DV Question

[SteveS]

its been buggin me because... i dont know the answer....

a dv valve. ok, it puts the air back into the intake before the turbo when foot is released from pedal...
blow off valve/spacer... just blows it into the air...

isnt a blow off valve bad for the car? or is it? better to have a dv to recerc the air?? 

[ub7rm]

AFAIK a blow off is bad because the various sensors are aware that a certain mass of air has entered the system, and if its just blown off to atmosphere it appears to the ECU that this air has just vanished so you might get error codes indicating a boost leak or similar.

I know that people fit the blow of valve to the 1.8T's and they seem to run OK for a while but then folks have problems when the ECU goes into limp mode.

HTH

[AlanD]

To my knowledge the only thing a blow off valve does is make your car sound like a Scooby

[SteveS]

i know they just make a sound, but wasnt sure if they actually affect the car...

i know the MAS monitors the air from the intake... but if the dv just drops the air, how would it know?

[vRStu]

Any air after the MAF is metered, either by the MAF itself or the MAP (Manifold Absolute Pressure) sensor.  Some cars deal with the loss of the pressure better than others and the more common reason for a VTA (Vent to Atmosphere) type valve is to alleviate turbo stalling.

1.8T's really don't like it.  The 2.0TFSi isn't so bad but on the TFSi it's nothing more than a noise maker.

[SteveS]

on the TFSi it's nothing more than a noise maker

so it doesnt affect the performance or errors? i know it wont do anything but noise.. just curious.

[SteveS]

...

[neg]

It has something to do with putting air back to the turbo to keep it spinning so when you back on boost it can react quicker, dumping air out means the turbo will have to spin up again wasting time/power - something like that anyway...

Plainly the 1.8T and 2.0T have been designed to re-circ the air unlike other TC'd cars so its best to keep it that way.

[RedRobin]

Plainly the 1.8T and 2.0T have been designed to re-circ the air unlike other TC'd cars so its best to keep it that way.

....Exactly! Isn't it even called a Recirculating Valve now?

[SteveS]

It has something to do with putting air back to the turbo to keep it spinning so when you back on boost it can react quicker, dumping air out means the turbo will have to spin up again wasting time/power - something like that anyway...

Plainly the 1.8T and 2.0T have been designed to re-circ the air unlike other TC'd cars so its best to keep it that way.

I understand, however DOES it ACTUALLY keep the turbo spinning, if its just put back into the intake, then its not exactly pushed into the turbo to keep it spinning....  i know thats the idea, but is it fact!