Decoking...

[SR71]

P_G,

Audi ain't going to do anything about it if owners don't make an issue of it. Just like they didn't do anything about the DRC until various owners got off their a**es and complained.

You are right, this is BIG business.

You may be quietly surprised about what they will do if you contact them. Check your PM's mate.

Whether or not you believe the deposition is detrimental to the cars performance is up to you to decide.

(Whatever other posters would have you believe, we have actually measured the difference in airflow in Rob's car pre and post modifications.)

Whether or not you believe the deposition is detrimental to the cars longevity is up to you to decide.

There is a terribly simple solution to the whole problem which will cost Audi a (relatively) minimal amount.

This is what owners should be seeking.

[ArthurPE]

P_G,

Audi ain't going to do anything about it if owners don't make an issue of it. Just like they didn't do anything about the DRC until various owners got off their a**es and complained.

You are right, this is BIG business.

You may be quietly surprised about what they will do if you contact them. Check your PM's mate.

Whether or not you believe the deposition is detrimental to the cars performance is up to you to decide.

(Whatever other posters would have you believe, we have actually measured the difference in airflow in Rob's car pre and post modifications.)

Whether or not you believe the deposition is detrimental to the cars longevity is up to you to decide.

There is a terribly simple solution to the whole problem which will cost Audi a (relatively) minimal amount.

This is what owners should be seeking.

what is this inexpensive, simple solution?

since this affects ALL cars by all makers with DI, why have they not determined this?

[ArthurPE]

You are right, none of the pictures shown so far show gunk on the valve seats BUT there are pictures of valves that seem highly likely to be 'leaking' - they are not from my car so it's for me to post them, If the owner is reading this and is willing to put them in the public domain............

Why else would you have two valves side by side, one completely caked in crap (as you would expect) and the one right next to it being almost almost clean in places? I appreciate you need to see the pics to evaluate but it looks highly likely the heat/flame etc is making its way up in to the inlet from the cylinder head, via the leaking valve and cleaning/burning off the buildup in doing so.


To a point, it does look like the buildup can be there without affecting performance to a notable extent. That said, I am certain the buildup doesn't just stop after a set amount - it keeps stacking up on top of itself the more the car is driven - so when does it become a problem? 20k,30k,40k,50k etc

I believe the build-up is self limiting...it will reach a point where:
1 it can't adhere
2 the velocity has increased sufficiently due to the restriction that it will keep the valves scoured...

I bet you look at a car with 10k miles and one with 50k miles, very little difference

diesels have used DI for decades, and this is not an issue...

[pippyrips]

Having seen pics of cars with 2,3,5,10,19 & 40 thousand miles on the engine, you can see a clear & constant deterioration rate, if you're right and it does stop eventually, by this point there will be so much obstruction around the valve that there is just no way on earth performance won't be affected.

As for the buildup shown in the Cayanne, i've seen worse in a sub 40k RS4.

[ArthurPE]

Having seen pics of cars with 2,3,5,10,19 & 40 thousand miles on the engine, you can see a clear & constant deterioration rate, if you're right and it does stop eventually, by this point there will be so much obstruction around the valve that there is just no way on earth performance won't be affected.

the pics I've seen from cars at various mileages actually look pretty much the same...an initial build-up, then the rate decreases significantly...

that would be an interesting series of pics:
2k miles, 5k, 10k, 20k, 40k

there are many ways it would not affect performance, several of which I have shown mathematically, that the obstruction has no appreciable impact on flow or pressure drop, and the engine as a system can compensate for that...

I've seen a test between a new car (2-3k miles) and a long termer (40k miles), the valaves were never cleaned...

the higher mileage car was faster...most likely due to it being 'loosened up'

[pippyrips]

Agree about viewing the pics in order, I'll see what I can do.

[SR71]

Dude, EGR systems in diesel cars are a HUGE problem.

My inlet manifold was almost totally blocked at 90K miles on my 2.0 TDi A3. I had to clean it out a few months ago because it got so bad the car wouldn't idle properly.

You can find 100's of pictures of the phenomenon on the WWW.

IMHO, anyone who calls a design which deposits as much s**t in the inlet as Rob's car has in 2000 miles, inspite of a sophisticated three stage cyclonic separator needs their head examined.

What self-respecting engineer would sign that one off?

The same one that signed off an iteration of the C5 RS6 DRC presumably...

Whether you want to construct an argument that the deposition affects power delivery in order to get Audi to investigate the matter is for individuals to decide.

[ArthurPE]

Dude, EGR systems in diesel cars are a HUGE problem.

My inlet manifold was almost totally blocked at 90K miles on my 2.0 TDi A3. I had to clean it out a few months ago because it got so bad the car wouldn't idle properly.

