Well... im totaly confued.
Does anyone know if the MY99 comes with a dump valve?
after trying to find information on this it seems taht they
come with a pretty good one but evry one i talks to tells me to replace it.

does it have some sort of known problems that i'm not aware of?

Thnks,
Rotem

All impreza's have dump valves as standard. These are more commonly known as the closed loop variety. This means that the excess pressure is looped back into the system,.i.e. you don't here any whooosh.

If you want to get the sound, change to any piston type valve which vents to atmosphere.

Shaun.

Rotem,

They also called "Blow off valves" or BOV's ...

Thanks

Gavin

Does this mean that the dump valve loops the gas
while the blow off valve free's it to atmosphire?

if it is so which one is better for removing the turbo lag?
and at what cost ( does it decrese the PSI at max boost?)

thanks,
Rotem

Rotem,

Your car MY99 has a perfectly good recirculating blow of valve (aka dump valve, aka air-bypass-valve). Replacing it will not make a large difference to lag but if you want to make whoosh whistle and pop noises everytime you change gear you could fit an externally venting one.

It may be worth looking into a BOV change if you are running significantly higher than standard boost and/or you have evidence that the standard unit is leaking boost significantly.

If you are running standard engine management you may get some small running problems if you do fit an externally venting unit as the engine meters all air going into the system and maps fuel accordingly, so it goes rich if you dump air away from the system.

If it's noises you are after, you will find that fitting a decent cone-filter (Blitz, for instance) will yield a noticable improvement in performance and a subtle set of new noises to enjoy. A con filter will amplify the operational noises of the standard subaru recirculating BOV nicely.

Moray

EvoZero,

IIRC, WRC cars don't run dump valves anymore as they are incompatible with the current generation of turbo anti-lag systems.

Have you fitted a vent-to-atmosphere valve to a Subaru or is it on an Evo? They aren't exactly identical engines. http://bbs.scoobynet.co.uk/wink.gif

Moray

To re-iterate Moray's comments in a single sentence..

don't bother with a dump valve on a MY99, fit a Blitz cone instead
http://bbs.scoobynet.co.uk/smile.gif

I have fitted a forge motorsport Vent to atmosphere dump valve, comes with everything you need and stiffer spring for running higher than standard boost. Easy to fit and wrc ish sounds http://bbs.scoobynet.co.uk/wink.gif
I have no running problems at all.

Good luck

Ian

Moray

Just ordered the recirculating Forge Dump Valve and will get the Blitz on soon + a bigger turbo - dont want to feel left behind!

When are you going to sort out the ECU then?

and are you up for the Power run?

Moray / Robert,
Sorry, forgot to add that the VTA dump valve is fitted to my my99 scoob. I know wrc cars don`t run a dump valve, that`s why i said WRC ISH sounds http://bbs.scoobynet.co.uk/wink.gif

Still i like the chirp, chirp, pssst sounds.

Cheers

Ian

Steve,

Sorry, I have just contracted a very serious, infectious desease and I won't be able to attend anywhere with a Rolling road for at least a hundred years... Bu88er, I would have looked forward to it otherwise. http://bbs.scoobynet.co.uk/wink.gif
(Not that I'm afraid at all, you understand http://bbs.scoobynet.co.uk/smile.gif ).

New turbo eh, I will mail you off-line and ask about it. Looks like the Power Engineering melting my pistons incident has severely bu88ered my turbo's bearings, so it won't last much longer. http://bbs.scoobynet.co.uk/frown.gif

EvoZero,

So, you admit it, you have a scoob and name yourself after an Evo! Have you no shame? http://bbs.scoobynet.co.uk/wink.gif
How much is the forge unit and does it have a twin valve sequential mechanism ala hks/bailey?

Moray

I had a ride in a car fitted with a Forge vent-to-atmosphere dump valve last week, and it sounds most unlike any other valve I have heard. Kind of like it's deliberately pulsing the air. I've heard it's not supposed to confuse the AFM/ECU unlike all other dump-to-atmosphere valves. Don't fully understand the principles behind it though!

I think spending £100 on a vent-to-atmosphere valve isn't really worth it considering the possible fuelling problems it may introduce, and the fact that you can get a perfectly good psssshhht sound out of the standard recirculating valve by fitting a K&N filter (or similar) for around £70! (And get better airflow into the bargain!)

Andrew

moray was right about the blitz cone filter they sound great, fitted one on my95 wrx and have'nt regretted it.