Since I've seen this problem mentioned a few times on here, I thought I'd give my fix.

I have a stock engine, but was still seeing split BLMs at idle and part-throttle (around 2-3).

Well, I had a look at the individual cylinder fuel trim tables and noticed it biased the left side of the engine to be richer (which my BLMs reflected).

I made both sides of the engine the same. For example, where #1 was 1.05 and #2 was 1.06, I made them both the same; actually lowered both to 1.03.

Now my BLMs are even on both sides. Hope this helps someone else!

 

Thanks for the input. I myself after the porting assumed that there is no way these individual fuel trim cells can now be correct as stock so I put them all to 1.0.

I too have split BLM's of normally 2-3. Has anyone ever heard of any of the cylinders normally on a LT1 being a bit more starved than the others? I just wonder why the factory stock is not at 1.0. Seems strange unless there is a standard bias within the engine to feed other cylinders a bit less/more than others. A typical bias would be nice to hear about.

I would like to eliminate my split, but is it split because the calibration is off on my 02's, do I have a plugged injector? Many causes could account for it.

Ben

 

I think the front two cylinders tend to run the leanest and the rear two the richest. Then the middle two are somewhere on that spectrum.

I played with these tables back when I first got TC but never noticed much of a difference. Probably because I had other issues masking it (ignition).

 

What makes you think this about the cylinders? If you have heard of something somewhere, I shure would like to know. I really don't want to be starving any of my cylinders if I don't have to.

To me this is very valuable information. I have actually contemplated putting a bung in each of my exhaust pipes before they come together in order to truly see what each cylinder is doing with AFR.

Ben

 

It's a combination: it seems logical to me that the closest cylinders to where the air enters would receive the most air.. and the farthest ones back would receive the least. I believe I've also heard this from people running big power adders... that the front two tend to go first from more power being made there.

Also, the stock PCM has more fuel going to the front two cylinders, intimating that they are receiving more air.