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Hi,

Recently bought some new Bosch DVs for my S4.

I know they are a weak point on the S4, and as my car was a little jerky at low speeds especially when running on a trailing throttle I thought the dump valves might be at fault.

Was going to just check them out, by removing them, pressing in the plunger then holding a finger over the vaccum port and see if the plunger stays in place. (this shows that the diaphram is intact)
Also you can check the valves are sealing properly by blowing into the two ports one at a time, you should find that you can't as they should be sealed by the plunger.

However considering they are only about £20 each I thought I'd just replace them anyway.
Also there is a newer part revision now which is apparently better #034 145 710B (my old ones were #034 145 710A)

Removing the old ones is quite easy, just need to remove the bit of trim on the engine with the BiTurbo writing on it and the DVs are directly below.

They are held in by two 1inch (ish) jubilee clips and a smaller 1/4 inch (ish) crimp on one for the vacuum pipe.

The first one I removed (drivers side) was fine and passed the tests described above, but I replaced it with a shiny new one anyway. (I don't have the correct tool for the crimp clip, so I used some cable ties, but will get some small hose clips next time I'm at Halfords)

The second one (passenger side) was a bit more reluctant to leave the engine, but when I got it out I found (almost to my relief) that it was faulty. The plunger wouldn't stay in place when holding a finger over the vacuum port and although the plunger sealed the bottom port ok, blowing into the side port caused air to whistle out through the vacuum port (a sure sign of a ruptured diaphram)

So I replaced it with a new one too.

I also kept getting a recurring couple of fault codes relating to rich mixture, I suspect these were due to charge air escaping into the vacuum used to operate the DVs.

I cleared these using VAG-COM and then took the car out for a spin. Whilst it is no faster, it's definitely more controllable when stop-start type driving, which I assume is due to the engine now having more control over the boost pressure.

I took the old (broken) DV apart, and there is a small tear about 5mm long in the side of the diaphram, which explains why it didn't work.

I also realised that if one valve is broken, then the other won't work either as they are connected together via a tee-piece, which I hadn't realised before.

Anyway, jobs a good 'un, the car is running well and it was quite a simple proceedure. [img]images/graemlins/clap.gif[/img]

I'll post pictures of the broken diaphram when I can get my hands on a digital camera.

My advice: if your S4 seems a bit jerky when driving slowly (I tended to notice it more when I had passengers and so was driving more sedately [img]images/graemlins/blush.gif[/img] then suspect that you have a blown DV, mine is certainly more controllable now)

Cheers [img]images/graemlins/beerchug.gif[/img]
-Dan

Thanks Dan,

I reckon mine has the same problem> I will probably upgrade to FORGE BPV's.

Joules

Good luck with it, just be careful not to drop any hose clips into the depths of the engine!!!

It's also a good time to check the integrity of the TBB and Fpipes which are apparently also a weakness on the S4.

I'm told also that so too are the intercooler endcaps, but I assume you need to get under the car to see those?... [img]images/graemlins/confused.gif[/img]

Cheers
-Dan

I'm running these:
http://www.bonalume.it/

Very nice! [img]images/graemlins/thumbs.gif[/img]

Which way around do you have them?

There was some discussion recently on which way DVs should be mounted. Apparently the orientation with regard to inlet and outlet on the S4 and S3 is different.

-Dan

I'm running these:
http://www.bonalume.it/

Look good ..but

Are these sealed or can you carry out maintenance on them as per forge items??

Joules

I put an RS6 DV in my S3, after i fitted it the hesitation and funny noises stopped.

cheap too

which way?..... this way....

ohh....and yes, you do can open it, for the maintenance...

English link for those interested...http://www.bonalume.it/index_eng.asp?a= ... _prod&id=7

Joules

When I had AMD carry out the remap. I also had them fit a couple of Hyperboost DVs.

I'm not entirely convinced that they are working as well as they should.

Do any of you guys with chipped S4s notice turbo lag on changing gear? I mean do you have the full boost immediately after changing gear or is there a momentarily lag about 0.5 sec?

I was sold these based on the following:

1. The old Bosch units were notorious for failing.
2. The After market DV's like forge, Hyperboost etc. were supposed to eliminate this turbo lag effect on changing gears.

It's quite noticeable as my mate took a shot in my car the other day and he noticed it straight away without even mentioning it. ALthough I have no running problems or fault codes logged.

At £140 for the two Hyperboost DV. You'd expect them to be a damn site better than the £40 Bosch units.

I'm tempted to check the old Bosch ones which weren't that old and see if the lag is there. [img]images/graemlins/crazy.gif[/img]

I use a couple of the Forge 007 units. I must admit that more than occasionally I lose boost, which can be provoked by lifting off the accelerator at, say 80 in 4th and then flooring it again, then repeating this again.

I recently serviced the units with new pistons and seals. They are holding the vacuum fine but I'm thinking that for £40 it may be worth trying the latest Bosch ones just to see if it is the DV's or something else.

This comes down to the types of springs you are using in the DVs. I'm currently running Forge DVs and the red springs. My DVs came with green.

Might be worth a try. I would definately try with the Bosch ones first.

Good point - I'll give Forge a call. [img]images/graemlins/thumbs.gif[/img]

Forge may tell you that the Red ones are too strong and they are for Scooby boost junkies, blah, blah, blah. They will try to give you the Blue ones, try and push for a set of Reds also. Apparently you can feel which spring is best.... Not sure I did!! Anyways another point to get to Red status may be to mention that you are running up to 1.8-2 bar [img]images/graemlins/wink.gif[/img] .

I'm no expert but are any of these aftermarket valves better than the standard bosch ones in terms of response etc?

Dunc [img]images/graemlins/s3addict.gif[/img]