Originally posted by Zoomer
Ahh, apart from the rice factor of installing a BOV that vents to atmosphere.
You will throw out the A/F ratio during gear changes.
If you vent the BOV to atmosphere in an XR6T you won't affect the A/F on gear changes. The MAP sensor is mounted in the manifold after the throttle body. The PCM uses the reading from this to calculate how much air is going into the engine, once it knows how much air is going into the engine it knows how much fuel to inject. If the BOV doesn't affect the manifold pressure then it won't influence the air fuel ratio. Whether the outlet from the BOV is plumbed back or vented to atmosphere the MAP sensor can't see it so it doesn't care. MAP sensed cars are therefore quite immune to air leaks in the intake ducting.
, if your cars has a MAF (mass air flow) sensor, this actually measures the amount of air going into the engine. It is normally mounted before the turbo, so if any of the air going through the MAF doesn't make it to the engine (because it is being vented by the BOV for instance) the PCM doesn't know this and still injects the full amount of fuel, causing the richness. MAF sensor car don't like air leaks at all, but make things like EGR calibration easy, but that's another story...