Whats the deal? bovs bad for all turbo cars or what?

[RayArroyo]

Originally Posted by teh DIRT

ok thats enough. back to the topic at hand.

Dont know if it was explained already but a maf sees how much air is being injested then gives fuel according to that. If it sees air going in then that air excapes through a BOV, you run rich because the fuel is for all of that air, not just the air that didnt go out the BOV.

pete we can tune for that on the emanage and thats also why placement plays a big role.

[teh DIRT]

good deal. Do you think power will be better once a bov is on. I figure since the turbo is fighting air in between shifts it will be better when its not fighting.

[RayArroyo]

Originally Posted by teh DIRT

good deal. Do you think power will be better once a bov is on. I figure since the turbo is fighting air in between shifts it will be better when its not fighting.

it will help between shifts dramatically as it prevents the wheel from decreasing speeds and staling plus it will make the turbo last

[teh DIRT]

yeah lasting is good too.

[D Money]

I used to run a recirc valve on my car and now I have a HKS SSQV and I feel the car is feels smoother with the bov on. With the bypass valve the car would bog in between shifts etc but not it's a monster. Oh well...

[teh DIRT]

I would run a recirc bov, but i have nothing in front of my turbo.

[RayArroyo]

Originally Posted by teh DIRT

I would run a recirc bov, but i have nothing in front of my turbo.

pete youll be fine with out recirc

[Tiny]

BOV's were made to stop the intercooler from popping it's welds. Thats the only practical reason for them. It doesn't harm the turbo to have no BOV.

[teh DIRT]

I dont know mike......i cant see forcing air out the turbo to be a good thing.

[Driven]

As was said before, a vented to atmosphere BOV after a MAS or MAF will result in a rich condition when the throttle plate is closed. My solution for this is not to let the throttle plate close during a run.

BOV's serve more purposes than preventing intake manifold welds from breaking, like preventing the reversion of air through the turbo? How about preventing throttle bodies from breaking (anyone who's run a mustang TB on a boosted car will know what I'm talking about)?

[highmilehatch]

Originally Posted by Tiny

BOV's were made to stop the intercooler from popping it's welds. Thats the only practical reason for them. It doesn't harm the turbo to have no BOV.

?????????????

There's positive pressure in the intercooler piping before it reaches the t-body. BOV's don't stop IC's from breaking. If the welds were a problem, they would break before any of the pressure reached the t-body.

[wgknestrick]

Originally Posted by Tiny

BOV's were made to stop the intercooler from popping it's welds. Thats the only practical reason for them. It doesn't harm the turbo to have no BOV.

Please step away from the computer now.

No BOV on a turbo is about the quickest way outside of antilag to make that hair dryer nothing more than a leaky paper weight.

Taken from Garrett:
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it.

[Tiny]

Originally Posted by wgknestrick

Please step away from the computer now and quit mis-informing the public here.

No BOV on a turbo is about the quickest way outside of antilag to make that hair dryer nothing more than a leaky paper weight.

Taken from Garrett:
The Blow-Off valve (BOV) is a pressure relief device on the intake tract to prevent the turbo’s compressor from going into surge. The BOV should be installed between the compressor discharge and the throttle body, preferably downstream of the charge air cooler (if equipped). When the throttle is closed rapidly, the airflow is quickly reduced, causing flow instability and pressure fluctuations. These rapidly cycling pressure fluctuations are the audible evidence of surge. Surge can eventually lead to thrust bearing failure due to the high loads associated with it.

"This produces a fluttering noise as the air passes backwards through the turbo, which is often unwanted. There is also a school of thought that a blow-off valve can improve turbocharger longevity or, in extreme cases, prevent damage to the turbo."

I would like to see something from someone that has no interest in selling BOV's tell me that there is actually a detrimental effect to a turbo caused by closing the TB.

Not being a smart ass, just actually interested in seeing some measured proof. I know of at least 3 cars that are actively racing, one of which is operated on the street, that do not run BOV's and are seeing 30+psi from the turbo.

[RayArroyo]

Originally Posted by Tiny

"This produces a fluttering noise as the air passes backwards through the turbo, which is often unwanted. There is also a school of thought that a blow-off valve can improve turbocharger longevity or, in extreme cases, prevent damage to the turbo."

I would like to see something from someone that has no interest in selling BOV's tell me that there is actually a detrimental effect to a turbo caused by closing the TB.

Not being a smart ass, just actually interested in seeing some measured proof. I know of at least 3 cars that are actively racing, one of which is operated on the street, that do not run BOV's and are seeing 30+psi from the turbo.

mike are these cars running autos or stick shift? its different in a manual car as the turbo stalls / slows down in between gears and picks up again which can cause potential bearing damage. in an auto car the car is constantly under boost with minimal drop between gears because the turbo pretty much stays spooled the entire run.

[wgknestrick]

Auto or not, it doesn't really matter.

Any car that has a throttle body, needs a BOV. When you close the throttle body, you are effectively sealing the charge pipe system. Problem is the turbo is still spinning around 80-100K (depending on size) RPM. This turbo rapidly, and I mean rapidly slows down to around 1K RPM (idle speed) in about .5 sec because the volume is fixed now and there is a pressure spike. This pressure spike in return acts on your compressor blades and wheel (newton's law is a biach) to slow it down.

Anytime you start putting big force spikes on any type of bearing, you are going to see failure.

This rapid decelleration is what causes the "compressor surge" or "wooble" noise on some cars. I had it bad enough to actually shake my entire car until I adjusted my BOV properly. That is the maginitude of force we are talking here.

No BOV cars may be running in strict drag apps, or by people "not really" knowing what they are doing. They may be fine now, but will be smoking their turbos soon enough.

One analogy I can think off is like trying to stop your turbo wheel at full spin by sticking something into the blades. Surge isn't quite this extreme because it is acting evenly over all the blades, but fundamentally the same.

[awdlaserbeam]

Yea, i think his original question was pertaining to the mechanical pros/cons to a BOV not just having a blow thru/draw thru maf and tuning issues.

[TalonTsi97]

hmmm my car has 240,000+ miles on it and has no bov. I was planning on putting an extra bov i have on it but i figure it lasted this long no big deal.

[RayArroyo]

Originally Posted by TalonTsi97

hmmm my car has 240,000+ miles on it and has no bov. I was planning on putting an extra bov i have on it but i figure it lasted this long no big deal.

does it have a diverter valve or surge valve lol

[TalonTsi97]

Originally Posted by ray@turbotek

does it have a diverter valve or surge valve lol

It has nothing on the pipe from the turbo to the throttle body, supposedly it has a emergency release valve. I havent been able to find much info on it other then when im beating on the car while its at full boost it will just open and you hear a major air leak and it keeps boost from going any higher.

[teh DIRT]

look it a bov or bpv wasnt neccesary, it wouldnt come stock on most turbo cars. Wrx, dsm, evo, whatever....ill trust the engineers that get paid the big money