Carbon issues with direct injection engines

[996GT2]

It seems like DI is the way of the future for internal combustion engines, and soon there may not be any engines with port fuel injection left on the market. With that said, it also seems like many manufacturers have not been able to fix the carbon deposit issues in DI engines, which is caused by particles from intake air getting deposited onto the back of the intake valves. In a traditional port-injected engine, fuel is sprayed over the back of the intake valves, which washes away any deposits before they have a chance to accumulate. In a DI engine, the injector is inside the cylinder and there is no fuel flow over the back of the valves.

I know Toyota has found something of a workaround with a hybrid system that uses 1 DI injector and 1 port injector per engine, but most companies have not. So, is the carbon build-up issue here to stay, especially as newer cars with DI engines accumulate more miles?

Some examples:
Ford F150 Ecoboost:

Audi RS4:

BMW:

Porsche Cayman:

Mazdaspeed6 after 36k miles:

Audi 2.0T after 28k miles:

Here's a picture of a non-DI GM V6 engine with 140k miles, showing absolutely no carbon deposits around the valves due to the fuel being sprayed there:

 

[NutBucket]

I dunno, might have to run seafoam every so often?

Basically there's no easy fix for this from what I gather. Just another $$$ item for the dealer. At least it's actually needed instead of their favorite "fuel injector cleaning".

 

[996GT2]

I dunno, might have to run seafoam every so often?

Basically there's no easy fix for this from what I gather. Just another $$$ item for the dealer. At least it's actually needed instead of their favorite "fuel injector cleaning".

A $500 walnut shell blasting service to clean the intake valves every 30-50k miles more than offsets the small mpg gain offered by a DI engine. Kind of like taking 1 step forward and 2 steps back.

The before/after pics on a BMW DI engine (50k miles) which had walnut shell blasting done are pretty amazing:

 

[basslover1]

I dunno, might have to run seafoam every so often?

It wouldn't help any as there isn't any way for seafoam to splash onto the intake valves.

I wonder if any of these issues will be covered under warranty, as there is literally zero preventative maintenance an owner could conceivably do to prevent this..

 

[slag]

It wouldn't help any as there isn't any way for seafoam to splash onto the intake valves.

I wonder if any of these issues will be covered under warranty, as there is literally zero preventative maintenance an owner could conceivably do to prevent this..

Maybe, but how would you know that you have an issue? We have 46k (I think) on the explorer sport (3.5 liter ecoboost), and it appears to run fine, but we wouldn't be able to tell if it was more sluggish than when it was new because we drive it daily and would have gotten used to how it runs.

 

[Ramses]

It wouldn't help any as there isn't any way for seafoam to splash onto the intake valves.

I wonder if any of these issues will be covered under warranty, as there is literally zero preventative maintenance an owner could conceivably do to prevent this..

You suck it into the intake tract directly, cleans the throttle body and intake valve backsides. Works pretty well for cheap as it is, most of those pics would take several applications ime. Makes a crazy smoke show on really icky motors, I question if all that smoke would hurt a cat or 02 sensor but have no evidence to support the idea.

 

[basslover1]

Maybe, but how would you know that you have an issue? We have 46k (I think) on the explorer sport (3.5 liter ecoboost), and it appears to run fine, but we wouldn't be able to tell if it was more sluggish than when it was new because we drive it daily and would have gotten used to how it runs.

I would imagine that if the build up was bad enough causing valves to not seal correctly you'd get worse MPG. It would rely on typical users actually paying attention to how their car operates, however.

You suck it into the intake tract directly, cleans the throttle body and intake valve backsides. Works pretty well for cheap as it is, most of those pics would take several applications ime. Makes a crazy smoke show on really icky motors, I question if all that smoke would hurt a cat or 02 sensor but have no evidence to support the idea.

True, I was thinking strictly dumped into the gas tank but yea that's an option.

Now that you mention it, that's what I did on my Passat a time or two, and yes it does make for a fun smoke show.

 

[996GT2]

You suck it into the intake tract directly, cleans the throttle body and intake valve backsides. Works pretty well for cheap as it is, most of those pics would take several applications ime. Makes a crazy smoke show on really icky motors, I question if all that smoke would hurt a cat or 02 sensor but have no evidence to support the idea.

I question whether Seafoam could clean out some of the engines pictured above, even with multiple applications. So far, the only method which has been proven to work is walnut shell blasting of the intake valves (or another method of cleaning the valves by hand).

Based on some quick searching, the consensus is that Seafoam will do nothing for caked-on carbon deposits in DI engines:

http://www.northamericanmotoring.co...ean-caked-on-carbon-build-up.html#post3500257

http://forums.vwvortex.com/showthread.php?5789596-Can-I-get-rid-of-carbon-buil-up-with-Seafoam

 

[shabby]

I wonder if any of these issues will be covered under warranty, as there is literally zero preventative maintenance an owner could conceivably do to prevent this..

I would imagine there will a class action lawsuit in the future and dealers will simply offer cleaning service for free to all affected cars.

 

[NutBucket]

Yeah, but what good would it do? One free cleaning?

What will likely happen is the cleaning will become a part of the maintenance schedule....and something you definitely can't DIY. I can't say I'm unhappy neither of our cars is DI.

