Audi FSI Engine Carbon Build-up Megathread

[Fourplay]

How is carbon build-up related to oil dilution by fuel? What is the connection here? Better yet, exactly how is the oil getting diluted by fuel in the first place? I would assume this can only be achieved in an FSI engine through either faulty injectors and/or failing piston rings?

Simple. Oil diluted with fuel is more volatile and thus produces a greater volume of gas when heated. This means that the PCV system (which is already inadequate on the B7 RS4, especially at high RPMs) is more easily overwhelmed because it has a much higher volume of oil vapors to contend with.

The BNS runs rich (log your fuel trims sometime and see - factory tune is always quite rich), which leads to excess fuel in the cylinder after combustion. Even with piston rings in the proper spec, fuel wash on cylinder walls will dilute the oil in the crankcase. If you go to a forum like bobistheoilguy and read up on Blackstone reports for early generation VAG FSI engines, you'll see that all have quite a bit of fuel in the oil.

So, you have a bit of a perfect storm with the early FSI motors:

-Lots of fuel dilution due to the motor naturally running rich
-Greater volume of oil vapor in the crankcase due to increased oil volatility
-PCV/oil separator inadequately designed to handle the amount of oil vapor it seems, particularly in high RPM operation
-Excessive valve overlap (EGR) used to achieve emissions requirements, exposing intake valves to un-burnt combustion products

I guess we differ in our perspective on this.

I used the OEM oil filter, Castrol Edge or M1 full synthetic 0W40 oil (changed every 4k miles), brand new OEM air filter (not a K&N as the oil destroys MAFs), only filled the car with 93 octane V-Power, and took it to redline at least once every drive. Guess what? Still had carbon buildup. None of those things affect buildup, except (as I said before) more frequent oil changes to prevent the oil from becoming too diluted.

[jschrauwen]

Simple. Oil diluted with fuel is more volatile and thus produces a greater volume of gas when heated. This means that the PCV system (which is already inadequate on the B7 RS4, especially at high RPMs) is more easily overwhelmed because it has a much higher volume of oil vapors to contend with.
Is this still the case with the B8 FSI engines? Then there's the difference between turbo applications vs naturally aspirated engines as well. Is it possible forced induction engines (like your RS4) could introduce an even greater amount of oily vapours into the intake plenum vs my naturally aspirated 3.2L which would lead to a greater/earlier amount of carbon build-up?





The BNS runs rich (log your fuel trims sometime and see - factory tune is always quite rich), which leads to excess fuel in the cylinder after combustion. Even with piston rings in the proper spec, fuel wash on cylinder walls will dilute the oil in the crankcase. If you go to a forum like bobistheoilguy and read up on Blackstone reports for early generation VAG FSI engines, you'll see that all have quite a bit of fuel in the oil.
I'm not surprised that the factory would have their fuel maps richer then stoic. It's just one way of preventing potential detonation from a lean condition leading to engine failure. I believe it's just a self protection measure applied by the factory to protect themselves from owner claims of engine failures. I've seen (and experienced personally) what off-the-shelf tunes are like with my highly modified TT 300ZX. I gained substantial HP and TQ when I switched from an overly rich off-the-shelf chipped tune and had my 300ZX dyno tuned which eliminated all rich conditions.
Were any of those Blackstone reports from BITOG for any B8 engines?



So, you have a bit of a perfect storm with the early FSI motors:

-Lots of fuel dilution due to the motor naturally running rich
-Greater volume of oil vapor in the crankcase due to increased oil volatility
-PCV/oil separator inadequately designed to handle the amount of oil vapor it seems, particularly in high RPM operation
-Excessive valve overlap (EGR) used to achieve emissions requirements, exposing intake valves to un-burnt combustion products
Have you considered installing an oil catch can into the PVC system? I've been seriously considering it for some time.



I used the OEM oil filter, Castrol Edge or M1 full synthetic 0W40 oil (changed every 4k miles), brand new OEM air filter (not a K&N as the oil destroys MAFs), only filled the car with 93 octane V-Power, and took it to redline at least once every drive. Guess what? Still had carbon buildup. None of those things affect buildup, except (as I said before) more frequent oil changes to prevent the oil from becoming too diluted.
From my readings from BITOG, it's the euro Castrol that should be used and not the North American version. Also, Mobile 1 was downgraded from Group IV to Group III almost 10 years ago. I've been using Motul exclusively but have been contemplating switching to LiquiMoly as both are good Group IV oils.
I use a K&N filter which I clean and re-oil twice a year. I follow very stringent cleaning/oiling procedures (which usually takes about 2 days to complete) where there's zero oil residue to be drawn into the intake. I've been using K&N filters for almost 30 years on all my cars and my Ducati.

