My RS4 Carbon Build-up Story (Now with Before/After Dyno)

[NoogMan]

it actually has 8 flaps, 1 in each manifold intake runner, each bank of 4 is operated by a vacuum actuator on a common shaft...with a common control valve for both banks
they switch long to short at high speed...can't tell if it's
>5000 rpm AND 200 kph or
>5000 rpm OR 200 kph


the deflapping refers to an extra flap on the airbox, nit intake manifold...

Sweet, I feel at home with 2 cars using "flaps". The RS4 actually works now because of the cleaning. I suggest everyone get it done.........they don't know what they're missing.

[2manytoys]

Guys, I'm going to have some VERY interesting video and pictures for you within a couple of hours. I'll start a new thread as it highlights some other stuff, but I'll post a link here.

Stay tuned.

Mal.

[NoogMan]

Guys, I'm going to have some VERY interesting video and pictures for you within a couple of hours. I'll start a new thread as it highlights some other stuff, but I'll post a link here.

Stay tuned.

Mal.

We will be anxiously waiting........btw......see that you like Sea Doo's, I just picked up my 2nd Sea doo last week......... an RXT-Is 260...it's a beast. Love the suspension!

[2manytoys]

Here it is guys. I'd say enjoy, but there is nothing enjoyable about it:

http://www.audizine.com/forum/showth...arbon-Build-up

[mattlqx]

Okay, here it is. I got the car back. First thing is first, my impressions. I drove it about 30 miles home and I'll say that it does indeed feel faster. Most notable to me is how much smoother it feels. The near 6k RPM hesitation is gone and overall the engine goes through the revs faster. I'll be getting it dyno'd next week and should have a few hundred more miles on it. That will give it ample time for the ECU to adjust completely. In the meantime, I have a track day tomorrow and will be putting the fresh(er) car through the paces. It definitely feels good and it does "push you back in the seat" more. I won't say it's a massively huge difference like the jump between an S4 and RS4 but it is 100% noticeable by anyone who has been in both a car with at least 10k miles and a brand-new car.

Remember, my car NEVER threw a check engine light. Nor did it show any obvious signs of something malfunctioning. This is all because of concern I had from others' experiences and the dyno results I got on various occasions. Keeping this in mind and the fact that no one yet has presented evidence of their car being "clean" after some amount of milage, it is my OPINION that EVERY RS4 looks similar to mine and that this is definitely a very real issue.

Now, the pictures...

After cleaning (gotta build suspense):



And now... before the cleaning:



Dyno results to come mid to late next week.

[ArthurPE]

thanks for the feedback...
for 23k miles yours do not look nearly as bad as some of the others that have been posted...
what process did they use to clean them?

[jalas]

Have to agree with ArutherPE. Did not look that bad for 23k.

FYI, was at the dealer yesterday having a squeaky seat fixed and they have a RS4 there that "special engineers" are coming to see on Tuesday. Apparently the car is throwing codes and the service advisor says it is carbon build-up. They had the owner use a few cans of some fuel additive with zero results. Audi corporate wants to see his car. He also mentioned to me that they have been cleaning numerous cars already and that this is getting old because they can't tell their customers want is really happening. This was all volunteered information, which I found somewhat amusing and troubling but at the same time made me hope for the best.

[silverRS4]

it actually has 8 flaps, 1 in each manifold intake runner, each bank of 4 is operated by a vacuum actuator on a common shaft...with a common control valve for both banks
they switch long to short at high speed...can't tell if it's
>5000 rpm AND 200 kph or
>5000 rpm OR 200 kph


the deflapping refers to an extra flap on the airbox, nit intake manifold...

