Garey Cooper

I picked up my car a couple of hours ago from the dealer. The diverter valves were replaced, the part number used was #993-110-337-50, the nomenclature Porsche uses is; "air cut off valve". I had hoped to see the old units but they were sent to Porsche (so I'm told) for Post-Mortem analysis. The work sheet says it is 1.40 hours to replace the valves. First impressions are that the infamous "honk" is gone. Also, the power on seems much crisper now than before, maybe the valves were wreaking some kind of mayhem besides just noise? But she seems to answer calls to the engine room more smartly than she used to before the new valves.

I have also by now seen, held, and poked around at the Forge Co. after-market diverter valves. They certainly look solid enough and one can see the piston in the bore. I haven't seen the Bosch OEM unit so I can't compare on a side to side basis but the Forge units are "pretty" enough.

By the way I also had the pleasure of replacing my right rear tire. I thought it had a slow leak and was hoping it was coming from around the Schroeder valve but no such luck. There was a HUGE self-taping screw in the tread, I mean it was really BIG. It was old and rusty and the threads were gone on it but it made a nice javelin to go through my tire! So guys and gals, check those tires carefully, you don't want one to give up the ghost or air pressure at triple or even double digits of MPH!

fc-racer

The air cutoff valve or more correctly, the compressor bypass valves are a very important part of a turbo design. Porsche uses the Bosch valve mainly for noise considerations. If ultimate performance were the target (they already do well enough with the Bosch valve), Porsche would use a nice metal valve with a much stronger spring, such as the Forge valves.

I've seen real evidence of improvements when going from the 993 valve (which is better than the older vales by a long shot) to an aftermarket unit. I've purchased a Forge valve and will dyno the results. I'm anticipating less lag and better response. The problem with the stock valve are three fold:

1. Cannot accept high boost levels without bleeding off. At 17psi, they start to bleed.
2. Sometimes, the valve does not seat correctly allowing boost pressure to escape until you shut the throttle thus opening the valve again, this time hoping that the valve shuts correctly.
3. Slow, lazy response. The valve is quite lazy in operation. Apply a vacuum source to it vs. aftermarket and see the difference in response.

Aftermarket valves may create more noise, but Porsche induction systems are pretty well insulated for noise. Adding an aftermarket valve to the 944TS resulted in slightly more noise and it's a nice noise too

fc-racer

Jack

fc-racer:

Any experience with Bailey valves? Some of the Audi guys were having problems with the Forge valves--I thought?

Oak

I have used both the Bailey and Forge units. And the Baileys are much better, I had problems with the construction of the Forge units, and the Forge needs constant re-lubing and maintenance. The Bailey unit is much better in terms of reliability and construction. Also the Bailey valves are maintenance free unit that is sealed along with a delrin piston valve. The stock Bosch units are of a diaphram construction. Go with the Bailey's much better, also the Forge units don't have a 90 degree vacuum fitting that the 996tt needs.

Jack

Oak:

Thanks for the info. Have you taken your car in for this issue also.

BTW, I believe we got our cars at the same dealer (Pacific) approximately 2 weeks apart.

Oak

Jack, I think I saw your car in the service bay, when I brought my car in for some noises I have been experiencing during idle a ticking/clanking at around 950rpm. Also brought it in for the "honking" sound. Nothing was done, they said the ticking/clanking is normal, and they claim they heard no honking sounds. I really didn't pursue it, I knew exactly what the honking is due to working on VW/Audis turbos engines. I just wanted them to get it on the records/file for the future. I will probably retro fit/mod to the Bailey DV. I have had excellent results with them, also sounds pretty cool! PSHHHHH!

By they way are you the owner who requested no dealer prep on your turbo? Due to some damage caused by the detailer on a previous turbo you had ordred?

Are you also experiencing the honking sound?

Jack

Oak:

Yes, I'm the **** wacko who had his own detail guy come to the Dealership and do the cosmetic prep on the new car. Pacicic is a great Dealership and Eric Prince is the best salesman. BTW, I believe the damage was done at port PDI and not the Dealership, FWIW.

As for the honking sound, I haven't heard it yet. I'm aware of the diverter valve problem on some Audis, since I have some current S4 experience.

According to a very knowledgeable and trustworthy Porsche Tech, the clanking sound at idle is, indeed, the chain tensioners and is normal--I was told it has something to do with the vario-valve set up and the minimal lift (3mm) at idle (if I got it right???). Every TT I have heard at cold start up has had this sound, and of course, I was told they all do it.

JBH

Any recommendations for where to buy the Bailey valve?

Flat6

Where will I find this valve on my car? And do I need two of them... the S4 uses two of them does it not?

Flat6

Garey Cooper

Flat Six; You'll need two of them sir. And the S4 is also a twin turbo I believe so they use two as well.

Fried Chicken Fred

I had the same honking on my old Audi S4. It uses the same valve. I put the Bailey Valves in and they eliminated the honking and I got the boost back.

I've since sold the car and put the valves on the Porsche. No more honking, better spool up. I got them from these guys...
http://www.awe-tuning.com

Forge Motorsport

Hello
I heard about the discussion and thought I would introduce FORGE.

We manufacture many type of Diverter and Blow off valves for all cars.

We have a valve, the 007P that is a great option on any Bosch application.
The valves are serviceable and guarnteed for life .

The internal of the valve is piston driven, the piston is manufactured from aluminium.

The valves are avilable from our USA distributor www.stratmosphere.com
If you have any questions regarding our diverter /blow off valves , please contact me

Todd/A.W.E.

Greetings to rennlist readers:

We have recently been overrun with information requests regarding the Bailey Motorsport DV30 diverter valve we exclusively import into the US from the UK.

Please visit our website for basic information and pricing on this product:
http://www.awe-tuning.com/products/p...PPT=Drivetrain

Our experience is that the OEM Bosch valve, found on many Porsche/VW/Audi turbo applications, is not up to the task as handed to it by the factory, let alone if the boost is increased via chipping, etc. One of the symptoms of a failing valve is the "honking" noise Mr. Cooper describes above.

We, and thousands of users around the world, have found the Bailey Motorsport unit to be the final fix for the problematic OEM valve.

Please contact us directly with any questions or comments.

1Carnut1

Todd:

Spoke with your people yesterday, liked what I heard. Going to bring my car in for at least the bailey's and probably the giac upgrade. You have a good staff.

Todd/A.W.E.

We look forward to meeting with you and discussing your needs!