Do direct injection engines almost require fuel system cleaners?

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Ok, I know I am old school, and do not understand the workings of the modern engines, but can someone explain , in simple terms, what causes carbon to form on the intake valves when, as I understand it, the only thing going past them is clean air on a DI engine. Seems like they are the ones that should never need cleaning. What am I missing?
It's not solely clean air...you're forgetting about the recirculation from the crankcase.
 
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So I have a new 2022 Forester, and at the risk of getting ridiculed, I am running intake valve cleaner ahead of each oil change. No one seems to know if this preventive maintenance will work if done regularly from the start, so my plan is to do it and get some pictures around 20k miles to see if this process is effective.
 
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Toptier fuel is a good start. DI still has injectors. I am glad that at least one person mentioned that. And, burning fuel will leave deposits on the pistons and combustion chambers. Gotta love those piston carbon deposits, some crud that can break/float away/around, that cause LSPI, PI, or detonation. Won't know if the carbon control prevents the crud that's pushed down and forms in the ring pack area.

These injector/cc/piston pictures are worth looking at, as is reading this article. The product is not available anymore, but IMHO, was no better/worse than any other PEA based fuel system cleaner from any brand:

@stangguy, every time you shut off your engine, the residual vapors cool. This cooling condenses fuel/oil crud which forms, sticks and builds itself up everywhere. Fuel washing, from carbs and PFI engines, clean that hardening condensation buildup from the manifolds/port/valves... downstream of the fuel travel(with quality fuel or when using enough detergents/dispersants/solvents). GDI doesn't have any fuel traveling thru the manifold, thru the intake ports, or past the intake valves.... so there is nothing to 'wash' those areas regularly. The deposits occur when your engine is cooling after running.... condensation/caking/building up. It is not all from the PVC system. As the oil degrades, you'll get more oil vapors. As your engine degrades, you'll get more oil consumption, even more cruddy oil and additive vapors, that condense/coat/buildup over time. The short tripper, pathetic oils/filters, and foolish extended intervals... exasperate the situation. Catch cans are not a solution as PCV is not a primary cause.

I've used IV cleaners, sprays/metered aerated drops/liquid vapors, and they did an excellent job of cleaning the ports/valves. There was no need for pick/scraping or blasting the valves. But, that's a good profit maker for the shop when the clueless schlep shows up with his neglected higher mileage engine. They'll have no choice but to push the "sale". And yes, @thunderfog, it is definitely excellent PM.

Step one.... don't let the deposits get out of control. Use, and rotate among, all the available valve/intake cleaners, at least yearly or every 10k miles, whichever comes 1st. You should never need to get to the point of scraping or blasting the crud off. I am at double that interval because I am DIY capable and its too easy not to do.

Step two... keep the oil/filter changed often enough. So, all you repeat filter users, 10k mile, or blind OLM extended excessive intervals, are asking for problems. Severe service interval should be considered, quality filters used, along with best oils you can afford.

Step four... control the fuel spray pattern with clean injectors and reduce the carbon buildup. This is easy with TOPTIER fuel and/or by using a bottle of quality PEA/PIB/solvent/ester.... based fuel cleaner added to fuel. Your budget determines interval but try at least 1 bottle every 10k miles. No point in being brand fanboy so rotate among what is available in the stores around you and avoid the cheap stuff.

Step five... short tripping is bad, very bad. Multiple full or partial cool downs, without the ol' EyeTalian tuneups, without good hot highway runs, can increase buildup. You need to get 'er hot enough to burn off everything. The water injection, from a driving in a good thunderstorm, or idling thru the car wash, could also aid the 'cleaning'. Water/meth injection can reduce the buildup but is beyond the budget and skill set of most.

The VVT back washing that a few automakers used was pathetic and a failure. It might've extended the build up time a little. Not impressed!

My 2.4GDI.... oil/filter change severe service 3750 miles(4-6 month OCI) give or take a week of driving. Synthetic and 3.5+ HTHS oils always. Blend or full synthetic oil filter changed at every OCI. Toptier fuel most of the time and grade not too relevant but premium over the summer heatwave. FI cleaner added every 4-6 months. GDI cleaner every 4-6 months(just before OCI). Thumbing nose at the auto manufacturer's conventional 20 grade 7500 mile interval and pathetic OE filter!

