HardcoreRM125

Hello,

Just getting started tuning. And I am having a difficult time understanding my split BLM issue. My car will have very closeLeft and Right BLM's in one cell but EXTREMELY far off in others.

Example:

In BLM Cell 16 (idle) I usually read around the following:

BLM Left - 128
BLM Right - 154
Integrator Left - 128
Integrator Right - 128


In BLM Cell 12 I usually read around the following:

BLM Left - 128
BLM Right - 128
Integrator Left - 133
Integrator Right - 134

In BLM Cell 17 I usually read around the following:

BLM Left - 126
BLM Right - 126
Integrator Left - 128
Integrator Right - 128

In BLM Cell 18 I usually read around the following:

BLM Left - 118
BLM Right - 149
Integrator Left - 123
Integrator Right - 123



So what can cause split BLM's to be intermittant?

Thanks,

Joe

HardcoreRM125

FWIW - I've noticed Cell 16 and 18 giving me the trouble. Other cells the BLM's are not split much at all? What the hell? Anyone?

bobdec

Joe, I was waiting for someone with more experience with highly modified setups to chime in. My setup is mild and I don't experience split BLM's at idle, but I have read quite a few posts about bigger cam'ed cars having this problem. It's a problem with the cam overlap causing erratic exhaust characteristics and/or erroneous O2 readings at the lower operating speeds (BLM 16 TPS=0, speed =0 & BlM 18 TPS=0, speed > 0, RPM below 1000). Sometimes takes modifying the TPS Closed timing (Upping to 30-32 or so degrees in the 400-1200 RPM blocks). If it's cam LSA caused it should go away as the RPMs come up and the CAM kicks in. Key is to get the idle smoothed out as much as possible using air flow and timing, the assumption is you do not have any intake or header leaks. If so they need fixing first. Also if all else fails there are the individual cylinder fuel trim settings that are used during low RPM operation , but that s/b the last resort.