Bov on 1ggte ? engine doesnt seem to like the bov ! engine dies when bov vents

[Toy77]

The usual answers are improved off to on boost response and turbo protection.

Often just for the cool sound - some like, some dont - i have a BOV...

People will argue both point back and forth.

Alot of factory cars do use them - and technology has improved, so just because your car never came with one, doesn't mean it wont be beneficial. ie my celica came without a turbo, which was a mistake on the factories part, which i have remedied.

But this thread is not about whether or not to have one - but why is it messing with his car, so lets not get too far off track...

Cheers
Stew

[auto351]

when you install the BOV do you do anything to the wastegate, The way im thinking the BOV would never open unless you have the boost setting on the BOV set below the wastegate ?

[Z2TT]

Well it has a spring, you can tighten or loosen the spring tension so it is harder to open, so you can stop the BOV from opening yes, or make it only vent at high boost so it doesn't annoy you all the time.

[mullett]

when you install the BOV do you do anything to the wastegate, The way im thinking the BOV would never open unless you have the boost setting on the BOV set below the wastegate ?

Different situation. A BOV does not regulate boost.

There is a hose in the top of the BOV, plumbed after the TB. When the throttle is open and there is positive boost, the pressure across the BOV piston is equal (pressure on one side from the intake plumbing, pressure on the other side from the manifold) The spring simply keeps the balance in favour of the intake side.

When you close the throttle, you create a pressure differential across the piston, as the intake manifold is now under vacuum, and the intake plumbing still has boost pressure (and as the turbo does not instantly spin down like an SC does to match the engine, you actually have a boost 'spike' as the air has nowhere to go, can cause damage to the turbo/throttle body in extreme cases)

BOV prevents the turbo from 'stalling', which decreases the spool time when you open the throttle again...it also goes 'pssst', which is why they're so popular. There's a (fairly irrelevant) argument that recirculating BOVs are re-introducing hot air into the system, and while it's well founded, it's also not worth worrying about for a street application.

Atmospheric BOVs have no practical advantages for a street car, but they can have major disadvantages (like making AFM cars run like pigs), they're illegal in a lot of places, and they attract attention that you don't really need...

A wastegate, on the other hand, regulates exhaust flow through the turbocharger. When it's closed (normally) all the exhaust flow travels through the turbo, building boost as quickly as possible. When the boost pressure reaches the set level, it overcomes the spring in the actuator, which is usually a diaphragm connected by a hose to the inlet manifold. The actuator then opens the wastegate, diverting a portion of the exhaust flow around the turbo, holding the boost pressure at the set maximum.

The exception to the above is a 'pop-off valve', as fitted to some of the early F1 turbo cars. They ran without wastegates, up to 45+psi of boost, and a valve similar to a BOV was fitted in the intake, but minus the control line from the intake manifold. It had a fixed spring pressure, and when the boost exceeded the set maximum, it opened, functioning in much the same way as a wastegate.

-RM.