You got the mechanism right, but the rest is incorrect. You even posted yourself that they are TUMBLE FLAPS. That's what they are. The power flap in the airbox is what opens at 5000 RPM and/or 200 kph. The manifold tumble flaps, which are vacuum operated as you pointed out, are closed until 3500 rpm, then open at RPM speeds above that. That is not in any literature, but I've logged it numerous times. They will even stay open as the engine speed drops below 2500 rpm, but then close if the RPM doesn't pick up. The tumble flaps are open or closed, they do not vary in position. The RS4 is a single length runner manifold with tumble flaps- completely different than the 4.2 Q7 or 4.2 B7 S4 engines, which are true dual length manifolds. The Q7 manifold actually is dual length with tumble flaps as well. This is all spelled out in the 4.2FSI engine literature that you refer to. People have "de-flapped" the airbox as you pointed out. A handful of people have also removed the tumble flaps from the manifold. The main idea is to keep from having one less part getting buildup on it. The differences in low or high RPM mass flow, low RPM engine smoothness and cold starting are not measurable or detectable by the seat of the pants. Which means its inconsequential whether they are in or out. My car makes the same torque at all RPM's with regardless if the tumble flaps are in or not. Interestingly, the trademark surge in torque that should occur at 5500 RPM in the RS4 does occur (in a healthy car) even if BOTH the power flap and the tumble flaps have been removed. This dispels many forum legends that either of those flaps are individually responsible for the surge. It is simply the designed natural point of peak efficiency of the motor. The power flap actually opens at 5000 rpm in an effort to accomodate the pending increase of volumetric efficiency of the engine at 5500-6500 rpm. The tumble flaps have nothing to do with torque or volumetric efficiency. They work in conjunction with the splitter vanes in the intake port to create tumble at very low RPM. The tumble flaps and vanes are highlighted in the VAG patent that's been refered to numerous times. They appear to do nothing except get coated with oil vapor and hydrocarbons and then get cooked with internal EGR gases. That's my take on the manifold flaps.

[RS4POWER]

Have to agree with ArutherPE. Did not look that bad for 23k.

FYI, was at the dealer yesterday having a squeaky seat fixed and they have a RS4 there that "special engineers" are coming to see on Tuesday. Apparently the car is throwing codes and the service advisor says it is carbon build-up. They had the owner use a few cans of some fuel additive with zero results. Audi corporate wants to see his car. He also mentioned to me that they have been cleaning numerous cars already and that this is getting old because they can't tell their customers want is really happening. This was all volunteered information, which I found somewhat amusing and troubling but at the same time made me hope for the best.

Jose,

A "special engineer" looked at my car a year ago during clean-up. Took samples, photos and everything. I have not seen any progress. Hopefully the engineers there are superspecial.
How is your RS? Long time...

[mattlqx]

Well, if it were "that bad", the engine would've been throwing codes. Regardless, after coming back from another drive, it's ridiculous how smooth the engine is now compared to before. WOT you could feel it stuttering ever so slightly, almost like it were gasping for air.

Not that bad compared to other RS4s (or other FSIs for that matter) perhaps, but pretty freaking bad overall nonetheless.

[RS4POWER]

Well, if it were "that bad", the engine would've been throwing codes. Regardless, after coming back from another drive, it's ridiculous how smooth the engine is now compared to before. WOT you could feel it stuttering ever so slightly, almost like it were gasping for air.

Not that bad compared to other RS4s (or other FSIs for that matter) perhaps, but pretty freaking bad overall nonetheless.

It was.

Mine felt the same way, it was out of breath snailing up the speedo. After the clean-up top end was recovered and the long lost 5.5krpm surge was pinning me in the seat like when the car was new.

[ArthurPE]

looking forward to some dyno pulls (for what they are worth, imo) or some 3rd gear 3k to 8k runs...
see if your mileage improves any also

[jalas]

Car is running like a champ! I had a chance to stretch its' legs a few times with a couple local NSX folks and can proudly say that I leave them baffled.

So my preventative maintenance has been the following.
- Shell 93 Octane gas. Always since the cleaning.
- Run a can of Seafoam once every two weeks through the intake......hoping for the best come December when I pull the intake again.
- Run Lubromoly fuel injector cleaner every other fill up.
- Almost time to change the oil. ~2000 miles.

My goal is not to prevent it entirely but to limit the massive buildup to make future cleanings easier. Still feeling the oh-so-nice surge at 5500rpm. No complaints really.

