No BOV

[racepar1]

Originally Posted by Z33dori

some one really needs to do an official BOV write up...

About what? The ONLY purpose of a BOV that I have ever heard of, untill this thread, is to protect the turbo from comperssor surge. How would a BOV possibly improve engine response? All it does is blow off excess pressure in the intake piping when the throttle is closed suddenly. The turbo has to build boost all over again when the throttle is re-opened. I would actually think that no BOV would improve response because there would still be a small amount of residual pressure in the intake piping when the throttle was re-opened.

[Silverbullet]

Originally Posted by murda-c

Oili pressure:

Approximate Discharge pressure : kPa (kg/cm^2, psi)

You didn't post a value for the pressure. kg/sq cm is a kPa.

Originally Posted by J ROK

wow, I barely understand what the fuck it is you just posted. just lookin for some simple numbers people see on their gauges.
thanks for tryin to help though

numbers don't mean anything without units... you could say just your pressure is just 20. Is it 20psi or 20kpa? A simple mistake like this costed NASA the Mars Polar Lander some years ago.

[murda-c]

I thought it had more to do with the fact that the turbo has to spin up to speed again, vs already being at speed.

[Grenade180sx]

Originally Posted by racepar1

About what? The ONLY purpose of a BOV that I have ever heard of, untill this thread, is to protect the turbo from comperssor surge. How would a BOV possibly improve engine response? All it does is blow off excess pressure in the intake piping when the throttle is closed suddenly. The turbo has to build boost all over again when the throttle is re-opened. I would actually think that no BOV would improve response because there would still be a small amount of residual pressure in the intake piping when the throttle was re-opened.

why would say we are wrong when u dont even know the "correct " answer?

here..

Definitions

A compressor bypass valve (CBV) also known as a compressor relief valve is a vacuum-actuated valve designed to release pressure in the intake system of a turbocharged or centrifugally supercharged car when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor.
A blowoff valve, (BOV, sometimes hooter valve, dump valve) does basically the same thing, but releases the air to the atmosphere. This creates a very distinctive sound desired by many who own turbocharged sports cars. Some blowoff valves are sold with trumpet shaped exits that amplify the "boooooom" sound, these designs are normally marketed towards the tuner crowd. For some owners this is the only reason to get a BOV. Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere. In the United States, Australia and Europe cars featuring unmuffled blowoff valves are illegal for street use.

Disadvantages

The unique sound caused by a blowoff valve (but not a compressor bypass valve) sometimes comes at a price. On a car where the blowoff valve is mounted after the mass airflow sensor, venting to atmosphere confuses the engine control unit (ECU) of the car. The ECU is told it has a specific amount of air in the intake system, and injects fuel accordingly. The amount of air released by the blowoff valve is not taken into consideration and the engine runs rich for a period of time. Engines with a manifold absolute pressure regulated ECU or where the blowoff is mounted upstream of the MAF sensor are not affected.
Typically this isn't a major issue, but sometimes it can lead to hesitation or stalling of the engine when the throttle is closed. This situation worsens with higher boost pressures. Eventually this can foul spark plugs and destroy the catalytic converter (when running rich, not all the fuel is burned which can heat up on and melt the converter or leave heavy carbon deposits).

Purpose

Blowoff valves are used to prevent compressor surge. Compressor surge is a phenomenon that occurs when lifting off the throttle of a turbocharged car (with a non-existent or faulty bypass valve). When the throttle plate on a turbocharged engine running boost closes, high pressure in the intake system has nowhere to go. It is forced to travel back to the turbocharger in the form of a pressure wave. This results in the wheel rapidly decreasing speed and stalling. The driver will notice a fluttering air sound.

Operation

[murda-c]

Originally Posted by Silverbullet

You didn't post a value for the pressure. kg/sq cm is a kPa.



numbers don't mean anything without units... you could say just your pressure is just 20. Is it 20psi or 20kpa? A simple mistake like this costed NASA the Mars Polar Lander some years ago.

Yeah i just copypasted the fsm.

how is a kg/cm2 a kPa?

[racepar1]

Originally Posted by Grenade180sx

why would say we are wrong when u dont even know the "correct " answer?

here..

Definitions

A compressor bypass valve (CBV) also known as a compressor relief valve is a vacuum-actuated valve designed to release pressure in the intake system of a turbocharged or centrifugally supercharged car when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor.
A blowoff valve, (BOV, sometimes hooter valve, dump valve) does basically the same thing, but releases the air to the atmosphere. This creates a very distinctive sound desired by many who own turbocharged sports cars. Some blowoff valves are sold with trumpet shaped exits that amplify the "boooooom" sound, these designs are normally marketed towards the tuner crowd. For some owners this is the only reason to get a BOV. Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere. In the United States, Australia and Europe cars featuring unmuffled blowoff valves are illegal for street use.

