DV or not?

[DJones]

Having driven cars with diverter valves and cars without i can honestly say i have never noticed a difference..

Does anyone have any proof of turbo's dying as a consequence of not having a DV. I appreciate that we all say they will but do we have any proof?

I would have thought that the shock waves of blasting the boost straight into the nose of the turbo would be more damaging to the bearings than the turbo slowing down rapidly due to the over production of compressed air. Audi didn't fit them to works cars either and i wouldn't think it was due to the technology not being available at that time..

Would be intrested in your thoughts??

[Acidburn]

Me and s2driveruk was going to try this with a spare turbo on his car to see if that anything bad would happen or not, still ain't got around to do this yet.

[newsh]

Personally I think nothing bad will happen, my ur runs without one and always has, but the turbo will stall which slows you down between gears.

[dubmeister]

Even though they sound chavvy- i prefer atmo dump valves- i know that they mess up with some newer engines electronics, but the recirc. valves are dumping hot gases into a turbo that likes coool air!! but both types have their fans and detractors.............

[S2central.net]

My only caution to the 'works UR quattro rally cars ran without DVs' is to remember that Audi Sport changed the turbos after every event...

The noise is cool without a DV - no doubt - and yes it hurts in gear acceleration by 'a tad' cos of the stalled compressor, but I would just have the niggling doubt about the stresses on the turbo when all these shock waves run through it... Its only gotta break a tiny part of one blade off to cost an engine rebuild.

True about the recirculating TBV - it does feedback a burp of compressed/warmed air into the compressor inlet - but only during gearchange to keep the blades turning... by the time you are back on the gas then the turbo is ingesting all cold air again... but yes a little bit increased air temp could be attributed to a recirc'ing TBV.

So in theory - the atmospheric dump variety are the best as they prevent turbo stall without any possibility of increased IAT - unless (like me) you hate that chavvy sound on every confounded gear change...

The turbosmart adjustable TBV/DV is the best compromise available - not cheap, but you can set that up for all recirc, all dump or a variable blend of both...

The rally style UR 'chirp' is easily had on any TBV or DV install by simply removing the control hose from the manifold - and blocking it off to prevent air leaks... An easy 'mod' with some sort of air valve - one could wire up a solenoid for this into a cabin switch if you really wanted to be nifty.... Instant 1980s rally sound on your S2 - for as long as your turbo blades will put up with.

chikko-dukko-doh (repeat rapidly for turbo stall impression)

[Jamo]

It's quite simple to visualize why a dump valve is required.

I'll simplify as much as possible.

You got two sides to the compressor inlet and outlet, air goes in one side and comes out compressed other side with the wheel turning clockwise ( for arguments sake )

When you get surge / throttle closure your getting air going in the opposite direction up the outlet trying to force the compressor wheel to turn anti clockwise when incoming air is turning clockwise.

This leads to rotational stress on the compressor wheel, shaft and bearing as you have two forces opposing each other, which leads to eventual turbo failure, commonly by broken shaft or broken blades.

[S2central.net]

There was an oul fella called Isaac Newton... He had a few good rules... One of which was 'Every action (force) has an equal and opposite reaction' !

It is a wonder the turbos don't just explode after 10 gear changes without a DV.

[Jamo]

I was told when I had my old ovlov hybrid turbo built that a turbo charger is like a boxer in a boxing match.

They can take repeated blows without being knocked out but the blows would eventually tell and your turbo will hit the floor.

Other times one heavy blow and it's a knock out.

a DV helps the turbo dodge some of the punches aimed in it's direction

Wish I noted the guys name at Turbo Active who told me this.

[UrS4boy]

I don't think you can name a modern car manufacturer with turbo cars that does either have a by-pass valve (BPV) or a diverter valve (blow-off valve (BOV)). Technology has evolved from the early Audi rallye days. One way or the other, the turbo will last longer if it doesn't get stalled out by a rapidly closed throttle body plate (valve) and have the pressure wave bounce back to the turbo (think water hammer when you shut a water line down too quickly). A BPV or BOV prevents this pressure wave from hitting the turbo.

The other issue between a BPV and a BOV with the Motronic ECU is the air flow that went by the MAF is expected to hit the engine. With a BOV, some of this air is lost and, as a result, the engine will run rich for an instant when you get back on the throttle. Not necessarily the end of the world but easily solved by using a BPV that simply recirculates the air and does not lose it.

You might want to read this post that I put together for the UrS4/S6 forum on AudiWorld (It has the diagrams that Jamo tries to paint with words):

http://forums.audiworld.com/s4s6/msgs/150046.phtml

[jogi730]

I note all the above arguments and bow to some of the knowledge on here. I do recall however, that under my old set-up with the T34 it operated an internal wastegate with no DV whatsoever. Many people commented on how this would quickly destroy my turbo. I did between 8 and 9000 miles with that set-up and my turbo was still going strong. It was only changed to try and get some more power.
My tuner did explain how and why there was no problem on this size turbo. I can't remember all he told me, but what I can remember is him saying 'why would you want to build up all that boost just to let it go to atmosphere?'
Does the wastegate not do a similar job?
Having said all of that, when the much bigger T61 was fitted with external wastegate (35mm - plenty large enough with excellent control), a DV was fitted too .
So maybe it is dependant on the size/
Chris

[Jamo]

The wastegate bypasses gasses from the turbine to the exhaust. If it's closed then the gas escapes via the turbine.

It's a true one way system with the only way you get a build up is with a blocked or restrictive exhaust, which you will instantly notice.

In relation to what your tuner said Chris, think of it this way, the inlet system can only hold so much air, when you shut the throttle or your turbo produces more air than the engine can ingest the inlet system fills up.

If it fills up then as your still adding more air it has to go somewhere and the only place without a DV is back through the turbo causing stall.

A dump valve is basically an overflow system that equalises the system by recycling or removing excess air.

Each to own I suppose, no way would I risk a £1000-1500 turbo without a DV just to have nice sound compressor stall which will break your turbo in the end.

[s2driveruk]

Personally I think nothing bad will happen, my ur runs without one and always has, but the turbo will stall which slows you down between gears.

....and it sounded sweet as.

On a k24 which doesn't have bags of lag, I doubt there would be much loss running without a DV.

Once Pete has his K24 out, I'll run my 186k miler without the DV and we'll see what happens