Theory on combating carbon buildup:

[4ringcircus]

I've read all the threads on the carbon buildup problem and there is little to no consensus on how to preempt the initial build up. From time to time, someone mentions running the engine hot to burn off the carbon, but this theory hasn't had much debate: If it is true that hotter engines burn off the carbon, a possible solution might be chipping, resulting in more heat from the turbo and quicker burning off of carbon.

Most 2.0T's I've read about have experienced carbon problems between 25K and 75K. I bought my 5.5 2.0T with 90K; the previous owner drove 75 high way miles per day so I know that engine was good and hot every time he turned it on. I've had no carbon problems. Conversely, many 3.2's experience carbon problems earlier than the 2.0T's, at about 5K to 20K. These engines are direct injection, but not turbo, so they likely take more time to heat up as the intakes are not blasted by hot air off the turbo.

So, would a stage 1 or 2 APR upgrage for example, help heat up our intakes faster, resulting in carbon being burned off and delaying carbon buildup to the possible equivalent of a non-direct injection engine?

[vortexjunkie]

I think you have come up with a logical theory

[nramsey]

Interesting theory, but I doubt the intake air just from the turbo would be hot enough to burn off the carbon. Seems like you'd need to to be well above 300 degrees f, which even the stock intercoolers probably prevent.

[colt45]

a meth kit would do the trick. it should burn off any carbon build up.

[Nikoman]

What about seafoam through the air intake temp sensor hole? I've done that 3 times along with BG induction cleaning service once over the last 6 months. I'm at 47k. Am I wasting my time with seafoam? Nope. I use a whole bottle each time and do it just like I did my GTI in the past. It takes me less then 10 minutes for the whole process. I make sure she sucks the whole thing fast rather than taking time like some people like :) This way there is much more liquid depsoted in the intake for the soaking process.

Seafoam $6x3 = $18
rubber hose = $3
misc stuff = $15
BG induction service at Audi dealer = $160 (with Xmas gift certificate they sent me)

Total for 6 months of carbon build up maintenance = ~$200

My car idles perfectly and there is no carbon build up. I know this, saw the valves with a borescope. I would rather not have to spend my valuable time doing this maintenance though....

[RVT]

OP...Sorry, cant support the theory and think that heating your motor outside normal specs is a recipe for damage. In fact, I think you will find just to opposite. Carbon LOVES high heat, and can survive intact it in environments ranging in the thousands of degrees. It is considered one of the highest temp elements in existence. Adding a few extra degrees to your engine will not faze it in the least.

Nikoman is probably more on target, although I remain on the fence with the Seafoam product.

I'll offer a little crude knowledge, more from a common sense angle, and let you science whiz's debate how any of it relates to Audi's engine design. This has probably been discussed among similar threads here before.

Carbon forms on the valve for a couple reasons. Impurities of the combustion process is the primary culprit, (which has existed in internal combustion engines since the beginning), and high temperatures of the valve easily allow the carbon to deposit itself on the metal surface. A colder valve surface rejects carbon deposits as is evident by most "normal" engine tear-downs (Intakes are always cleaner than exhaust as they run cooler due to incoming air/fuel mix, whereas the exhaust valve site in the heat at all times.) Valve overlap is another contributing factor. This basically means the combustion processes is still in progress when both intake and exhaust valves leave their seats and begin the exhaust/intake stroke of the 4 cycle process. With the burn still in progress, the intakes expose themselves and allow carbon residue to adhere.
In the past, intakes were very easy to keep clean, as the airstream passing by them entering the cylinder carried both air and fuel. This mixture often kept the carbon on the intake valve in a much softer state, and the addition of cleaners would even help break it down further.
Our Audi's eliminated both the added cooling of an air/fuel mix, and the softening of the carbon deposits thanks to the direct cylinder injection system. This is why adding a intake cleaner to our fuel system no longer works for our engine design. Softening and cleaning of the carbon must now be done as Nikoman points out, by injecting a cleaner into the airstream that flows past the valve and valve stem.

Of some interest may be an "old school" process we used in carburated engines way back when... We often ran an engine till it got up to temp, then used a squirt bottle with ice water to pump shots of cold into the intake. Quite often the thermal shock would shatter carbon off the valve surface and expel them out the exhaust (puffs of black smoke). Recall that this was "pre catalytic converter" days so I would have reservations trying it on a modern motor less I plug a cat or something. A cleaner may clear the deposits in a slower/safer manor.

My 2 cents for today
Hope some of you find it of interest.

