Having just bought my first scooby complete with bailey dump valve i was quite suprised to find that they are not a recommended fitment after reading these forums. Is it really true that they can damage the engine ? If so why are they made and marketed for these cars ? I have had several other cars with dump valves with no problems so is it just scoobys that suffer. Any advice please as i happen to like the sound but will remove it if the rumours are true .

 

The standard one it came with is the best one for the job. The excess air is recirculated which the ecu is set up for. With a VTA that air the ecu is expecting back into the system is being dumped. So the fuel air mixture will be wrong.

 

the air fuel mixture will only be rich on lift off which isn't really dangerous on your average setup.

 

Yes, it's true, potentially. Although the severity and type of the symptoms varies from car to car, and from one valve to another, and very much depends on other things adding themselves into the mix.

For the same reason you can buy windscreen washer nozzles with LEDs built into them: Some people will buy any old sh*t.

As V5 says the Impreza's engine, air metering system, induction tract and ECU is designed in concert with the standard fit dumpvalve that recirculates dumped air back into the system immediately before the turbo. As Sponners says, dumping this metered air out of the system will confuse the ECU, with effects that are *usually* benign, but are not always so. Changing to a non-standard DV can also damage the turbo and the mass airflow sensor and it's this last item that has the most potential to cause serious problems.

You're unlikely to screw the engine up just by continuing to drive the car with the aftermarket DV fitted, but, as mentioned above, there is the potential to do so. Damaging the MAF sensor, in particular, has the potential to result in a grenaded engine if left to fester.

 

No but it will use a little extra fuel
I removed the VTA on my classic STI (it came with it) and the throttle response was so much smoother between gear changes and I didn’t look like a tw*t every time I lifted off

 

Get a dual vent dump valve. That gives you the best of both worlds as it doesn't affect the ECU and doesn't give stalling problems but will vent to atmosphere at high revs.

I use the APS one and it's awesome.

 

If it vents to atmosphere at all, it is affecting the ECU, period.

 

+1

I personally run recirc but this is because I dont like chactastic whoosh.

......if you like the noise and it isnt giving you stalling issues then leave it on......should be fine.

 

Still cant understand why they manufacture and market them if they potentially can damage the engine. Even recommends fitting them in a subaru book i have just bought !!!

 

I'll draw you another analogy: Cigarettes. People will sell any old sh*t if there's a market for it. Rightly or wrongly, there's a market for dumpvalves that look shiny or make attention-seeking noises. Or both.

On what specific basis was this recommendation made? There are certain circumstances, for example if you have the nasty plastic DV on the early cars, or with the 99-00 valve (where the spring had a habit of losing its temper) where you might opt to replace with something else for positive reasons, but even then the choice of replacement is all-important, the primary consideration being that it recirculates.

On a newage car there's no reason why most people would need to change, as the the original fit DV is pretty much perfectly designed.

 

there are to many people that over react about the damage of a vta bov i have had mine on for over a year no damage idials fine and runs fine, and you will get just as many poeple saying thers runs fine as others sayin it does damage, its an over reacted subject.

 

It's done your spelling and grammar no end of damage, have you tried removing it to see if they return to normal?

 

Bit of a mixed reaction then so none the wiser really ! Think i`ll leave it for now and remove it when i get bored with the noise.

 

yea if you like it then leave it on isnt eating any grass and they are made for a reason and on market for a reason.

 

The reason is to make the people making and selling them money. Nothing more complex than that.

 

Well it puts a smile on my sons face and thats good enough for me .