Fact or Fiction - No BOV = Bad?
 

This has been debated a lot as of late. Is a BOV truely a HAVE to? I never see turbo's failing due to compressor surge. MANY high performance cars don't even use them. Not saying I will be removing my BOV, I just want your opinion! :twothumbs: :skull1:

Which hi performance TURBO cars do not use them?

Are you sure that they do not have a BYPASS or RECIRC valve insted?

If you did not have one then when you let off the throttle the compressed air will have no where to go and the blades will be stopped very quickly. This is said to be where a failure can occur. I would not think one time would hurt it but over and over again might. But what will be noticable each time you want to get right back into boost (like during manual shifts during a run) is that the turbo will have to spool up again insted of still being ready, willing and able.

no hhrss HAVE to have a bov lol...the stock set up is fine. until you start pushing say past 400 and have a bigger turbo, maybe so then. i don't want one on my car...they were cool 10 years ago lol...

You've got it. Any boosted motor has to do something with boost when the throttle closes. In a modern EPA regulated motor blowing off excess boost is illegal if it goes into the atmosphere.

Just because it's not labeled as BOV doesn't mean there is not an internal way to dump pressure somewhere...then the excess is fed back into the motor to be burned.

This is an age old arguement, BOV's are not a necessary item on a forced induction car, especially a stock or lightly modified motor. Not running one isn't going to hurt your turbo!!!!! Now with that said here is why you may want to run one AND why the HHR SS came from the factory with one.....Performance and fun factor!!! If you know how a turbo works then you'll understand this, it spins at very high rpms while making boost, the bov allows you to keep the turbo at those rpms between shifts otherwise without it the compressor wheel will slow down between shifts and you will have a lag in power until the turbo spools up again. That's pretty much it. If you run a bigger turbo that flows a lot of air then its even a better idea to have one.

Running boost over a modest amount say 7psi a bov/bov is needed. Abive modest pressures a turbo will get damaged over a period of time without using one. As stated above the compressed air that is between the turbo anf the throttle body inside the charge pipes has nowhere to go once the throttle is closed. The only place for it to go is where it came from...the turbo. So what happens is it slows down the turbine very abruptly. The higher the boost and more pressure the more abruptly it slows the turbine as the air tries to exit where it came from. Now if when the throttle is closed the air has somewhere else to escspr then there is no harm being done to the turbine. Now imagine this....the turbo us spinning at 100,000+ rpm at 15psi(stock ss) and the throttle closes...what effect is that high boost pressure going to have on tgst turbo that is spinning that fast? No it wont damage it if it happens one time or maybe even 100 times but eventually it will. The experts at garrett have said that under 6-7psi doesnt require a bov but anything over you should use one.

I am hoping to achieve around 25 or so Pounds of Boost and I understand why you need a way to release the pressure from the system at times and that the HHR SS comes from the factory with a way to deal with the factory pressure level.

My questions are;

1, at what point is it necessary to considering a different way of releasing the pressure

2, what or who’s systems should be considered and has a proven track record.

I had a 930 Porsche with a K-27 Turbo and a 1-Bar spring and just the factory Waste Gate and Waste Gate pipe that vented out the rear of the car into the atmosphere and never had to deal with upgrading the Waste Gate so I’m on a new learning curve here.

Wastegate is completely different then a blow off or bypass valve. The waste gat limits the amount of boost and is on the exhaust side of the engine. The BOV or release/bypass valve is on the intake side and is for releasing the already built up boost when the throttle blade snaps shut. I like the recirc/bypass to put that compressed air back in front of the turbo so that it can help to keep the turbo spooled.

The stock system works fine and there really is no need to upgrade it other than a turbo swap or if you just like the sound.

I get the fealing that many think of a BOV as the atmospheric ones that make the loud sound. Not all BOV's blow off to atmosphere. You can get BOV's that work in a recirc setup. Even the Greddy's have different nozzles that can be put on them to vent to atmosphere or to recirc.

Thank you very much I guess I won't worry about changing anything in regards to that issue then.

I know they csn be recirculated. But again the only real reason to change the stock bpv recirc setup is a big turbo setup or if you like the sound. Why go from the stock setup and spend 400 bucks on a recirc setup? Doesnt make sense....its just spending money on nothing.

I never mentioned anything about when or why you would change it. I merely pointed out that BOV's are not always for the sound as they do not have to blow off to atmosphere.

$400 for a BOV??? EEEKKKKK.. You can get the block off plate for the factory one for $36 then around $100 for a name brand BOV and down to $40 for the average copy on ebay. The another $30 or so for a pipe with the correct flange.

Correct but on our application the only 2 reasons to change from the stock setup is big turbo or sound. Really no need to argue this point.

A tial q is $240
Block off is 35
Recirc or tial q is 40
Flange for tial q is 25
Fee to weld flange and recirc fitting (need aftermarket metal intake here and assuming you already have upgraded piping) 75....not to mention repowdercoating where the fittings were welded.

Total...415 for a recirc assuming you already had aftermarket metal charge piping and an aftermarket metal intake. Yeah a vent to atmosphere setup will be a bit cheaper but yes my ballpark figure was correct

You are the only one arguing that point. I again am not talking about why and when at all.

Not sure how blowing off excess boost to the atmosphere is an EPA violation, especially since it is plain "air" with nothing else added. Fuel is not in the mix till the boost is inside the engine in an HHRSS.