Audi A3 – Forge Diverter Valve Install
13Jul10
Problem:
A couple weeks ago my Check Engine Light (CEL) came on while driving. Initially I didn’t notice any performance problems while driving under normal conditions. After driving a little more, I noticed that the turbo blowoff/diverter hiss was a louder than usual. Upon hooking up my VAG, I saw an error code of – P0299 Turbo/Supercharger Under Boost.
Diagnosis:
I did a quick physical inspection of all the turbo hoses from end to end and found no visual holes or leaks. The next thing I checked was the stock turbo diverter after reading numerous post from other 2.0T FSI owners having the same problem.
The turbo diverter valve (DV) is located directly on the turbo housing near the rear passenger side of the engine and can be accessed from the underside of the car. Upon removal and inspection of the stock DV, I found that sure enough, the diaphragm was torn.
Audi A3 Torn Stock DV Diaphragm
Analysis and Decision:
I found some great info on various Audi/VW forums about the various solutions to this problem as well as performance testing of the Forge DV valve. Out of all the info I came across, there was only one review that stood out above the rest which is well worth mentioning. Crew219 in the vwvortex forums posted a very thorough review of his test in comparing the Forge vs. Stock DV. His tests was conclusive that the stock DV had less latency in boost when compared to the Forge DV. This was primarily attributed to the stock’s electronic controlled solenoid being faster than the vacuum operated solenoid and manual piston/spring operation of the Forge DV. In his write up, Crew219 ultimately ended up removing the Forge DV after evaluating his data.
His basic findings were:
- Forge vs OEM showed no significant improvement in boost holding capability
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Forge vs OEM showed no significant change in boost ramp-up
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Forge exhibited no improvement in mid-range and upper RPM boost over OEM
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Forge showed a ~.3s decrease in response over OEM when recirculating boost
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Forge exhibited comparable rate of releasing boost to OEM
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Forge increased backpressure on turbine compared to OEM, as observed by a 3-5psi pre-throttle body spike.
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The Forge valve is still a mechanical diverter valve and still relies on vacuum from the throttle plate for recirculating boost, whereas the OEM DV relies on electricity to retract the piston and recirculate boost.
(His write up can be found here: http://forums.vwvortex.com/showthread.php?3336171)
From the results of his testing, I chose to go with the Forge DV regardless of the performance variance for the following reason:
- Although it took 25K miles for the original stock DV to tear, I know it will happen again and I didn’t want to be bothered replacing in the future.
- The ~.3s decreased response found in the Forge DV was minimal for everyday street driving and in my honest opinion, you would probably never notice this latency.
- The Forge DV is adjustable to accommodate various boost pressure should I chose to remap the ECU or upgrade to a larger turbo.
I’m not racing my car in any timed events nor do I plan to in the future. What I am looking for is a reliable valve that can be adjusted to accommodate future boost updates most likely from a Stage I or 2 ECU remap.
Forge DV Purchase:
I found the cheapest Forge Valve at Parts4Euro.com. they were $20-30 cheaper than the other popular Online Euro car shops and they even offered free shipping to Hawaii.
Let you be warned.. Parts4Euro has terrible customer service and they are not a reliable company. I don’t think I would ever do business with them again (however that’s a different story).
My suggestion is that you buy your Forge DV from somewhere beside Parts4Euro and be assured you’ll receive your part in a timely fashion. The BS is not worth the $20-30 you save.
Forge DV Install:
The Forge DV came with mostly everything needed to do the install except for tools and LocTite. They gave plenty of silicone tubing to do the job, even room for mistakes.
You will however need extra zip ties to secure the silicone tubing from the PCV pressure tap that sits on the top of the engine to the DV that sits on the turbo at the bottom of the engine.
I would have loved it if the Forge DV kit came with metal hose clamps instead of nylon zip ties. I tried searching locally at various shops for small metal hose clamps and no one had them. I check gardening shops, moped shops, auto repair shops and hardware stores. I did find a pinch type metal hose clamp that would work great at Kargen/Checkers Autoparts however it could only be purchased in a assorted pack which contained only one or two of the right size clamps. It would have cost me $20 bucks for 8 stupid metal pinch clamps. I ultimately ended up using the nylon tie straps included in the kit. I figure if that’s what Forge included then its good enough.
As of May 2009 the kit is supplied with an additional uprated “Yellow” spring in case you upgrade your boost. The DV is sent with the standard “Green” spring for standard stock boost pressure.
Complete Forge DV Kit (MFG Part #: FMFSITV)
Close up of Forge Diverter Valve
Close up of Vacuum Tap
Close up of Solenoid
Close up of Bracket
Close up of Extra Yellow Spring
Close up of Silicone Tubing
To do this install you will need the following tools:
Tools
Blue LocTite
Four Step Install
- Install the vacuum tap
- Run the silicone tubing from the vacuum tap to the DV.
