Zach, USM

<ul><li><a href="https://forums.audiworld.com/s4/msgs/971091.phtml">bov</a></li></ul>

QCRAZY

If you notice all the people Dan claim use BOV's are racers. There's a reason for this. You can use BOV's safely in two instances....

1) MAP sensor systems
2) Cars w/o cats

The racers fall in #2.

It's known that using BOV's on an MAF car (like you have) will cause an instant rich condition when the BOV is used. This is simple to understand since you are losing metered air. A loss of metered air will cause too much fuel.....i.e. rich condition.

This rich condition can easily be seen in the racers that he mentions. If you ever watch a race at night you can see flames come out the back of the exhaust on these cars right before corners. This is essentially the rich condition. The extra gas is being burned off in the exhaust.

There is simply no way around this rich condition with an MAF system. The reason that it's okay for racers is becasue they don't have cats.

However, you have cats!! This means that over time you have the possibilty of ruining your cats. The extra gas will get burned up by your cats causing them to get too hot and melt. The result can be a cat that ends up being a big cermaic mass that allows no flow!

IMHO, BOV's just don't make sense on an MAF equipped street car.

Zach, USM

I do understand that thought since the car is looking for the metered air and it's in the atmosphere.

I do realize that causes a problem but the car has been running great...except for the gas mileage due to me running so rich.

Singletrack

The bigger issue is long term fuel trim from what I understand.

People have run BOVs without any CEL (which would come on if they were running rich). I just don't agree with the whole methodology, of throwing them on there and then tweaking it so it "works".

I have yet to see ANY logging of a 2.7T with BOVs. I'd love to though.

-st

Singletrack

There needs to be logging done with them of various blocks in various conditions. This will put all these various arguments to rest once and for all : )

-st

QCRAZY

The 2.7T uses an MAF system not MAP. Therefore, BOV's don't work (as well) on this type of system!!

Singletrack

Actually it uses a MAF and a MAP. Pressure sender G31.

QCRAZY

The MAP is just used a pressure sensor. The MAF is used for fuel injection.

Singletrack

value. So it CAN adjust based on what it is actually seeing. That's why people say it affects LTFT when you run BOVs.

-st