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Hey everyone, was recently at my local dealer for the recall on the front passenger seat of my 2015 Sedona EX. Purchased an oil change bundle (which makes it cheaper to have done at the dealer rather than by me) and had that performed, along with a multi-point inspection. One of the issues that they pointed out with my Sedona is the need for what they refer to as a GDI service. I know that these direct-injection engines are more susceptible to carbon buildup but I'm unclear on what a proper GDI service entails. Do I just add some type of fuel additive that cleans the system out, or do I need to manually clean the carbon buildup off the valves? Thanks in advance for the help.
 

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Thanks for the info, Steve. I guess what I'm getting at is if a solution like this spray is sufficient or if there are more steps recommended to removing the carbon buildup?
 

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Gasoline Direct Injection means the fuel is injected directly into the combustion chamber. I would think it is much less susceptible to carbon build up on the valve, if not eliminate it entirely. Prior to GDI, fuel injectors are mounted upstream of the intake ports and spray mist toward the intake valves. That's why they were called port injection. With GDI, only air passes through the intake valves.

It doesn't hurt to use Techron or Seafoam occasionally, as carbon build up on piston crown can still be a problem, but I wouldn't worry about the intake valves.

That "GDI service" sounds like a profit adder. Why not ask them exactly what is done? If they cannot explain it clearly what is it that you are paying for, forget it.
 

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... With GDI, only air passes through the intake valves .....
Not the case, given the recirculated exhaust gas coming in as well. And that's what can cause deposits on the back of the intake valves, because there is no gasoline washing it off, as there is in port injected engines.

The real question is how much of an issue these deposits become over time in the Kia/Hyundai engines. It's well known that there were quite a few problems in the past with a number of Euro vehicles (mainly German), due to excessive valve deposits. Expensive cleaning, such as walnut blasting, was often needed in order to keep those deposits under control. However, it's much less clear (so far) how much of an issue it is on the direct injected Korean engines.

I've seen virtually no accounts of valve deposits causing a specific performance issue on a direct injected Kia/Hyundai engine, and subsequently being resolved via valve cleaning. Not saying it can't be happening, only that I haven't seen it being reported so far.

And another thing that's very unclear is just how effective these various cleaning products are at removing carbon deposits from intake valves. There is one guy on this forum who has reported definite success removing valve deposits, based on borescope observation, using a CRC product that goes directly into the cylinders. Outside of that, I'm not aware of anyone else showing evidence of intake valve carbon being removed by any of these cleaning products (which are typically sprayed into the intake in one way or another).

And one thing that's almost never discussed is the possibility of damaging effects of the cleaning products on the engine. Some percentage of the cleaning agent must be getting into the oil, and eventually come in contact with seals and gaskets. Yes, the amount getting into the oil is likely to be very small, and I have no idea if it could actually cause significant engine damage. I guess I just don't like the idea of dumping something into the engine which is (supposed to be) strong enough to dissolve carbon deposits. Just my uneasy feeling about that, but clearly not supported by any published facts.

Bottom line for me is that, when I'm eventually forced to own a direct injected engine (which won't be a Kia/Hyundai), I will not be doing an valve cleaning process, unless there is a clearly established and documented need to do so.
 

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Gasoline Direct Injection means the fuel is injected directly into the combustion chamber. I would think it is much less susceptible to carbon build up on the valve, if not eliminate it entirely. Prior to GDI, fuel injectors are mounted upstream of the intake ports and spray mist toward the intake valves. That's why they were called port injection. With GDI, only air passes through the intake valves.

It doesn't hurt to use Techron or Seafoam occasionally, as carbon build up on piston crown can still be a problem, but I wouldn't worry about the intake valves.

That "GDI service" sounds like a profit adder. Why not ask them exactly what is done? If they cannot explain it clearly what is it that you are paying for, forget it.
Fuel/air mixture introduced into intake ports on MPI engines 'washed' away contamination on intake valves, with GDI engines gas from combustion chamber makes it back into intake valves passages contaminating intake valves with carbon buildup. This is a major issue with GDI engines so intake valves need cleaning.
 

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@ kiaguy002:

just run CRC cleaning a day or two before doing oil change.
I've never seen even one report of anyone having a performance issue in a direct injected Kia/Hyundai vehicle, which was proven to be caused by carbon deposits on the valves. If you know of one (or more), by all means post the link to it here.
 

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Fuel/air mixture introduced into intake ports on MPI engines 'washed' away contamination on intake valves, with GDI engines gas from combustion chamber makes it back into intake valves passages contaminating intake valves with carbon buildup. This is a major issue with GDI engines so intake valves need cleaning.
Actually, it's unatomized "wet" fuel that causes coking on intake valves. That fuel in liquid phase is the contaminant. If the fuel mixture is well atomized and/or vaporized, there is little to no liquid phase left, and any clearing/scavenging effect in the intake valves is no better than with air alone.
 

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Not the case, given the recirculated exhaust gas coming in as well. And that's what can cause deposits on the back of the intake valves, because there is no gasoline washing it off, as there is in port injected engines.
There is no Exhaust Gas Recirculation (EGR) system in the 3rd-gen (YP) Sedona. Correct me if I am wrong. I find no mention of it in the service manual: Third generation YP (2014-2019)
 

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There is no Exhaust Gas Recirculation (EGR) system in the 3rd-gen (YP) Sedona. Correct me if I am wrong. I find no mention of it in the service manual: Third generation YP (2014-2019)
I didn't say anything about an EGR system, only that the deposits were caused by exhaust gas (i.e. combustion by-products).