- Remove stock DV
- Install new Forge DV
Step 1 – Installing the Vacuum Tap
Remove engine cover
Disconnect PCV hose at the intake manifold
Connect silicone tubing and nipple plugs to vacuum tap
Clip the vacuum tap onto the Intake manifold an reattach the PCV hose
Step 2 – Silicone Plumbing
Route the silicone tubing from the vacuum tap to the DV (Highlighted in Red)
Step 3 – Removing Stock DV
Locate stock DV from under the car, passenger side rear engine
Unscrew stock DV. (Helpful hint: Screws will come out easier if the engine is completely cool )
Turbo casing w/ Stock DV removed.
Step 4 – Install Forge DV
Attach solenoid bracket and tubes to the Forge DV
Mount Forge DV to the turbo housing using the original screws and attach the vacuum tap line to the solenoid
Finished with the Install.
NOTE: In my case, I had to erase the error codes on the VAG to turn of the Check Engine Light.
Enjoy!
Filed under: Audi A3 (8P) | 10 Comments
Tags: 2.0T, 2006, A3, Audi, Diaphragm, Diverter, DIY, Do, DV, Forge, install, It, Review, Torn, TSI, Valve, Yourself
The Sauce 
really big help! dealer just diagnosed the same problem on my audi A3 today. thanks a lot.
Hey! so i have a 2008 mkv gti and i honestly think that i have a boost leak, and i think its the diverter valve. the engine light turned on and the car felt normal and after a while, i notice a major power decrease when i would floor the car. the car is only boosting a little around 3 to 5 pounds. i cant really hear any atmosphere air coming out, the car feels normal it just feels like….the car doesn’t have any balls. my car is chipped but i dont know what kind of chip it is but, it has to be stage 2 because the car peaks at 24.6. i have warranty but, the dealership wont work on it because my ECU has be “flashed” therefore they wont work on it cuz my warranty is void. im very stress out because, i really don’t know how to change the DV on an FSI but i found your post, seems pretty hard, but…. idk if i should give it a go. to be honest, im not even sure if its the DV but im 80 percent sure it is because of the fact on the symptoms of the car and other forums with the same problem and their solution was a new aftermarket DV.
Ivan,
It sounds like you’re in a similar situation as me however my Audi A3 is a 2006 out of warranty. I was pretty stressed when i was going through this also. The one thing I would recommend is that you dont drive your car too hard while you have a torn DV because it does cause the turbo to work harder (so I read.).
As for Diagnosing the problem. It may seem overwhelming to you but Im pretty sure its the DV but in any case, id recommend you start there to help isolate the problem. Its very simple to check the DV. The check should take you approx 45 minutes being that you are unfamiliar with the engine and location of the DV. That was my biggest hesitating/procrastinating factor. Three bolts hold it on (wait til the engine cools completely before unscrewing these bolts as it will make it easier to come out. All you need is a simple 5mm allen wrench, the cheap L one will do. Its worth the time and peace of mind to know what the heck is going on with your car. Remove it, if its torn then at least you’ll know where to go from there.
Jack up your car. You’ll need to look on the passenger rear side of the engine. Scoot yourself under the car can look up at the engine. you head should be near the right front axle. You will find the DV there. Its pretty decent size, black, with a wire harness connecting to it. It should be the only thing there that you see wires going to.
All I can say is you may as well just check the DV to get some peace of mind in know if its the problem or not. If it is the problem, dont fret… simply put the original torn DV back on your car and you’ll be able to drive it like normal until you decide what to do. Most likely, you’ll decide to go with forge since the Stock DV is almost equal to the cost.
As for the Forge install… its very easy and straight forward. Trust me on this! If you can follow instructions, you can do it. There is nothing tricky about it. The hardest part for me was identifying where the components needed to be placed or removed.. so in my blog, thats what I tried to target to help bridge the gaps that you’ll see in other peoples forum or blog post about the forge DV install.
Feel free to write back.. and i can help you to my best of my ability.
good luck.
Brad
i have 06 a3 my self and this best post i seen..good job im actually on gt35r turbo with 17lbs boost 435whp 483wtq and this diverter valve works better with higher boost then stock one just some tips
Isn’t your vacuum tap in the wrong place? In the installation instructions of the Forge DV the vacuum tap seems to be positioned somewhere else.
See http://www.namotorsports.net/docs/FMDVFSITV.pdf page 4
It appears the instructions that came with my kit is updated as compared to the .pdf’s found on the internet. Also the Vacuum tap is totally different compared to that one shown in your link.
Very well written and informative. It seems that it doesn’t matter which source you use for the vacuum tap. This is my assumption so I may be mistaken.
You are a lifesaver.
Hi there. I wanted to know what symptoms did you have when the dv was torn. Iam not sure if it is the same problem iam having at the moment, my car just looses power, dumps fuel and has a flat spot when I take off. Please can you help me with some info. And where can I get the dv from iam in SA. Thanks
Please re-read my blog. The information you ask is clearly outlined. Thank you