Evildead

Anybody running without dump on the Impreza?

Listen to this lovely compressor stall:
http://www.webity.com/prospeed/videos.asp

take a look and listen to the first evo6 movie

grrrr

-Christer

Adam M

pat has run without a dump valve for some time.

Evildead

Could pat tell me if the sound is similar?

Driveability on half throttle is quite different also, right?

ssubaru

the site is in french not all of us can speak it so what do you click on to hear sound

Evildead

swedish!!

Well, click on the first windows media file 1.3MB

It is a swedish tuning company, they have an english version of the site too, go check it, they sell 500bhp kits for the Impreza too!

-Chris

[Edited by Evildead - 5/17/2002 5:57:46 PM]

pat

Hiya Evildead!

The sounds is partly familiar. I get a similar kind of sound from mine but not after high boost, also mine is more of a pulsating whooshing sound that a chirping sound. I guess this is to do with the compressor design... the MHI G series compresor wheels just don't seem to make that kind of a noise.

The driveability is somewhat altered because the pressure release mechanism in the intake system is altered by the lack of a dump valve. If lifting of for a short time then re-applying you have mor residual pressure than you would otherwise have, and so the thing picks up better.... also there is no possibility of having a leaky dump valve

Cheers,

Pat.

UkLegacyT

i run without a dump valve on my legacy turbo (same as impreza engine).....also 1.4bar

get a hell of a loud chatter on gearchange or backing off

Evildead

Thanks for answering!

Still, i wonder, how important the dump really is in a performance aspect? it can't be that important for the car since it is not monitored by the ECU.
I ran my good old XT for many years without dump, and it wasn't running stock :-)
I wonder if it is just a cosmetic product, evolved from theories and not that much really hard evidence?...well, just babbling and questioning something all take as granted, nothing proffesional.

UkLegacyT

the dump valve isnt monitored no, but the standard recirc one means it doesnt need to be as its closed loop.
what i mean is that whatever amount of air is measured by the afm stays in the system.

ive run without one for about 4months now, running 1.4bar. however, it does put more strain on the turbo bearings and also the hoses from turbo to engine etc.

they are just there to protect the turbo really and reduce lag through the gears, but if you get the gearchange quick enough, theres no difference. pick-up from low revs in-gear is better without one i think, but others may disagree ???

cheers, ian

Evildead

*what i mean is that whatever amount of air is measured by the afm stays in the system.*
sure, when i think about a failing dump, it can be the vacuum hose that breaks, making the dump sitting tight (well in theory)like running with no dump at all, and the effect of this would be the strain on the system. This can't be that bad(at least on std Boost) since it is not monitored...dumping in athmosphere will just make the car run rich.

Anyway, i dig the sound of it, i cannot mentally project the cost of a HKS DV compared to this

UkLegacyT

no, wouldn't worry mate, just remove the dump valev, and block both pipes

nice chatter. what air filter you using? you'll need a foam induction such as a pipercross to hear it the best

Evildead

Running K/N induction among lots of other goodies...

I was just curious...well i'll give it a try, my 'old' S3
gave me better quarter times without dump..so i guess, when quick enough shifting you can benefit from the positive pressure still in the system

UkLegacyT

exactly my thought