this might be a stupid question,
i had a stage 3 cosworth a few years ago, i removed dump valve that was fitted when i bought it and the wastegate chatter sounded awesome,
i now have a stage 3 cosworth powered mk2 escort and without the dump valve fitted the 'chatter' the wastegate makes is more a dump valve sound! why is this?

Wastegates dont chatter.

The sound you hear is the air stalling the turbo, when you let off the throttle the pressurised air produced by the turbo hits the closed butterfly in the throttle body and has no where to go, a dumpvalve releases this, no dumpvalve and it hits the compessor wheel and makes the noise you on about. The noise is much louder when you have a cone filter fitted.

Probably not the best explanation but you should hopefully understand what i mean.

I blame Jerermy Clarkson for people calling it wastegate chatter, the only wastegate noise you will ever hear is if you havent got the preload of the actuator set right it will make a horrible vibrating noise. Or if the penny fell off you would probably hear it pinging through you exhaust whilst thinking why has my car just turned into a 1.6L.

I think this is a good explanation, direct and to the point.
A few days ago for me lad I removed the DV pipe and blocked it to get chatter, he loved it, but christ did it kill the performance through the gears, still at least putting the vac pipe back on let me hear it's eaten another diaphragm!!
tabetha

the idea of a dumpvalve is to get the compressed gasses out of the turbo as quickly as possible so that they dont slow it down, to reduce turbo lag. ive got HKS on my RX7 with the purple tip and although it dosent flutter it sounds great. and very loud. makes ur ears ring if ur near it

sorry to hijack the thread, so i presume that a hks d/v is a good valve. well better than bailey's ?

as long as it dosent leak when closed an releases when the vacume is applyed i cant see much difference

Honest opinion guys.
Dump valves $HIT or GOOD.

Have took mine off the S1 and was wondering if it would cuase any probs?, i just dont want my car sounding like a chav tastic S1..

I know certain tuners/engine builders hate them n some love them..

cheeRS
Barney

good for efficiency IMO. there are ones on the market that are virtually silent.

failing that, plumb it into a box (similar to a catch tank, a hole at each end though) with some pillow stuffing in it, or padding lol. sounds odd but i have a picture in my head, it'd be similar in principal to a backbox.

Or back into airbox if you've still got it on.

or just buy a recurcluating valve instead of a dukmp valve

you dont need a dumpvalve unless your running high boost... they where first made for rally cars to stop what they call back spin! running 15psi a dump valve isn't needed!

I hate them - had 3 baileys ones in 6months

petty much what he said, at low boost they arent really necasery, just sound cool.

I am only running 17 psi or so, the difference was a HUGE amount, with DV unplugged, enormous lag with no dv for me, just try it.
tabetha

Its not just the boost its the size of the turbo also...

is it a hks ssqv?

love the sound of those with the 3 blade tips.

DV were NOT at all made for rally cars to stop "back spin", they were actually made for NVH, Noise Vibration Harshness reasons, and to help performance.
If the air entry could actually cause enough force to spin the turbo backwards, it would snap the shaft, it would also be amazingly effecient to generate this much boost that the inlet is ahead of the exhaust side.
The almost stalled air at lift off merely gets buffeted violently by the impeller with no dv, but it most certainly does not stop.
tabetha

you might want to do some research before saying other people are not telling the truth!
some web site you can look at....

http://en.wikipedia.org/wiki/Dump_valve

http://www.vdub-performance.com/turb...explained.html

http://www.envyperformance.com/index...roduct_ID=1073

http://www.jperformance.co.uk/subaru...lver-p-49.html

so what if your running a gt30 for instence??

i would !! i run one on my car.

i was watching a re run of 5th gear where tiff drives a lotus esprit (iirc) with twin turbos and he comes off the throttle, gets chatter and says "thats what i call a wastegate"

i've always thought why/who did start the "wastegate chatter" expresion

Thats probably who Jeremy Clarkson got it off . I think i remember the 5th gear your on about, i think its the one with Rods car on where they are trying to get the Esprit to do over 200mph.

As for the earlier comment about dump valves being invented for rally cars, i find this hard to belive as they had ALS and dump valves dont work with this.

Isn't a dump valve vacuum operated? Hence the vac pip connected to it?

All thats needed is a valve to stop the vac when ALS is in use.

Having said that, ALS just keeps the turbo spinning so the DV will release when it's upper boost limit is reached, the turbo on rally car will boost enough to keep it open while the gear is changed since it's tiny amount of time. Giving almost full boost as soon as the throttle is opened again since the inlet is at full pressure already.

Dont really get where your coming from mate. There is no vacuum when using ALS, when you let off using ALS the pressure on either side of the butterfly is equal so the dump valve is useless, has nothing to do with boost pressure. Just something else to leak IMO so i doubt very much that they would fit them.

The vac pipe is to do with DV as you know.

The turbo can spin faster and still hold the same boost if a DV is working like an overflow. Without DV the air has no where to go and is ultimately controlled by boost limiter, which will top out quick with all that air backing up in the inlet. All the DV needs to do is overflow a few PSI above the normal max boost pressure.

That way it wont leak under full boost, and only opens over it to allow turbo to spin as fast as possilbe while the butterfly is closed/closing for gearchange.