Dump valves

  • Thread starter dantheram1
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how do you know which cars have them?

I've heard a few cars on replays with them but is there anyway to tell without buying them and taking to the track.
 
Not all cars with a BOV have them vented to the atmosphere. My car IRL has it routed back into the intake, so there is little to no noise noticeable when it opens. I couldn't really tell you what cars are like this in the game, however.
 
The view you use can mask the sound of the BOV as well. Go to a replay and watch from another view and you'll likely hear it on cars you thought were really quiet. Not too realistic as my Evo's recirculated BPV is super loud in the car and out, and it's just got an open filter like the nicer one on GT5.
 
Anything with a turbo engine has a BOV.

No it doesn't. The ones that do though aren't all 'Vent to Atmosphere' which is where you get the noise, some recirculate back to the intake and barely make any noise at all. Although there are recirculating valves that are a sort of hybrid between the two, they recirculate the majority of it but vent maybe 5-10% to Atmosphere for thoes that want the 'noise' :rolleyes:
 
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hmm i have a really old car, i think it was a '79 Mitsubishi Mirage that i fitted with a turbo. you can hear the BOV hiss with that lol (i think it was the Mirage?)

also, i know the STI that you buy from the premium dealership also has the BOV hiss
 
Anything with a turbo engine has a BOV.

this isn't true... there were many turbo cars that were manufactured in the 80's that didnt have BOV's ... the theory then was they weren't pushing the boost to damage anything (it was an added cost they didnt need)...

but technically anything with a turbo SHOULD have one, longevity is the key
 
Many modern cars have wastegates instead of dump valves. Performance dump valves aren't that loud anyway unless on an engine running really high boost.

There is a reason your average boy racers DV hisses: Its restricting the flow of air escaping from the intake system.
 
No it doesn't. The ones that do though aren't all 'Vent to Atmosphere' which is where you get the noise, some recirculate back to the intake and barely make any noise at all. Although there are recirculating valves that are a sort of hybrid between the two, they recirculate the majority of it but vent maybe 5-10% to Atmosphere for thoes that want the 'noise' :rolleyes:
A Dump Valve/BOV/Recirculation system/Wastegate all serve pretty much the same general purpose.


@tdshelby

You're entirely correct, but I'm not sure of which makes/models those cars are in the game, and most of them when equiped with a turbo upgrade would likely have a BOV or Generic BOV sound to go with them.
 
Many modern cars have wastegates instead of dump valves. Performance dump valves aren't that loud anyway unless on an engine running really high boost.

There is a reason your average boy racers DV hisses: Its restricting the flow of air escaping from the intake system.

Every turbo car has a wastegate, otherwise they will over boost, but dump valves vary greatly with sound, depending on how they are made and what they are on.
 
Yeah exactly they vary with sound. If they are made to make a noise and let everyone know you've got a turbo they're noisy. If they are made to dump boost pressure as quickly as possible they make a noise that can be barely audible.
 
Yep, and the long loud ones can be worse for performance, as they leave out too much air. As far as I remember you only want to vent the back pressure pulse and not all the air out of the system. I prefer the sound with no dump valve personally, just a cone filter so you can hear the flutter of the back pulse. Apparently not great for the turbo but never had any problems.
 
... sorry, but I had to laugh a little at some of these responses. Just a note to you guys, and you know who you are ... be sure that the information you are repeating is the truth before you try to regurgitate it as fact.

Several people have had good input, but a few ... wow.

Back to the OP's original question, I'm pretty sure they all have a BOV sound if there is a turbo. It may just be quieter on a stock car.
 
Yep, and the long loud ones can be worse for performance, as they leave out too much air. As far as I remember you only want to vent the back pressure pulse and not all the air out of the system. I prefer the sound with no dump valve personally, just a cone filter so you can hear the flutter of the back pulse. Apparently not great for the turbo but never had any problems.

Depends on the style bearings used in the turbo and the compressor wheel. I run Holsets on my cars and they don't require a recirculator or dump as they don't run them on used on trucks. I had a greddy RS on my stock engine and it made a choo choo choo woo woo sound similar to compressor surge that you are talking about. As someone pointed out, atmospheric valves are a waste of pressure. recercing is better and you can still hear the sound.

here is how mine sounds with no valve at all. First couple seconds.

