ok..... i have a dump valve that u bought for my turbo indy (didnt cost much), its not a noisey one but still will make a wooshing noise if i fitted
it, is there a benifit of using one or are they just boy racer snake oil crap ?
[Edited on 18/2/07 by graememk]
There should be a genuine benefit but of course its a choice boy-racer add on!
The idea is that without a dump valve when the throttle is shut quickly (eg between gear changes) the turbine blades begin to slow but remain spinning
for a time thus building boost with nowhere for it to go.
Sometimes this produces pressure spikes of up to 50psi and can bend throttle spindles amongst other things. The other alleged benefit is that with the
boost vented the turbine is less likely to stall and can keep its inertia in readiness for the next generation of boost (eg when the next gear is
selected) - a kind of anti-lag idea.
A dump valve is usually fitted from the factory in production cars but it recirculates the "dumped" air back in front of the turbine blades
and isnt heard very easily.
It could be argued that in a BEC when you hardly lift off the throtte between gear changes, the pressure spikes are less of an issue but I included
mine as a kind of safety valve.
Its worth mentioning that Rally cars have entirely different anti-lag system where an injector in the exhaust manifold opens and spools the turbo up
artifically. It sounds unbelievably brutal and on a friends Sierra Cosworth, I thought I was about to see bits of molten metal under the car when he
switched it off!
Geoff
[Edited on 18/2/07 by jambojeef]
A mate who works for a ECU company has been playing about with a customers group N evo at the moment. He was explaing the anti lag system to me, it was on a night out and I had drunk a few, so the details are a bit sketchy, but im sure he said that the throttle was constantly open and the car speed was controlled using the anti lag, meaning the turbo was always up to speed. Sounded crazy as you were always trying to hold the car back. Will find out the proper details when he gets back from his trip (at Kyalami with a customer and his ex Ferrari F1 car! Lucky bastard!)
quote:
Originally posted by graememk
ok..... i have a dump valve that u bought for my turbo indy (didnt cost much), its not a noisey one but still will make a wooshing noise if i fitted it, is there a benifit of using one or are they just boy racer snake oil crap ?
[Edited on 18/2/07 by graememk]
not sure if i would get a kicking if i turned up to a meet making wooshing noises
A dump valve basically does what is says on the box, it's a valve the dumps excess pressure in to the atmosphere. Make sure that you get the pressure set right or your engine could go bang.
I'm going to be sticking with the factory fit one on mine. Had no issues with lag when the engine when it was in a tin top. The air is
recirculated, but it still has to pass throught the intercooler before reaching the intake, so it shouldn't be hot.
quote:
not sure if i would get a kicking if i turned up to a meet making wooshing noises
quote:
Originally posted by marcjagman
Make sure that you get the pressure set right or your engine could go bang.
quote:
Originally posted by zilspeed
the car now has a free flow air filter
as a scooby owner for 4 years...here goes.
1. if you are happy with a normal re-circ fitted and not interested in the woosh noise...then leave that on.
2. if you want the Whoosh noise, choose a piston type and not a diaphram type.
3. as for sounding like a pratt...each to their own....but think about this, what do you think you look like in a small 7 type. especially with a
screaming engine.
quote:
Originally posted by meany
3. as for sounding like a pratt...each to their own....but think about this, what do you think you look like in a small 7 type. especially with a screaming engine.
Its not what you have, its what you do with it,
problem is, there is too many idiots out there that have now given the scooby a bad name...mine has a re-circ one on so is quiet....as i said...each
to their own.
anyhow...going off topic here.
1. I reckon all turbo engines should have a dumpvalve on, for smoother responses and reduced turbo lag.
2. no power gains to be had from a VTA dump valve...maybe slight better response through gear changes.
this is all from my own experiences, yes i had a VTA on my previous scoob, a Forge one, not too loud, just right, in my opinion.
What management are you using to run the engine, or more to the point how does it sense engine load? MAF/AFM systems do not like atmospheric dump valves, MAP sensors however are fine with them. Atmos valves are not good with a MAF because they are generally dumping metered air out of the system, the ecu doesn't see this so fuels as if the air is still there (so it overfuels). The lambda sensor then sees a rich exhaust and tells the ecu to cut a bit of fuel, just as you are whomping the throttle back on. Most of the time you'll be alright, but if your engine is tuned close to it's limits it could be enough to push you into detonation