Pictures of my inlet ports....

[ArthurPE]

any pre-ignition, consistent in nature, like deposits, will set codes...

this is how it works...
the ecu sets operating parameters or 'setpoints' for:
fuel rate (metered jets in the old days, now pwm injectors)
timing (vaccum or the good old Bosch -008 mech advance, now computer driven coils
cam phasing (not happening in the old days)

based on inputs:
rpm
throttle
temp(s)
load/torque calculations
used to be vacuum ~ to throttle position ~ 'load'

if the ecu sets timing at 25 based on all the inputs, but is over-ridden by the knock sensor to 15 or whatever, that is only allowed to happen so many times before it sets a code...I want 25, but keep getting over-ridden by knock...there is a problem that won't go away...
if deposits retarded timing, all cars would have this error code set...they don't

[2manytoys]

any pre-ignition, consistent in nature, like deposits, will set codes...

this is how it works...
the ecu sets operating parameters or 'setpoints' for:
fuel rate (metered jets in the old days, now pwm injectors)
timing (vaccum or the good old Bosch -008 mech advance, now computer driven coils
cam phasing (not happening in the old days)

based on inputs:
rpm
throttle
temp(s)
load/torque calculations
used to be vacuum ~ to throttle position ~ 'load'

if the ecu sets timing at 25 based on all the inputs, but is over-ridden by the knock sensor to 15 or whatever, that is only allowed to happen so many times before it sets a code...I want 25, but keep getting over-ridden by knock...there is a problem that won't go away...
if deposits retarded timing, all cars would have this error code set...they don't

I agree with the above in theory, but even though mine is being retarded there are no "soft errors" at this stage (I understand that the engine light is what is called a "hard error"). At saying that the dealer wants to send "the file" to Germany as they can extract these soft errors. Mine never triggered a "hard error" even with major detonation. Maybe what you say above doesn't work properly, or other factors cause it not to show??

I wouldn't say ALL cars are suffering from heaps of carbon, and that even all these are causing detonation. I would say that at some point, assuming the carbon is getting worse, the ECU will pull timing, and if left, will detonate.

[lugars4]

any pre-ignition, consistent in nature, like deposits, will set codes...

this is how it works...
the ecu sets operating parameters or 'setpoints' for:
fuel rate (metered jets in the old days, now pwm injectors)
timing (vaccum or the good old Bosch -008 mech advance, now computer driven coils
cam phasing (not happening in the old days)

based on inputs:
rpm
throttle
temp(s)
load/torque calculations
used to be vacuum ~ to throttle position ~ 'load'

if the ecu sets timing at 25 based on all the inputs, but is over-ridden by the knock sensor to 15 or whatever, that is only allowed to happen so many times before it sets a code...I want 25, but keep getting over-ridden by knock...there is a problem that won't go away...
if deposits retarded timing, all cars would have this error code set...they don't

What is the limit before an engine light or fault code is generated though?

I have previously been told that the max CF is somewhere between 15 - 21, which in most cases would not cause a fault codes in the majority of cases.

I do believe the carbon is causing loss of performance and power, the amount of carbon seen, and the rate of its appearance, it is more than likely that it will cause trouble in one way or another. Most likely through pre-igntion, and carbon buildup around the head in general after that. There are reports of carbon deposits on the injector nozzles, with many having to be replaced as a result.

[SR71]

P_G...no idea what that level of timing is worth...its hard to check what it does to BMEP!

When I tested my car against Rob's prior to it going to MRC this was one of the things we noticed. I could run ~30 degrees of advance but his car would only run ~20.

Check http://www.rs246.com/index.php?name=PNp ... ght=timing

This agreed with what SilverRS4 observed below albeit there was no assumption that my car was "clean".

It looks like that level of timing is worth ~0.2 secs on a FATS run (i.e. between 4200-6500rpm)?

(Without wishing to stir the debate up further, what might that mean over the 1/4? About ~0.4 secs? Which is a hp deficit of a good size! That said, to be fair, in this configuration Rob was running a catback Miltek and we all know that fitting a Miltek without a remap actually robs you of power so that might be the reason...)

Regards CEL's, unless we know the algorithm, we're all speculating.

But here is a thought...

Maybe Audi knew that buildup would be significant so they've set the limit at which CEL's are thrown to be wide enough to cope with the expected levels of buildup. Cars which accumulate carbon at the expected rate throw no CEL's but those where the accumulation is, for whatever reason, worse than expected, spit their dummy out.