 
A Dump Valve/BOV/Recirculation system/Wastegate all serve pretty much the same general purpose.

Umm...no. A BOV and a wastegate do not serve the same purpose. Not even close. This is painfully apparent due to the fact that the wastegate is on the turbine side of the turbo while the BOV is on the compressor side of the turbo.
 
Depends on the style bearings used in the turbo and the compressor wheel. I run Holsets on my cars and they don't require a recirculator or dump as they don't run them on used on trucks. I had a greddy RS on my stock engine and it made a choo choo choo woo woo sound similar to compressor surge that you are talking about. As someone pointed out, atmospheric valves are a waste of pressure. recercing is better and you can still hear the sound.

here is how mine sounds with no valve at all. First couple seconds.

Yep pretty much sounds like my 180sx without a dump valve, but I've been using the standard airbox on mine a while now, so no sound.
 
OK, so some people are talking about "pulses" (from what?) and others are talking about "surge". Now, I wasn't paying attention at the time, but I seem to remember something about surge conditions for pumps, linked with pressure differences between the inlet and outlet of a pump (a compressor is a pump). Is this the same kind of surge, or is it a different definition?

Most turbo set-ups are "blow-through", right? As in the compressor discharges through the throttle. Going from full-throttle, full boost to suddenly shutting the throttle "triggers" the BOV, which, as its name implies, is built like a "safety" pressure-release valve. Without a BOV, this means the discharge pressure could potentially skyrocket, depending on the throttle. Is the closing throttle the source of the "pressure pulse"?

Does the (pump definition) surge occur because the discharge pressure is now so much higher than the inlet that the laws of thermodynamics want to have a word with the compressor wheel? So I'm assuming that recirculating BOVs dump to the inlet side of the compressor (and not into the intake of the engine...) to minimise this difference and prevent wasting compressed air? But then it'd leak out the air filter...

Just thinking out loud...

EDIT: Meh, I need to read up on this stuff. I'm thinking that venting behind the throttle body without putting any extra fuel in is dangerous; adding more fuel is good for anti-lag, but not so much for economy and noise...

Anyway, I'm off-topic now. All the BOVs sound very similar in GT5, but I can't hear the wastegates on those big turbo'd racers - maybe they're welded in GT5 :dopey:
 
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A Dump Valve/BOV/Recirculation system/Wastegate all serve pretty much the same general purpose.

Yes I know, but the OP is talking specifically about Dump Valves/BOVs which as I said, not every car with a Turbo has. Yes they will have a Wastegate But thats not what the OP was asking about.

So I'm assuming that recirculating BOVs dump to the inlet side of the compressor (and not into the intake of the engine...) to minimise this difference and prevent wasting compressed air? But then it'd leak out the air filter...

Just thinking out loud...

Yes, back into the turbo compressor inlet, it just gives the pressurised air an alternate path when the throttle is closed.
 
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OK, so some people are talking about "pulses" (from what?) and others are talking about "surge". Now, I wasn't paying attention at the time, but I seem to remember something about surge conditions for pumps, linked with pressure differences between the inlet and outlet of a pump (a compressor is a pump). Is this the same kind of surge, or is it a different definition?

Most turbo set-ups are "blow-through", right? As in the compressor discharges through the throttle. Going from full-throttle, full boost to suddenly shutting the throttle "triggers" the BOV, which, as its name implies, is built like a "safety" pressure-release valve. Without a BOV, this means the discharge pressure could potentially skyrocket, depending on the throttle. Is the closing throttle the source of the "pressure pulse"?

Does the (pump definition) surge occur because the discharge pressure is now so much higher than the inlet that the laws of thermodynamics want to have a word with the compressor wheel? So I'm assuming that recirculating BOVs dump to the inlet side of the compressor (and not into the intake of the engine...) to minimise this difference and prevent wasting compressed air? But then it'd leak out the air filter...

Just thinking out loud...