.......

[Tomieg]

Hey guys,

Here's a shot of the build up on my intake port dividers just ~2k after a carbon clean. Always ran 91 oct Shell V-Power & Castrol 0W-40 European formula.



Thanks,
-Tom

[jschrauwen]

What carbon cleaning method was used? Media blasting with soda or walnut shells or by hand using solvents?
Was an oil catch can system installed after the carbon cleaning?

Hey guys,

Here's a shot of the build up on my intake port dividers just ~2k after a carbon clean. Always ran 91 oct Shell V-Power & Castrol 0W-40 European formula.



Thanks,
-Tom

[Tomieg]

What carbon cleaning method was used? Media blasting with soda or walnut shells or by hand using solvents?
Was an oil catch can system installed after the carbon cleaning?

The valves were blasted with walnut shells. Here's a before and after shot of the valves during the time of cleaning ~85k. No catch can was installed afterwards. Has this been proven to reduce the oil trapped in the system on these motors? I find it difficult that Audi would omit this component if it was indeed such a critical component to the longevity of these motors.





-Tom

[jschrauwen]

The valves were blasted with walnut shells. Here's a before and after shot of the valves during the time of cleaning ~85k. No catch can was installed afterwards. Has this been proven to reduce the oil trapped in the system on these motors? I find it difficult that Audi would omit this component if it was indeed such a critical component to the longevity of these motors.
-Tom

The introduction of an external oil catch can system between the PCV valve and the return line back to the plenum has shown to reduce the amount/degree of oily film entering the plenum (which naturally gets deposited onto the backside of the valves) and limiting the amount/degree of carbon build-up. I would imagine Audi may not have done a long term evaluation to determine or even recognise this byproduct of an FSI engine. The 3.2L FSI engine was Audi's first FSI engine introduced in 2005. It replaced the previous non-FSI 3.0L engine and had better HP/TQ ratings as well as better MPG ratings. Perhaps they weren't too concerned at the time considering it's positive results over it's predecessor. I'm assuming they didn't do a long term / long mileage test of the engine.
Audi is not the only car company to find out (after the fact) that an FSI engine will encounter significant carbon build up due to the fuel not being sprayed over the backs of the valves like in non FSI engines. BMW, Toyota and others have experienced the same thing. Toyota has recently addressed this by adding extra fuel injectors to spray into the plenum to "wash" the backs of the valves. The BMW group, I believe, were the initiators of the walnut shell blasting process for their FSI type engines and that process has now migrated to other manufacturer's engines.

[iconoclast]

whatever happened with all this data that was collected?
outside of manual scrubbing or media blasting there hasn't been a solution or resolution to this issue?

[AudiB720TS]

@ the members who have done a cleanup already:

What are the best solvents/chemicals to use? I see Berryman B-12 Chemtool mentioned a lot online for these kinds of issues, as well as Sea Foam. I can't get those products locally though so I am looking for some other good options.

Thanks

[Zoltar]

What's the negative impact on neglecting to inspect/ clean the valves? Just poor engine performance or possible engine damage to valves then pistons?

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[vrmm]

I skimmed fairly well but not entirely. Any instances where compression dropped substantially. Like say 30psi in one cylinder. I am very aware there is a million other more likely possibilities, but seeing as I have never see this before, it would be a lovely issue, far easier to solve.

[jschrauwen]

I skimmed fairly well but not entirely. Any instances where compression dropped substantially. Like say 30psi in one cylinder. I am very aware there is a million other more likely possibilities, but seeing as I have never see this before, it would be a lovely issue, far easier to solve.

Is this your thread? - https://www.audiworld.com/forums/aud...ngine-2945852/

[jschrauwen]

whatever happened with all this data that was collected?
outside of manual scrubbing or media blasting there hasn't been a solution or resolution to this issue?

Like Toyota and other manufacturers, Audi has addressed this carbon build-up issues in their newer engines now - but not all of them. And of those, none are going to be making their way to North America just yet. Only available in Europe foe the time being. Too much money to be had in the secondary servicing arena in North America until organizations like C.A.R.B and/or the EPA or similar step up and apply some pressure/leverage.

