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Direct injection offers numerous benefits over port fuel delivery but could it be a bigger headache than it’s worth?

The automotive industry has gradually switched to direct injection over the past decade or so and for good reason. Spraying a precisely controlled amount of fuel right into an engine’s combustion chambers can result in improved efficiency and greater power density; tailpipe emissions are generally cleaner as well.

In spite of these advantages, this technology isn’t perfect. DI has a handful of downsides including additional noise, particularly at idle and dramatically higher costs, though there are other concerns.

And a big one has to do with carbon deposits. We’ve heard rumblings that blackened buildup on the backsides of intake valves is a major problem and something that could be disastrous for motorists in the coming years. To get to the bottom of this potential top-end issue we did some digging.

What’s Really Going On?

Ford has been pushing its EcoBoost engines as a way of improving fuel economy without sacrificing performance. The real-world results of this strategy may be mixed, but one thing is not: all of these powerplants feature direct injection as well as turbochargers and advanced control software.

These engines have been on the market for a number of years now and to get some empirical evidence from the front lines about how they’re holding up we reached out to Brian Laskowski, a Ford Factory Certified Technician. He also has a YouTube channel, FordTechMakuloco that highlights all sorts of automotive repairs.

Responding via e-mail Laskowski said, “Carbon deposits in Ford engines are not a widespread issue due to the advanced engine technology.” But he also mentioned that it has happened in some low-mileage EcoBoost units.

“As of today the issue seems to be isolated to certain markets with varying factors such as fuel quality,” said Laskowski. If carbon buildup becomes severe he said it can result in all kinds of issues from drivability woes to misfires, turbocharger issues and even catalytic converter damage.

Survey Says…

Assuaging potential sky-is-falling fears, Michael Karesh, the developer of TrueDelta.com said carbon buildup is “not an issue for all direct-injected engines” based on the data he collects. His website surveys nearly 100,000 drivers of all makes and models to acquire relevant and timely data about vehicle reliability and fuel economy among other things.

But of course there are some instances of deposit-related issues that have popped up. Karesh said, “The only engines it’s reported quite a bit is [with] the VW/Audi 2.0T and then the Audi V6s.” He also said, “I know there are some BMWs that end up with carbon buildup as well.”

As for the frequency of reported problems with these Volkswagen cars he said his numbers indicate “it can be as high as one in six over the last two years,” which “is a high number” and one that he said is consistent across different models.

The 2008 Audi A3, which offered a 2.0-liter turbocharged four-cylinder engine, also popped up in the TrueDelta data. Karesh said it’s puzzling why 2006 and 2007 models aren’t having similar carbon issues. Leaving us with more questions he said, “I’m not really seeing GTIs [popup],” which are mechanically similar to the A3.

“If there is a non-German car there might be something happening in the [Cadillac] CTS,” said Karesh, but once again he cautioned that it’s “too scattered and sporadic” to draw any definitive conclusions. Additionally he said, “I have one report of decarbonizing the engine in a Chevrolet Equinox.” Unlike the other instances, he has quite a large sample size for this particular vehicle, which clearly indicates that deposits are not a major problem at this time ...
For all the details on this story, Is Carbon Buildup a Problem With Direct-Injection Engines? please visit AutoGuide.com.
 

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The harder you drive a direct injection vehicle the better it will be. That's why the GTI doesn't present the problem as much as the A3. Customers of the GTI are more likely to drive their cars hard.
 

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Sure is a problem. 2.4 Ecotec, 3.6 High feature, and even the all new Ecotec3 engine family. Our shop just put a 5.3 Ecotec3 back together the other day (collapsed AFM lifter on cyl. 4) with 21600 miles. The intake ports on the non AFM cylinders were almost as bad as the AFM cylinders. It ridiculous how much carbon was on those valves. The pistons were quite dirty as well. Oil residue from the PCV at the top of the intake ports as well.
 

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Sure is a problem. 2.4 Ecotec, 3.6 High feature, and even the all new Ecotec3 engine family. Our shop just put a 5.3 Ecotec3 back together the other day (collapsed AFM lifter on cyl. 4) with 21600 miles. The intake ports on the non AFM cylinders were almost as bad as the AFM cylinders. It ridiculous how much carbon was on those valves. The pistons were quite dirty as well. Oil residue from the PCV at the top of the intake ports as well.
A new afm engine with carbon and oil residue issues, who would of thought... Your old Afm engines were horrible for it, I can see the new ones following the trend
 

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This was discussed at length within the last few months on GMI. One of the posters is an expert on the issue, and posted several important facts and observations, so it might be worthwhile to review that thread.
Port fuel injection cleans the intake valves, while DI engines can have exhaust gas re circulation deposits build up on intake valves.
The german engines seem to be the worst, but unless there is some gasoline port injection cleaning the intake valves, there will be deposits.
Apparently (some?) toyota engines use a combination of port and direct injection, cleaning the intake valves, and eliminating or greatly reducing the problem.
 

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How does driving harder have any material impact on oil vapors depositing onto valves?
Known in some circles as the "Italian tuneup," it's known that running the **** out of your car from time to time helps blow the carbon out.

