A3 2.0 TDI Flutter valve???

wtf is a flutter valve?

If you mean dump valve, like chavtastic Scoobys, no, diesels don't use them nor do any of the current range VAG petrol engines, they use diverter valves.

LMFAO @ a flutter valve. Whats wrong with scoobies

There's no such thing as a 'flutter valve' -Not that I've ever heard of, at least.

There's a blowoff valve 'dumping to atmosphere', which can 'chatter' if it has a large mechanical hysteresis, as opposed to a gentler pressure-regulating chracteristic.

If people have started accepting the name 'flutter valve' then it strikes me as another sad day for the language...

It's also significant that a dump-to-atmosphere blowoff valve effectively opens the otherwise sealed air-metering system, resulting in significant errors in fuel requirement prediction for the engine management system. -Changing the valve alone "because I like the sound" is basically self-indulgent at the cost of engine performance.

-But of you want to do it, go right ahead. -People who care about the good running of their vehicle more than the briefly gratifying noise it makes however, will most likely not be able to advise you.

And ...ferfuxsake... it's a DIESEL. You'll have diesel clatter punctuated by valve chatter as you climb through the gears... -I've never actually heard it, but it sounds like the recipe for a comedy sound effect to me...

-Maybe ask elsewhere?

Keith

There's nothing wrong with Scoobies, just one to55er who drives through our village at 50mph sounds like a total cvnt and 20mph over the speed limit. Rant over.

The reason why atmospheric dump valves are of no use on VAG turbo engies as VWAddict says is the engine is designed for a diverter valve, fitting a dump valve will sap the engine of power on throttle lift.

Diesels don't use diverter valves at all and certainly don't need a dump valve, Forge made a pseudo dump valve for diesels some years ago, but they were sound only and expensive at about £300. There are some companies on fleabay who make a loudspeaker type unit which farts on throttle lift.

Why spoil the tractor-like noise? It's fun blowing Civic Type Rs away with a gentle sound of the diesel rattle, makes them know they've been DTurboed! (That's like Tangoed, but with black smoke)

HERE is a thread three days ago about diesel dump valves you might want to read. Below is a copy of one of the posts i made.
Petrol engines have a throttle mechanism which restricts the flow of air between inlet (turbo-compressor) and the engine combustion chamber, necessary to keep the air-fuel mixture in the ignitable range while controlling the engine's power output. Both mass of air taken in and fuel added must be carefully controlled.

When you close the throttle on such an engine the compressor is still pushing air into the inlet and it suddenly has nowhere to go. The overpressure could deform a throttle butterfly, and will inevitably slow the turbo down due to back pressure (thus also putting more back pressure on the exhaust), leading to turbo lag when the throttle is opened again. The solution is to provide a pressure-actuated valve, which reacts to an excessive difference in pressure between the two sides of the throttle, opening and dumping the excess pressure to the ambient (dump valve) or back into the inlet (recirculating blowoff, which does a much better job by equalising the pressure on both sides of the turbo). Without this, throttles and turbos would have to be much more heavily engineered and throttle response would suffer.

So dump valves are about throttle response at gearchange and other sudden transient events, not about performance in the leadfoot top-speed way of thinking.

The need for a dump valve is a weakness of turbocharged petrol engines, putting another contraption in the inlet side which disturbs the gas flow and is a point of failure. I find it mildly astonishing that anyone should be proud of their car farting on the overrun. But then I run a diesel so I'm probably disqualified from having an opinion.

Diesel engines have no throttle. Power output is controlled by the fuel quantity injected at each stroke. Gas flow around the compressor-combustion chamber-turbo impeller loop is always uniform. This makes diesels much better candidates for forced induction.

A dump valve can only do harm to the performance of a diesel. Turbo wastegates are not dump valves, they limit the pressure on the impeller (exhaust) side of the turbine to prevent the turbine from overspeeding when the engine's gas flow becomes too high i.e. at high rev's. The higher-performing VAG turbos use variable-geometry inlet vanes and have no wastegate.