To blow off or not to blow off
 

I'm having a bit of a dilemma i'm not sure weather to get rid of my dump valve or not. i've upgraded the turbo and have a bit of lag now and after swapping my dump valve with my brothers re-circulating i think its better althou not quite sure if its in my mind. Is there any science in it or is it down to personal preference?

The single biggest problem of an atmospheric DV that isn't suited to your car is what I'd call 'idle bounce'. Basically, when you come off boost to change up or down, instead of engine revs just dropping down to idle until you go back on gas, they'll drop down, shoot back up a little by themselves (a couple of hundred rpm), then drop back again, all in quick succession. It'll depend a bit on the intake setup on your car and how loud the exhaust is whether it's very noticeable, but it will near enough certainly be happening some amount, unless your ECU's been mapped specifically to run with an atmos DV.

The reason it happens is that the engine ECU is constantly having to adjust and re-adjust AFR for the amount of air it thinks is still in the intake, which would normally include the air that gets sent back there from the recirc DV. If that blows out instead, the ECU loses track of the total intake air volume, and has to recalculate all over again, and it can never do it quite quick enough.

The downsides science-wise are extra stress on the MAF and higher fuel consumption. Personal preference-wise, if your intake layout and choice of exhaust happen to highlight the sound of the idle bouncing around, the noise alone can become very irritating.

May I point you in the direction of this thread.... some real experts on there LOL

https://www.scoobynet.com/scoobynet-...000-turbo.html

its all a personal preference,i dont have any running issues at all with the HKS SSQV d/v and love the noise, im not into sleeper cars,if a car can dump some air,let it so !!

some others think its chavy and report running issues so then yeah,go recirc.

if no running issues and you like the noise, keep it,but you have running issues so either get a better one that suits the car or go recirc and have the sleeper impreza,also remove the un-equal length headers to get rid of the burble too ;):thumb:

If you do decide to get one, and it is purely your choice, make sure you get a good quality one (forge are well made) as cheaper ones can leak boost and cause problems in the long run. I have a DV that was on the car when I bought it, and has been mapped to accomodate it. I doubt there is any significant difference in performance on a road car, but it doesn't annoy me, so why change it.

Dan

Turbosmart Dual Port Valve!

I had a forge D/V on here and swapped it with my bro. it was mapped with it on but in putting the re-cir on it feels like i'm not waiting two weeks for the turbo to spool up after a gear change and the gear change is alot smoother ie. is doesn't snap my neck now. I do love the sound of the VTA but if its no good for car i'm guessing its better to keep the re-cir on.

Ive run with HKS & Blitz DV no problems what so ever. Some are just crap which fail or get stuck open. Now ive decided to blank it off :D.

I personally prefer a recirc rather than vta, I find the gearchanges are a lot smoother, plus the noise did my head in after a while ... lol

However I can still hear the recirc working away which is nice, and I also had a ride in my mates new evo the other day, he has a forge recirc on, and you can really hear it inside the car on gearchanges so best of both worlds, just without sounding like the number 10 bus .. lol

ps not sure if his induction kit had anything to do with the enhanced noise at all?