Effect Of Disconnected Diverter Valve?

[GoremanX]

How would a disconnected diverter valve affect engine performance?

I just did a boost leak test on my car, and I noticed that the line from the N249 to the diverter valve was popped off, probably has been for weeks. The car is currently undrivable (ECM being reprogrammed), so I can't take it out for a spin to find out if re-attaching it has fixed anything. But I was curious to know how a diverter valve that isn't hooked up to vacuum would affect engine performance.

I did the boost leak test because boost has been limited to about 5psi on my 2001 A4 avant TQM. Should be 10-11psi. I was trying to determine if it's caused by a boost leak, a clogged cat (been getting a lot of P0420's lately) or some other issue... like perhaps a disconnected line to the diverter valve?

[Scientist]

I'll tell you what will happen because I had the same problem. You'll get a CEL (P1176)

http://wiki.ross-tech.com/wiki/index...4/P1176/004470

[M-Hood]

Well it depends on which valve you have and how it is installed. If it is the stock valve in the correct way then it might not cause any issues if the vac line has come off since the boost isn't pushing on the valve to force it open. If it was installed incorrect with the bottom of the valve toward the boost side of the turbo then you can end up with lower boost levels because there is no added pressure from the IM to help keep the valve closed.

[GoremanX]

I'll tell you what will happen because I had the same problem. You'll get a CEL (P1176)

http://wiki.ross-tech.com/wiki/index...4/P1176/004470

I did not have any DTC that resembled that. The only DTC I ever had was P0420 (catalyst efficiency blablabla). Fuel trim was always spot on when I logged, although ignition timing was often retarded by a few degrees at WOT (4-7 degrees).

Well it depends on which valve you have and how it is installed. If it is the stock valve in the correct way then it might not cause any issues if the vac line has come off since the boost isn't pushing on the valve to force it open. If it was installed incorrect with the bottom of the valve toward the boost side of the turbo then you can end up with lower boost levels because there is no added pressure from the IM to help keep the valve closed.

I installed a DV from 034 Motorsport about a month ago, in the same orientation as the factory original one. It's all black and unbranded, so I have no clue who makes it. Boost levels were low before that installation and did not change afterward.

I'm really looking forward to getting my ECM back so I can do more testing. In the meantime, I've bypassed the N249 and hooked the DV directly to the intake manifold.

[walky_talky20]

With the line detached and the DV in the factory orientation, you will get compressor surge on throttle lift. This is because there is no vacuum supply to open the valve when the throttle plate slams shut. Since you were only boosting at 5psi though, the surge is minimal and you really aren't hurting anything. Just get her hooked back up and you'll be fine.

[GoremanX]

Thanks! I was wondering if this detached line might be a symptom of the low boost, but it doesn't seem to be the case the way you're describing it.

[M-Hood]

Thanks! I was wondering if this detached line might be a symptom of the low boost, but it doesn't seem to be the case the way you're describing it.

It can be if the BPV is sitting the wrong way.

[GoremanX]

Low boost situation was present before I installed the new DV. Nothing changed after I installed it. And it's pretty self-evident which way it goes... same way as the OEM one did.

[M-Hood]

Low boost situation was present before I installed the new DV. Nothing changed after I installed it. And it's pretty self-evident which way it goes... same way as the OEM one did.

Well here is the kicker, the Audi factory actually installed the stock valve in either direction when the cars were manufactured which was fine for stock boost levels. So the stock valve could have been in the wrong direction to start with.

Correct position of BPV
Stock valve or diaphram valve goes in with the boost to the tube on the side of the valve body. A piston type valve gets installed with the boost to the bottom tube (opposite of the vac line nipple).

[GoremanX]

So this is backwards?

[GoremanX]

So far, all the installation instructions of aftermarket DVs I've found online has them installed in the orientation that I have mine. But by your description, it seems I have it in backwards?

edit: turns out it doesn't matter. For the boost levels I run (which has only been stock so far), the orientation of the DV makes no difference whatsoever. This is not a factor in my low boost levels at all.

[marknad113]

there is no added pressure from the IM to help keep the valve closed.

spammer this dude is in multiple threads just copying/pasting lines from other posts!

[M-Hood]

So this is backwards?

That is the correct way of installing the stock BPV and aftermarket valves that use a diaphram like the stock valve.


Here is a diagram showing the correct way the stock BPV should sit. Nearly all aftermarket piston type BPV's get installed the opposite way.




Picture that came off a B6 A4 1.8t.

[GoremanX]

Whelp, whatever the problem was, it's fixed now. While the ECM was away being reprogrammed, I did:

- N249 delete
- SAI delete
- Suction Jet Pump delete
- Constant Vacuum delete

This also resolved the boost/vacuum leak that was occurring from the disconnected line at the N249 valve.

Friday I received my reprogrammed Stage 2 ECM from J-Fonz Tuning. Now the boost LEAPS up to 17psi without hesitation, it's like night and day compared to before. So somewhere in all that stuff I deleted, I fixed whatever was keeping boost down at 5psi.

P.S. the DV is still in backwards. Doesn't seem to affect boost levels at all, and it responds very fast. I may turn it around in the near future and see if anything changes, or I may upgrade to a Madmax DV. We'll see. Meanwhile, I'm happy with it as-is.