[jalas]

looking forward to some dyno pulls (for what they are worth, imo) or some 3rd gear 3k to 8k runs...
see if your mileage improves any also

Ha! My mileage has gone down. I can't seem to stay out of the accelerator pedal! It is too much fun.

The only time I get decent mileage is when I am driving the kiddo around.

[jalas]

Not that bad compared to other RS4s (or other FSIs for that matter) perhaps, but pretty freaking bad overall nonetheless.

I agree.

[RS4POWER]

Jose,

I am glad the car is running great. You guys had some cold weather down that way and the RS thrives in cooler temps.
/.
Your preventative measures seem spot on except for the frequent seafoam/injector application. You have to remember seafoam is a very strong chemical which will get introduced in your oil via fuel dilution. Even at 2k miles I wouldn't feel too good leaving those chemicals (and the contaminants that gets cleaned off the IV/IM) running the motor.

Something to think about...

[ArthurPE]

let's look at it from Audi's perspective:
what can they do?
cleaning seems very short term, more than a few pics, 1k, 2k miles, worse than mr perfects at 20k+...
so it happens fast, and is baked on by exhaust gases, once on, it ain't coming off, imo, not without some elbow grease
it doesn't seem like blow-by is a factor

so that leaves oil seals...and what can they do about that? way to expensive, new head and design, double seals or something...
thicker oil? less seepage?
add an injector in the manifold and revise the software?
can't eliminate the EGR, it's part of the emmission systems, EPA isn't buying that one... (does anyone know, is EGR only during warm-up?)
I don't see a 'solution'

but thankfully for me, I don't see a problem either, mr perfects car made 390 HP with the depsoits...
I don't think one will ever dyno much higher for several reasons: no ram air, no limiting load offered by the dyno, ramp vs steady state measurement, ECU torque management/ASC/etc.
but 390 is ~6% of rating on a car with 20k+ of deposits...

I'm very interested on how this will play out and I'm supossed to get a call late next week after their meeting (tele-conference), hope they follow through

[2manytoys]

I agree also, MP's carbon doesn't look that bad.

MP - Did you have a surge in power at all around the 6000 rpm mark before it was cleaned?

Once cleaned you said you noticed it was pulling better. In my experiance, nothing really changed to about 6000rpm. It was after that I noticed the increase. The car with the Carbon Build up in this video doesn't pull any harder between 6000-8000 also (http://www.youtube.com/watch?v=wAiViR8x0Qo). It will once it's cleaned, I guarentee that.

Mal.

[mattlqx]

Just got a call from a rep at AoA. It was a good conversation and consisted mostly of data gathering. I think the call stemmed from the original visit to the dealer in January for the "cold-start" issue. I explained I was more concerned about build-up in general and told him my results from the manual carbon cleaning. I told him I'd keep in touch with him as I expect the cleaning results to be temporary...

I should be able to get it on the dyno today...

[mattlqx]

Well, results are in... They only had time for one dyno run. I really appreciate Jeff at Vivid for fitting me in and helping me (us) out. The chart speaks for itself though... (as a side note, I got the car back on Friday, took it to a track day on Saturday and LOVED IT, finally got to getting it dynoed today roughly 320 miles after cleaning)



Result: +25 WHP @ 7600 RPM

You can clearly see the difference after 5000 RPM which is what most people have noted as the range where it "feels different". So it looks like peak HP is now 315WHP, which if you're using the 25% DT rule rounds out nicely to exactly 420CHP. We can argue all day long about WHP vs CHP but you can look at the MaHa sheet and see DT loss was 94HP@7570. So add 94 to 315 and we're at 409CHP. I do intend to get on the MaHa as soon as possible for another set of numbers. As I noted earlier, feel of the way the engine revs is way smoother in addition to the power increase in the top-end. I want to also point out that looking at the timing information from my ScanGauge while driving, it's running 30-40 degrees timing at various loads compared to 20-30 I was getting before cleaning. Finally, gas milage has indeed improved.



