Help: I have a weird issue going on with my car. I currently run open element cone filter, tbe, test pipe, and mbc. My friend helped me tune the car to around 325 whp at 22.5 psi. We tuned the afr to 11.7 target from 3500-6500rpms with it tapering to 11.2 6500-7500 rpms. Here is the weird thing, my AFR from 3500-5500 rpms keeps getting a whole point richer (10.6-10.9). Last time this happened we adjusted the afr leaner in that range and then got knock. So we just reflashed with the original tune with target afr of 11.7 and viola my afrs were back to the targets. Now two weeks later my afr is in the 10s again from 3500-5500 but I have not adjusted the tune and am using the same fuel (shell 93). The really odd thing is my afr is only affected in the 3500-5500 rpm range after 5500 rpms my aft is back to the target. Any ideas? We used ecuflash to tune and evoscan to log. I have a innovate lc1 wideband.

 

I'm in to see what kind of feedback you get. I've seen similar before but not to this extent.

 

Was lean spool left on?

 

Probably related to the mid load fuel trim being used under 1600Hz.

Or lean spool issues.

Or potentially continuous knock causing enrichment?

 

What's the midload fuel trim?
We disabled lean spool After a certain rpm. My friend who helped me tune doesn't think it's leanspool because it's disabled during that rpm range

 

Mid Airflow HZ cutoff point is what he is talking about. There are a few posts about it here and a post specifically related to your point (is your LTFT Mid changed from when you tuned?)

Also, you could simply have a leaky BOV at high boost causing your problem.