What exactly are BLMs based off of, as in, what factors into a BLM? How do I know they are accurate?

 

Up in the sticky's in the Tuning Guide Book thread. Look for the '8063/'8746/'7747 section. There are links to several articles one of which is fueling.

In a nutshell, the BLM will be as accurate as the O2 sensor. There is a set point for the O2 sensor voltage that the ECM targets. If too far from that set point the INTegrator moves. Once the INT moves away from it's set point of 128 the BLM will move.

As the BLM moves the INT will return to it's set point of 128 (+-).

RBob.

 

I think you might be asking for "what to change" to make BLM better. VE table (volumetric efficiency) is key. Lower VE makes BLM go up. Higher VE makes BLM go down. You'll know they're pretty accurate if you're able to hold a specific RPM and MAP for an extended time, during the same intake air temperatures and engine coolant temperatures. You'll also need your injector size/cylinder displacement correct before you start tuning.

 

Still Using the 749 ECM and $58 making better improvements each time. I restarted with a Fresh one to get the tuning back in order. I know the car is running really rich and I have discussed with you about INT & BLM. Something else that I have discovered. The BLM's won't move until AFR is learned. It will continue to stay at 128 no matter where the INT is until AFR is learned. Is this normal?

I was having a problem with the check engine light coming on and using the Snap-on scan tool it was telling me either TOO RICH.. So using the VE tables under F29c, I dropped the 600-1000 RPM range watching INT until it was faily close to 128. Low and behold the check engine light doesn't come on any more at idle.

I have the INT adjusted now using F29c Closed Blade throttle and it stays from between 125 -131 and it goes into closed loop within 30 seconds. Then within a few seconds later it learns AFR.

Then I adjust the F29 VE tables to get my BLM's to 128. I did have to drop both of this quite a bit also. I still have to get out and tune for higher than idle consistant RPM and Map.

What I am asking does it look like I am on the right Track?

 

Yeah, sounds like you've got the process right. Good luck! When you say "learn" I'll assume you mean it has reached stoichiometric, and the O2 crosses the middle, which is a sign of INT. BLM is the block learn multiplier, but I guess you could call it the remembering multiplier, hehe. BLM is the slow learner, but doesn't forget.