[jschrauwen]

What's the negative impact on neglecting to inspect/ clean the valves? Just poor engine performance or possible engine damage to valves then pistons?

Poor performance as in poor acceleration, hesitation and power output. IE: loss of HP
Poorer gas mileage.
Increasingly more difficult cold engine starts.



Strange question to ask though.
Is it because we're not willing to do what's necessary in light of imminent future sale of the car?
IE: Can it be put off almost indefinitely without risk to damaging the engine so we can save a few $$$ prior to sale?

[Zoltar]

Poor performance as in poor acceleration, hesitation and power output. IE: loss of HP
Poorer gas mileage.
Increasingly more difficult cold engine starts.



Strange question to ask though.
Is it because we're not willing to do what's necessary in light of imminent future sale of the car?
IE: Can it be put off almost indefinitely without risk to damaging the engine so we can save a few $$$ prior to sale?

Where did I say I was selling it?

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[jschrauwen]

Where did I say I was selling it?

You didn't. But being such a strange question to ask, it just seemed to indicate there must be some sort of extenuating circumstances to warrant such a question - hence the query.

[Zoltar]

You didn't. But being such a strange question to ask, it just seemed to indicate there must be some sort of extenuating circumstances to warrant such a question - hence the query.

Let me rephrase. If the valves are left and not cleaned has there been cases were build up could cause engine damage? Like spark plugs if left unchanged you'd get poor mileage hestiation etc but no engine damage. Just check engine misfires etc.

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[jschrauwen]

Let me rephrase. If the valves are left and not cleaned has there been cases were build up could cause engine damage? Like spark plugs if left unchanged you'd get poor mileage hestiation etc but no engine damage. Just check engine misfires etc.

I suppose anything is possible. Knowing that the valves can accrue enough build-up to the point where pieces may break off and enter the combustion chamber. Or possibly build up to a point that the valves can no longer make a perfect seal and compression can drop significantly.
There must be a good reason why BMW established published servicing intervals for walnut shell carbon cleaning.

[Fourplay]

What's the negative impact on neglecting to inspect/ clean the valves? Just poor engine performance or possible engine damage to valves then pistons?

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Loss of power primarily, but I have seen an RS4 that was never cleaned (at 150k miles) shoot red hot pieces of carbon material out of the exhaust. I doubt it damaged the engine, as the carbon is softer than any metal inside the engine. But it's certainly not ideal for your cats to have molten carbon passing through them.

[knctrnl]

I have a 2008 S5 with the magnesium intake manifold. I am at 70,000 miles and decided to do a carbon cleaning.

I know someone who is a mechanic at the local VW dealership and has had training on Audi.
He said he would do the cleaning and started work a couple of weeks ago.
Once the intake manifold was removed he removed the dividers and cleaned the intake ports with brake cleaner. He said this is the exact process VW uses. When he was done the ports still looked like they had not been touched.
I went and bought a media blaster and cleaned them properly with walnut shells.

Several days later he came back and did the assembly. (manifold flaps were only wiped down as I was scared to get wallnut shells in the intake manifold and didn’t know how I would clean it out.)

Once everything was back together I was getting random misfires, low fuel rail pressure and manifold flaps stuck open and closed.

The VW tech came back and after investigation found that he had used his electric driver to tighten the manifold bolts and the battery was low and did not provide any torque so I guess the manifold was moving around and loosing vacuum.

After tightening the bolts we were still getting CEL and codes that I cant recall at the moment but I know they included flaps, low fuel rail pressure and random misfires.

He decided to take the manifold back off and check everything again.
This time he noticed that he put the intake port dividers in upside down. This was keeping the intake manifold flaps from cycling fully.
These were put back in properly and reassembled.

Once everyting was back together I was still getting CEL with random misfires and low fuel rail pressure, but no flaps stuck. I was noticing more misfires on cylinder 2 and 4.

My plugs and coil packs are 2 months old but I decided to pull the plugs and change them anyway. Plug in cylinder2 smelled of fuel so I started to suspect leaking injector.

After plug change everything stabilized to only high misfires on cylinder2 and cylinder disable.
I changed plug and coilpack from cylinder 2 to cylinder 1 and still got misfires on cylinder 2 and cylinder disable.
I was also still getting low fuel pressure but this went away after a bit of time.

At this point I decided to install new injectors on cylinders 1-4 myself.

