Do we bother with dump valves anymore?

or are turbos strong enough these days to handle it?

Lyndon.

or are turbos strong enough these days to handle it?

 

Lyndon.

You need one if you run a decent amount of boost or you will split the IC/blow off pipes, HKS racing is the only one ive found that opens quick enough, turbosmart is rubbish, tial is pretty slow an all.

I split the IC open on my red car when it never had a bov, Colin did the same on the doluck car when that never had a bov.

No matter how strong a turbo is you don't want any stall if you can avoid it, in my opinion.

Any type of shock loading can't be good, and releasing or recirculating the pressure will provide a nicer drive with a quicker pick up.

Atomospheric ones make a funny sound to keep you entertained as well, and help surprise on lookers as you drive by always keeps me entertained anyway .

If you are running 9 psi on a T04e on a NA-T, do you think you need one then?

If you are running 9 psi on a T04e on a NA-T, do you think you need one then?

Be ok most likely, id still fit one though.

There's a vast amount of rubbish talked about blow off valves. They were designed to stop customers complaining of "funny noises" on early turbo cars, they do nothing to aid spool, can be unreliable, add weight and complexity, and are now used to do the exact opposite of their original purpose. That is they are now used to make silly noises, a mechanical means of shouting "I have a big one" from under the engine cover of the car. (IMHO). To say they stop shock loadings is also incorrect. If they aided spool and added turbo reliability every turbo charged 24 hour Le Mans prototype, and every F1 engine in the turbo era would have had one. The fact is, none did.... Maybe all the drivers were supremely endowed?

Chris, I'm slightly playing Devil's Advocate here but this is a point of view I read on here a few years ago: suppose BOVs are effective at preserving turbo life (by preventing shock loading) whilst having the unwanted downside of releasing hard-earned boost pressure: that could be a reason why race cars don't have them but domestic cars do: the race teams could presumably fit a new turbo for each race, as long as each one lasted the duration of the race. Whereas domestic users are more concerned with turbo longevity.

In the F1 era turbos often didn't last a single race, so if a simple BOV would help them live longer, what do you reckon they'd have fitted?

Le Mans is won or lost on reliability, to a large extent. Again, a simple BOV would be fitted if it gained reliability. Honestly, a lot of the stuff on the net is garbage on this subject.

Interesting.

I have compressor surge. I found when changing the BOV it actually got WORST. The stock TT is fitted with an oem bov isnt it? They must of designed it for a reason, not sure I'd want to take mine off.

I wouldn't want to run an NA-T without a BOV, there is enough surge as it is IMO. Just get a quiet one if you dont want to sound.

The stock valve is a recirculating valve but a similar thing.

I'm with chris w on this. I have an engine builder who has run a sr20 in his bmw 3 series for 5 year with out on.

Sound ace when he lifts

Lyndon.

I would not bother fitting one on any of my cars, if theres one on there I dont mind leaving it.

I would not bother fitting one on any of my cars, if theres one on there I dont mind leaving it.

Sums up what I would do if I had a turbo'd car. My rule of thumb is, "unless you know why you should perform a modification that changes a car from standard spec, then don't."

Chatter vs Chhhh????

I think I'm going to remove mine. It's on the ic pipework down near the front wheel. I can only imagine as I also have no mud guard there it will get covered in crap and eventually fail. Just need something to bung it with

I'll always run with one. The only downside I can see from having one is that it's something else to fail, but given that the only one that's ever failed on me has been a stock one it doesn't keep me up at night. I've ran an HKS one for over 4 years and never had a problem.

Obviously the noise is for some and not for others but that's what the recirculation pipe is for.

Thinking about what the BOV does I can only see it being good for the whole system. I can't see any negatives from having it at all, only benefits. When the throttle is closed (after WOT) the turbo will continue to spin increasing the pressure in the intercooler/intercooler piping. Depending on what sort of boost you are running I can easily see this popping off intercooler pipes, Jamie has had them split, but he is running much higher boost than most. When the inertia of the compressor spinning is lost the back pressure from the intercooler/piping will stall the compressor, I can't see this doing anything but creating lag when it comes to getting the wheel back up to speed.

I agree that there won't really be any shock loads on the compressor wheel/shaft of the turbo though. It'll be like a spring the way the pressure inside the intercooler piping rises as the inertia of the turbo lowers. It won't be like a switch, the compressor speed will slow quickly but certainly not instantly.

Negatives for having the BOV? It might break at some point.

By shock loading, I was referring to the stall a turbo experiences, if pressure isn't released somewhere.

If you don't have a means to allow pressure release, whether that be recirculation or atomospheric a turbo will experience stall.

At higher or perhaps peak pressures with no pressure release this will cause judder, and that judder is the turbine stalling.

