Why no BOV/TT on stock cars?

[SF-SI-02]

Do audis, porsches, subarus etc have a BOV built into their cars? If not, why don't they? Also, how come those cars (stock turbo) can "get away with" no turbo times, and yet people hear make it sound like it is extremely important? Is there something that the stock cars have that we would be missing if we installed an aftermarket turbo?

Thanks

[EPHatchgirl]

Stock turboed cars in general, release the boost but recirculate it through the system of the car, instead of venting to the atmosphere. Especially with VWs, if you mess with the boost level by allowing it to vent to the atmosphere, the MAF sensor see a SUDDEN drop in boost. When the BOV goes off, the car runs funky because the ECU is trying to compensate for a change in boost/vacuum level.

Turbo timers, if you are running an extremely high boost application, can help extend the life of your turbo. It's not that you are at risk by NOT using one, but your turbo will not last as long. I was told by several mechanics that at the level of boost that I am running right now (9lbs on a huge azz turbo), I don't even need a turbo timer, and that it's a waste of cash unless I go extremely high boost.

Hope this helps.:cool:

[andy]

EPHatchgirl pretty much nailed the door shut on that, but I'll
add my 2 centavos.

On the WRX, the BOV recirculates the air instead of venting, like
EPHatchgirl said (she done smart herself ;) ).
Instead of a TT, though, Subaru implemented a "cooling" system,
where after you turn the car off, water or some sort of cooling liquid
condenses and helps cool down the turbo bearings.
If you change your oil regularly, it's hard to imagine a turbo going
bad, unless it's getting WAY hot and you immediately shut the car
off.

That said, TT can't really "hurt" anything and some of them function
in other ways (mine was a TT and a Heads up display boost gauge - pretty
nifty) as well.

[SF-SI-02]

When you say that the boost is released into the car's system... is that the same as say running a greddy turbo on the ep3 with no bov at all? If not, could you explain the danger in not having a bov on the system?

Thanks, I know it is probably not optimal to learn about turbos via posting, but I like hearing the take of turbo veterans on the matter.

Cheers

[D16Y8_Turbo]

Originally posted by SF-SI-02
When you say that the boost is released into the car's system... is that the same as say running a greddy turbo on the ep3 with no bov at all?

No. Without a BOV on an aftermarket system such as the Greddy for the EP, the air in the charge pipes is trapped once the throttle body closes and therefore the air goes back to the compressor wheel and turns it the opposite direction. This hurts the turbo. That is why a BOV is used.

What they are referring to as being "released into the car system" is having vented out through the filter or other device. On my Syclone, which does not come with a relief valve from GM, so the air is routed back out through the air filter as is the GN's from my understanding. In short, the air is released just not necessarily by a BOV.

Hope I helped, but sorry if I confused you.

[SF-SI-02]

gotcha! Thanks for the info. However (sorry!) is there a way to discreetly get rid of the air, i.e. all BOV seem to advertise the fact that they are loud, is there a quiet way of disposing of the air?

[D16Y8_Turbo]

Originally posted by SF-SI-02
gotcha! Thanks for the info. However (sorry!) is there a way to discreetly get rid of the air, i.e. all BOV seem to advertise the fact that they are loud, is there a quiet way of disposing of the air?

You could do what other factory turbocharged vehicles use by routing the air through the air filter but my Sy is still loud when I let off the throttle. However, most BOV's are adjustable. This allows you to adjust the BOV to be softer spring (air is released easily) or harder which requires more air to move the spring for the air to be released. Honestly, once you have a turbo and your BOV sounds for the first time, I don't think you will care much.

On a side note, I have had the Blitz BOV on my EX and now on my EP, and the sound is very different. It was much louder on the EX than the EP. Weird but true according to my ears and memory. BOV's vary in sound/loudiness :)

[emosubaru]

a recirculating blowoff valve is also called a diverter valve.

subaru wrxs come from the factory witha recirculating blow off valve, and if you remove the intake silencer(a piece of plastic similar to most stock muffler designs) inside the airbox you can hear the blow off sound, though it is still faily discreet.

subaru also used a turbo design that has an extra coolant resivior that is positioned above the turbo, and coolant that gets hot and turns to vapor rises out of the turbo, back to the extra resivior, where it condenses and goes back to the turbo to help it cool again. this is why there is no need for a turbo timer on a stock turbo WRX.

most turbos are not designed this way, and for your ep3 i would suggest a turbo timer simply because even at low psi (7-9) you are still spinning the turbine extremely fast (>90,000 rpm) and the bearings will become damaged if you shut your car off after being in boost for any serious amount of time. a turbo timer can't hurt and could possibly help a great deal to prolong the lifetime of your turbo. if it can't hurt, there's no use forgoeing one.

it is true most aftermarket BOV's are engineered to be loud, but blitz and a couple other companies do make recirculating valves that will be more discreet.

