Using the VE vs RPM vs MAP table, You can adjust the amount of fuel the engine recieves, but then there's the AFR vs RPM vs MAP, isn't it possible for these two tables to conflict depending on how you have them set? Like if you have the VE table on a rich set but the AFR table is trying to keep 14.7 AFR? Which would overrule the other?

 

Both the AFR and VE tables are in affect at the same time. They do have different meanings. If the VE table is correct, then a change to the AFR table will result in the proper fueling change to affect the desired AFR.

Another way to look at it: in a perfect world, when the VE is correct, a change to the desired AFR (or commanded AFR) will result in the actual AFR to be the desired (commanded) value.

Another way to look at it: if the commanded AFR is 12.0:1 and it is actually 13.0:1, then something else other then the commanded AFR table is incorrect. The VE table has the greatest affect on bringing the actual AFR in line with the commanded AFR.

But at the same time there are other nuances such as IAT and spark advance that affect the "as seen" AFR. I say "as seen' because usually the AFR is measured after the fact in the exhaust.


The commanded AFR does nothing more then to change the injector PW relative to the volume of fuel. Command a richer AFR and the PW increases. Command a leaner AFR and the PW decreases.

It is the combination of AFR, injector flow, displacement, MAP, airflow, inverse temperature, and a couple of others that determine the final injector PW.

Which in turn determines the AFR.

Note that the others are mostly closed loop AFR terms...

RBob.