Disadvantages

The unique sound caused by a blowoff valve (but not a compressor bypass valve) sometimes comes at a price. On a car where the blowoff valve is mounted after the mass airflow sensor, venting to atmosphere confuses the engine control unit (ECU) of the car. The ECU is told it has a specific amount of air in the intake system, and injects fuel accordingly. The amount of air released by the blowoff valve is not taken into consideration and the engine runs rich for a period of time. Engines with a manifold absolute pressure regulated ECU or where the blowoff is mounted upstream of the MAF sensor are not affected.
Typically this isn't a major issue, but sometimes it can lead to hesitation or stalling of the engine when the throttle is closed. This situation worsens with higher boost pressures. Eventually this can foul spark plugs and destroy the catalytic converter (when running rich, not all the fuel is burned which can heat up on and melt the converter or leave heavy carbon deposits).

Purpose

Blowoff valves are used to prevent compressor surge. Compressor surge is a phenomenon that occurs when lifting off the throttle of a turbocharged car (with a non-existent or faulty bypass valve). When the throttle plate on a turbocharged engine running boost closes, high pressure in the intake system has nowhere to go. It is forced to travel back to the turbocharger in the form of a pressure wave. This results in the wheel rapidly decreasing speed and stalling. The driver will notice a fluttering air sound.

Operation

Ummm, I already knew all that. I just didn't think about the compressor wheel actually stalling out. You didn't prove anybody right or wrong, you just posted an article. It takes actual numbers from a car with a BOV and the same car without one to prove either side right or wrong. Good job finding an article, but it really didn't add anything to the conversation other than the proper terminology of "blowoff valve" and "compressor bypass valve".

[Z33dori]

so how much better is it to have the BOV on the cold side than the hot side....

[murda-c]

Originally Posted by Z33dori

so how much better is it to have the BOV on the cold side than the hot side....

About three.

[bbejj123]

Originally Posted by murda-c

About three.

hahaha man if there was still rep i would give u +1 for making me laugh

[Syncade]

Guess what.

BPVs = BOVs = PRVs


all they are designed to do is prevent surging in charge pipes.

[racepar1]

Originally Posted by murda-c

About three.

I call bullshit!

It has to be 4.834723147832657943656812347845836957834626854321 87658761234785643875678234658763245876123484568123 548123468458123765678146572314091238952348756

Fo sho!

[Grenade180sx]

the point wasnt to prove anyone on anything. its so people know what they are talking about period.

[Leetheslacker]

i don't believe in blow off valves.

they aren't real. just like unicorns and fairies.

[smelly240]

this thread is out of hand... the most damaging type of compressor surge is when u run more boost than the turbo is capable of flowing (like all the retards running 16psi on their trusty t25's)

no bov will not blow your turbo apart, and having a bov isnt going to make your car faster. if you want one - run it... if not - who cares.

[MissShiftS13]

Im recirculated!!!!!..... But wish i had a battery for my car so i could find out the difference, womp womp womp!

[g6civcx]

Don't listen to strangers on the Internet. Ultimately you have to decide what you want to do with your car. As long as you fully understand the pros and cons of each decision, then whatever you decide is fine.

I personally recommend all OEM MAF setups to recirculate. Blowthroughs and MAP cars can vent to air or recirculate. Your choice.

I do not recommend running turbos with no BOV, but I know people who do and have no problems.

Also as an observation, depending on your tune, I know a lot of base tunes that "tuners" like to sell run their off-throttle maps really lean. So if you're on a MAF and you vent to air, you may have a slightly rich condition and won't be too overlean. They're pretty much designed for big BOV sounds that people like to run so the customer won't complain about their car stalling.

That's just my experience. Do what you wish.

[Def]

Originally Posted by smelly240

this thread is out of hand... the most damaging type of compressor surge is when u run more boost than the turbo is capable of flowing (like all the retards running 16psi on their trusty t25's)

no bov will not blow your turbo apart, and having a bov isnt going to make your car faster. if you want one - run it... if not - who cares.

That doesn't cause compressor surge. You'd have to be using a ginormous compressor and just manage to get to the left of the surge line with the throttle open. That is the type of surge that will kill a turbo with a quickness.


As far as recirc. BOVs improving response - it did in my case. It's not something I expected, but it was really obvious when shifting at say 4-5k RPM and half throttle. The response after the shift was noticeably better with the BOV recirc. Didn't notice much of a difference at WOT(18 psi) and shifting at redline.

It has been like that with two turbos that I ran both vented and recirc.(T28 and GT2876R)

[BillyTheKid]

Originally Posted by murda-c

Yeah i just copypasted the fsm.

how is a kg/cm2 a kPa?