This is about a 2 mpg improvement (shown after 20 miles of highway driving). All these signs seem to me to be smoking guns that the engine is indeed starved of air after carbon build-up. As most have noted, I wasn't even a severe case. Those unlucky souls will undoubtedly feel the stuttering more and check engine lights.

I'd say this is pretty good 'evidence'. The question was do carbon deposits affect power? The answer is unequivocally, YES.

[Sharkfin]

Well at least that proves it on one more RS4, 25WHP is a significant loss

[ArthurPE]

I'm not sure one sample is conclusive...did you only do 1 pull?
I looked at the historical weather data for the 2 runs...quite different
do you know what correction factors were used? the filter rate is different
+/- 10% is the repeatabilty of the machine
I'd like to have seen some simple timed runs, 3rd gear, 3 to 8k...takes all variables out of the equation...
mine gets ~25 cruising at 70...
you have software and exhaust correct?

[2manytoys]

Well done MP. I'm due back on the Dyno in April.

Arthur, I've been thinking about the 3000-8000 test. I even did a couple today. Do you run at 3000 and then plant your foot and hit the timer at the same time, or do you start at a lower rpm and hit start as you cross the 3000 rpm mark?

Also, the time between 6000-8000 is not even 2 seconds, so lets say you are 10% down on HP at 7000, not knowing the maths, but wouldn't that only be 0.2 second difference at the most. Therefore 8 seconds could be 8.2 in a "good" car or 8.4 in a bad car. I'm asking a serious question, because one of my runs were 9.4 the other 8.8.

PS: MP's carbon was not that bad, so I'm shocked he lost as much as he did. It does highlight what carbon does at the top end regardless of the actual numbers (just the shape of the graph).

Mal.

[ArthurPE]

Well done MP. I'm due back on the Dyno in April.

Arthur, I've been thinking about the 3000-8000 test. I even did a couple today. Do you run at 3000 and then plant your foot and hit the timer at the same time, or do you start at a lower rpm and hit start as you cross the 3000 rpm mark?

Also, the time between 6000-8000 is not even 2 seconds, so lets say you are 10% down on HP at 7000, not knowing the maths, but wouldn't that only be 0.2 second difference at the most. Therefore 8 seconds could be 8.2 in a "good" car or 8.4 in a bad car. I'm asking a serious question, because one of my runs were 9.4 the other 8.8.

PS: MP's carbon was not that bad, so I'm shocked he lost as much as he did. It does highlight what carbon does at the top end regardless of the actual numbers (just the shape of the graph).

Mal.

I start at 2000 and press the pedal so it's 100% at 2500 or so...

if you were down 10% power at 8000 or an average of 5% from say 4000 to 8000 I would expect a 1/2 sec difference...
9.4 is way out of range
I've got a database of 34 cars so far, over 150 runs (3rd gear, timed 3k to 8k)
average is 7.9
tossing out the 5% hi/low 8 flat
tossing out the 5% low only 8.1
the highest run is 8.5, and he ran better once he got the hang of it, start at 2000, start timer at 3000
magazines (avg of 4) got 8 flat using the gears for the same speed range
factory, mag and misc dyno times for 3rd gear 3-8k (36 to 96 mph) 8.4 sec
no discernable difference between cleaned or hi vs low mileage...

a couple of other things...
can you 'feel it'?
let's say your average accel is 5% faster, and your avg from 5000 to 8000 is 0.8 g...that's pretty high, lower gear...a 5% difference would be 0.04g, imo, no one could feel that, not even a fighter pilot...
how is the car driven? you get best accel from 4000 to 6000 or so, highest torque since the driving thrust = T x gear rations

HP only helps for high spped sustained runs, ie, top speed
this car has such a wide torque band, hi speed operation is not a big factor, as proven by my bunch of 3rd only runs ~8 sec vs the mag tests using ALL gears of 8 sec, almost no difference between shifting or not
my M3 has 145k miles, 4000 hours of operation, redline 8000
how much time has it spent >7800? 51.3 sec in 4000 hours
how many events > 7800? 231, about 2/10ths of a sec average...
real world driving, back roads, or track, if you keep these cars on a 'boil' 5000-6000 range, you will be flying...
iirc the BMW M3 time Ring runs avg gear is 3rd, with some 4th, and avg rpm of 5800 rpm, I have the telemetry at home, very few gear changes, I was surprised...

