Just wondering about timing and AFR readings. I know that timing will affect BLMs, but not sure I understand it. It seems that more timing causes BLM's to rise. I don't understand. Seems that with more timing, fuel would be more fully burned, causing BLM's to drop.

Can anyone explain this for me?

 

Your guess is right, but if too much timing is added then you'll get incomplete combustion, so therefore O2 is sensed in exhaust and blms think motor is lean.

 

If timing is added and more fuel is burned, then wouldn't that read as lean? That would make the rise in the BLMs make sense.

If I am at 128, and I had more timing, then I am at 134, then I am now running leaner because of more timing.

 

Don't get too concerned with timing, just give the motor the timing is runs best with.

 

timing can effect indictate AFR to some degree, for a number of reasons.

Some being, if the timing is too late then the combustion is incomplete, and a false richness can indicated. Too much timing, and the manifold vac can be changed a little, and move the lookup point on the VE table.

BLs, O2 voltages, WB's, are all just indicators. And all can be fooled to some degree. And none taken as an obsolute.

 

This is exactly the part I do not understand. The sensor is sensing Oxygen. Timing is too late = combustion incomplete = less O2 burned = more O2 in exhaust - shouldn't more O2 in exhaust cause the sensor to read lean? I know it does not, so I 'm missing something somewhere.

Knowing what fools them will help me use (or not use) these tools better