Vince

[a4dc89]

if you think about how the carbon buildup is occurring (crap from the pcv) then it would make sense that the higher intake temps burn off that crap before it gets a chance to turn into carbon deposits?? Just a guess bc i have personally seen the same correlation with carbon buildup from N/A vs FI engines

[RightonRed]

Agree with RTV on this one, valve overlap and lack of fuel in the intake makes it the prefect breeding ground for carbon crystalization. Heat will not remove the carbon buildup... That's the reason that cabon is used in high temp applications ie: Carbon ceramic brake discs and space shuttle tiles. Note that this issue hasn't shown up until the FSI engine was introduced (with the two major changes being direct fuel injection and valve overlap), don't get me wrong I love my car....

A better solution might be a dumpable catch can for the PCV system like the BSH kit and a secondary fuel injection system, like the systems used in high power autos. Having a secondary spraying fuel into the intake would help clean the valves on a regular basis, and reduce the duty cycle on the primary injectors, but i have no clue on how to program that into the ecu so that it can manage added fuel into the system. Also you would likely loose the benefit of the FSI engine with regards to mileage.

One of the questions I posed last year was what about a Nitrous wet kit, key in on the wet part... I do not know if this would add enough fuel into the intake to clean/maintain the valves but it might be a start... Also see the new VAST kit and note the secondary injector system that was mentioned...
http://www.audizine.com/forum/showthread.php?t=338492

Conversations like this are the way these problems get solved. Keep up the ideas and maybe one of these vendors can find solution. I know several are attempting this as we speak...

Red

[4ringcircus]

I agree that heat won't do anything once the carbon is caked on the valves. I am specifically interested in knowing if heat could 'delay' or mitigate the speed at which it builds. Once it is hardened, yes it is like a carbon ceramic brake. Once our engines get to that point, we all will have spend a fortune to tear down the engine and fix.

I'm more interested in preemption. If the impurities come from the PVC, they are in a liquid emulsion; if the engine is cold, they sit and solidify. But if it is hot, they burn off. If my assumption is correct, one could observe more carbon problems on cars used for short commutes. And correspondingly, high mileage commute cars like mine could hit 100K without any carbon problems.

Am I still off the mark? Anyone with carbon problems care to state how many miles on average you drive per day, and when you first experienced carbon problems? I'm at 100K, 75miles per day, and haven't had a problem yet.

[4ringcircus]

I agree that heat won't do anything once the carbon is caked on the valves. I am specifically interested in knowing if heat could 'delay' or mitigate the speed at which it builds. Once it is hardened, yes it is like a carbon ceramic brake. Once our engines get to that point, we all will have spend a fortune to tear down the engine and fix.

I'm more interested in preemption. If the impurities come from the PVC, they are in a liquid emulsion; if the engine is cold, they sit and solidify. But if it is hot, they burn off. If my assumption is correct, one could observe more carbon problems on cars used for short commutes. And correspondingly, high mileage commute cars like mine could hit 100K without any carbon problems.

Am I still off the mark? Anyone with carbon problems care to state how many miles on average you drive per day, and when you first experienced carbon problems? I'm at 100K, 75miles per day, and haven't had a problem yet.

[v_audi]

Nothing substantive to add, but I enjoyed reading the posts so far. Thanks. I Hope one of you smart guys can solve this problem.

[philaboy]

I guess fuel cleaner does nothing? I still use it every 4,000 miles in both cars. In my wifes 1.8T you can feel it after the tank in done. I think it works on the 2.0T, but it hard to tell! My Question to you guys is this- can it hurt the system?

[doctorheine]

I've read all the threads on the carbon buildup problem and there is little to no consensus on how to preempt the initial build up. From time to time, someone mentions running the engine hot to burn off the carbon, but this theory hasn't had much debate: If it is true that hotter engines burn off the carbon, a possible solution might be chipping, resulting in more heat from the turbo and quicker burning off of carbon.

Most 2.0T's I've read about have experienced carbon problems between 25K and 75K. I bought my 5.5 2.0T with 90K; the previous owner drove 75 high way miles per day so I know that engine was good and hot every time he turned it on. I've had no carbon problems. Conversely, many 3.2's experience carbon problems earlier than the 2.0T's, at about 5K to 20K. These engines are direct injection, but not turbo, so they likely take more time to heat up as the intakes are not blasted by hot air off the turbo.

So, would a stage 1 or 2 APR upgrage for example, help heat up our intakes faster, resulting in carbon being burned off and delaying carbon buildup to the possible equivalent of a non-direct injection engine?

I always noticed that my 2.0t tiguan reaches operational temperature 3x faster. My 3.2 "3.1" a4 takes along time to reach operational temp. Im pretty sure I have horrible carbon build up in my 3.2 right now, the ecu just went out and im waiting on audi to get my new one in. The power is not there anymore especially in the high rpms. It almost feels like it plateau's after 4800rpms. my 3.2 has just barely 23 thousand miles. but atleast I dont blow CBV's as much anymore

[doctorheine]

I agree that heat won't do anything once the carbon is caked on the valves. I am specifically interested in knowing if heat could 'delay' or mitigate the speed at which it builds. Once it is hardened, yes it is like a carbon ceramic brake. Once our engines get to that point, we all will have spend a fortune to tear down the engine and fix.

