LT1 cylinder trim

[myburb]

I didn’t want to piggyback on the estate wagon thread so a separate topic. Am I correct in thinking the individual cylinder trim is just a trim figure gm puts in to compensate for individual runner flows and is a fixed number and not changed by o2 corrections. The reason I look at that is I couldn’t see how 4 cylinders could be individually trimmed with one o2 sensor.

[NomakeWan]

You are spot on. They are a multiplier for individual cylinder fueling versus the VE/MAF table. You can tune them with individual wide bands or using an IR temperature gauge to check head temps. Or just leave them alone. ;)

[myburb]

Thanks for the reply. As I said I am obd1 so don’t want to fill other topics with my questions. How would a snapon scanner be able to identify individual cylinders rich or lean? I could see it saying a bank was over all rich or lean but don’t see how it could pick out individual cylinders. Any schooling would be appreciated.

[NomakeWan]

Your scanner cannot do what you are asking.

The only way to tune these trims yourself would be to weld in bungs for every cylinder’s exhaust and install wide bands, or to use a thermometer gun to tune the trims based on head temperature (try to make all cylinders the same temp, which should correspond to same fueling).