1 kPa = 1000 N/m2 , where a N is for "Newton" and it is a force unit ( not a mass unit, as Kg ), where 1 Kg exerces 9,81 Newtons under earth gravity ( 1 Kg * gravitational acceleration (9,81m/s2) )

so, simply, 1 kPa is the force exerced by 1,02 Kg on a square cm, on earth.

and roughly, 100kPa = 14,5 psi

[murda-c]

So what you're telling me is a kpa = 1.02kg/cm2

I thought you were saying that they are equal, which they arent, they're just different ways to measure pressure.

[BillyTheKid]

Originally Posted by murda-c

So what you're telling me is a kpa = 1.02kg/cm2

I thought you were saying that they are equal, which they arent, they're just different ways to measure pressure.

I totally agree, they aren't equal at all, a pressure just cannot be defined as a mass over a surface... saying 1kPa=1kg/cm2 is not true, but it's not far from being true... but anyway, who cares ?

as for BOV, it will just release the pressure without stoping the compressor wheel. Then, with a BOV, the turbo is still spinning when you step on the throttle, 1/2 second after... while re-circulating it will just keep the right air-fuel ratio...

what kills the turbo is the compressor blades stalling due to the reverse air flow and thus creating vibrations. What is going to fail in a turbo is the bearings, and I don't think they can fail because it suddently stops, they will fail because of excess stress, caused by vibrations ( turbo out of efficiency range or having violent surges ) Can the turbo handle it ? I'm pretty sure it will, just depends how long you consider a turbo is supposed to last...

and the excess fuel caused by the atmosphere venting won't do much at high rpms cause it'll be already out of your exhaust at the moment you step on gas, then your A/F ratio will be just right when you ask for power again. not sure if it will be the same at 4-5000 RPM tho, I didn't run atmosphere long enough to notice the difference...

[Grenade180sx]

okay a turbo spinning at 75,000rpm is not going to STOP at all. just the air rushing back towards it changes the flow and REDUCES the wheels velocity.

[kamikazekid]

BOV's are there to relieve the pressure surge from the turbo during a shift to keep the compressor side of the turbo spinning at optimal speed for the the next shift/ acceleration to cut down on TURBO LAG , recirculated bov are better for your car for the MAF reason sated above, your car will actually start backfiring on shifts (which i think is cool) because of the super rich condition it makes if the BOV is vented to Atmosphere. it also helps keep the compressor spinning by intoducing it back in front of the fins. The factory puts thousands of hours into these designs to get otpimal performance, emissions and gas mileage, Its there for a reason. No MAF no recirculation needed. In the Poster's case, ur fine, its not a big deal to not run one for a bit. just keep the boost at stock, shit you could do 12 no problem, but it wears on your spindle bushings.

[SoSideways]

Originally Posted by kamikazekid

just keep the boost at stock, shit you could do 12 no problem, but it wears on your spindle bushings.

So will my suspension bind up now because I'm running at 12 boost?

[Jadeskyline]

Originally Posted by SoSideways

So will my suspension bind up now because I'm running at 12 boost?

msglength

[Matman03]

So speaking of lagg, since bov doesn't help how about running no filter on the snail and just a velocity funnel? What about sucking up bugs and birds and shit?

[murda-c]

Originally Posted by Matman03

So speaking of lagg, since bov doesn't help how about running no filter on the snail and just a velocity funnel? What about sucking up bugs and birds and shit?

Run a filter.

unless you REALLY REALLY need a few extra horsepower to the point that you don't care if your engine sucks up sand and grit.

At the vert least run one of those fine screens over the turbo intake.

Stick an apexi filter on it and be happy is what i say.

[Zerolift Autolab]

I have heard alot of mixed arguments with regards to blow off valves on Short Charge Pipe Setups....

I spoke to a few people from Garrett that laughed at the need of blow off valves with their new GT Turbos. Claiming that the bearing system is plenty strong enough to withstand surge and back pressure on a standard engine.
I am sure the story is different with a Diesel or Race Motor with Huge PSI numbers.

We have assembled quite a few 450+ hp SR's with GT Turbochargers and same story for Honda motors, being that they are 90% street driven we installed valves in the system, most commonly used the HKS Race Valve.

For our Vert we are assembling, it is a V Mount system, with the longest charge pipe approximately 12" we will not be using a valve, but it is 100% a track car that will be run on race fuel. So the hours of usage will be way down from a Street Car.

Not sure if this helps or not, hope it does.
Thanks,
Robert

[VQMaxFan]

Originally Posted by murda-c

Run a filter.

unless you REALLY REALLY need a few extra horsepower to the point that you don't care if your engine sucks up sand and grit.

At the vert least run one of those fine screens over the turbo intake.

Stick an apexi filter on it and be happy is what i say.

You actually lose hp from running screen over your turbo inlet versus an actual filter, A good air filter organizes the way the air flows into the turbo.

[jakerps13]

Crack TB, lean AR's = No BOV

[murda-c]

Originally Posted by VQMaxFan

You actually lose hp from running screen over your turbo inlet versus an actual filter, A good air filter organizes the way the air flows into the turbo.

there we go, filters are good.