cat
Anything else?
Dealer mentions a Knock sensor bulletin that could explain my issues.
Will post when data available, Thanks

<img border="0" alt="[Z06 Corvette]" title="" src="graemlins/z06.gif" />