If I understand this correctly:

a) The MAP signal that is sent to the ECU to show a zero reading for boost/vacuum. This is done either via check valve or ESM (in my case) to cap the voltage at 2.9 volts.

b) The V-AFC achieves the leaning and richening of fuel by modifying the MAP signal.

c) If you go to the plus range on fuel with the V-AFC, you will move the MAP signal above 2.9 volts thus letting the car see boost. It may not be enough to trigger a CEL, but it may be enough to make the car not run right.

Can somebody please validate these points for me?

TIA
-YS

 

That's correct. Thats why some day you can't really tune full throttle with a VAFC. However for most uses that a VAFC sees (N/A) you typically want to lean out not add fuel, therefore it is still functional.

VAFC for forced induction is not a good idea because you have to rely on a fuel pressure regulator to compensate for the fact that the ECU does not actually know what the engine is doing...... <rinse/repeat go get a standalone argument - god I feel like a preacher>

For example if you're at 50% throttle, the VAFC will see full throttle because you're in positive manifold pressure, but you're not necessarily at full boost. If you're always going to be in vacuum or full boost then it would be OK, but this isn't always the case. Anything in between is a grey area which depends on some guesswork and your fuel pressure regulator.

Chris

 

[QUOTE]Originally posted by cjb80
[B]That's correct.

 

how in the world can this happen? VAFC reads TPS and MAP separately!