Lol not sure if all that's sunk in yet, but yes i think you are correct, the closing throttle is the source of the "pressure pulse" and the BOV vent's into the compressor side of the turbo not the intake. Some air will leak out the intake depending on how long the throttle is closed for I'd imagine.
I was hesitant to use the term compressor surge, as I've heard it being used before to describe what I'm talking about, but was never sure weather it's the right term or not.
I'm no expert just use my own terms to describe things.

I never really noticed much turbo sounds in GT5, I use "bumper cam" and would have thought i would of heard them more clearly.
 
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👍 Like a birdy in a tree.

Like tinkling glass....👍

My RUF Turbo IRL uses a C2 BOV....but the wastegates are adjustable with spring combos...I use 1 bar boost, others use between .8 and 1.2 bar.... the higher the number the closer to detonation....:scared:

And yes...I am a boost-a-holic..... :D
 
...

Yes, back into the turbo compressor inlet, it just gives the pressurised air an alternate path when the throttle is closed.

Ah, thanks! 👍
I'm sure if I'd ever actually looked at the plumbing on a modern turbo, I'd have noticed it.

Lol not sure if all that's sunk in yet, but yes i think you are correct, the closing throttle is the source of the "pressure pulse" and the BOV vent's into the compressor side of the turbo not the intake. Some air will leak out the intake depending on how long the throttle is closed for I'd imagine.
I was hesitant to use the term compressor surge, as I've heard it being used before to describe what I'm talking about, but was never sure weather it's the right term or not.
I'm no expert just use my own terms to describe things.

I never really noticed much turbo sounds in GT5, I use "bumper cam" and would have thought i would of heard them more clearly.

Thanks for your input on this, it definitely helped! I though I was going mad, I was sure I'd seen "compressor surge" somewhere...

I've just spent a wee while trying to weed out the definitions of things. It turns out that there is a tendency to use different terms to mean the same thing, and the same term for different things. :dunce:

Anyway, apparently "surge" is what happens to the compressor wheel - it's any change in its acceleration (rotation rate), which is basically happening all the time as it scoops up fresh fluid and when it chucks a "slug" of compressed fluid off the vane out the other end. If this gets to a high level, it will start to knacker bearings and fatigue the compressor wheel. Good mechanical and aerodynamic design of the compressor can minimise this kind of "surge".

On top of that, any sudden change in the speed of the discharged fluid will cause a pressure wave. Change the throttle position, or suddenly change the compressor speed etc. and it will start a pressure wave. On a turbo car, this reverberates between the throttle and the compressor, causing a change in the acceleration in the compressor wheel - it causes it to "surge" / "jerk" / "jolt" / "lurch" more. Add to that the potentially destructive nature of these acoustic waves, and you can see why its big business trying to prevent them in industrial kit, especially for liquids. I don't think they bother with this on road cars, given that air is compressible. Expansion tanks in the flow-line, anyone?

Finally, "compressor surge" is a slightly different animal. It was a big problem in jet engines for a while - although they call it "stall", as may be more appropriate there. Anyway, Wikipedia knows what it is. So, on a turbo-charged car, shutting the throttle off means the discharge pressure builds to a point that the compressor can't maintain the pressure ratio (discharge / inlet), so reverse flow occurs whilst the compressor is still turning - but, all that energy has to go somewhere, so it gets hot and slows down. Now I can see why venting to the inlet is preferable.

That probably clarifies nothing, but I enjoyed wasting my time on it. :P

-----------

I use bumper cam, too; I'm using the stereo mix and almost never hear the turbo sound effects. I suppose they're still struggling to find the middle-ground after GT2!
 
This conversation may have gone a little stale now but I don't see people offering up suggestions as to which ones in the game have a distinguishable dump/blow off valve sound.
I've got over 500 cars and have only ever heard it on a Daihatsu Copen!!
 
... sorry, but I had to laugh a little at some of these responses. Just a note to you guys, and you know who you are ... be sure that the information you are repeating is the truth before you try to regurgitate it as fact.

Several people have had good input, but a few ... wow.

👍 No doubt.
 
Turbo chatter is the bird like noise you hear. Sounds much better than the whoosh from an atmospheric BOV but can harm some turbos. Alot of competition cars use screamer pipes now too.
 

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