anyone who knows anything about cars will be able to tell that your car is f/i just by the whine of your turbo while boosting. i'd recommend a larger width exhaust to go along with the turbo kit as well (in the neighborhood of 2.5") because any smaller (like stock) will be too restrictive and backpressure will increase lag and make your turbo system less transparent and drivable.

a turbo system is worth the added profile. it is expensive, and for many people unaffordable, but it is still every bit worth having a higher profile. boost is amazing!

i know i am probably beating a dead horse with my post, but i wanted to reiterate what everyone else said just to try to clarify and give my scope on the whole situation. hope this thread can be of help to people!

boost rules!:cool:

[swampdonkey]

Thats the name for a BOV that recirculates the air back into the intake. The reason that stock turbo cars do not vent to the atmosphere is that they use more sophisticated engine management than a turbo kit. The mass airflow sensor reports density and volume of air being take in. If the air that passes through the valve was vented into the atmosphere in one of these cars it would run rich esspecially after a shift.

The danger of having no BOV or CBV is this. When you are driving (especially at WOT) and it is time to shift what happens.....? The throttle slams shut, BUT the turbo is still trying to cram air into your engine. So in an instant the preasure starts building back towards the compressor..in effect creating a wave of preasurized air back though the turbo plumming towards the turbo! Normally there is a valve in the pipe that opens when it "sees" Vacume. The vacume occurs just as the peasurized wave begins to pass the valve. The door to the atmosphere opens and the preasurized air travels out into the atmosphere. If no valve was there....the "wave" of air would travel all the way to the turbo where bad things would happen. Compressor surge occurs when the air reaches the turbo. This can be so catastrophic as to destroy the turbo, or it can be mild so that it merely spools very slowly when the shift is completed. There are a few turbos made with ceramic ball bearings that are incredibly resistan to surge, but they are very expensive so you're better off just avoiding it altogether.

Ok I'm done for now.......peace

[eurosteez]

Originally posted by emosubaru




most turbos are not designed this way, and for your ep3 i would suggest a turbo timer simply because even at low psi (7-9) you are still spinning the turbine extremely fast (>90,000 rpm) and the bearings will become damaged if you shut your car off after being in boost for any serious amount of time. a turbo timer can't hurt and could possibly help a great deal to prolong the lifetime of your turbo. if it can't hurt, there's no use forgoeing one.






informative thread.

Isnt letting the car idle for a few minutes after driving it the same as a turbo timer? And does it spool up that high when cruisin or only at WOT?

[swampdonkey]

Yes, idling for a minute or two is just as effective as a a turbo timer. The problem is its hard to be disiplined about it. Every time you are late or something you will just shut it off so a turbo timer is better.

[EPHatchgirl]

Originally posted by emosubaru
a recirculating blowoff valve is also called a diverter valve.

...

most turbos are not designed this way, and for your ep3 i would suggest a turbo timer simply because even at low psi (7-9) you are still spinning the turbine extremely fast (>90,000 rpm) and the bearings will become damaged if you shut your car off after being in boost for any serious amount of time....

it is true most aftermarket BOV's are engineered to be loud, but blitz and a couple other companies do make recirculating valves that will be more discreet....

anyone who knows anything about cars will be able to tell that your car is f/i just by the whine of your turbo while boosting. i'd recommend a larger width exhaust to go along with the turbo kit as well (in the neighborhood of 2.5") because any smaller (like stock) will be too restrictive and backpressure will increase lag and make your turbo system less transparent and drivable.

a turbo system is worth the added profile. it is expensive, and for many people unaffordable, but it is still every bit worth having a higher profile. boost is amazing!


boost rules!:cool:


This guy knows his shit.
... and I still want an STI.:D ... I can't help it, I test drove one.:D :D

[EPHatchgirl]

Originally posted by swampdonkey
Yes, idling for a minute or two is just as effective as a a turbo timer. The problem is its hard to be disiplined about it. Every time you are late or something you will just shut it off so a turbo timer is better.

...this guy knows his shit, too.....


But...!! Like he said, I don't always wait. There are Monday mornings when I am too late to sit and wait.:confused: :angel:

[87gn]

No. Without a BOV on an aftermarket system such as the Greddy for the EP, the air in the charge pipes is trapped once the throttle body closes and therefore the air goes back to the compressor wheel and turns it the opposite direction. This hurts the turbo. That is why a BOV is used.

What they are referring to as being "released into the car system" is having vented out through the filter or other device. On my Syclone, which does not come with a relief valve from GM, so the air is routed back out through the air filter as is the GN's from my understanding. In short, the air is released just not necessarily by a BOV.

on both my gn and your syclone when the throttle blade slams shut the air IS forced back threw the compressor housing. the reasion why we dont have bovs is because there automatics.

btw, turbo timers are USELESS, they defiently dont have anything to do with the levels of boost that your running. as long as you let you car cool down for a few mins before shutting it off you will be fine.