dump valve?
Thread Starter
Scooby Regular
Joined: Apr 2008
Posts: 370
Likes: 0
dump valve?
Ive read a few posts on dump valves and the general consensus is dv do not improve initial accelleration and post gear change accelleration? I have a bog standard STi type uk my05 which ive just added a forge dv to and i think there is an improvement in accelleration, noticably especially when changing gear. any opinions? v grateful for info as its my first scoob cheers all
apart from the sound...after i fitted my forge dump valve to my classic...i actually noticed a slight, not much, but smoother acceleration. it prob has nothing to do with acceleration what its jobs for, as its just dumping air into the atmosphere. i think its a mental thing cuz ull know to put ur foot down exactly to get the sound just right...therefore leading u to driving it a bit better, lol. philosophy of a dump valve eh... strange that i actually noticed i used a little less petrol after fitting it too..........:S
Scooby Regular
Joined: Jun 2008
Posts: 225
Likes: 0
From: MK
A dump valve won't make the car quicker but should help reduce lag/spool up time after a stall period.
When you lift your foot off the gas pedal the throttle plate in the thottle body closes. This prevents air entering the intake manifold. However this air then backs up thru the induction setup and intercooler all the way to the turbo.
As you have lifted off the throttle pedal, the exhaust gas flow has reduced, this alone has meant the turbo is not spinning as quickly as it was before. However combine this with the high pressure air stuck between the TB and the turbo then it will almost stop the turbo spinning at all (well comparatively speaking).
The dump valve (or BOV) release this high pressure air when the TB is closed. This means it tries to help keep the Turbo spinning thus reducing lag.
In stock form most turbo cars have a recirculating dump valve, this means the high pressure air it releases it simple redirects back into the other end of the intake where the air filter is as this is on the other side of the turbo.
I would think the main reason for this due to noise suppression more than anything. If you where going to go to WOT (wipe open throttle) very soon after then if the this released air is still compressed you may see an element of compound compression from passing it thru the turbo again. However I suspect that as the open end of most intakes are not sealed this is not the case. One could also speculate that as this air has already been compressed it may also be hotter than the ambient air that would normally be sucked in.
So is recirculating better or worse??
Think in most cases it comes down to personal opinion.
A to atmosphere dump valve releases this air to the out side, this is usually louder. On high boost setups I can see this potentially being more desirable. Also many competition cars use a to atmosphere setup.
And many high performance road cars such as the Bugatti EB110 have to atmosphere dump valves, but then again it does have 4 turbo chargers...
But all in all a dump valve has only a minor affect on most setups. There is proof in two main forms:
1. If a dump valve could successfully remove or reduce lag then "anti-lag" systems like a Bang-Bang would not exist.
2. Turbo diesels - Diesels don't have a throttle body, so this high pressure air never gets trapped in the first place. Yet turbo diesels still suffer the same turbo lag. This supports the theory that the exhaust gas flow reduction is the biggest contributor to turbo lag. And funnily enough that is the area addressed by anit-lag systems.
When you lift your foot off the gas pedal the throttle plate in the thottle body closes. This prevents air entering the intake manifold. However this air then backs up thru the induction setup and intercooler all the way to the turbo.
As you have lifted off the throttle pedal, the exhaust gas flow has reduced, this alone has meant the turbo is not spinning as quickly as it was before. However combine this with the high pressure air stuck between the TB and the turbo then it will almost stop the turbo spinning at all (well comparatively speaking).
The dump valve (or BOV) release this high pressure air when the TB is closed. This means it tries to help keep the Turbo spinning thus reducing lag.
In stock form most turbo cars have a recirculating dump valve, this means the high pressure air it releases it simple redirects back into the other end of the intake where the air filter is as this is on the other side of the turbo.
I would think the main reason for this due to noise suppression more than anything. If you where going to go to WOT (wipe open throttle) very soon after then if the this released air is still compressed you may see an element of compound compression from passing it thru the turbo again. However I suspect that as the open end of most intakes are not sealed this is not the case. One could also speculate that as this air has already been compressed it may also be hotter than the ambient air that would normally be sucked in.
So is recirculating better or worse??
Think in most cases it comes down to personal opinion.
A to atmosphere dump valve releases this air to the out side, this is usually louder. On high boost setups I can see this potentially being more desirable. Also many competition cars use a to atmosphere setup.
And many high performance road cars such as the Bugatti EB110 have to atmosphere dump valves, but then again it does have 4 turbo chargers...
But all in all a dump valve has only a minor affect on most setups. There is proof in two main forms:
1. If a dump valve could successfully remove or reduce lag then "anti-lag" systems like a Bang-Bang would not exist.
2. Turbo diesels - Diesels don't have a throttle body, so this high pressure air never gets trapped in the first place. Yet turbo diesels still suffer the same turbo lag. This supports the theory that the exhaust gas flow reduction is the biggest contributor to turbo lag. And funnily enough that is the area addressed by anit-lag systems.
Last edited by 300bhp/ton; Jun 10, 2008 at 09:39 AM.
Thread Starter
Scooby Regular
Joined: Apr 2008
Posts: 370
Likes: 0
ive read ur post now bout 4 times ive come to the conclusion im just not qualified enough to understand what ur saying LOL!!!
Top reply much appreciated and A* for effort.
Also im looking to purchase an exhaust im liking the blitz nur spec its mainly for the sound not too fussed about power gains although a bit more would b welcome, would u advise anything to accompany the exhaust ie new air filter etc cheers
Top reply much appreciated and A* for effort.
Also im looking to purchase an exhaust im liking the blitz nur spec its mainly for the sound not too fussed about power gains although a bit more would b welcome, would u advise anything to accompany the exhaust ie new air filter etc cheers
get the after burner exhaust from scooby world
keep the re circ on, car is much smoother and if u do fit an induction kit in the future,i get the noise anyway through the air filter.
keep the re circ on, car is much smoother and if u do fit an induction kit in the future,i get the noise anyway through the air filter.
im voting for a blitz mate...hear some of the video links on this thread, heres the link to it
https://www.scoobynet.com/scoobynet-...ust-worth.html
https://www.scoobynet.com/scoobynet-...ust-worth.html
im voting for a blitz mate...hear some of the video links on this thread, heres the link to it
https://www.scoobynet.com/scoobynet-...ust-worth.html
https://www.scoobynet.com/scoobynet-...ust-worth.html
classic= nur spec
newage= after burner
Thread
Thread Starter
Forum
Replies
Last Post
shorty87
Wheels And Tyres For Sale
0
Sep 29, 2015 02:18 PM