 

[basslover1]

Yeah, but what good would it do? One free cleaning?

What will likely happen is the cleaning will become a part of the maintenance schedule....and something you definitely can't DIY. I can't say I'm unhappy neither of our cars is DI.

Well most people don't keep cars that long, so one free cleaning will be great for the current owner but in 50k miles the next owner will run into the same problem.

I know it'll eventually become an issue in my car, but the platform is still pretty young for it to have developed, but I'm planning on keeping this car well past 100k miles and I imagine that means I'll be media blasting the intake valves a few times throughout the course of ownership.

 

[tweakmonkey]

My co-worker / "the mechanic" has talked about this for about 6 years, warning it'll be a problem more and more as everything switches to DFI. Everyone's heralding it as the miracle to end all, but nobody's addressing the maintenance concerns and there's uncertainty with longevity.

We work on Porsches specifically and the Mezger (non-DFI) variant. But I know the Porsches have had a lot of issues with DFI as all the cars switch over.

 

[master_shake_]

You're welcome

 

[Yuriman]

How much does DI actually help? Honda and Toyota both have gasoline engines which are nearly as efficient as TDIs (close to 40%) and already have very high compression ratios, and these particular engines are not direct-injected. Is it a bandaid for poor head design?

 

[NutBucket]

It's not a band-aid. It allows for very precise metering of fuel in the combustion cycle. There are definite technical advantages. The carbon build-up issue is a definite downside.

And FYI Honda has moved to DI for most of their engines now. Not sure about Toyota.

 

[LTC8K6]

Got a pic of a DI GM engine?

 

[Ramses]

I question whether Seafoam could clean out some of the engines pictured above, even with multiple applications. So far, the only method which has been proven to work is walnut shell blasting of the intake valves (or another method of cleaning the valves by hand).

Based on some quick searching, the consensus is that Seafoam will do nothing for caked-on carbon deposits in DI engines:

http://www.northamericanmotoring.co...ean-caked-on-carbon-build-up.html#post3500257

http://forums.vwvortex.com/showthread.php?5789596-Can-I-get-rid-of-carbon-buil-up-with-Seafoam

I dunno, I've had it clean some pretty gnarly looking stuff given enough time to soak in(diesel EGR passage in an euro intake most recently), the trick is, and the bottle used to say as much I think, that you basically have to choke the motor off with the stuff in order to completely soak into the carbon on the valves, then let it sit, then do it again to blow out the soaked (and in theory dissolved/loosened) crud. Preferably with hard, high RPM driving. I'd rather not put chunks of carbon like that through my motor personally, I've seen carbon pieces hard enough to bend valves. I'd also rather not put chunks of walnut through. Nothing that just blows some solvent across briefly is going to take off serious hard baked carbon, it's got to soak into it one way or another, or use mechanical removal. Wonder if some anti-stick coatings on the back of the valves would help? All of that carbon cleaning stuff works by dissolving the goo bonding the carbon together/to whatever it's attached to. I'd imagine regular treatments before it becomes so dense and packed would be helpful too. I've also used oven cleaner, the more environmentally un-friendly the better, to eat carbon.

 

[eng2d2]

How does one determine what type of fuel injection is in the engine?

 

[Ramses]

How does one determine what type of fuel injection is in the engine?

Look up the specs for your make and model, or ask here.

 

[echo4747]

You can use a pcv catch can system.. to substantially slow carbon buildup on direct injection engine... doesn't totally solve carbon buildup but does greatly slow the process

 

[NutBucket]

Got a pic of a DI GM engine?

Same problem. The corporate 3.6 V6 definitely has the same buildup.

 

[996GT2]

Got a pic of a DI GM engine?

GM 3.6L DI LLT V6, supposedly with only 8k miles on the clock:

Compare that to a picture of the non-DI GM 3.6L V6 with 140,000 miles on the clock, which shows zero carbon deposits around the valves.

 

[Yuriman]

You can use a pcv catch can system.. to substantially slow carbon buildup on direct injection engine... doesn't totally solve carbon buildup but does greatly slow the process

I would assume nearly all of the carbon buildup would be from PCV and EGR. I'd add a replaceable filter to them any day of the week to prevent having to take the head apart.

 

[Ramses]

They say at least some is overlap in the cycle, worse with variable cam timing.

 

[Brian Stirling]

A $500 walnut shell blasting service to clean the intake valves every 30-50k miles more than offsets the small mpg gain offered by a DI engine. Kind of like taking 1 step forward and 2 steps back.

The before/after pics on a BMW DI engine (50k miles) which had walnut shell blasting done are pretty amazing:

Why does a walnut blasting cost $500? Surely the cost of the material is only a few dollars and I'd imagine much of it could be reused at least a few times.

How long does the treatment take? I could see it taking at least 5 minutes with setup and breakdown taking an additional 25 minutes or so making the total time in the ballpark of 30 minutes.

Do they have to disconnect the exhaust to prevent shells from going through catalytic converter?


I have a DI engine in my 2012 Ford Focus and so far no one I've talked to has had to have any work done on the engine for carbon. I've followed FocusFanatics since before getting the car and there's been talk about carbon issues but not with the FF.


Brian