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Discussion Starter #1 (Edited)
I can recall a time when carbon build-up was the subject of quite a few threads. In those days (years and years ago) it seemed related mostly to VW/Audi, but that could've just been due to them having more DI offerings. I don't scour car forums quite like I used to but I don't see too many threads on it now. Is this something that has been worked out over the years?

We've yet to have a car with DI, so not sure what to expect. We're considering a new SUV with a 3rd row and our top 3 choices (Tiguan 2.0 FSI and Sorrento/SanteFe 2.4L) are DI engines.

If it helps, I would likely be the one driving it. I have an 11 mile commute (20-25 minutes) -which is roughly 50/50 city/highway (60-70mph top speeds). Wondering how a DI engine will fare in that instance.

Thanks in advance.
 

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Yes.

You'll still see carbon build up with time.
Toyota has made efforts to resolve this with dual fuel injection, so there are still port injectors to supplement fuel and keep things clean.

All of the PCV crud that is kept clean by multiport fuel injection, is no longer addressed by DI.

From all I've seen, it appears that a catch can to help condense crankcase vapors significantly reduces carbon buildup.
All in all, its not unreasonable to expect that most direct injected engines will need a carbon cleaning within their life cycle.
On a turbo engine, expect it'd come sooner. Seeing as all engines have some blow by, with a turbocharger adding cylinder pressure that does increase.

I cant speak for others, but I've seen many a coked up 2.0T, it seems those driven hardest are impacted most quickly and severely. Typically cars would come in with a lumpy idle or slight cold miss around 90-120k miles, then a quick clean later life is good.


Good luck shopping!
 

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Considering how cheap carbon cleaning services have become, I wouldn't even worry about it any more, especially as manufacturers continue to mitigate it with each iteration of DI.
 

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Yes.

You'll still see carbon build up with time.
Toyota has made efforts to resolve this with dual fuel injection, so there are still port injectors to supplement fuel and keep things clean.

All of the PCV crud that is kept clean by multiport fuel injection, is no longer addressed by DI.

From all I've seen, it appears that a catch can to help condense crankcase vapors significantly reduces carbon buildup.
All in all, its not unreasonable to expect that most direct injected engines will need a carbon cleaning within their life cycle.
On a turbo engine, expect it'd come sooner. Seeing as all engines have some blow by, with a turbocharger adding cylinder pressure that does increase.

I cant speak for others, but I've seen many a coked up 2.0T, it seems those driven hardest are impacted most quickly and severely. Typically cars would come in with a lumpy idle or slight cold miss around 90-120k miles, then a quick clean later life is good.


Good luck shopping!
I don't understand why we're still not in a closed loop system for this. Why is there a possibility that your intake air can get oil contaminated? How have we not found a way to proxy this system so that intake air is as clean as possible? Even just for emissions sake?
Why aren't we just using a vacuum pump or a vacuum system composed of generated vacuum of some sort for the PCV if this is LITERALLY a problem we have to deal with now because MPFI isn't taking care of it?
 

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Yes.

You'll still see carbon build up with time.
Toyota has made efforts to resolve this with dual fuel injection, so there are still port injectors to supplement fuel and keep things clean.

All of the PCV crud that is kept clean by multiport fuel injection, is no longer addressed by DI.

From all I've seen, it appears that a catch can to help condense crankcase vapors significantly reduces carbon buildup.
All in all, its not unreasonable to expect that most direct injected engines will need a carbon cleaning within their life cycle.
On a turbo engine, expect it'd come sooner. Seeing as all engines have some blow by, with a turbocharger adding cylinder pressure that does increase.

I cant speak for others, but I've seen many a coked up 2.0T, it seems those driven hardest are impacted most quickly and severely. Typically cars would come in with a lumpy idle or slight cold miss around 90-120k miles, then a quick clean later life is good.


Good luck shopping!
Wait what? The cars that are driven harder are less likely to have build up problems. I think you have it the other way around, cars that are regularly driven without high revs are more likely to develop buildup.
 

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I don't understand why we're still not in a closed loop system for this. Why is there a possibility that your intake air can get oil contaminated? How have we not found a way to proxy this system so that intake air is as clean as possible? Even just for emissions sake?
Why aren't we just using a vacuum pump or a vacuum system composed of generated vacuum of some sort for the PCV if this is LITERALLY a problem we have to deal with now because MPFI isn't taking care of it?
Forgive me if I'm misunderstanding, but the crankcase gases have to go somewhere, and venting it to the atmosphere is not an option (for emissions). Regardless of how the vacuum is generated, that crud has to pass over the intake valves to get into the cylinder to be burned off. Port injected engines have the exact same setup but the constant wash of solvent (gas) keeps them clean.

A catch can in the PCV line can catch most of the gunk (visualize a Dyson vacuum vortex that causes the dust/particles to fall out). Not sure why those haven't been implemented on the OEM side - maybe too-frequent maintenance instead of every 3-5 years like an intake valve cleaning?
 

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Wait what? The cars that are driven harder are less likely to have build up problems. I think you have it the other way around, cars that are regularly driven without high revs are more likely to develop buildup.
No, its due to being in boost all the time, with VWs poor breather system, excess blowby causes extra oily buildup and boom carbon.

The italian tune up you're thinking of only applies to PORT injected engines, where the air fuel mix crosses the intake valve and thru the port.
Direct injection, fuel goes right into the cylinder, thus all you get is metered air plus hot dirty PCV air to coke up on the valves.

