A little while ago, VW released a revised version of the infamous diverter valve. Now known as the revision D valve, it replaces the diaphragm seal with a much stronger piston type. Previous revisions (B, C, and G) had diaphragms that were known for ripping and subsequently failing to hold boost. Some of these failures were under stock boost levels. The G version is the stoutest of the diaphragm valves with fewer failures reported across the forums.
Of course luck plays a huge role in this. Some people have reached 30,000 miles on the stock C valve. I reached at least 45,000 miles on my C valve. Then again, I tend not to use my right foot aggressively. If you feel that your car is losing power or making funky noises, pull the valve to check. Look for tears in the diaphragm. If you have a boost gauge, it’s even easier for you. The car will not hold peak boost easily or at all.
The new valve simply bolts right up to where the old one sits. It seems to have a good track record at the forums. There has been a report or two of it failing but the causes were unknown. Maybe a factory defect? MJM Autohaus currently (1/19/2011) has the best price at $65 shipped.
There are several kits that solve the diaphragm problem by using a piston type mechanical valve, or a vacuum actuated diaphragm valve. BSH, Eurojet and AWE all sell mechanical kits. Forge sells one that has ecu control but still relies on vacuum. I have the BSH valve relocation myself, a great piece of kit but I wanted to hand control back over to the ECU.
Why try this over a mechanical valve?
- It allows the ecu to control when and how the valve opens
- Quicker to open when the throttle is released (mechanical valves rely on vacuum and pressure differential to open up)
- Cheaper (65-90 dollars and no additional parts required)
- Less hassle at the dealership (oem part)
- Maintenance free
There are certainly arguments for using a mechanical valve such as the ones included in the BSH diverter valve relocation. A mechanical valve is simpler and pretty much bulletproof. There are no electronics to worry about, they just work. In the case of the 2.0t FSI engine (and TSI as well) the mechanical valve is also open at part throttle (under vacuum). This allows air to bypass the intercooler and turbo and go straight from the intake to the throttle. This supposedly leads to smoother throttle transitions. This only works for mechanical valves used in a relocation kit. I can’t comment on that, I’ve completely forgotten how the car first felt without the BSH kit. With the kit on, the car ran perfectly well. Now the exact amount of benefit this provides is debatable but the logic is sound, path of least resistance.
If you’ve tried the new revision, let me know what you think of it in the comments!