Taken from: http://www.rs246.com/index.php?name=PNp ... 2e6fe221c2

The picture is painted, fellas. First of all, the power loss is due primarily to retarded timing caused by carbon chunks all over everything from the manifold flaps to the valve seats. This has been documented in NA. RS4 with 23k miles, no CEL (MIL), no other signs of a problem EXCEPT the timing was around 20 degrees under load (rather than the normal 30 degrees or so with 92 US octane). Owner thought car was fine, but had noted lower top speeds on the straights during track days. Mustang dyno confirmed with 273 WHP and flat curve from 6-8k. Manifold removed to reveal the CB shown above (I presume OP's valves look similar). Valves cleaned, put back on dyno with the same fuel in the tank and intake air temp within 3C of original run. Power went up to 315 WHP and timing was back to normal, with much less retardation. Interestingly enough, this RS4 had used RLI oil from very early on. Its not oil, its not how you drive it, its not the venturi separator and its certainly not coil packs - its simply a by-product of direct injection which is exaggerated on the RS4 by a rather long period of passive overlap.

There were 2 other cases on the same dyno with RS4 owners REGAINING 30WHP+ simply by cleaning the valves. One of those owners was also sure there was no CB on his engine. To my knowledge, the number of RS4's to display CB with their manifolds removed is still 100%. Its not a pretty picture.

and

You're not looking hard enough, and what you are finding you are interpreting incorrectly. Three cases that I can think of immediately, the owner had zero CEL's and no indication of a problem. They had no vacuum problems, no flap problems, not even 1 misfire, zero. Only consistent complaint was loss of top end power. In all three cases, the CB is removed (all else is the same) and the normal power character returns (along with 20-40 hp due to the ignition retardation decreasing normal levels). All had CB. Then, lets mention that EVERY RS4 that has had its manifold off has revealed some CB. That number must be close to 20 across all the forums. That does not include all the 2.0 and 3.6 FSI's. Yes, the manifold removal may have been necessitated for another problem. Stuck flaps (due to carbon) or bad injectors (due to carbon). You're saying the secondary problem causes (or worsens) the CB, when actually the CB is there all along and it takes a secondary problem for Audi to actually remove the manifold and see the CB. After 8k miles without the vanes, my valves were as cruddy as they were after 8k with the vanes. The patent seems to have more to do with valve surface treatment anyway - not really the scraping mechanism. Is it possible the surface treatment portion of the patent isn't even in production yet? The one thing made clear from the patent is that CB is a problem with direct injection - hence the tremendous effort to resolve it. Some DI cars see the CB at an advanced rate. For whatever reason (probably the more aggressive valve overlap and higher intake valve temps) the RS4 can see accelerated CB compared to the other VAG DI engines. Minor CB does not create a terrible problem. But eventually the ignition timing is no longer optimal and power (especially top end) will suffer

[P_G]

No doubting what you re saying SR-71 as it makes sense however it does come back to the engine power rating schedule. This would involve an engine with CB so what is to say that the quoted 414bhp would not be exceeded with continuously clean valves? I don't know if the rating process is over 1k mile engine life, 10k or 100k miles and if the minimal output figure is quoted or the average? If the minimum is quoted and for arguments sake that figure was at 100k miles, then perhaps by cleaning you are temporarily gaining more power.

Who really knows apart from the engineers who developed the engine but unfortunately I can't see any of them coming on a forum to give an account any time soon. It may well be that we have a case where a 273WHP car then makes 315WHP after cleaning and a 3 degree change in temp but then we are still partially guestimating on losses based on dyno readout experience because none have been bench tested in the same conditions as the engine used to give the power rating in the first place.

[rsierra]

any pre-ignition, consistent in nature, like deposits, will set codes...

this is how it works...
the ecu sets operating parameters or 'setpoints' for:
fuel rate (metered jets in the old days, now pwm injectors)
timing (vaccum or the good old Bosch -008 mech advance, now computer driven coils
cam phasing (not happening in the old days)

based on inputs:
rpm
throttle
temp(s)
load/torque calculations
used to be vacuum ~ to throttle position ~ 'load'

if the ecu sets timing at 25 based on all the inputs, but is over-ridden by the knock sensor to 15 or whatever, that is only allowed to happen so many times before it sets a code...I want 25, but keep getting over-ridden by knock...there is a problem that won't go away...
if deposits retarded timing, all cars would have this error code set...they don't

You have no clue what you are talking about. The RS4 ECU will <beep> timing in excess of 10 degrees on a consistent basis without throwing a code. I suggest you get VAG COM and do some data logging before posting misinformation.