I'm not going waste any more time discussing this. Here's one (of many) sources that explains how carbon deposits form in direct injected engines. If you want to continue to push your opinion, you can argue with this guy. (or any one of the other people who say the same thing)

Why Direct Injection Engines Develop Carbon Deposits
 

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There shouldn't be too much performance degradation with carbon build up as it's not gonna block air intake to the level there is little air entering combustion chamber.
ECU would adjust air/fuel ratio anyway.
It's both - some (little) combustion product (exhaust gas) and oil vapor coming thru PCV that build up carbon. Valves' timing isn't perfect as well as valves' sealing for intake valves to be preventing some gas to go back into intake. Same happens on exhaust side, some (little) exhaust gas already out cylinder makes it back in thru exhaust valves at certain cycle points.
 

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I didn't say anything about an EGR system, only that the deposits were caused by exhaust gas (i.e. combustion by-products).

I'm not going waste any more time discussing this. Here's one (of many) sources that explains how carbon deposits form in direct injected engines. If you want to continue to push your opinion, you can argue with this guy. (or any one of the other people who say the same thing)

Why Direct Injection Engines Develop Carbon Deposits
given the recirculated exhaust gas coming in as well. And that's what can cause deposits on the back of the intake valves,
So... which part of "recirculated exhaust gas coming in" did I not understand correctly? ;)

When the intake valves open, there is tremendous negative pressure in the cylinder sucking air through the intake port. There is no chance that any remnants of exhaust gas left in the cylinder could possibly fight against this intake charge and make its way upstream to deposit on the intake valve surface. Even if there is, exhaust gas has no liquid phase fuel left in it that could possibly deposit on surfaces and form coking.
 

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How high could a negative pressure B?

So... which part of "recirculated exhaust gas coming in" did I not understand correctly? ;)

When the intake valves open, there is tremendous negative pressure in the cylinder sucking air through the intake port. There is no chance that any remnants of exhaust gas left in the cylinder could possibly fight against this intake charge and make its way upstream to deposit on the intake valve surface. Even if there is, exhaust gas has no liquid phase fuel left in it that could possibly deposit on surfaces and form coking.
The highest negative pressure possible is about -15 PSI relative to the atmosphere. With the use of forced induction you could get a higher negative pressure relative to the atmosphere but only if you can cram a higher volume of air into the cylinder than atmospheric presssure alone could accomplish. Out in space the air pressure is nearly zero PSIG. To get it any lower you could use mechanical or ion pumps, but the ultimate difference would be only a few millitorr. The highest negative pressure in nature is zero PSIA. Otherwise I tend to agree with your statement.
 

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The highest negative pressure possible is about -15 PSI relative to the atmosphere. With the use of forced induction you could get a higher negative pressure relative to the atmosphere but only if you can cram a higher volume of air into the cylinder than atmospheric presssure alone could accomplish. Out in space the air pressure is nearly zero PSIG. To get it any lower you could use mechanical or ion pumps, but the ultimate difference would be only a few millitorr. The highest negative pressure in nature is zero PSIA. Otherwise I tend to agree with your statement.
I work with purge enclosures for oil and gas applications to keep out explosive atmospheres. Can you guess how much pressure is required to do that? ATEX specifies 0.1" of water = 0.25 mb = 0.0036 psi. Most purge controllers regulates a bit higher than the spec minimum, but usually 1/2 psi or less.

I also work with Industrial high power lasers, which often use compressed air blowing out of a nozzle to keep the laser path clear of dust and other contaminants. The nozzle pressure required vary depending on distance to cutting surface, but just to keep out dust & debris from entering the nozzle itself takes only a few psi. In that application, SCFM is far more critical than differential pressure. Larger nozzle sizes could run 100's of SCFMs.

1 atm or 14.5 psi is plenty in the context of what we are talking about here.
 

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There shouldn't be too much performance degradation with carbon build up as it's not gonna block air intake to the level there is little air entering combustion chamber.
ECU would adjust air/fuel ratio anyway.
It's both - some (little) combustion product (exhaust gas) and oil vapor coming thru PCV that build up carbon. Valves' timing isn't perfect as well as valves' sealing for intake valves to be preventing some gas to go back into intake. Same happens on exhaust side, some (little) exhaust gas already out cylinder makes it back in thru exhaust valves at certain cycle points.
So do these benefit from using a catch can? I just purchased an LX 2019 and am contemplating installing a catch can.
 

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Someone posted a video from hyundai before on this forum, showing that in the 3.3 GDI engine, the injector actually inject a little bit of fuel when the intake valve is fully open, in order to clean the valve.
Therefore in this engine as long as you use good fuel with good detergent, you dont need a catch can or GDI service.
 

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Gasoline Direct Injection means the fuel is injected directly into the combustion chamber. I would think it is much less susceptible to carbon build up on the valve, if not eliminate it entirely. With GDI, only air passes through the intake valves.
You are woefully, horribly mistaken about the situation.

There is much research for you to do on this subject.
 
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