I used to take my parents' cars out, they had a cherry 79 Caddy and a 71 225 among others, and run hell out of them. A number of blasts at WFO throttle and you'd see the crud pouring out of the tailpipe. They were typical town drivers, probably never got over 2500 RPM and those cars just piddled around town most of their lives.

Machines need to be run hard from time to time. Like the human body.
 
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There are dozens of technical papers written about the problems of DI. Companies go from a mediocre combustion system to a good one, and then claim it's because of DI. DI causes WORSE engine-out emissions, and needs a strategy to heat the cat faster. DI causes more soot from stratified charge combustion. It will require soot traps in the next couple of years. So in addition to the initial expense, now we'll have to pay for more emissions controls. Fuel is injected while the intake valves are open; the 7% improved VE is BS. As far as I can tell, OEMs save a little time and money from not doing a proper valve job. It has loud injectors, a mechanical fuel pump that robs HP, and is harder to fix. imo it's totally not worth it.
 

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Put some Sea Foam though the intake once in a while?
 

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The article answered its own question, carbon build up is not a widespread problem in DI engines.
The article said nothing of the sort. It said that Michael Karesh, with his *extremely* limited dataset on truedelta, does not see *all* DI engines showing problems. That is a far cry from saying that carbon buildup is not a widespread problem. I have personally seen several dozen DI engines from at least 3 different manufacturers have major coking on the valves. With my limited dataset does that mean that *all* DI engines have carbon buildup problems?

The coking problems will end when PCV systems improve, or if port injectors are added in addition to direct injectors. I have actually wondered if throttle body injection would work to address this problem. A single TBI is a lot easier than adding 4/6/8 additional port injectors.
 

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I
The coking problems will end when PCV systems improve, or if port injectors are added in addition to direct injectors. I have actually wondered if throttle body injection would work to address this problem. A single TBI is a lot easier than adding 4/6/8 additional port injectors.
On DI engines, the fuel is injected when the valves are closed, at some 2,000+ psi. If the valves were open, there Would be Blowback, but my understanding is that the valves ARE closed, meaning the only things In the intake tract are incoming air and Re-circulated exhaust gas, creating the problem of carbon buildup.
With port fuel injection, the exhaust gas re circulation is occurs BUT the incoming air also includes gasoline, a very strong solvent that "Clean" the intake valves on the backside.
Anything in the gasoline would be injected into the combustion chamber, missing the intake valve stems, and an Italian tuneup would be Ineffective as well.
IMO fixing the problem is essential to avoid giving DI engines a bad reputation, and they better do it quickly!
 

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I have taken apart a few of the LNF engines and haven't seen significant issues at all. I would think that with FI velocities past the intake valve might be higher and do a little self cleaning? Which would support the Ford EB talk. Low mileage engines and engines that don't run under boost often might be more susceptible to it.
 

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With the intake valves closed, with the exhaust valves closed, the fuel is sprayed into the chamber. That means that NO fuel gets on the stem side of the intake valves, where the carbon buildup is an issue.
How many DI engines have you disassembled, and were you looking for carbon buildup or for some other reason?
Why would you think boosted engines would be any different?
 

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A little tangentially, but not completely - diesels have used DI and closed-circuit crankcase ventilation for a long time, and recent emission regulations now require EGR for diesels which gives problems with oiling/carbonising in the EGR itself but not of the valves AFAIK.

So why are the recent crop of DI gasoline engines affected and not all the DI diesels - just interested!
 

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The article said nothing of the sort. It said that Michael Karesh, with his *extremely* limited dataset on truedelta, does not see *all* DI engines showing problems. That is a far cry from saying that carbon buildup is not a widespread problem. I have personally seen several dozen DI engines from at least 3 different manufacturers have major coking on the valves. With my limited dataset does that mean that *all* DI engines have carbon buildup problems?

The coking problems will end when PCV systems improve, or if port injectors are added in addition to direct injectors. I have actually wondered if throttle body injection would work to address this problem. A single TBI is a lot easier than adding 4/6/8 additional port injectors.
Nearly every vehicle sold today has DI, if the problem was so epidemic, we would be hearing a lot more about it.
I suspect that a lot of the problem childs will be earlier versions but the majority of owners will care little about potential carbon build up, mostly because vehicles are moved on after around three or four years, it then becomes successive owners issue buried in the second hand market.

Not all engines are created equal, some PCV and EGR systems are quite different and this probably gives rise to why some engines are more trouble prone than others.As we get into cooled EGR and low pressure systems, the particles may not be as prone to sticking t the inlet valve stems..
 

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With the intake valves closed, with the exhaust valves closed, the fuel is sprayed into the chamber. That means that NO fuel gets on the stem side of the intake valves, where the carbon buildup is an issue.
How many DI engines have you disassembled, and were you looking for carbon buildup or for some other reason?
Why would you think boosted engines would be any different?
As I stated before velocities on the the back side of the valve are higher. During cam overlap events you also have higher pressure on the intake side. This will give different flow characteristics in the valve area. The real question is what exactly causes the build up to stick to the valve, is it just impingement? Is it a fusion temperature issue?

I have taken apart 4 DI engines, all were boosted, none of them really had any more carbon than other engines I have taken apart. I can only vouch for the quality of care on one of them.
 

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Ford's answer to carbon buildup on the ecoboost engines is to get new heads instead of trying some simple cleaners. Sounds legit brah.
 
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