Blow-Off Valves (BOVs)

[Two Lane Blacktop]

Blow-Off Valves can be an effective means of
combating/preventing turbo compressor surge.

O.K., but we all already know practically all there is to know about BOVs, right? ;)


But, here's something many people don't generally know about BOVs...

More than a few guys with Grand Nationals & Turbo Regals get all stone-age
and spastic, ready for a rumble whenever anyone even brings up the
topic of using a BOV on a Turbo'd Buick. This, despite the fact that many
have upgraded to much larger turbos and/or front mount intercoolers,
sometimes creating significant compressor surge conditions.

Still, just mention a BOV and eyes start glowing red, forehead veins engorge,
voices become guttural, wolfman hair pops out, and the knucks, knives,
whips and chains get busy for even daring to mention the forboten lil' BOV.

If you've never experienced compressor surge, suffice to say it can occur when you lift
under boost and can literally "BUCK" your car like a tinker-toy & loosen your dental caps.

Every turbo manufacturer (Garrett, Turbonetics, Innovative, Borg-Warner, etcetera)
is pro-BOV as a means to address compressor surge & prevent damage to their turbos.

BUT, according to many individuals with a GN or a TR, BOVs are summarily dismissed
as "stupid & not necessary on vehicles with automatics". "We don't need that Ricer-Crap"
they shout, while spending $1200.00 on a gigantic 8-second capable front-mount intercooler
for a street-car is NOT to be considered totally blingy "Ricer-Crap". You'll get the line:
"Well, the fastest Turbo Regals don't use them" as if anyone suddenly "lifts" in the 1/4 mile.

With $1400.00 to $2200.00 Buick turbos becoming the norm, what's "wrong" with
installing a $200.00 BOV as a potential protective assist for the cost of 4-5 oil changes?

[Dynoroom]

Re: Blow-Off Valves (Blow-Off Valves)

what's "wrong" with
installing a $200.00 BOV

Nothing...

to each his own :

[dieselgeek]

Re: Blow-Off Valves (Blow-Off Valves)

That's an awesome quote, I totally believe it's from a knowledgable source!! :D


/sarcasm

[VWMMP]

Re: Blow-Off Valves (Blow-Off Valves)

Ok here is my question from someone who has 0 experience with turbos but hoping to add one down the road. I do have a rudimentary understanding of a turbo setup. My question is with a BOV when upshifting, if the throttle was lifted, would the BOV cause enough pressure loss on the charged side to cause a slight loss of power? or Without a BOV the pressure wave coming back to the turbo causes it to slow down thus causing a slight loss of power.

I have read that with an intercooler the pressure wave is negated quite a bit.

Any thoughts?

[dieselgeek]

Re: Blow-Off Valves (Blow-Off Valves)

Ok here is my question from someone who has 0 experience with turbos but hoping to add one down the road. I do have a rudimentary understanding of a turbo setup. My question is with a BOV when upshifting, if the throttle was lifted, would the BOV cause enough pressure loss on the charged side to cause a slight loss of power? or With a BOV the pressure wave coming back to the turbo causes it to slow down thus causing a slight loss of power.

I have read that with an intercooler the pressure wave is negated quite a bit.

Any thoughts?

I think that during upshifting, the BOV is nice to have because it relieves pressure on the intake side, keeping the turbo spinning. Where it can hurt though, is if you overspeed the turbo. And although I am neutral in the BOV needs debate, I have to say I have seen far more turbo failures from overspeeding, than from surge. Anyways, I know that if you don't have a BOV, the turbo has to decelerate when the throttle closes but a BOV lets the turbo "freewheel" more. I know that it's bad to run a turbocharger without charge piping, because the exhaust pressure still spins the turbo to the moon without something on the intake side to help control turbine speed.

My $.02, and compared to others here, it's worth every penny ;)

-scott

[efi-diy]

Re: Blow-Off Valves (BOVs)

The trick here is to blow off just enough pressure to minimize the reversion and still keep enough pressure in the charge pipe to keep the turbine speed going into orbit.. Maybe open the waste gate to bleed off exhaust pressure at the same time.

[Robert1320]

Re: Blow-Off Valves (BOVs)

So, since a GN doesn't need one no one does.

It is not like the GN and type T were the pinnacle of turbo developement. As factory produced.

[Robert1320]

Re: Blow-Off Valves (BOVs)

BOV's are especially helpful for the Blow-thru guys.
By releasing the charge pipe pressure there are less
issues with carb, fuel pressure, and regulators.

[VWMMP]

Re: Blow-Off Valves (BOVs)

Here is another thought and please correct me if I am wrong. The majority of customers in the turbo market lately have been those running 4cyl street motors. These motors are driven daily. With stop and go traffic, short bursts of boost etc...... Would a BOV help the longevity of the turbo? Thus keeping the warranty claims down? Also, from experience a lot of the transmissions that are in these cars are not capable of handling hard shifts so these drivers shift with the throttle fully closed on every shift. Again with the constant surge causing pre-mature failure on the turbo.