BOV please explain

[WASP]

Hi
Would someone mind explaining the intricacies of a BOV.I am using the std one. What, if any are the benefits of changing a BOV.
Cheers
Steven

[TTT]

if your car has an Air Flow meter (it does) then the standard bov recirculates the air that is in the pipework when you shut the throttle and dumps it in the intake between the turbo and air flow meter..
this is not re-measured again by the AFM.

If you replace it for an atmo venting bov, the air that has already been measured by the AFM (and so the ecu has dumped the required amount of fuel for it to burn with) is vented out of the system.

When you then shift gears and get back on the throttle, there is a moment where you have "x" amount of fuel for the "y" amount of air it was expecting to be mixed with which is no longer there so you get a RICH spot. This is commonly seen as a puff of black smoke on gear change.

Not so much of a problem.

however, if you were coming to a stop, that moment of richness could possibly stall the car.

In reality though, they are generally there for an environmental reasons...sound, fumes etc.

on the track it will make bugger all difference.
On the street, a recirculating bov makes the car run nicer.

if you have an aftermarket ecu that does away with the AFM, then it makes no difference to drivability as the tune is different anyway.

TL:DR? if you have a stock one and don't worry about changing it.. there is no benefit.

[Nevyn72]

TL:DR? if you have a stock one and don't worry about changing it.. there is no benefit.

Except that the factory one used in the SE is recognised to have problems when you increase the airflow (CAI, intercooler, exhaust, etc.) and increase boost pressures.
That's why the Turbosmart Kompact is such a popular conversion.......

[TTT]

Fair enough...what problems does it have?
is it a flow issue or does it leak?

[NitroDann]

Both.

[Crapweasel]

TTT - Both. (Damm you Dann)

It's one of five "weak" areas on a stock SE.

BOV, rubber intake piping (swells, and can split under boost), intake (restrictive), exhaust (restrictive) and intercooler (prone to heat soak).

If the car is only being dríven normally with the occasional mild run through the twisties, then these aren't issues. But if you plan on tracking the car, or want more performance for spirited driving then these are the first areas to address, which then reveals the ECU easter egg.

Most call it the sudden switch to open loop fuel, or the afterburner effect, I refer to it as "slow, slow, slow, DEAR HOLY MOTHER OF GOD!"

[deviant]

My supercharger kit came with a plastic Bosch recirculating BOV as used in many OEM applications. Complete POS, it is a spring with a rubber disc on the end of it that will not hold 9psi. As it warms up it gets worse.

I junked it and bought a $50 ebay special that is surprisingly well made with the plunger being a solid slug of brass with a big spring behind it. No leaks from this one, ass dyno tells me I picked up a healthy amount of power and throttle response is massively improved.

Anyway that is my BOV story.

[Okibi]

Dann sells an upgraded inlet elbow and BOV combination, worth the coin for peace of mind that everything is working as it should.

[Aussie Stig]

[quote="TTT"]

When you then shift gears and get back on the throttle, there is a moment where you have "x" amount of fuel for the "y" amount of air it was expecting to be mixed with which is no longer there so you get a RICH spot. This is commonly seen as a puff of black smoke on gear change.

Ah so this must be why turbo cars have such horrible, nasty looking, coked up rear pipes.

[NitroDann]

N/a cars runs about 13 parts air per part of fuel by weight at full throttle.

Turbo cars run 11.x parts air depending on setup.

This is called the air fuel ratio, or AFR. So turbo Cars in general are running richer at full power. Also turbocars in general get much more modified in terms of engines and management than n/a cars so ytend to be less emissions friendly as a whole.

Dann

[gslender]

N/a cars runs about 13 parts air per part of fuel by weight at full throttle.

Turbo cars run 11.x parts air depending on setup.

Only when WOT, so the exhaust pipe would only look that way if the car is always tracked or dríven hard, otherwise the leaner burn at cruise should be a nicer lighter gray.

G

[NitroDann]

n/a cars and turbo cars with sensible sized turbos both go well into the top end of their respective VE tables just going up hill from a standing start.

Dann

[bear2230]

My exhaust is black as hell and my AFR is perfect and I never, never drive it hard………... Well, not often anyway…………..Well, maybe a little more often than I like to admit………………. Ok OK, I thrash the arse out of it……….Happy...

Richard.

[Aussie Stig]

TTT - Both. (Damm you Dann)

It's one of five "weak" areas on a stock SE.

BOV, rubber intake piping (swells, and can split under boost), intake (restrictive), exhaust (restrictive) and intercooler (prone to heat soak).

If the car is only being dríven normally with the occasional mild run through the twisties, then these aren't issues. But if you plan on tracking the car, or want more performance for spirited driving then these are the first areas to address, which then reveals the ECU easter egg.

Most call it the sudden switch to open loop fuel, or the afterburner effect, I refer to it as "slow, slow, slow, DEAR HOLY MOTHER OF GOD!"

Does the SP have the same sort of issues?

[Lokiel]

One of the differences between the SP and SE is that the SP is known to produce "more black smoke".