The AUSubaru.com.au Forums

chubby37 · Post by **chubby37** » Sun Jul 09, 2006 11:22 am

just woundering do they really do much.??is it worth running one.

tim_81coupe · Post by **tim_81coupe** » Sun Jul 09, 2006 12:35 pm

A BOV releives the pressure buildup between the turbo and throttle body that occurs when the throttle is snapped shut. It is definitely worth running one, they can increase the longevity of the compressor wheel (as there is no air rushing back against it) and they also reduce lag between shifts.

My personal preference is the plumb-back type, I am not a fan of the atmospheric 'pssht' noise. Either will work as good as the other, however on a MAF controlled vehicle the atmospheric type will confuse the ECU resulting in a momentarily rich mixture.

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Sun Jul 09, 2006 1:03 pm

As explained above they do perform a task in protecting the turbo, what are you going to put a BOV on Bill?

daza · Post by **daza** » Sun Jul 09, 2006 8:37 pm

Actually, a BOV is a type of wastegate that vents to atmosphere normally via a trumpet, the only difference between a BOV and the wastegate factory fitted to your car is the wank factor of everyone hearing the BOV...
Daza.

tim_81coupe · Post by **tim_81coupe** » Sun Jul 09, 2006 8:53 pm

daza wrote:Actually, a BOV is a type of wastegate that vents to atmosphere normally via a trumpet, the only difference between a BOV and the wastegate factory fitted to your car is the wank factor of everyone hearing the BOV...
Daza.

No the wastegate is the diaphragm actuated valve to the side of the turbine shaft that vents boosted air out the exhaust during periods of low throttle and high turbine speed (ie highway driving). In a nutshell it is the valve that controls the boost pressure.

Not at all to be confused with the BOV, which vents boost spikes that occur with the throttle shutting, as I said above. BOV's can vent back into the intake or to atmosphere.

Outback bloke · Post by **Outback bloke** » Sun Jul 09, 2006 9:05 pm

Not to be confused with the wastegate in the turbo itself. It opens once a preset pressure is achieved to stop over boosting. It is on the exhaust/waste side of the turbo.

A BOV is on the compressor of the turbo and is a vacuum operated valve. It is fitted between the turbo and throttle body. Under boost it remains closed and keeps the intake pressurised. When the Throttle body snaps shut it creates a vacuum in the plenum which opens the valve therefore releasing the built up pressure between the turbo and TB. With no pressure there it leaves the turbo open to "free spin" with no restriction. This keeps the turbo spinning nicely wich allows for quickspool up once the TB is open again. The more constant speed of the blades is also what prolongs the life of the turbo.

Atmo venting bovs may seem like pure wank factor but they can and usually do work better than the factory items. Factory items are generally too small for big boost/HP engines. It works on the same theory as exhausts. A small factory exhaust works but is very small and restricted. A good sports exhaust flows well and is usually larger in diametre. Factory BOVs on most EJ20s have a diametre of about 20-25mm. A good after market bov is any where from 30-35mm up.

Wank factor is the trumpet.

Outback bloke · Post by **Outback bloke** » Sun Jul 09, 2006 9:07 pm

LOL, you type faster than me.

MUDRAT · Post by **MUDRAT** » Sun Jul 09, 2006 9:35 pm

Another benifit of an atmo BOV are also that you're not putting hot air back into your turbo.

chubby37 · Post by **chubby37** » Tue Jul 11, 2006 6:35 pm

ok.....now to maybe sound like a fool but would it work on an auto as good as a manual.....was thinking an auto changes quick and it may help....i dont know

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Tue Jul 11, 2006 7:10 pm

Yep they work just as good on an auto, although an Atmospheric BOV can cause the engine to play up with the auto

Outback bloke · Post by **Outback bloke** » Tue Jul 11, 2006 7:41 pm

The only time the BOV will work is when you lift your foot. It will not vent at all under accelleration. If you are thinking it will "pssshh" between gears then you will be dissapointed.

MUDRAT · Post by **MUDRAT** » Tue Jul 11, 2006 9:51 pm

Yeah that. Cos the throttle stays open, there is no overpressurisation of the inlet tract. Wank factor here I'm afraid.

chubby37 · Post by **chubby37** » Tue Jul 11, 2006 11:10 pm

i,m not after the wank factor....i,m not after the noise but woundered if it would help the turbo at all....so it looks like my best way is the vent back style?

Suby Wan Kenobi · Post by **Suby Wan Kenobi** » Wed Jul 12, 2006 12:17 am

IMO i think they are a wise investment for any turbo vehicle

subanator · Post by **subanator** » Thu Jul 13, 2006 12:15 am

As told to me by a tuner today when picking up my car, more for high boost set ups, not really effective for old school engines like my EA82T.