I PERSONALLY don't believe that deposits cost HP, in large part due to my data (more tests please :) ) but regardless, we need to put these numbers in perspective...an 8% difference, if accurate, is not substantial, going from 80 to 40F will have ~ the same impact...or driving at an atl of 1500' vs SL

I'm out of this debate...I will wait and see what Audi does, seems like they are on the case, and until then just enjoy my car...
do some more runs...9.4 is really bad...8.8 is also not good...if functioning correctly imo 8 to 8.5 depending on EL, temp, wt, etc.

[koolade9]

Good work MP! I'm officially convinced...my car has almost 20k more miles then you and has never been cleaned. Manifold should come off in 2-3 weeks

[boostinfd]

Maybe someone should make a how-to on taking manifold off etc...

[Ill 3.0]

I'm not sure one sample is conclusive...did you only do 1 pull?

Just look at the overlay, the power and torque curves are almost identical under 4500 RPM. Seems like an ideal internal control to me. Sure 1 run is not conclusive, but in my mind CB robs higher RPM power, case closed.

[koolade9]

Maybe someone should make a how-to on taking manifold off etc...

There is on AW (or maybe it was QW), I'll see if I can find it...

[boostinfd]

There is on AW (or maybe it was QW), I'll see if I can find it...

I checked those sites... maybe i'm blind...

[two2]

i don't suggest anyone attempt to do this unless you have some type of mechanical experience and lots of patience.. looks a lot easier than it really is until you start digging in.

[PetrolDave]

Since the change is only noticeable above around 5000rpm I have an alternative theory what the problem was...

Above about 5000rpm there is a flap in the air cleaner that opens to improve the breathing. This flap is vacuum operated, so if the vacuum pipe that operates the flap is disconnected you get a power curve similar to your "before" curve.

Maybe, just maybe, your power gain above 5000rpm is not related to the inlet cleaning at all, but to the vacuum pipe being properly reconnected when the inlet manifold was refitted so that the power flap opens as it should?

That would fit perfectly with the difference in the two dyno curves.

Just my $0.02...

[boostinfd]

I think some of these guys that had the Manifold cleaned thad the flapper doors removed completely...

[mattlqx]

Don't you think the dealer would kind of, you know, catch on to that? I think they or at the least Audi would recommend that that be the first place to look to avoid the $1000 labor charge. Besides, I think it's pretty unlikely that the 5 or so cars that have had this documented with the same results would "only" be caused by that scenario.

[Tugboatguy]

Some individuals have been very vocal in the CB threads, that it is not an issue. They grasp at straws trying to come up with explanations for the results shown after cleaning that would point to something else, anything else than admitting that they could be wrong. I guess we can expect them to sell their cars when it finally happens to them, since fixing it would be admitting the issue was real Then again they might just quietly get the CB cleaned and say nothing to save face

[silverRS4]

Granted, vacuum problems were found on early RS4's and they can cause serious issues. Sometimes without a CEL, which is mind-boggling. There was a chap in UK who had power issues after a dyno, got his vacuum line fixed, then recovered some power on his next dyno. Then there are the people who disconnect the vacuum lines to the valves on the mufflers without plugging them and have similar power problems. That is a legitimate concern. But a few people cling to these examples as if they are the rule for RS4 power deficits despite mountains of evidence that shows that CB disrupts ignition timing and lowers power output (in 100% of the cases where CB is discovered).

[2manytoys]

From memory you don't need to remove the air box to remove the manifold. The air box flap is not likely to be the cause in these cases.

