Newbie with a dump valve question
 

Hi everyone,

Just upgraded from a sluggish 2.0GX and finally got myself a 1998 turbo wagon. It currently got an ugly looking dump valve, which looks ready for the bin. But i still want one on the car.

What is the name of these dump valves I keep seeing that give off a differnt noise than the usual "tish" and sound more like the world rally cars? You know what i mean, the "chatter"

Anyone?

The chatter is the wastegate; your car needs a re-circulating dump valve; like Subaru fitted it with.

Well said. :)

But how come it doesnt make that noise from standard? Do you have to do anything else to make it noticeable?

You could wear a bizarre form of headwear, if all you want is to be noticed. :)

Beer anyone? :D

Ooooh.... ta. TK!!!PSsssssssss!!!! Glug.... glug....... :)

Oooohhhhh!...Yes Please.

I'm still haven't recovered from the last session we had ! :D


Psssshhhhtttt...
Glug...
Glug...
Buuurrrrpppp........

Or, if you really wanted to be noticed....

...You could remove the DV altogether and replace it with a referee's whistle :thumb:

A re-circulating dump valve will keep all of the metered and fueled-for air in the inlet tract. A vent to atmosphere dump valve (as seen of 2fast 2furious and many a Morrisons carpark after closing) will allow it to escape and the unneccessary fuel will wash your bores, but its shiny and it makes a nice noise. The choice is yours.

Yeah funny mate. Wanna just answer the question or take the p*ss. Sorry but Im just curious about this noise i keep hearing

Excuse me everyone for asking questions

I saw a video recently of two American tossers who got a VTA dump valve with a duck call on it for f*cks sake!

REV REV Quack!

Calling REV, corradoboy, wah, Tiredeyes, T5NYW, andypugh, Beastie, 7 Foot, Granby, fiestaboy, MarksWRX, Gutman pug and STILee.


The Bar Is Open
:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D:D

class vid

FPMSL.... :lol1: :cry: :lol1:

What's that thing that clowns have? The thing that goes VVvvvvrrrrrrwweeeeeeeeeeeee!!!!!


:lol1: [choke] :D:D

Double G&T if you're buying, please ;)

Wow this is hilarious, cheers

Think I'll keep clear of dump valves

Your question is a little vague Chrissy, but I have answered it as best as I can. The chatter noise that you mentioned is the wastegate operating; the wastegate allows wxcessive boost presure to be released. If your car makes a 'pssst' noice then I assume it has an aftermarket VTA dump vlave on it (a standard dumpvalve amkes a 'whooo' sound). VTA dump valves are pony, for the reason I explained, irrespective of whether its made by HKS or anyone else. The best thing you can do is remove it; hope your bores arent shagged and fit a standard fit re-circ dumpvalve.

Simon

Pass me a beer will you?

You know it makes sense. :D

I'm Bubba, by the way... pleased to meet you. :)

Ive looked at my Generation-X album and you definately look like Billy Idol's dad.....

Have I missed anything??? move over lads, got a beer there fiestaboy ;) ooooh and I have the corner too :D:D

He's older and weedier than me, you Scoobygeneral-based troll. ;) :D

Bailey motorsport do this very effective and pleasing to the eye part


http://www.123imprint.com/img_s/7105033s.jpg

improve your street cred instantly

What exactly does a dump valve do?

Dump Valves When accelerating hard, as you take your foot off the gas (e.g. to change gear) the flow of air into the engine drastically reduces. The turbo however will still be spinning and trying to force-feed air into the engine and as a result, the turbo starts to slow down due to the reduced airflow. When you reapply the gas again, the throttle opens and air can flow again allowing the turbo to spin up freely again. The time where the turbo impeller loses speed and has to regain it again is felt as turbo lag.

What a dump valve does is to allow the pressurised air to vent when the throttle is lifted. It can either vent to atmosphere or back though the intake plenum (which is called a recirculating system). The standard system as fitted to the Impreza is a recirculating one although some people do opt to change for the atmospheric type. Atmospheric venting systems produce that familiar "PTSHH!" noise as venting takes place. This venting process reduces the restriction on the Turbo impeller, so that it doesn't slow down as quickly. The result is less Turbo lag.

Uprating your dump valve from the standard one will allow air to vent more quickly and will thus reduce Turbo lag even more. Also when running higher boost pressures the standard item may not be able to cope and could leak and will then not allow full boost to be applied (as the dump valve should shut tight when accelerating). :)

But the above omits to say that venting metered air to atmosphere will mean the fuelling is incorrect (the ECU doesn't know the air has been vented and therefore you have overfuelling). This means a rich mixture, less power and possibly some bore wash which will increase engine wear. It only lasts for a short period, less than a second, but it might offset any benefit you think you have gained from the psssoooo sound. Fitting a VTA dump valve to a standard engine WILL NOT improve performance and will likely make it WORSE. If you want a psssooooo sound enough to accept a hesitation then fair enough, it's your money.

Engineering is all about compromises and trying to find the optimum performance point for your needs. If the pressure on the charge side (compressor side) is reduced beyond a certain point because of venting then it will take longer to generate the same level of boost when you apply the throttle again. So venting more air does not necessarily mean better throttle response, it all depends on the characteristics of your engine.

The standard recirc dump valve is generally agreed to be very well matched to the standard engine and provide the best throttle response after venting (internally). If you are running increased boost then an aftermarket recirc dump valve would be a good idea to maintain that boost, but you would need to properly adjust it to ensure you are getting the best throttle response.

HTH.

So because I have full decat with air induction.... does that mean I dont need a dump valve? I still get that great sound when changing gear.

Sorry I'm late lads, pass me a beer willl ya?

Soulgirl, you still hear the noise if you have an induction kit and the standard recirc dump valve, although it's a softer sound than an aftermarket one. The standard one seems to work up to silly boost levels as long as it's in good condition, although IIRC, some respected names around here (Bob Rawle to name just one) reckons that if you must go aftermarket, go for a Forge re-circ (Disclaimer: it's early, I've had a bad nights kip so my memory may be playing tricks on me ;) )

Soulgirl, your car already has a dump valve, a recirculating one I presume if the engine is otherwise standard (?). If you are happy with the sound, there's no reason to even consider replacing the standard recirc dump valve with a VTA item :)