RS4 Piston Damage from Carbon Build-up

[2manytoys]

As some may know, I've been suffering from Carbon Build-up. See here for pictures and details:

http://www.audizine.com/forum/showth...ghlight=263whp

During the whole process, back and forward with Audi, the car began to ping (knock/detonate). It become very bad, pinging multiple times. Audi claimed that the car has in-built protection against this. I agree, the timing can be pulled back, and yes, we saw this on the logs, but it can only go back so far.

Below you'll see a video of a good piston (yes some small marks but nothing major) and then you'll see my piston. This looks bad!

http://www.youtube.com/watch?v=n7I4OAQHm7c

WARNING - If you notice your car pinging stop driving it (mine was noticed initally by driving in 2nd gear at 5000 rpm, then pressing 100% throttle. Later it was easy to re-create with gentle throttle in light traffic)

I've also got some video from the same bore scope of some major carbon build-up. This is not my car. I drove the car in the next video no more than 500m, and as sad as it is, I can immediately feel if an RS4 suffers from Carbon Build-up. I got out of the car and said to the owner that this car has carbon build-up 100%. This is what we found:

http://www.youtube.com/watch?v=wAiViR8x0Qo

So, what are everyones thoughts on the Piston?

Thanks, Mal.

PS: I'd like to thank Franck from Gosford European Car Services for going out of his way to help with all of this. http://www.europeancarservices.com

[2manytoys]

Now, this is the bad part. The Carbon is coming back, and the pinging is starting again. This is what the build-up looks like only after 2000km.



Interesting, from what I understand (I may have mixed things up) Audi say the pinging/carbon was caused by the fuel regulator, however the pinging is back now that the carbon is there again!

[FWP!]

Could be me, but I don't see any piston damage, I see areas where maybe the piston was touching carbon built up on the underside of the head, but what are you seeing that maybe I'm not?

And wow, how would you prevent this from happening? An oil catch can?

[NoTec]

Some believe a catch can is not the answer. We are waiting for the results from those who use meth injection.

[ess_four]

Sorry to hear the news 2many. Now let me get my reading glasses and comfortable. This could be ong one

[ArthurPE]

there is a TSB out on the fuel regulator

my opinion
deposits back 80% of max in 2-3k miles, and taper off at ~100% after 6-8k and stop increasing

I see no real piston damage
what I do see is some minor pitting due to detonation, most likely caused by pre-ingnition from lean mixture...my guess

[mattlqx]

Damn, Mal. Sorry to hear about your continued troubles.

I'm in agreement with Arthur's estimations (as much as I'd hope it's not that quick). I'll dyno as frequently as possible after I get mine back because I'm thinking this is a good unobtrusive measuring.

[Sharkfin]

Ouch

[2manytoys]

Thanks. Yep, the reason I posted the video here was to get some feedback if people thought the piston wasn't damaged too bad. Just to clarify, the first part you see is a piston from an RS4 that has not been pinging. Once you see the front of my car you then see my piston.

What is more concerning is the amount of pitting. If you see my piston, around the valve cut-away, you'll see the corner blasted away. Compare it to the "good" piston and you'll see the valve cut-aways are nice and clean (sharp). My concern, and the mechanic, is not so much the small pits (as the camera can make these look huge anyway) it's mainly the large piece taken away near the valve cut-away.

If I'm being paranoid, I'm happy to get told a few times that it's not bad and don't worry about it. I just want to make sure, cause it sure doesn't look good.

Thanks, Mal.

[ArthurPE]

they both look the same to me, and they both look damaged
are they both in the same bank?
do you have pics of the other bank?

I'm the last person you want advice from I'm sure, but here goes
be careful of what you post, it may come back to haunt you
be careful of positing a conclusion like deposits damaged your engine, at best inaccurate because no one knows what happened, at worst, libel

how does the car drive?
is the ECL on? steady or flickering?
when did Audi diagnose the pinging re: fuel regulator?

answer only if you are comfortable doing so, obviously

[2manytoys]

Yeah, I was told by Audi that the only way the car can ping was wrong fuel. I said I always use V-Power. The only conclusion they could come up with was that bits of carbon was falling into the chamber and causing the pinging. They did talk about the carbon restricting airflow and that may have caused it (but I'm not sure how). So yeah, I'm only saying carbon because that was what I was told. (even if it was restriced airflow, it was still carbon).

Remember, the first piston was from another car, but yes, both from the same bank and the exact same location. I can get other video of the other bank. They all look roughly the same, but some not as bad.

The car doesn't throw up no errors. Unfortunately it never has with relation to carbon. The only way Audi found it, was by logging low air volume, and sending this to Germany (they said), and that's when the took the manifold off.

from memory it was early November when it starting pinging. It was very random at first, maybe once every few days or so. By the time it was bad (pinging multiple times a day) Audi were on to it (still took a few weeks).