You can find 100's of pictures of the phenomenon on the WWW.

IMHO, anyone who calls a design which deposits as much s**t in the inlet as Rob's car has in 2000 miles, inspite of a sophisticated three stage cyclonic separator needs their head examined.

What self-respecting engineer would sign that one off?

The same one that signed off an iteration of the C5 RS6 DRC presumably...

Whether you want to construct an argument that the deposition affects power delivery in order to get Audi to investigate the matter is for individuals to decide.

anybody who states someone 'needs their head examined' for having an opinion contrary to theirs, doesn't need their 'head examined'...they are too far gone for help it's the internet buddy, lighten up...

over the road trucks run 100,000's of miles without valve deposits...

the reason it was signed off on?
it's NOT A PROBLEM in reality...only in your mind...
it does not affect performance...it's all speculation...

it does not impact air flow as I have shown
it does not increase pressure drop, as I have shown
it does not decrease power as I have shown

whether you believe it or not, does not matter...
I don't believe in gravity...but if I jump out the window I will

[SR71]

Go on, I dare you...

[P_G]

Arthur does have a point in all this, why go to all the trouble of designing a cyclonic separator when what I believe is being proposed on here is a valve or hose back to the sump could have been more easily and cheaply done?

And I don't believe Audi employ a bunch of numpty engineers. As much as C5 RS6's have DRC problems, is this just something that affects the UK models because our roads are so bad? Similarly so for us on our RS4's. What friends I have in Germany who have owned a C5 RS6 (of which there are 2) never had any issues with their DRC. Did the US C5 RS6's have as many DRC problems? Do US spec RS4's have as many DRC issues?

SR71, you are far more knowledgeable about these things than I am as is Arthur and you are both entitled to your opinion on an internet based forum, just don't let you passion and enthusiasm regress to sarcasm and insults.

[matthew.lewis2]

As much as C5 RS6's have DRC problems, is this just something that affects the UK models because our roads are so bad?

Unfortuantely not. This is a global problem. I live in Dubai where the roads are good, there are very few corners to test the suspension, and most of my driving is done using cruise control so very little front to rear pitching from accelleration and decelleration. Yet, I have so far had both front shocks fail once, and now one of those front shocks replaced approx 3k miles ago has gone again.

[aidanjaye]

But why are they (DRC) failing - surely Audi (or others) must have some idea - is it ridging on the rod buggering the seal?? Or is it due the fact that the internal pressure is too high??

[silverRS4]

it does not impact air flow as I have shown

A few textbook +/-, smilies and periods...do not .... close the book .. on this...sorry . A flowbench test with clean valves versus severely crudded valves is the only way to even begin to shed light on this issue.

it does not increase pressure drop, as I have shown

Much design work goes into the stem shape design and valve seat angles to decrease the pressure drop. Crud that is 4-5mm thick at the base of the stem, decreasing to 1mm thick near the perimeter of a valve that opens 12mm changes the flow pattern dramatically. As noted above, the effect can not simply be white-washed with first-order calculations. Saying that a high level of buildup does not effect flow into the cylinder is like saying ice buildup on a wing doesn't effect the lift of an aircraft.

it does not decrease power as I have shown

You stated yourself that the your buildup was minimal (similar to Pippys current level) and that your trap was 108 (or whatever). That is meaningless really. Likewise, if you mean the zero decrease is power was "shown" by calculations derived from the simplistic ones related to the flow past the valves, then you are just washing with the same brush.

The effect of gravity can be "shown" clearly with a first order calculation. Sub-sonic velocities of fluid around a crudded up valve and its effect on the efficiency of an engine can be approximated while making many, and possibly some erroneous, assumptions, but not "shown".

[ArthurPE]

Go on, I dare you...

I believe in gravity

[ArthurPE]

Arthur does have a point in all this, why go to all the trouble of designing a cyclonic separator when what I believe is being proposed on here is a valve or hose back to the sump could have been more easily and cheaply done?

And I don't believe Audi employ a bunch of numpty engineers. As much as C5 RS6's have DRC problems, is this just something that affects the UK models because our roads are so bad? Similarly so for us on our RS4's. What friends I have in Germany who have owned a C5 RS6 (of which there are 2) never had any issues with their DRC. Did the US C5 RS6's have as many DRC problems? Do US spec RS4's have as many DRC issues?

SR71, you are far more knowledgeable about these things than I am as is Arthur and you are both entitled to your opinion on an internet based forum, just don't let you passion and enthusiasm regress to sarcasm and insults.

what folks don't realize is that Audi did not design the DRC (KYB iirc) nor the cyclone unit (Mann?)

yes, it seems like the DRC issue affects US cars too...in fact there is a formal policy/recall out for the RS6...