What is a dump valve for? Do I need one?

What is a dump valve for? Do I need one?

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Discussion

Ecurie Ecosse

4,812 posts

217 months

Saturday 19th September 2009
quotequote all
Anti lag on the other hand....

http://www.youtube.com/watch?v=hEK7POxpVeE

MGJohn

10,203 posts

182 months

Saturday 19th September 2009
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My original equipment recirculating BOVs ( Blow off valves) on my Rovers are relatively silent but, do make a noise ~ kind of a "sigh" sounding like "Harrrrr" when lifting off the throttle on boost as the throttle valve plate closes so that the pressure builds up and causes the BOV to release that surplus pressure without slowing the spinning turbine in the turbocharger down too much. Bear in mind that turbochargers spin up to around 120,000 rpm IIRC, even those fitted to average saloons like my Rovers and MGs.

I have fitted a Forge direct replacement to one of my cars and that makes a loud explosive hiss sound when changing up at high boost. It can be quite loud and it does attract attention from some drivers who look down their superior noses at my aged 'lesser' Rovers when say 'matching strides' at the TLGP. Drivers of VAG diesels always seem to be ready to participate and as soon as they hear that blow off sound, by which time the old Rover has nosed ahead, they usually chuck the towel in and adopt a 'I'm not playing after all' mode .... I have to admit I enjoy this and do not think I'll ever tire of it.... I see it as a bonus. Yes, I really know I'm opening up to all kinds of PHer holier than thou stuff but, at least I'm honest and I would bet a nice few quid, most PHers have participated in some TLGPs at least occasionally.

All done in the best possible taste obviously ...smile

So Chav or not, it has its positives for this aged Rover driver ... wink .... I would not cut a boost hose to insert an after market BOV, only use the direct replacement jobbies Forge supply for the OE T25 Turbochargers. Thus, it's easy to return the car to bog standard. As far as I'm aware, there is no performance advantage ~ indeed, there may be a very marginal loss with the release to atmosphere BOVs for all I know. I cannot detect any perfromance variance either way ... just the noise difference which I like to hear.

Maybe someone with a better appreciation of the finer aspects of these things can enlighten me one way or another.
.
Edit to add @ 20:47

Here's a direct replacement BOV fitted to a car I bought some years ago. Had I not bought this car, I'd never had considered fitting one to subsequent cars purchased:~



Edited by MGJohn on Saturday 19th September 20:47

williamp

19,217 posts

272 months

Saturday 19th September 2009
quotequote all
When 5th gear tried to nake an Esprit do 200mph, they went for an external dump valve. For a really silly/wikkid noise (depending on your age) have a look here, at about 4 mins 10 secs onwards

http://www.youtube.com/watch?v=ZVaYjmAUZig&fea...

I've never heard of a dump valve so big. Mind you, I have seen a chav car with four of them- you'll never need more then one unless you're an 80s F1 car with two turbos spaced wide apart.

Scuffers

20,887 posts

273 months

Saturday 19th September 2009
quotequote all
one of the other reasons for using dump valves is that in some high boost applications, the throttle plate would get blown clean into the engine if you suddenly lift off at high rpm/loads, not good as even if it did not make the inlet ports, the engines still got an open throttle 100% of the time!

Fort Jefferson

8,237 posts

221 months

Saturday 19th September 2009
quotequote all
300bhp/ton said:
Fort Jefferson said:
Dump valves, are the automotive equivalent of spitting in the street.
Take it you've not read any other the other posts in the thread then and don't know what one is. Ok smile
I'm more than aware what one is, and I take it you've not read my post on your thread, about turboing a RV8, offering you some turbos and SU's.

300bhp/ton

41,030 posts

189 months

Saturday 19th September 2009
quotequote all
Fort Jefferson said:
I'm more than aware what one is, and I take it you've not read my post on your thread, about turboing a RV8, offering you some turbos and SU's.
No sorry, I'll have a look. Cheers smile

HalfMoon

296 posts

187 months

Sunday 20th September 2009
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EDLT said:
And it allows you to plumb in a duck whistle:
http://www.youtube.com/watch?v=VbNxugO-uf0
That is just fantastic!
laugh

cstar504

4 posts

111 months

Wednesday 10th December 2014
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Hi Everyone

i have just bought a 2014 ST 2 250 bhp

i have been into cars since i was just a boy and have now managed to bag myself an ST not the greatest but ive always been a ford boy.

I have a question for you professional petrol heads

i understand my turbo car has a dump valve, this being a recirculating valve (STOCK) i am keen to purchase something slightly better but im not sure about the atmospheric ones, i do like the tone/noise they make when you take your foot off the pedal but would like to know whats better for my car, i have read the post already on this website but still cant decide . recirculating or atmospheric could you guys point me in the right direction, i am a fan of the noise but dont want to balls my car up.

thanks again

Cstar504

tickious

1,392 posts

173 months

Friday 7th April 2017
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I've just got a Colt CZT. I asked a Colt tuning specialist what I needed to have done to safety reach 200bhp with a remap. He said you need a scorpion precat back exhaust, kn induction kit and forge rs valve.
I believe this isn't the noisy kind, and is actually of use.
I'm not sure what it is, but I often hear a car drive by my house, and even at low revs it dumps a large "Ppssst!!" at every gear change.
I'm not after that. I want it to look and sound standard. Just have a bit more poke.
https://www.dynodazeperformanceparts.com/shop/mits...