944 Turbo - Diverter / Bypass Valve Problem

[dlknight]

Hi Folks,

Been troubleshooting a strange boost issue in my turbo where intermittently the car stops hitting maximum boost, so far I've found a loose inlet manifold banjo bolt so tightened that up and then I turned my attention to the diverter valve that I got from Promax a few years ago.

I pushed the piston up with my finger to test the vacuum (by placing another finger over the vacuum port to seal it) and then letting go to to check the operation. It worked the first time but didn't seem to open very far so I pushed it again and then it jammed and wouldn't release.

I've opened it up via the 6 small allen head bolts and removed the piston and spring, there appears to be some moly grease inside the valve to lubricate the piston but it is very sticky so I'm checking if anyone knows what it should be lubricated with? Looks like the o-ring / seal they use on the piston reacts with the lubricant that was put in at the factory and swells causing the piston to seize. Quite how long this has been going on I don't know but I'm pretty sure this is what has been causing my weird issues, hopefully it hasn't damaged anything.

Found lots of forum posts on other car forums where people were experiencing issues with the Bailey (and to some extent Forge) aftermarket diverter valves and the piston seizing in the body due to either lack of lubrication or swollen o-rings (which appears to be the case with mine).

Looking through old forum posts I can see that Bosch stopped supplying Porsche with the OE diverter valves a few years ago and now they are made by a company called "Kayser" but are only available directly from Porsche! at the princely sum of £150... I've been lucky and managed to find someone selling a new one for £50.

From what I can tell looks like Bailey may have gone out of business? their website is still up but says they were moving to a new website in 2013... also no other shops appear to sell them.

So there are few replacement options unless you want to gamble with an expensive Forge, Turbosmart or APR diverter valve or chance it with a Febi Bilstein for the Audi 1.8T...

Looking forward to fitting the replacement and seeing if my boost issues are cured, if not my next plan is to temporarily remove the Lindsey Racing boost enhancer that was on the car when I got it in 2007, I'm concerned that the boost enhancer maybe allowing the turbo to overboost in certain conditions...

 

[bmnelsc]

Very interesting. Would a new o-ring cure the problem for a few years? (Is that the replacement you refer to?)

 

[dlknight]

Very interesting. Would a new o-ring cure the problem for a few years? (Is that the replacement you refer to?)

Not sure about a few years I measure the inside and outside and forget to measure the thickness [] so need to take it apart again but not in a rush now I've got the OE replacement coming. I do think that people aren't told about the maintenance / issues with these solid piston type bypass / diverter valves and dump valves. It soon became clear when I was looking into it that they need servicing regularly to maintain smooth operation, cleaning out and re-lubricating, and o-rings replaced as necessary.

The o-ring in the Bailey DV30 is a square section o-ring with an indent 1/2 way up the side profile, I emailed their sales address but I think they must have closed down sometime ago

 

[PSH]

I used to run with a DV30, the first one failed, the piston had worn the bore on one side, I didn't bother to investigate why?, just replaced it for another. Today I run with a dump to atmosphere type, not had any issues with that and it wasn't new, just an old one taken off my son's Cossie BTW, the symptoms you describe are the same that I experienced before finding the culprit which was a failed OEM valve. It was the original and failed soon after the car was mapped to 282bhp, causing overboost to kick in due to IIRC its failed diaphragm.

Pete

 

[dlknight]

I used to run with a DV30, the first one failed, the piston had worn the bore on one side, I didn't bother to investigate why?, just replaced it for another. Today I run with a dump to atmosphere type, not had any issues with that and it wasn't new, just an old one taken off my son's Cossie BTW, the symptoms you describe are the same that I experienced before finding the culprit which was a failed OEM valve. It was the original and failed soon after the car was mapped to 282bhp, causing overboost to kick in due to IIRC its failed diaphragm.

Pete

Hi Pete- Thanks, I couldn't see any wear on the bore but the o-ring was as baggy as a pair of 70s flares.. []

Not getting any overboost protection kicking in but periodically it stops boosting at full and feels like 50% or so.

 

[944Turbo]

I have a turbo dynamics one https://www.turbodynamics.co.uk/shop/blowoff-valves-turbo-dynamics-dumpvalves-c-987_1291_1179_1197.html on the coupe though I do also have a Tial I never got around to installing 1st one down on this page I think, though mine is black , a bit bigger than the baileys but just enough space for it on a standard car, had it apart once to clean out but that was about 60K miles after it went in and it just needed a clean - had some debris in there if I remember correctly - was giving me compressor surge on a drive through Kielder - was fine after re-assembly. They also do Tial and turbosmart if you click up a level.
Tony

 

[dlknight]

I have a turbo dynamics one https://www.turbodynamics.co.uk/shop/blowoff-valves-turbo-dynamics-dumpvalves-c-987_1291_1179_1197.html on the coupe though I do also have a Tial I never got around to installing 1st one down on this page I think, though mine is black , a bit bigger than the baileys but just enough space for it on a standard car, had it apart once to clean out but that was about 60K miles after it went in and it just needed a clean - had some debris in there if I remember correctly - was giving me compressor surge on a drive through Kielder - was fine after re-assembly. They also do Tial and turbosmart if you click up a level.
Tony

Those Turbo Dynamics ones look good value, I'd already spotted the Turbosmart one which does look good but pricey again and the Tial appear to be dump to atmo only and incredibly expensive.

Will see what happens when my Kayser OE part arrives, I also ordered a new silicon elbow to fit it as the original factory one was starting to crack (due to the enormous bulge on the Bailey ports).

FVD Brombacher seem to make a nice one but can't find a supplier in the UK, also the APR R1 looks good - http://www.goapr.co.uk/products/r1.html

 

[dlknight]

Well I got a new OE diverter valve from Kayser and a replacement silicon elbow from ASH fitted and I'm glad to say full boost service has been resumed!!!

So looks like the Bailey was sticking open and losing boost all the time.... great... I may try and repair it with a new o-ring but it's working now so probably best not to mess with it.

Also found an issue with the vacuum ports on the inlet manifold, the port that connects with the 2-port banjo bolt and feeds the KLR has come loose in the manifold, I tried my best to remove it using a combination of different spanners and pliers to try and unscrew it but it wouldn't come out so I made sure it was tight and and filled the gaps around it with some araldite until such point as I get work done on the inlet manifold.

 

[marty]

Wow. I fitted my Bailey DV30 in 2004 and haven't given it a thought since.
It seems to be working ok but I wonder if I should strip it down and have a look.
As a matter of interest if it was stuck open or closed would that affect the air/fuel ratio?

 

[dlknight]

Wow. I fitted my Bailey DV30 in 2004 and haven't given it a thought since.
It seems to be working ok but I wonder if I should strip it down and have a look.
As a matter of interest if it was stuck open or closed would that affect the air/fuel ratio?

Stuck closed = bad... very bad - the reason you have a bypass valve is so that when you come off the thottle the pressure is released to prevent the vane in the turbo from stalling
Stuck open = not 100% sure but the air within the system has passed the Mass Airflow Sensor so it shouldn't affect air/fuel ratio it will just lead to reduced power and boost, also possibly cause other problems as a result of the turbo system trying to build-up and maintain boost with the open valve.

They are easy to remove and test, all you need is a object that you can depress the piston with (without damaging it) a dowel of some sort works fine and then place your finger over the vacuum port. Let go of the vacuum port and the piston should spring shut and close the valve, if it is stuck open this won't happen.