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RB26 Rear 3 cylinders running slightly lean

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Hi all,

I have finally put my Haltech Elite into my GTR and have started some basic tuning. Very impressed so far, (bar a few trigger issues with the AEM CAS disk.. sorted now tho!) the thing fired right up!

Now, I have carried out some rough fuel tuning on the road and it looks as if my rear 3 cylinders (dual wideband NTK) are running slightly leaner than the front 3. I know the RB26 suffers from this higher in the rev range but I am slightly surprised to see this from idle to 3000 rpm. I would say there about a 5% difference. (see pic) Obviously, when I turn on O2 control, it sorts it right out. I am now planning on putting compensation tables.

My question is, is this quite normal on an RB26? or any engine with banked O2 widebands?

Big thanks in advance!


Attached Files

Just to make sure you don't have a sensor calibration issue.... What happens if you swap the O2 sensors? Does the lean follow the sensor, or is it unchanged?

Hi David,

I have just swapped them over and I am getting exactly the same results. Definitely not a sensor issue. Am I right in thinking the RB26 should be pretty well matched at low rpm? I am inclined to think my throttle body linkage needs re-calibrating...


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