Does the RS6 engine build boost pressure when in neutral or park?

[Aronis]

I'm wondering if my drivers side IC is cause of the leaking air I can hear while driving (RPM above 4K). I cannot hear the noise if I race the engine in park.

Does the RS6 engine build boost if you race the engine in park??

Thanks,

Mike

[skribe]

No it does not build boost in park, only under load.

Have you checked your upper and lower IC hoses for a slipped clamp?

[Aronis]

Too hard to even see them!

I'll get to the dealer this week.

Warrantee almost done!

Mike

[JCviggen]

No it does not build boost in park, only under load.


Not entirely true, the IC's do see some positive pressure if you rev it in N or P. They are before the throttle body but post turbo which means they don't see negative pressure, cruising at 3K rpm steady you usually get 2-3psi positive pressure just from the turbos spinning. Idle its around 0 but revving it up you can get several PSI...not as much as while driving though so that can influence the audibility of any leaks.

[Chung]

Sounds very similar to what I experienced a couple of weeks ago except on the driver's side instead of the passengers side. I now have silicon hoses and constant torque clamps based on the recommendations from the group here.

This link might help you find the hose
http://www.rs6.com/showthread.php/20852-Installed-Venair-hoses-and-stainless-t-bolt-clamps

[skribe]

Not entirely true, the IC's do see some positive pressure if you rev it in N or P. They are before the throttle body but post turbo which means they don't see negative pressure, cruising at 3K rpm steady you usually get 2-3psi positive pressure just from the turbos spinning. Idle its around 0 but revving it up you can get several PSI...not as much as while driving though so that can influence the audibility of any leaks.

Thanks professor. Yes, there may be some negligible positive pressure. The question was does it build boost. It does not build boost. You won't hear a leak revving the engine at idle. It will build 3 psi if you power brake. Not a good idea or a good way to diagnose.

Mike, the upper IC hoses are easy to see. The lowers are under the splash guard which you can pull in 5 minutes on ramps. If a clamp is loose but the hose is still on it could create a leak like you describe. If hoses and clamps look good I would find a good Indy mechanic to smoke test next before replacing ICs.

I wonder what the bill would be if I went to the dealer when I had issues with my lower IC hoses popping last summer...

[JCviggen]

Thanks professor. Yes, there may be some negligible positive pressure. The question was does it build boost. It does not build boost. You won't hear a leak revving the engine at idle. It will build 3 psi if you power brake. Not a good idea or a good way to diagnose.


Boost is measured in the intake manifold, behind a mostly closed throttle valve at idle. The intercoolers see much more "boost" than the sensor in the intake manifold in such situations where the throttle valve is barely open. I bet one could see a brief 5psi in an intercooler in N or P giving it a good rev, not entirely negligible.
I only bring it up because in the past I had a boost gauge in the WG actuator line of my other car when I was troubleshooting some boost issues....and was surprised just how much pressure there is behind the turbo even while running a vacuum in the manifold.

[skribe]

You won't hear an IC leak while revving the engine in neutral or at the low levels of boost the RS 6 builds when power braking. The rest is not relevant to the OPs question.

[JCviggen]

I would say it depends on the leak (and if you use someone to actually go and listen for it with the hood up)

Only trying to help, every situation is different and given the fact positive pressures that can definitely be reached standing still it could, in some cases, be audible. Whether that's true in his case or not neither of us can say conclusively at this point.

Anyway if he's on stock ICs chances are they leak, not many air tight ones out there.

And his actual question was, does it build boost while revving it in park. I believe my answer was in line with that question (yes, some )

[Aronis]

Thanks all. I did not want to start a war!

My upper hose clamps appear to be tight. I looked this afternoon. The upper pipe can be changed without pulling the bumper?? Looks doable. Bottom hoses I checked when I changed the oil a few weeks ago.

I suspect the leak is the drivers side IC.

Question is can one JB weld a hole if it can be seen without digging the IC OUT?

I can see some oil residue on the bottom front of that IC.

MIKE

[JCviggen]

You're not going to be able to fix it without getting it out first unfortunately. Once out there are some things you can use to plug holes, like JBweld though I think there are some better epoxies out there for the job.

Mine are leaking too but i just went for wagners, the stock ones are just too unreliable if you plug 1 leak they may spring 5 others.

[Aronis]

Well if get to the point where I need to change the IC's then that would be an option, but I got 114,000 out of the stock ones! And they fit without any modification LOL..

Mike

[JCviggen]

And they may have been leaking a bit for much of that time. Just not enough to be that noticeable. I wouldn't say shortening the plastic air ducts with a sharp knife is much of a modification, but that's personal opinion. I liked the fact you are pretty much guaranteed to never have an IC leak again, and way better cooling in the process. I would try repairing the stockers rather than go for new ones. If done carefully and with the right epoxy they would be as reliable as new ones which are not exactly cheap for what you get. But they do need to come out in order to prepare the surface and leak/pressure test them, they often leak in multiple places.

[JSRS6]

You're not going to be able to fix it without getting it out first unfortunately. Once out there are some things you can use to plug holes, like JBweld though I think there are some better epoxies out there for the job.

Mine are leaking too but i just went for wagners, the stock ones are just too unreliable if you plug 1 leak they may spring 5 others.

This is why you plug everywhere it can leak! :lovl: That's what I did anyway.

[Aronis]

Update:

I used silicone caulking to plug up the bottom part of my drivers side intercooler where the oil residue is.

Let it dry over night.

Did a couple hard runs after letting the car warm up and the SOUND WAS GONE. After a bit the silicone plug failed (as I expected) but confirmed my suspicion that the IC's leak where STONES can hit them!

I spoke with the service department at a busy Audi dealership and they said that stone damage is not uncommon and the IC always develop leaks in the front side only!

So, the next step with the help of someones foot on the gas will be to spray a mist of water on the intercooler and find the hole! Then use JB weld.

I somehow doubt that the Wagner IC's are impervious to stone damage but I could be wrong!

Mike