I've been playing around with CATS, what's BLM and usec?

-Mark W.
<A HREF="http://www.angelfire.com/al3/thegreycar">'88 SC Camaro w/ 305 TBI</A>

 

BLM is block Learn multiplier

It is Long term fuel trim. Values range from 0-255, 128 is perfect +/- 5 is where you want to be. The range of 0-128 and 128-255 are equal to 100% add or subtract fuel. High numbers add fuel due to a lean condition; low numbers subtract due to a rich condition.

How BLM works: One BLM value is stored in the ECM for each cell in the fuel table, and fuel is therefore modified.

How BLM is calculated:
The oxygen sensor constantly fluctuates back and forth across 450 or 500 mv (I forget which) the ECM counts these, you may notice a monitor named "cross counts" You should also notice the Sensor voltage as displayed fluctuating as I said, each of these values is added up and averaged using cross-counts... thus giving an indication of rich or lean, this value is represented as the "Integrator" or short term fuel trim again, a 0-255 monitor with 128 as the value that equates to 14.7:1 air/fuel ratio. BLM is Calculated from the Integrator.

Use BLM as your tuning aid for part throttle / idle closed loop operation. Use this value only when the integrator value is at or very near 128.

 

usec is "Micro second" - the measurement of the time of a electrical signal.

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Hank
87'IROC Z28
Hanks 87 IROC