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Discussion Starter · #1 ·
I am wanting to change the dump valve on my Evo 1, Could some one advise which one to go for and why and where to buy from.
Also what type of prices these go for.

Many thanks,


Discussion Starter · #2 ·

There are a couple of types, Re-circulating and 'atmospheric'. The re-circulating types
are like the original equipment types fitted to turbo-charged cars, when these things blow off the
air is piped back into the air filter pipe before the turbo and they have 3 connections.
The atmospheric type, have only 2 connections because when they blow-off they vent it into the atmosphere and make a loud tcshhhhhh!under the bonnet, and are more fun.
However, because of how the air is metered in lancers, the atmospheric types can cause the
engine to run rich because of the lost air.

There are lots of manufacturer's of dump valve try looking in EVO mag or Max Power.HKS make dump valves but these tend to be on the expensive side circa £250.
I tried a Bailey Motorsport one on my evo6 but after a short time it was leaking vacuum.
This was because the valve had actually stuck in a position whereby it didnt leak boost, but
leaked vacuum from the inlet manifold connection causing me idle problems. When I removed it and oiled it, it started to work again but I've gone back to the OEM one for now.

I do miss the tcshhhh! though.
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