Mal.

[2manytoys]

The manifold is off again, this time due to a leaky actuator (it's the one that moves the intake runners).

Anyway, looking at the valves, I noticed that a piece of carbon had broken off.

When I first looked at it you could see the shiny valve showing though. This photo was taken a few days later, so the shine has gone, but you can still see where the carbon has broken away



I assume this is the source of my pinging again, but would this cause damage. My local mechanic seems to think so, as the carbon is hard, and would be like dropping a very small rock into the intake. I assume this is not the only piece that has fallen in too.

Thoughts?

[CHECKERED]

TI assume this is the source of my pinging again, but would this cause damage. My local mechanic seems to think so, as the carbon is hard, and would be like dropping a very small rock into the intake. I assume this is not the only piece that has fallen in too.

Thoughts?

It might be ‘hard’ but it’s far too soft to damage metal, nothing like an actual rock.

[2manytoys]

Ok thanks. Maybe I have it mixed up, the hot carbon would cause detonation (pinging), and that causes the damage (pitting)? This is the part of the carbon build up problem that I'm not sure about. It's really the other side effects.

Cheers.

[handyvorb]

Ok thanks. Maybe I have it mixed up, the hot carbon would cause detonation (pinging), and that causes the damage (pitting)? This is the part of the carbon build up problem that I'm not sure about. It's really the other side effects.

Cheers.

This is plausible in theory (and absolutely the ONLY possible way for carbon on the intake valve to cause detonation), but I believe the results of your detonation are MUCH more likely to be caused by fuel quality. The intake valve carbon is on all the FSI engines (but builds up with poor fuel quality and always baby'ing the engine). Just because the gas station you've been going to for years says 91-93 octane on it does not necessarily mean that's what's going into your tank (yes by law it's SUPPOSE to be). I use V-power in my S4, but since you're experiencing an issue swap to BP premium or another top tier (anything but what you're currently getting!). This will help determined the cause.

Has the dealer monitored ignition timing with the scan tool? Bad fuel will show up immediately with this test.

[2manytoys]

Yep, fuel was the first thing I changed. I thought it was a dodgy service station (it was V-Power) so I switched to Mobile 8000. That didn't help either. I use 4 service stations and they are about 70 miles apart. It wasn't until the carbon was cleaned that the pinging stopped. When we logged timing the first time (before the valves were cleaned) it was about 9-15 degrees.

My main concern at the moment is piston damage through detonation.

I do a lot of freeway driving where the car would sit on 3000rpm for 40 minutes at a time. While I've done one drive day, it has not been tracked. I do give it a run (8000rpm) once or twice a day.

Would the highway driving be making this worse?

[handyvorb]

Yep, fuel was the first thing I changed. I thought it was a dodgy service station (it was V-Power) so I switched to Mobile 8000. That didn't help either. I use 4 service stations and they are about 70 miles apart. It wasn't until the carbon was cleaned that the pinging stopped. When we logged timing the first time (before the valves were cleaned) it was about 9-15 degrees.?

Was the ignition timing checked directly before and directly after the de-carbon? I'm wondering if a piece of carbon made it into the combustion chamber prior to the cleaning and just eventually burnt up or found it's way out (not directly related to the cleaning itself).

My main concern at the moment is piston damage through detonation.

Was each piston face inspected? If the damage is close to even across all pistons this detonation damage it's much more likely to be caused by that faulty pressure regulator your mentioned (causing a lean condition in cylinders).

As far as the damage itself, I've seen race cars running over 100 hp per cylinder operating 100% normal with this minimal piston face detonation damage on them. Small amounts of detonation will do this to the piston face, but the contact surfaces will be completely ok. If the car is still under warranty you can try purusing engine replacement, but may possibly be denied to "engine operating as designed". It will be a call from the higher ups on the warranty chain. If you no longer have a warranty I wouldn't be worried about it. If there was consiquential damage (low compression for instance) you would be seeing cylinder load contribution/balance faults in the ECM.

I do a lot of freeway driving where the car would sit on 3000rpm for 40 minutes at a time. While I've done one drive day, it has not been tracked. I do give it a run (8000rpm) once or twice a day.

Would the highway driving be making this worse?

Unfortunately (in order to reduce emissions, also taking place of the EGR function) the variable timing camshafts are at the largest overlap while cruising with little load. This is the root cause of the carbon buildup in FSI engines. Giving the engine a run to let it breath (preferrably in a taller gear, 3+...) with the engine hot, on the highway once or twice a day, and quality fuel are really your only defenses as of right now. I have been hearing Audi has been working on better means of cleaning the valves (they have tried many methods already, and by hand is still the best) and a solution to the problem.

[RS4POWER]

Handyvorb- I would rep you but.. oh wait we cant do that anymore.

