Quick list of mods to date: Corsa Indy, Donaldson Intake, LS6 Manifold, LAPD Airbridge and a MAFT... Thats it.

Anyway, to get to my problem. I took the C5 out for an auto-tap run today to tune it with the MAFT. From 2k-4k everything was perfect:
2k-4k RPM
29 deg. Timing
0.0 knock
-1.3 short trims
.870-.880 O2s

Then from 4k-6.2k the knock came on like a hammer
4k-6.2k RPM
Down to 21 deg. Timing
up to 5+ degrees of Knock
-1.3 short trims
.880 O2s

Dont know what to check first. The exhaust seems pretty solid and with the exception of the knock/timing everything else was fine.

Running TR55s gapped at .5 with MSD 8.5mm wires (less than 200 miles on them). I threw on the LS6 intake and MAFT last night, but didnt get a chance to a-tap it before the install. Either way, the manifold and MAFT shouldnt cause knock if its not running lean, right?

Anyone have any ideas?

Thanks,

Mike
00 C5 Hardtop

Previous ride:
(MikeWS6)
98 WS6 Ta M6
ARE Stage II Heads, TR224 on a 112, grotts, and all the other bolt ons.
407 RWHP
380 Torque

 

This is actually a Computer Diagnostics and Tuning section question. I'll transfer it after I reply.

You are still running catalytics on the car, and they do promote some detonation, especially with the cast exhaust manifolds which retain heat in the system.

I'd recommend:

-Installing a 160F T-stat to cool the engine a bit
-Adjusting the MAF-T so that your O2 readings fall between 0.890-0.900, and if that still shows KR, go ahead and richen it a bit to 0.910 range. Don't worry so much about STrims, keep an eye on the LTrims and get them as close to 0 as possible. +/- 5 on LTrims is okay though.

Tony