The 2.0t's that ran the best were those owned by normal people who just wanted a sporty hatchback, but dont race around. They also seem to generally avoid breather failures for a longer interval.
 

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I don't understand why we're still not in a closed loop system for this. Why is there a possibility that your intake air can get oil contaminated? How have we not found a way to proxy this system so that intake air is as clean as possible? Even just for emissions sake?
Why aren't we just using a vacuum pump or a vacuum system composed of generated vacuum of some sort for the PCV if this is LITERALLY a problem we have to deal with now because MPFI isn't taking care of it?
Despite his previous claims catch cans are not solving or even barely reducing the problems. I was probably one of the first people to run a catch can on a 2.0T Audi/VW, still had issues with carbon build up.

People have stupidly completely removed/blocked off their PCV systems and still had issues with carbon build it.

The real issues here are NOT due to crank case gases getting sucked into the intake tract via normal PCV type systems and conditions. DI cars just burn crappy/dirty, which is why they are getting particulate filters now. A lot of the build up is simply from the valves opening into a dirty ass combustion chamber and closing with those gases trapped in the inlet ports of the head. Mix in that running dirty with lack of port injection or a system that can't keep up and you have this build up.
 

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No, its due to being in boost all the time, with VWs poor breather system, excess blowby causes extra oily buildup and boom carbon.
They are not in boost all the time :screwy:


The 2.0t's that ran the best were those owned by normal people who just wanted a sporty hatchback, but dont race around. They also seem to generally avoid breather failures for a longer interval.
Actually the normal people had their PCV system fail 40k miles ago they just never realized. The stock normal driven cars that rarely see boost don't know that their car is making 20psi to get the stock 7psi to the intake manifold. The guy with the tuned car isn't necessarily having more frequent PCV failures they just notice it because now when their tune wants 20psi and they only get 10psi they go look for the source of the problem.

It's the same as the BS with people saying tunes broke something on their car, no that part failed 9 months ago you just didn't realize, or yes it failed a week after but was 99% on the way out and would have just failed 3 weeks later had they not gotten tuned.
 

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Wait what? The cars that are driven harder are less likely to have build up problems. I think you have it the other way around, cars that are regularly driven without high revs are more likely to develop buildup.
Can confirm, my MK6 GTI is at 97k miles and still didn't get a valve clean up, no issues. I will be doing the service at 100k with waterpump and other maintenance bits. I make sure to step on it at least once a day while merging on the freeway. Sisters Tiguan needed a valve clean up at 73k miles(misfiring), it was previously owned by an older couple.(sister is also a slow driver)
 

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Wait what? The cars that are driven harder are less likely to have build up problems. I think you have it the other way around, cars that are regularly driven without high revs are more likely to develop buildup.
Yeah, I've never had a problem with buildup and always attributed it to track days, where you can run about 100x harder than on the street. Of course, it does create other problems...like wheel bearings. :laugh:
 

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No, its due to being in boost all the time, with VWs poor breather system, excess blowby causes extra oily buildup and boom carbon.

The italian tune up you're thinking of only applies to PORT injected engines, where the air fuel mix crosses the intake valve and thru the port.
Direct injection, fuel goes right into the cylinder, thus all you get is metered air plus hot dirty PCV air to coke up on the valves.

The 2.0t's that ran the best were those owned by normal people who just wanted a sporty hatchback, but dont race around. They also seem to generally avoid breather failures for a longer interval.
A version of the Italian tuneup is listed in the patent by VW for maintenance of the FSI engine.

https://patents.google.com/patent/US6866031?oq=valve+coating+carbon+VW
 

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Discussion Starter #17
Considering how cheap carbon cleaning services have become, I wouldn't even worry about it any more, especially as manufacturers continue to mitigate it with each iteration of DI.
Okay, so I read mixed things about this and some of it was admittedly from non-car people so they may have not fully understood what they were quoted. Some quotes were of cleanings in excess of $1K+, but others were saying $400 which IMO is not cheap, but at least doable every 60-80K miles.

I'm guessing the cheaper cleaning is the less invasive "induction cleaning" as opposed to the full cleaning where they remove the intake manifold and scrape the valves with a flathead screwdriver (which for some reason just sounds archaic).
 

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The ones in Europe with port injection also get carbon buildup too.
They do? Then what's the point? Seems like a swing and miss then by VW on the dual injection design. Or was that done for some WLTP requirement purposes?
 

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Discussion Starter #19
No, its due to being in boost all the time, with VWs poor breather system, excess blowby causes extra oily buildup and boom carbon.

The italian tune up you're thinking of only applies to PORT injected engines, where the air fuel mix crosses the intake valve and thru the port.
Direct injection, fuel goes right into the cylinder, thus all you get is metered air plus hot dirty PCV air to coke up on the valves.

The 2.0t's that ran the best were those owned by normal people who just wanted a sporty hatchback, but dont race around. They also seem to generally avoid breather failures for a longer interval.
Interesting - yeah I actually thought the harder they were ran was better. There's a lot of conflicting info out there and maybe there's too many variables to recommend a certain way of driving IDK.
 

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Can confirm, my MK6 GTI is at 97k miles and still didn't get a valve clean up, no issues. I will be doing the service at 100k with waterpump and other maintenance bits. I make sure to step on it at least once a day while merging on the freeway. Sisters Tiguan needed a valve clean up at 73k miles(misfiring), it was previously owned by an older couple.(sister is also a slow driver)
Same here, I have a 2.0T with 143,000 and no carbon cleaning has been done. It runs and drives fine.
 
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