I removed the intake manifold and noticed during this process that the ground bolt for the injectors 1-4 was very loose, The clip that attaches to the top Variable Intake Manifold Runner Motor is broken (note that this motor does cycle properly when vehicle is started). The clip for the flap motor is gnawed up looking I guess from him trying to get it to release.

I replaced the injectors and reassembled.

At this time I am not getting any misfires or any fuel rail pressure codes but now I am getting consistent

Intake Manifold Flap; Bank 1
P2006 - 001 - Stuck Closed
And
Intake Manifold Flap; Bank 2
P2007 - 001 - Stuck Closed

I have looked in basic settings for bank 1 and bank 2 and I can see the position change on bank 1 when I press on the linkage slightly. Bank 2 shows 0 position and does not change when I press on the linkage. I am not sure if this is a proper way to check this.

When I do the output tests and it gets to the portion of these flaps they do not move. They also do not move when the car is started.

Can anyone shed any light on this situation?

[jschrauwen]

knctrnl
Oh dear. Such a calamity of issues here.
1. It seems this VW tech was not all that he was cracked up to be and I suspect may be the underlying issues to why you've encountered so many subsequent problems.
2. Ask that tech if he manually rotated the engine by hand during his brake cleaner process. I suspect he probably didn't and as a result that brake cleaner would have entered those cylinders where the intake valves were not completely closed?
3. The knarled up connection and poor injector ground connections caused by the VW tech would surely prevent the injectors from working correctly. As a result would have given you the injector codes. Either the brake cleaner in the open cylinders and/or the poor injector connectors were probably the cause factors and as such, I believe that the VW tech is on the hook for this. You either didn't need new injectors and/or e tech should be responsible for their replacement. IMO
4. Seeing as the tech had put the flaps upside down and you had to correct this. Did you also ensure they were correctly orientated? IE: There's a forward/backward facing orientation for them. Try pulling a couple and rotate sideways 180* and compare to others. It is difficult to discern but there is a correct orientation to them in this regard as well.
5. Have a look at a couple YT videos on carbon cleaning Audi's. I distinctly seeing the odd one purposely show the flap orientation.
Hope this helps a bit.

[knctrnl]

jshrauwen,

Thanks for the reply.
I know he did not rotate the engine when he did the cleaning with the brake fluid. I specifically did rotate the engine when I did the walnut blasting and noticed the same cylinders were open that were open when he first took the manifold off.

The knarled up connections were not on the injector connectors but on the connectors going to the manifold flap motors and sensors. I do believe they are making a connection however.
My thought about the injectors was that some of the walnut shell dust got into the high pressure fuel lines that were sitting on a table next to where i was and blasting. I don't think they got sprayed out before reassembly and i think some junk got into injector #2.
I went ahead and replaced all 4 injectors because I didnt want to have to deal with taking the injectors somewhere to get seals replaced since they would need replaced after removing the fuel rail.

The dividers that go down the middle of the ports are what were put in upside down. it was determined they were upside down by comparing with a picture I took under the hood right after he removed the manifold.

My primary concern right now is the manifold flaps stuck open and the motor not actuating.
Do you know if there is any adaptation in vcds that I need to do with the manifold flaps, sensors, or anything else after taking it all off and putting back on? I know there are for the B8 S4 but i cant find anything like that for the S5.

Do you know of any way to test the actuation of the manifold flaps from within VCDS to narrow down whether the motor is burned or if the flap linkage is binded up?

Thanks

[jschrauwen]

I would follow the same steps as the B8 S4 for the flaps.
As far as the dividers go, a lot of people mix up the forward/backward orientation of them since they will slide in in both directions.
That's about the extent of my knowledge in this area, sorry.

[RayX]

Carbon build-up on the inlet valves and intake manifold as the issue in direct injection petrol engines? It is all caused by the nature of any engine running lean with λ > 1 ... NOx stay behind it all, to fight it, engine manufacturers use EGR technics, either external or internal, instead of NOx storage catalyst. So EGR is the main source for carbon build-up on inlet valves and its surroundings, PCV is just accompanying that.

VAG and others knows that very well ...

Variable valve timing leads to:
- very effective inner exhaust gas recirculation, whereby combustion temperature and nitrogen oxides are reduced, and
- also improved torque development.

On FSI (=TFSI=TSI etc. any GDI) engines, a high amount of exhaust gas recirculation is necessary to reduce nitrogen oxide emissions.
In order that the amount of exhaust gas can be pushed up to its limit, it has to be calculated precisely.