Just back on the 8 second third gear thing. If the difference is 0.5 seconds, that's huge. If the 3000-5500 is identical (as I've seen, most look good around these rpms) then the time difference is going to come from the upper rpm range, then 0.5 seconds is a mojor difference. I'm not sure how useful this test really is. It may make some "feel" good because they got into the 8 sec bracket, but my real measure is if you have that strong turbo pull at 5500. To measure from 5500 to 8000 would be more accurate, but like I've pointed out, even a 0.02 second variation I think would be big (again, I'm not the maths wize, but just looking how short the time is, it's full of errors.... probably worse than a dyno)

[two2]

he's talking about the flap in the mufflers which can cause a leak if the lines aren't sealed off, or the vacuum line under the manifold.. mines were darn tight... after the car sat a week when i took the lines off i heard lots of air hissing so mines didn't have that problem. seems to be a good thing if you can hear the air when removed.

[duud40]

You got the mechanism right, but the rest is incorrect. You even posted yourself that they are TUMBLE FLAPS. That's what they are. The power flap in the airbox is what opens at 5000 RPM and/or 200 kph. The manifold tumble flaps, which are vacuum operated as you pointed out, are closed until 3500 rpm, then open at RPM speeds above that. That is not in any literature, but I've logged it numerous times. They will even stay open as the engine speed drops below 2500 rpm, but then close if the RPM doesn't pick up. The tumble flaps are open or closed, they do not vary in position. The RS4 is a single length runner manifold with tumble flaps- completely different than the 4.2 Q7 or 4.2 B7 S4 engines, which are true dual length manifolds. The Q7 manifold actually is dual length with tumble flaps as well. This is all spelled out in the 4.2FSI engine literature that you refer to. People have "de-flapped" the airbox as you pointed out. A handful of people have also removed the tumble flaps from the manifold. The main idea is to keep from having one less part getting buildup on it. The differences in low or high RPM mass flow, low RPM engine smoothness and cold starting are not measurable or detectable by the seat of the pants. Which means its inconsequential whether they are in or out. My car makes the same torque at all RPM's with regardless if the tumble flaps are in or not. Interestingly, the trademark surge in torque that should occur at 5500 RPM in the RS4 does occur (in a healthy car) even if BOTH the power flap and the tumble flaps have been removed. This dispels many forum legends that either of those flaps are individually responsible for the surge. It is simply the designed natural point of peak efficiency of the motor. The power flap actually opens at 5000 rpm in an effort to accomodate the pending increase of volumetric efficiency of the engine at 5500-6500 rpm. The tumble flaps have nothing to do with torque or volumetric efficiency. They work in conjunction with the splitter vanes in the intake port to create tumble at very low RPM. The tumble flaps and vanes are highlighted in the VAG patent that's been refered to numerous times. They appear to do nothing except get coated with oil vapor and hydrocarbons and then get cooked with internal EGR gases. That's my take on the manifold flaps.

The surge is due to the throttle (body) not opening all the way untill that rpm and because of cam advance changing.
Good luck finding it in the ecu file though.

[silverRS4]

Yes, the torque limit imposed in gears 1-3 (whether ESP is on or off). I'm aware of that. The torque limit has been removed in my car, so now the throttle body plate follows the throttle pedal all the time in the lower gears. Much better. But even with the torque limit removed, there is a noticeable (and loggable) increase in torque at 5800-6000 rpm. I'm sure the cam timing is changing as you suggest, but my point was simply that the peak efficiency of the motor is around 6000 rpm and the airbox flap opening is to prepare for that air demand. It (and certainly not the manifold tumble flaps) does not create the bump in torque.

[ArthurPE]

Component Description:
7. ENGINE AND ENGINE COOLING:EXHAUST SYSTEM:MANIFOLD/HEADER/MUFFLER/TAIL PIPE Bulletin Number: 24-08-26
Bulletin Date: Jun 2008
Vehicle: 2,008 Audi RS 4
Summary:
AUDI: POOR PERFORMANCE BECAUSE OF LEAK IN VACUUM SYSTEM. POOR ENGINE PERFORMANCE BECAUSE OF INOPERATIVE INTAKE MANIFOLD TUMBLE FLAPS OR AIR FILTER BOX POWER FLAP. ( NHTSA ITEM NUMBER - 10025981 )