This isn't good for any turbocharger at all.

My personal experience with such stall on twin turbo'd V6 engine at higher pressure was 100% cured by fitting a blow off valve, providing me with a smoother drive on and off throttle and to me a quicker pick up too.

Each to there own I guess.

By shock loading, I was referring to the stall a turbo experiences, if pressure isn't released somewhere.

 

If you don't have a means to allow pressure release, whether that be recirculation or atomospheric a turbo will experience stall.

 

At higher or perhaps peak pressures with no pressure release this will cause judder, and that judder is the turbine stalling.

 

This isn't good for any turbocharger at all.

 

My personal experience with such stall on twin turbo'd V6 engine at higher pressure was 100% cured by fitting a blow off valve.

 

Each to there own I guess.

I know what you are referring to bud, but I don't see the physics in your explanation.

Pressure isn't a switch, it increases at a rate. With no BOV when the throttle is closed the pressure in the intercooler/piping will increase with each revolution of the compressor wheel. The rate that the compressor spins at will decrease as the back pressure from the intercooler/piping increases (while the exhaust gas isn't powering it that is). In other words, as the pressure rises the compressor speed slows. As the compressor speed slows the increased back pressure will vent backwards through the compressor wheel. At the same time the exhaust gas will keep the compressor moving forwards rather than backwards. This is the reason you get the funny stall noise.

There is no sudden jerk or motion in all of this. Even though it all happens in a matter of miliseconds it's gradual rather than instant.

I know what you are referring to bud, but I don't see the physics in your explanation.

 

Pressure isn't a switch, it increases at a rate. With no BOV when the throttle is closed the pressure in the intercooler/piping will increase with each revolution of the compressor wheel. The rate that the compressor spins at will decrease as the back pressure from the intercooler/piping increases (while the exhaust gas isn't powering it that is). In other words, as the pressure rises the compressor speed slows. As the compressor speed slows the increased back pressure will vent backwards through the compressor wheel. At the same time the exhaust gas will keep the compressor moving forwards rather than backwards. This is the reason you get the funny stall noise.

 

There is no sudden jerk or motion in all of this. Even though it all happens in a matter of miliseconds it's gradual rather than instant.

Perhaps this is different when having to run twin air metering units, where the pressure becomes backed up with no where to go.

This was my personal experience, and all I know is when I fitted the twin atmospheric blow off valves just before the twin throttle bodies it 100% stopped the problem.

And yes I quiet agree with you, we are talking milli seconds indeed.

Still made for an awful drive in my experience without it.

NB: On my car when I experienced the said stall/ judder, there were no noises at all lending to my above explanation.

I stand by what i said 100%, if you run any decent amount of boost on a supra a good quality BOV is a must have item, when i split the ic open on the red car that was only running 1.6bar, same on colins do-luck car, im also sure i read of one of the whifbitz race cars splitting a Intercooler because they tried it without a bov.

Same with the black car, anything but a hks racing bov and there is nothing i can do to stop pipes blowing of, no other bov i have tried will open quick enough and the pressure as i let off blows the pipes off.

Saying not to run one is bad advice imo, i know for a FACT that my car would not last one full boost/wot run without either popping a pipe or even worse splitting the IC open, a low boost supra might get away with it, Id still want a bov though.

Sums up what I would do if I had a turbo'd car. My rule of thumb is, "unless you know why you should perform a modification that changes a car from standard spec, then don't."

Stock TT supras have bov's as standard so thats your theroy blown out of the water.

i have x2 blow off valves and x2 wastegates on mine lol but i like my woosh lol

I stand by what i said 100%, if you run any decent amount of boost on a supra a good quality BOV is a must have item, when i split the ic open on the red car that was only running 1.6bar, same on colins do-luck car, im also sure i read of one of the whifbitz race cars splitting a Intercooler because they tried it without a bov.

 

Same with the black car, anything but a hks racing bov and there is nothing i can do to stop pipes blowing of, no other bov i have tried will open quick enough and the pressure as i let off blows the pipes off.

 

Saying not to run one is bad advice imo, i know for a FACT that my car would not last one full boost/wot run without either popping a pipe or even worse splitting the IC open, a low boost supra might get away with it, Id still want a bov though.

 

 

 

Stock TT supras have bov's as standard so thats your theroy blown out of the water.

I 100% agree with you Jp.

i have x2 blow off valves and x2 wastegates on mine lol but i like my woosh lol

Ha.... I bet that sounds fantastic.

Ha.... I bet that sounds fantastic.

haha when it works lol

but yes 100% sounds great..

tbh my 2 blow off valves are recirc now as it causes stalling on heavy runs when back to idle.