I am tuning a new minirammed 383 with a fairly aggressive cam for street (236/242@.050, .560 lift, rhoads v-max lifters). I am using TunerPro RT, an arap bin as a starting point, and a widband to verify tune. This is a completely different tune than my last superrammed engine. I have the car running well with near perfect driveability but I am still having an issue that I can't quite figure out. At certain points, especially low cruise, the WB averages about 13.9:1 rich but my BLM's are pegged high showing a perceived lean condition. The BLMs never ever drop below 128. I am thinking I should focus on the Rich/Lean Threshold vs. Airflow table and lower the voltage readings, which I have done somewhat to achieve a WB reading of 14.6:1 for idle but the persistent high BLM's are confounding. I just replaced the stock NBO2 so that should not be the issue. Am I barking up the right tree or perhaps someone who has dealt with this issue before could steer me in the right direction. Maybe MAF Scalar? Thanks.

 

yeah that's what i thought. man, i miss grumpy...

 

Low cruise as in low load cruise? If so there may be reversion due to your cam and lack of vacuum. ECU may be adding gas unnecessarily hence the high BLM. In fact may be adding more than BLM can report. I trust the WB being accurrate.

What does the BLM look like under load?

Try running OL for a test to see how it runs without BLM feedback in that same area of low cruise load?