Fitte a forge dumpvalve to my classic impreza about 12 monthes ago, all worked fine up until about a week ago when it seemed to only dump at higher revs??? Before i used to get a small dump at lower revs and a large whoosh when giving it some. now its only after about 4000 revs and it is at the same volume all the time.
Had a look round it ant it all seems fine apart from when i disconect the vac hose, you can see it close inside, cant remember it ever doing that before.
Could it be the spring thats fooked over time? or is there a way to adjust it?

 

You can get different springs (weaker - stronger etc) to tune the valve. I've been experimenting this weekend with mine, I find that a harder spring makes less of a noise but holds the boost better, whereas a weaker spring dumps at lower revs, and is loud at higher revs, but IMO the car isn't as good to drive. You can get a spring tuning kit from forge for the right side of £20.

 

You can add a shim to up the spring rate, a bit of silicon grease might loosen it up a bit.

HTH

DunxC

 

Give Forge a call Forge, ask for a service kit aswell as replacing the seals and re-greasing it may also solve the problem.

 

Sounds like it just needs a clean and re-grease. I used to clean mine at every oil change (3-4k miles).

 

Same happend to mine the spring wore and got too soft. sort it quick or it could cause fueling problems like mine

 

can you advise which grease to use, and which bit to grease please, I'm assuming its the big silver bit which the spring sits in. very technical I know

 

Just grease that and the seals and your away

 

what grease do you reccomend?

 

On the subject iv got some issues with a forge dump valve not releasing (99 V5). Opened it up to find a blue spring, piston slides freely.

Im using a silicon samco hose for the vacumm pipe.

Reckon it needs a yellow spring?

 

worth trying a yellow spring, it is softer than the blue one