I doubt driving style has anything to do with it. Many rs4 owners (over at QW) that have had their IV/IM cleaned... changed to a more aggressive driving style and found that CB came back at the same mileage causing CEL lights and performance loss. Plus audi approved oils have a low flash point so those who choose to drive the car in the manner it is intended should change their oils more frequently than recommended OCI's.

However you are right that AoA is looking for causes and remedies. We will see what comes from their efforts. It gets rather pricey to maintain this or any FSI car on a yearly basis.

[drivenRS4]

Some believe a catch can is not the answer. We are waiting for the results from those who use meth injection.

What I have heard is that a catch can with a baffle and water meth injection kit will keep carbon levels down. The real fix is to remove the possibilities of contamination to the valve. I think a Magnusson Supercharger would help because they come with fuel rails and port injectors mounted. Install the supercharger, get it tuned, go play.

Also, carbon only sticks to the valves at certain temperatures. The RS4 loves to hang out right in the carbon build up range of temperatures. 195-290 degrees centigrade with 200 degrees centigrade being the sweet spot. (383F-554F sweet spot of 392F). These temperatures relate to the valve temps, not the air or oil temps. The goal is to keep it colder to prevent carbon sticking to the metallic surfaces, or hotter to to remove the carbon. Watch the video below, it’s very interesting and helpful.

Italian Tune Up... Engineering Explained
https://youtu.be/5C9Ie4BcYew

[ZimbutheMonkey]

Dude, forget the carbon build up. As others have said, even if it dropped in, it's not hard enough to damage a piston. CHECK YOUR INJECTORS!!!!!!!!!!!!!!!!!!!!!!!!!!! It's a known fact that the injectors on these cars get plugged with carbon which 1) interferes with their spray pattern which in a direct injection car, with that high a compression ratio has to be VERY precise and VERY finely atomised in order to not detonate. 2) eventually it clogs the injectors to the point where they don't spray enough and you run lean.

That kind of pitting is caused by one of two things 1) a piece of metal gets in there like a nut or 2) detonation. There are NO other ways to pit a piston like that....

I posted links to an article in the engine tech section here. I'll see if I can find the pics of the injectors it's extremely damning evidence.

[JimmyBones]

What I have heard is that a catch can with a baffle and water meth injection kit will keep carbon levels down. The real fix is to remove the possibilities of contamination to the valve. I think a Magnusson Supercharger would help because they come with fuel rails and port injectors mounted. Install the supercharger, get it tuned, go play.

Also, carbon only sticks to the valves at certain temperatures. The RS4 loves to hang out right in the carbon build up range of temperatures. 195-290 degrees centigrade with 200 degrees centigrade being the sweet spot. (383F-554F sweet spot of 392F). These temperatures relate to the valve temps, not the air or oil temps. The goal is to keep it colder to prevent carbon sticking to the metallic surfaces, or hotter to to remove the carbon. Watch the video below, it’s very interesting and helpful.

Italian Tune Up... Engineering Explained
https://youtu.be/5C9Ie4BcYew

Way to necrobump a nine year old thread!

Catch cans and water meth injection don't work to reduce carbon buildup. Multiple people have tried it and found that it doesn't help.

The supercharged cars do have less carbon buildup. A few local guys with the JHM or APR superchargers have noticed slower carbon buildup from what I have seen.

I like the Engineering Explained channel. It is nice how he spends a lot of time to actually researching the topic along with posting links of his sources. If you want to check out a cool video then look at the water injection video for the M3 GTS where they recover 50 horsepower from heat soak. It is a good solution for a track car that is going to see 20-30 minutes long track time because the intercooler water is going to heat soak during that long of a track driving session. For short 11-12 seconds long dragstrip passes the water injection isn't going to help much.

https://youtu.be/PhShcJZ3JAk

[ZimbutheMonkey]

Way to necrobump a nine year old thread!

Catch cans and water meth injection don't work to reduce carbon buildup. Multiple people have tried it and found that it doesn't help.

The supercharged cars do have less carbon buildup. A few local guys with the JHM or APR superchargers have noticed slower carbon buildup from what I have seen.

I like the Engineering Explained channel. It is nice how he spends a lot of time to actually researching the topic along with posting links of his sources. If you want to check out a cool video then look at the water injection video for the M3 GTS where they recover 50 horsepower from heat soak. It is a good solution for a track car that is going to see 20-30 minutes long track time because the intercooler water is going to heat soak during that long of a track driving session. For short 11-12 seconds long dragstrip passes the water injection isn't going to help much.

https://youtu.be/PhShcJZ3JAk

Actually, what will work best to stop carbon buildup is to park the exhaust cam at full lobe seperation unless you're WOT... But that requires retuning and a willingness to accept a loss in MPG.