Blow-Off Valve installed !!

**mitch_gti** · 13-03-2008, 08:58 PM

Originally Posted by ryan_GTI

i'm still on p's

Copy that

**Spec83** · 16-03-2008, 05:34 PM

Originally Posted by Kai

A plumback bov will always be better then atmo.

You are keeping more air in the system...

Depends if your car runs a MAP or MAF sensor

**Kai** · 16-03-2008, 06:41 PM

Originally Posted by Spec83

Depends if your car runs a MAP or MAF sensor

why

.....

**WHTPOLOGTI** · 16-03-2008, 10:45 PM

any video of it on youtube yet?

**Bubu** · 17-03-2008, 12:30 AM

Originally Posted by Kai

why

.....

Its quite simple really. But first you have to understand what each one means.

MAP = Manifold Absolute Pressure

MAF = Mass Air Flow

A MAP sensor meaure the absolute pressure in the manifold to determine how much fuel to feed the motor. Therefore if the BOV vents to the atmosphere completely the MAP sensor will not detect the air and will not feed any fuel. On the other hand if the BOV is not an atmo then it will detect the air and it will give fuel as requiered.

The MAF sensor meaures the amount of airflow going into the engine, just after the air filter. Turbo cars that use a MAF sensor have the ECU programmed to feed extra fuel when the throttle is closed and the BOV has been opened to compensate for that air that is being re-fed into the intake from the BOV. Its important to note that the air from the BOV is fed into the intake after the MAF sensor. Therefore the ECU assumes that the air from the BOV is going back into the intake and has no way of knowing that the air has gone to the atmosphere. Because it assumes that the air has gone back into the intake it compensates by giving the engine more fuel so that it does not run lean. The car ends up running too rich for that brief moment and thats why it creates problems.
Factory turbo cars have the ECU programmed this way because they dont expect you to change the BOV to an atmo unit as this is against pollution laws in most if not all countries.

Obviously there is more to it than just that, but we wont get too technical to answear a simple question.

**Spec83** · 17-03-2008, 08:46 PM

Spot on explanation Bubu... it is also why you hear a number of wrx / sklines / silvias et al backfiring on gearchanges due to the engine running very rich and not completly burning all of the fuel...

Can also cause O2 sensor and cat converter issues in the long run