Atmospheric Dump Valve.

[MaverickUK82]

Is it true that an atmospheric dump valve, as opposed to the WR1's recirculating dump valve is increase performance slightly:

"The Impreza is already fitted with a recirculating dump valve, however this can be removed and a atmospheric dump valve installed to give a loud " woosh" sound when changing gear and a slight improvement in turbo lag." Scoobyworld.co.uk

[John Mc]

I think this was discussed on here before and there was no performance improvement over the recirculating iirc...?! Just a preference over the noise!!

[Megaman]

I know on other cars that dump valves actually slow the car down marginly but I dont know about the scoobs... Probably not much in it either way...

[CAVEMAN]

come on think about it for a little bit...

why is it there, what does it do?

So why waste air by pumping it back into the atmosphere, when you can put it straight back into the intake system?

Keep it as it is...if you want noise at a gear change then run with anti-lag!

[MaverickUK82]

Keep it as it is...if you want noise at a gear change then run with anti-lag!

??

[CAVEMAN]

Keep it as it is...if you want noise at a gear change then run with anti-lag!

??

pop....bang??? happens when you lift off the throttle i.e. gear change...unless you flat shift

[jimmy]

it doesnt give any power but maintains boost

[MaverickUK82]

"Run with anti-lag"?
"Flat shift"?
lol - i'm new to all this.

[jimmy]

anti-lag breaks your turbo and flat foot breaks your clutch lol

[CAVEMAN]

anti-lag is just a simple way to keep the turbo spooled up when your not on the gas.

When you lift off the car bascially retards the ignition but still dumps fuel into your cylinders, so it passes straight through and actually burns when it hits your hot manifold...so explodes (hence the pop n bang and flames) and the hot gases hit the turbo keeping it spinning.

Now when you floor it again (say out of a hairpin) the turbo is already up to speed and gives you boostage - hence the name anti-lag. Using a tad of left foot braking also helps to keep everything on boost too.

Flat shifting in most after market ecu's, with manual gearboxes is just a fuel cut...just change gear as normal but you can keep your foot to the boards and the fuel cut will happen preventing blowing your engine. But as you are not lifting off then you don't get the anti-lag type explosions....

[spraggol]

anti-lag breaks your turbo and flat foot breaks your clutch lol

Well said

Dump valves may sound cool but think of all that wasted air. Stick with the original setup and be happy with the amazing sound of the flat 4!

[CAVEMAN]

not if you have the right parts to start with...

[dynamix]

Flat shifting in most after market ecu's, with manual gearboxes is just a fuel cut...just change gear as normal but you can keep your foot to the boards and the fuel cut will happen preventing blowing your engine. But as you are not lifting off then you don't get the anti-lag type explosions....

... unless you run anti lag and flat shifting cough cough bang bang BANG