I'm more interested in preemption. If the impurities come from the PVC, they are in a liquid emulsion; if the engine is cold, they sit and solidify. But if it is hot, they burn off. If my assumption is correct, one could observe more carbon problems on cars used for short commutes. And correspondingly, high mileage commute cars like mine could hit 100K without any carbon problems.

Am I still off the mark? Anyone with carbon problems care to state how many miles on average you drive per day, and when you first experienced carbon problems? I'm at 100K, 75miles per day, and haven't had a problem yet.

like the old saying.... If you let it sit it goes to sh*t

[vbrad26]

redline once a day...nothing cleans things out like WOT

/thread lol

[Boosted6Speed]

Has anyone come up with a fix yet. What about the weld in tip that makes vacuum with the exhaust? I'm really tired of the epa dictating that we run waste through our engines.

[esandes]

a meth kit would do the trick. it should burn off any carbon build up.

Agreed 100%. Even just using water without meth.

Forced air helps to overcome the negative effects of carbon buildup too. So I'd never consider a NA DI unless it's hybrid port and DI.

[EvolutionArmory]

Has anyone come up with a fix yet. What about the weld in tip that makes vacuum with the exhaust? I'm really tired of the epa dictating that we run waste through our engines.

Water methanol will help wash the back of the intake valves. A decent methanol kit costs as much as a walnut blast so it pays for itself over time.

[Audi 4 Life]

Methanol will not clean it will only slow build up. There is nothing that will stop it on DI. Anyone who has have ever tried cleaning it would know this.

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[EvolutionArmory]

Yes. Methanol or water will only help wash the valves. There’s no burning going on with meth like that poster from 10 YEARS ago posted. 🤣

And yes, you can’t really eliminate carbon build up on these cars, just slow it down because the build up happens from carbon being deposited on the valves as they close. There’s no way to burn it.

I’m explaining it badly so forgive me.

But I agree with you. You can’t eliminate it. Only slow it down.


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[Boosted6Speed]

So its not all to blame on emissions... Is this why I've seen a few instances of 1.8t swaps in B7s? Maybe a slow release seafoam injection could be fabricated. If we microdose seafoam constantly.....

[EvolutionArmory]

No parts store chemical cleaner works. None.

Methanol works well because it is spraying the valves as it is running.

[Jeevan]

So its not all to blame on emissions... Is this why I've seen a few instances of 1.8t swaps in B7s? Maybe a slow release seafoam injection could be fabricated. If we microdose seafoam constantly.....

I did carbon cleaning in 2020 May by removing intake and all. Just for my satisfaction, I ran multiple bottles seaform and liquimoly valve clean to see it had made any difference before cleaning(you know it wont work but I gotta see result my self). after removing the intake, I didnt even see 1% cleaning done by them. It just waste of 50-70$.

Also, make sure you fully clean intake manifold before reinstalling. I did the hard part of cleaning the valves and intake ports but never cleaned the intake as none of the youtube videos did. I still have intermittent and once in a blue moon cold misfires under 45 temp. Probably caked up carbon inside the intake runners and flap motor is causing this


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[oVeRdOsE]

if I can add, catch can wont do shit. I did a full carbon clean and 10k km after I got a injector leak. so I took apart the intake manifold, and valves were dirty af. Not as much like my previous 80 k km valve, but still.

I have a meth kit, I will see if I have the motivation to look at my valves in 30k km. But technically, when water touch a over 100°C part, it steam, thus clean the metal part.

But engine need to be hot af, and push the car so the meth kit spray.

[Jayz691]

I did carbon cleaning in 2020 May by removing intake and all. Just for my satisfaction, I ran multiple bottles seaform and liquimoly valve clean to see it had made any difference before cleaning(you know it wont work but I gotta see result my self). after removing the intake, I didnt even see 1% cleaning done by them. It just waste of 50-70$.

Also, make sure you fully clean intake manifold before reinstalling. I did the hard part of cleaning the valves and intake ports but never cleaned the intake as none of the youtube videos did. I still have intermittent and once in a blue moon cold misfires under 45 temp. Probably caked up carbon inside the intake runners and flap motor is causing this


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Well yeah, if you pull the intake to do carbon clean, ya clean everything. Don't do half the job, lol.

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[BecksA3]

What about the Hot Shot Secret stuff that’s out now?
It’s supposed to be a in tank cleaner for injectors and carbon deposits.
And since it’s in the fuel, should get to the heart of the matter.

