Luminous

iTrader: (3)

I'm not particularly mechanically minded. But I do have an interest in my car, and have been reading up about dump valves. I thought I was understanding them, but I'm left with one question.

I thought that the reason Subaru fitted a recirc valve was to try and reduce turbo lag. So that when you change gear, the pressure from the turbo outlet is fed back to the turbo inlet, keeping it spooled up to some degree.

The boy racers tend to fit VTA dump valves because they sound "cool". So that is the hiss you get when all that pressure is dumped to atmosphere.

So how come my standard MY99 scoobie makes the same sort of noise, although to a much lesser extent when I come off the throttle?

john banks

You are hearing it going back into the intake even though it is very subtle compared with a VTA.

Luminous

iTrader: (3)

Ah, thanks. I thought there may have been something else starting to come into play

ALi-B

iTrader: (1)

Do you have an induction kit/cone filter???

The OE re-cric sounds more or less like a VTA dumpvalve if you have a cone filter fitted.

Luminous

iTrader: (3)

The whole car is totally standard. Inc exhaust and filters, for now