[P_G]

And your information is based on what? Forgive my cyncism but with a posting history of 4 all related to refuting other comments made it gives little confidence that what you are saying is any better than misinformation?

You may as well have constructively contributed to the thread like Golfather did.

[Sims]

And your information is based on what? Forgive my cyncism but with a posting history of 4 all related to refuting other comments made it gives little confidence that what you are saying is any better than misinformation?
...

With respect, IMO your challenge of this newbie does smack of partisanship & a bit of prejudice.

I don't know if what RSierra says makes sense, but do you?

[P_G]

You are right Sims, it is your opinion and sadly wrong.

It would be like me coming on to the forum for the first time with no previously stated history and saying the RS4 is crap. How?

Where facts are necessary as in this thread and rsierra's comments they are lacking. I wasn't being rude to him and asked him to expalin his statement. So how is that partisan because that would imply I am a supporter of this subject or a person which I am not or indeed prejudiced because I would have to have formed an opinion of him which I have not?

[JackS4]

If you think CB isn't an issue that affects performance check this out

http://audisrs.com/ftopic13519-0-asc-13 ... 9e757ad687

I thought my CB was bad (see pics on prev page on link) but the MRC picture is something else.

J

[P_G]

Thanks Jack, that was the SRS thread I made reference to on page 3 of this thread.

[lugars4]

You are right Sims, it is your opinion and sadly wrong.

It would be like me coming on to the forum for the first time with no previously stated history and saying the RS4 is crap. How?

Where facts are necessary as in this thread and rsierra's comments they are lacking. I wasn't being rude to him and asked him to expalin his statement. So how is that partisan because that would imply I am a supporter of this subject or a person which I am not or indeed prejudiced because I would have to have formed an opinion of him which I have not?

To be fair to Rsierra, his comment is quite sensible, and more than likely true. I have personally seen Correction Factors of more than 12, with no sign of engine fault logs.
They have to allow CF's to be present in the ECU without warning lights, as poor quality fuel is a cause of higher CF's, and in most cases, the odd tank of poor fuel is acceptable, where higher octane is not available. You would not expect engine warning lights when using lower octane fuel, but a decrease in performance in this case would be expected. A similar scenario to carbon induced detonation, which cannot be differentiated by the ECU as being caused by either poor fuel or some other means (carbon)..

[P_G]

I wasn't saying his information was wrong, just asked how he arrived at what he was saying. You are right it does make sense and would need to be there to compensate for the difference between 95 and 102RON in UK markets for example but in fairness what was said was a bit of a sweeping generalisation which is why I ask rsierra to elaborate on how he drew those conclusions.

[silverRS4]

..It may well be that we have a case where a 273WHP car then makes 315WHP after cleaning and a 3 degree change in temp but then we are still partially guestimating...

The 273 and 315 whp numbers were corrected, so technically a small 3C ambient temperature would be transparent when reporting corrected numbers. However, the peak ignition timing of the RS4 is sensitive to intake air temps. A dyno run at 15C ambient and one at 30C will yield significantly different corrected results since the hotter test will have less actual ignition timing and much less actual power, not to mention less uncorrected power due to less inlet density. The simple point of the 3C ambient difference was that ignition timing differences that were due strictly to inlet air temp were negligible. The air density difference is considered in the correction, any effects the inlet density has on actual ignition timing is not.

You make it sound as if they made one dyno run, got 273 whp, cleaned the valves, did one more run and got 315. When actually, the car did several runs prior and several runs after with the general 40+ hp difference fairly obvious. Similarly, the peak ignition timing went was 18-20 degrees for weeks prior to the clean then went to 28-30 after. And the peak MAF, which had been 142/144 for several weeks prior to the clean went up to 156/158. This before/after drama is not limited to just this car, but many...all without CEL's or vacuum problems.

This is not about engine semantics, dyno operators or correction factors. There are people who tune and program RS4 ECM's and know in detail how they operate, especially the closed loop ignition timing. As far as I know, none of them think that carbon does not had a dramatic effect on the engine's performance. With the nature of most of these threads, I can assure you that they do not take time to contribute.

[P_G]

Just to be clear on your last sentence, did you mean to say that the engine tuners do not take time to contribute?

As for the WHP figures, having seen my cars on few over the years I realise that it wasn't a reading taken on one run pre and one post and apologise if it came across that way. There is one part of what you have said which is the unquantifibale though, and that is the definition of 'dramatic'; same as 'significant'.

What one tuner defines as 'dramatic' or 'significant', can we be sure Audi agree to that?