My 1.4TGDI... oil/filter changed every 5k miles, about 4-6 months, with fuel cleaner prior week before OCI, and IVD cleaning morning before OCI. Full synthetic oils always, with oversized synth or blended media filter, even though large for engine OE filter is wired back full synthetic which isn't too bad. . Oil grade 20-25% 40 grade synth with remainder 0w20 VW508. Thumbing nose at the 10k interval, overprice dealer filter, and thin oil which seems to be showing consumption issues with many owners.

This isn't a Hyundai thing. This isn't just a GDI thing. This is not a gasoline engine thing. This is not a piston engine only thing. Burning any fuel, vapor condensed deposits, oil consumption, oil/filter quality/interval, carbon buildup, fuel quality, .... affects everything... but at different accumulation rates. GDI moved the crud issue from TDI's and rotaries, and some failed emissions PFI/carb's, to daily higher volume popular products. The methods haven't changed. The reasons have increased drastically.
 
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Ok, I know I am old school, and do not understand the workings of the modern engines, but can someone explain , in simple terms, what causes carbon to form on the intake valves when, as I understand it, the only thing going past them is clean air on a DI engine. Seems like they are the ones that should never need cleaning. What am I missing?
With current emissions system s I'd say it hasn't been "clean air" for a couple of decades. Blowby gases are re-routed into the intake to be burned off regardless of injection method.

Port fuel injection by design allows fuel to wash over the valves and keep them clean. Injectors in DI engines spray directly into the combustion chamber, bypassing the intake valves. Automakers have had to design PCV systems which do a better job of removing heavier oil mist prior to sending gases in into the intake with DI setups

That's it in a nutshell.
 
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We know that direct injection designs can allow carbon build up unlike other designs. Does this mean that they should probably have maintenance doses of fuel system cleaners or is there a different way to keep deposits low?
@Trav has some advice with regards to how the internals of DI injectors age vs PFI. All fuel sold in the US has detergents to keep injector tips clean.
 
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My understanding is by definition, fuel doesn't come in contact with the intake valves and so a fuel cleaner would have no effect. With BMW there is a walnut blast procedure to remove the carbon. I think Toyota (or one of the mfg) combines both direct and port fuel injection so that fuel can still clean the intake valves.
You are correct. Actually, both Ford and Toyota both utilize this and I wouldn’t be surprised if other manufacturers take advantage of that approach.
 
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Would a catch can attched to the pcv line help to minimize deposits on a GDI engine as it prevents some of the crankcase fumes/junk from being burned?
 
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Would a catch can attched to the pcv line help to minimize deposits on a GDI engine as it prevents some of the crankcase fumes/junk from being burned?
The deposits don't come from the PCV line. The the misnomer condensation can doesn't do much if anything. What the can collects wouldn't be added to IV deposits. So, buy it, install it, and still clean your intake valves as needed.
 
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The deposits don't come from the PCV line. The the misnomer condensation can doesn't do much if anything. What the can collects wouldn't be added to IV deposits. So, buy it, install it, and still clean your intake valves as needed.
I used one on my previous vehicle, a 2011 Kia Optima with the 2.4 Gdi. I probably got 500ml of brownish/yellowish junk between oil changes in the winter and maybe 200 ml in the summer. I don't know if it actually helped the engine but it was running strong when I sold it in 2021. If that junk is not recirculated through the the pcv system to be burned, then where does it go?
 

dnewton3

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@stangguy, every time you shut off your engine, the residual vapors cool. This cooling condenses fuel/oil crud which forms, sticks and builds itself up everywhere. Fuel washing, from carbs and PFI engines, clean that hardening condensation buildup from the manifolds/port/valves... downstream of the fuel travel(with quality fuel or when using enough detergents/dispersants/solvents). GDI doesn't have any fuel traveling thru the manifold, thru the intake ports, or past the intake valves.... so there is nothing to 'wash' those areas regularly. The deposits occur when your engine is cooling after running.... condensation/caking/building up. It is not all from the PVC system. As the oil degrades, you'll get more oil vapors. As your engine degrades, you'll get more oil consumption, even more cruddy oil and additive vapors, that condense/coat/buildup over time. The short tripper, pathetic oils/filters, and foolish extended intervals... exasperate the situation. Catch cans are not a solution as PCV is not a primary cause.
I would agree with your end result assessment, but going to take exception to some of what you said, only in principle.