"A possible solution would be to keep these sources of deposits away, for example, from the intake valve, by completely eliminating exhaust gas recirculation and the introduction of blowby gases into the intake port. However with the combustion behavior of modern reciprocating internal combustion engines, at least external exhaust gas recirculation and the introduction of blowby gases into the intake port are absolutely necessary for reasons of emission control and fuel consumption, so that this approach is not possible. "

[Ape Factory]

B8.5 RS5 carbon clean DIY if you're interested. Most of the good stuff starts on page 2 of the thread.
https://www.audizine.com/forum/showt...n-cleaning-DIY

[jschrauwen]

B8.5 RS5 carbon clean DIY if you're interested. Most of the good stuff starts on page 2 of the thread.
https://www.audizine.com/forum/showt...n-cleaning-DIY

*Understatement*
This is a full blown from A to Z comprehensive How-To. Well documented doesn't even come close to how well Ape Factory chronicled the process.

[jschrauwen]

[Porttac]

Anyone know if the Mk3 TT, TTS has the same problem with carbon build up?

[jschrauwen]

Anyone know if the Mk3 TT, TTS has the same problem with carbon build up?

The MK3 TTS still uses the 2.0TFSI engine and will still succumb to carbon build-up.

[Audi Junkie]

Lubrizol seems to think reduced SAPS oils like VW 504 can reduce the chances of intake valve deposits in DI.

It's the top mfg spec...

https://online.lubrizol.com/relperftool/pc.html


https://www.bobistheoilguy.com/forum..._Direct_Inj_In

[Audi Junkie]

For god sake's use an OE paper air filter. A gauze filter lets dirt blow onto your dry intake valves. Plus excess silicon dirt = excess ring wear = oil consumption.

[rk4S5]

Had a question. Hopefully someone can help me and tell me what this is.

Found this when I removed the intake manifold,
plastic valve thingy2.jpgplastic valve thingy.jpg

Had a CEL code of P2004 and I assume this small plastic part was stuck in the runner. I also would receive a flashing CEL of misfire(P0305) at WOT.

I greatly appreciate any help. Thank you.

[thenofjboy]

Bumping this up. Any comments to the post above? just curious

[jaybquick@JHM]

Bumping this up. Any comments to the post above? just curious

Had a question. Hopefully someone can help me and tell me what this is.

Found this when I removed the intake manifold,
plastic valve thingy2.jpgplastic valve thingy.jpg

Had a CEL code of P2004 and I assume this small plastic part was stuck in the runner. I also would receive a flashing CEL of misfire(P0305) at WOT.

I greatly appreciate any help. Thank you.

That is the inside of your intake manifold falling apart. Those are the parts that hold the flap shaft inside the manifold, about 2 per cylinder between. I bet you lost some torque too down low, I would suggest a new manifold since the manifold will fall apart more and more and potentially cause a similar issue or worse. I own a 2008 S5 as well and these manifolds are just a shorter version of the more problematic C6 S6 and D3 S8 V10. The S5 V8s rarely due it vs how frequent with the V10 but now with the age it is not a surprise seeing this. Hope this helps.

[thenofjboy]

yikes. thats no good but thx for the info Jay

[psinclair]

This problem has absolutely nothing to do with gasoline or injectors - or Audi.

Every direct injection engine from every car manufacturer has it.

Put simply, the oil that gets into the intake manifold because of the crankcase ventilation system coats the back side of the intake valves and stems as air enters the engine and gets cooked onto them from the heat of the combustion process. The buildup continues every time the engine makes a single revolution. My cayenne had about ¼” of deposits after about 100k miles.

The reason this problem is new is because old cars used to inject fuel ahead of the intake valves rather than directly into the combustion chamber. This washed the oil off of the back side of the valves prior to combustion cooking the oil. Also, prior to most fuel injection systems, the crankcase vented to the atmosphere, not into the intake manifold.

The only fix is periodic bead blasting of the intake valves using walnut shells.

It’s not an Audi problem. It’s an industry-wide issue. And there is no fix short of a redesign which no one wants to do, as the problem typically shows well after warranties expire.

I did my own walnut blasting of my Cayenne. It took the better part of a day. I would describe it as taking moderate mechanical skills and experience. It felt good to do it, but I’m not sure it mattered much other than my perception that my engine was breathing better. With two intake valves per cylinder, must high performance engines can tolerate quite a bit of buildup on the back of the valves, as the primary restriction to engine volumetric efficiency is the gap between the valve and the valve seat, which is not that big.

Just my 2 cents on the issue.