I wouldn’t expect it to deep clean years of build up, but maybe keep it clean after a carbon clean?


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[EvolutionArmory]

What about the Hot Shot Secret stuff that’s out now?
It’s supposed to be a in tank cleaner for injectors and carbon deposits.
And since it’s in the fuel, should get to the heart of the matter.

I wouldn’t expect it to deep clean years of build up, but maybe keep it clean after a carbon clean?


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I meant what I said

And being direct injection, being in the fuel means nothing since fuel NEVER passes over the valves. That’s sort of how the DI thing works.


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[BecksA3]

I meant what I said

And being direct injection, being in the fuel means nothing since fuel NEVER passes over the valves. That’s sort of how the DI thing works.


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Duh! Sorry, brain fart.
I saw a commercial and didn’t do the math.


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[Jeevan]

As per my common sense, let's say if those cleaners actually work and clean the fuel tank, where would all that crud go? Fuel pump mesh filter, fuel filter wont it clog injectors. Most of them are snake oils




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[Jayz691]

As per my common sense, let's say if those cleaners actually work and clean the fuel tank, where would all that crud go? Fuel pump mesh filter, fuel filter wont it clog injectors. Most of them are snake oils




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Well, it should dissolve it, not just loosen it. So if it actually works, it won't hurt anything. Some injector ckeaners work well, just don't help valve buildup on DI cars, thats all.

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[Jeevan]

Well, it should dissolve it, not just loosen it. So if it actually works, it won't hurt anything. Some injector ckeaners work well, just don't help valve buildup on DI cars, thats all.

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Lol you think all that rust and gum is going to be dissolved(only acids have that capabilities)? Kidding right? Either it's magic or you believe in fairies and pixie dust


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[BecksA3]

Lol you think all that rust and gum is going to be dissolved(only acids have that capabilities)? Kidding right? Either it's magic or you believe in fairies and pixie dust


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I’ll try pixie dust if it makes me faster.


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[Okedokey]

Lol you think all that rust and gum is going to be dissolved(only acids have that capabilities)? Kidding right? Either it's magic or you believe in fairies and pixie dust


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Solvents dissolve solids. If the solvent is correct, the materials should be passed in solution through the combustion chamber or solidify out in the tank.

[Audi 4 Life]

Edited

[Audi 4 Life]

Solvents dissolve solids. If the solvent is correct, the materials should be passed in solution through the combustion chamber or solidify out in the tank.

sorry no it doesn't work like that with carbon deposits.



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[EvolutionArmory]

The only way you’re getting rust/gunk out of the tank is to drain the fuel and hand clean it and the only way you’re going to clean carbon out is with a media blast or manual removal with a pick or scraper.

These are the facts of DI life.

Fuel additives might help clean your fuel lines or the injectors but all they are is a fuel additive with more detergent. A higher concentrate of detergent. It will not break up large build up. And not only does carbon build up deposit on your valves but the unburnt carbon can also deposit on your injector tips and clog the jets. A cleaner won’t clean this.


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[Jayz691]

Lol you think all that rust and gum is going to be dissolved(only acids have that capabilities)? Kidding right? Either it's magic or you believe in fairies and pixie dust


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Wow dude, not rust and gunk, "carbon", lol. Solvents do dissolve carbon, like carbon cleaners. Thought the thread was about carbon buildup?? Also, anything loose in the tank would be screened by the pump screen. Was talking about injectors and maybe any varnishes in the lines. Not chunks of rust..maybe you can put some brakecleaner in it

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[EvolutionArmory]

Why doesn’t anyone understand that fuel never hits the valves?

It’s literally the reason why we have this issue in the first place. Because there’s no fuel washing them...like at all.

Putting anything in the tank will only be like putting a 5 dollar bill in there. You have no 5 dollar bill anymore and there’s something in your fuel tank that doesn’t belong in there and it won’t clean your carbon. 🤣🤣


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[Jayz691]

Why doesn’t anyone understand that fuel never hits the valves?

It’s literally the reason why we have this issue in the first place. Because there’s no fuel washing them...like at all.

Putting anything in the tank will only be like putting a 5 dollar bill in there. You have no 5 dollar bill anymore and there’s something in your fuel tank that doesn’t belong in there and it won’t clean your carbon.


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We do understand, thats why I said injectirs and lines. Think "most" know it can't work for valves, but maybe not, lol.

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[Theiceman]

wasn't it Mercedes that resolved it by putting an auxiliary injector back behind the valves that they turn on under certain conditions ? ? I thought i remember reading that somewhere. ? to me thats the only real answer.

edit : just found this .... worth a spot in this discussion i think.
https://www.caranddriver.com/news/a1...ect-injection/