The PCV, if it vented to atmosphere like the good old days, would not contribute to the residuals in the intake plenum and on the back of the intake valves; it would be impossible to coke or condense something that wasn't present in the first place. However, because PCVs are routed to re-introdce the vapors to the engine intake tract, they most certainly are the culprit! It's not that a PCV itself causes the issue, but it IS the pathway that directs the vapors to those places where they then cool and cause the residual you speak of. Plus, even during long sustained operation, the heat of the intake valves does cause some coking of those byproducts the vapors carry with them; the intake valves can be upwards of 500 degF or more, and that's more than hot enough to coke petroleum byproduct vapors.

I'm just nit-picking. It's part of what you claim, but it's also part of what I claim. It's a combination of those two which causes the problems. Essentially, it happens both during long sustained hot operation AND during cool down.

The catch-cans most certainly do help; see this video; good info starting at 3:00 min

They won't eliminate the problem; they can significantly reduce the problem. Here are some considerations for the success of a catch can:
- must have proper volume for the amount of vapor the engine will produce; if it's too small it will just pass the vapors along without cleansing them
- must be installed correctly; longer lines of sufficient diameter make for a better chance to cool the vapors on the way to the CC
- must have a good design and proper elements; cheap CCs often are lacking in the elements needed to trap the residuals in the vapor. You need not only a baffle system, but a tight mesh screen and it helps to have the pathway alter course
(The goal is to condense the residuals out of the vapor; "make it rain" so to speak). So the two most effective things for promoting condensation of the vapors is to have several changes in direction, and as much cooling effect as possible. The direction changes slow the vapor velocity, which allows the residuals to drop our of suspension easier; the more things the byproducts physically touch, the more likely they are to cling to a surface and not continue in the air path. And cooling promotes condensation, which also helps with the undesirables dropping out of vapor suspension).
If you can do these three things, you can eliminate MOST (but not all) of the vapor byproducts:
- slow the velocity of the vapor path; slowing the flow makes for a pressure drop, as well as gives time for the next step to occur
- redirect the vapor path multiple times to promote byproducts hitting surfaces and clinging to them
- cool the vapors to promote making the byproducts "heavy" and further promoting them dropping out of suspension

With the turbo-DI engines, it's more difficult to install a CC on the system, but it can be done if proper check valves are in place. With n/a DI engines, it's as simple as re-routing the PCV to atmosphere; who needs a CC when the vapors are directed outside the engine? (not that it's legal to do so, but just saying).

If I had a modern gas turbo engine that was both DI and PI, I'd still want a catch can. Anything I could do to improve my odds would be my choice of roads to take.
 
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as I understand it, the only thing going past them is clean air on a DI engine. Seems like they are the ones that should never need cleaning. What am I missing?
There is some reversion of exhaust gases (and crud) into the intake at the beginning of the intake stroke.
Many engine with variable valve timing use this effect for EGR.
Some speculate deposits come from PCV fumes, but one study disabled PCV and there were still intake valve deposits (slightly more in fact!):
 
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Would a catch can attached to the pcv line help to minimize deposits on a GDI engine as it prevents some of the crankcase fumes/junk from being burned?
Doubtful.
The largest source of oil deposits on an intake valve actually comes down the valve stem, through the valve stem seal, from under the valve cover.

Catch can can't fix that source of oil.
 
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Supplied by CHEVRON . States on front and back of bottle . Use TECHRON 10 once bottle 1 or 2 times a year . Try to use TOP TIER gas as much as possible for the '18 ACCENT and its 1.6 Ltr. w/ D.F.I.. The 20 ounce bottle ( pictured ) would be a double dose of TECHRON 10 ounce for the ACCENT and its 11.9 gallon gas tank . KIA fuel system cleaner is the same as the HYUNDAI .

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