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Carbon buildup on valves in GDI

indiMjc

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I'm fairly new to the car scene and have a quick question about direct injection engines. I have a LOT to learn so I'm sorry if this is a dumb or previously answered question.

I bought a 2018 civic si as a daily driver and have been doing a fair bit of research into the L15B7 motor. One of the things I stumbled across was about direct injection in general and has to do with carbon buildup on the valves.

It's pretty easy to understand why port injection keeps the valves clean by spraying gas on their backsides and how injecting directly into the cylinder means they don't get the same cleaning.

I've read that in the newer Honda gdi's this isn't as much as a problem. I also read in one place that the reason it's not a huge deal on these motors is because there's actually 2 injectors per cylinder, one that injects directly and a secondary injector in the port where it normally would be. I'm probably still going to get an oil catch can because it just feels better to know I'm keeping that gunk out, but I still would like to confirm whether or not thats true about the set of secondary injectors.

So the question is, does the L15B7 1.5T in the newer civics actually have that second set of injectors in the ports or is what I read false? I've been unable to confirm it. Thanks for reading.



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Gotch

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One set of injectors confirmed, just had mine replaced.
 

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From a bunch of trials by aftermarket companies, our cars don't need a catch can apparently, as the stock system does a really good job even with more boost. I don't hear a catch can being a needed mod if you track your car like other cars I've had like a BRZ for example.
 

NeoDragons

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This is normaly what i clean out of the can every 3k miles. i am fully tuned and i do track my car.

1593581654283.png
 

kimtyson

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This is normaly what i clean out of the can every 3k miles. i am fully tuned and i do track my car.
You might want to consider the fact that your alteration of adding the catch can has created what is being caught in it. A self fulfilling prophecy. You have altered the design implemented by the Honda engineers.
 

Hollywoo0220

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I'm fairly new to the car scene and have a quick question about direct injection engines. I have a LOT to learn so I'm sorry if this is a dumb or previously answered question.

I bought a 2018 civic si as a daily driver and have been doing a fair bit of research into the L15B7 motor. One of the things I stumbled across was about direct injection in general and has to do with carbon buildup on the valves.

It's pretty easy to understand why port injection keeps the valves clean by spraying gas on their backsides and how injecting directly into the cylinder means they don't get the same cleaning.

I've read that in the newer Honda gdi's this isn't as much as a problem. I also read in one place that the reason it's not a huge deal on these motors is because there's actually 2 injectors per cylinder, one that injects directly and a secondary injector in the port where it normally would be. I'm probably still going to get an oil catch can because it just feels better to know I'm keeping that gunk out, but I still would like to confirm whether or not thats true about the set of secondary injectors.

So the question is, does the L15B7 1.5T in the newer civics actually have that second set of injectors in the ports or is what I read false? I've been unable to confirm it. Thanks for reading.
There is only (1) Set of injectors - thus, DI platform.
If it had (2) Set of injectors, then it would be a Multi-Port.

More modern manufacturing has taken precautions and improved the secondary effects of "blow-by" in direct injection platforms (especially turbo charged engines). This has really come into place about 4years ago (after the manufacturing) and the focus has been on the PCV systems. Mind you, that without a port injection setup spraying over the valves, eventually they will get covering in carbon based particulates. Over time it will build and build and "cake" on (sort of speak).
However, keep in mind what many compain about: Oil Dilution. That fuel in the oil is actually "complimenting" the disformation of carbon making its way out of the combustion chamber, around through the air intake, then back through the intake manifold. The blow-by that does find it's way through that path is now more than just a carbon based break down, it is layered with hydrocarbon distillates which together decrease the chance of adhering to the valves.
What I am suggesting is that if you use a Synthetic Oil (in of itself) you will decrease the Carbon Footprint in the Engine; as opposed to using a non-synthetic oil (which are highly Carbon based). The Synthetic will be far less likely to ACIDIFY & OXIDIZE on metal.

I always suggest using Synthetics that have the highest content of Detergents & Dispersants. This way, you allow the additives manufactured into the oil do absorb as much carbon based elements in their surroundings.

Suggestions:
Oil Changes
* Warm the engine up
This will assist with flow of the drain and allow it to peel from the frictional surfaces.
 
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indiMjc

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However, keep in mind what many compain about: Oil Dilution.
That is something that I was also going to ask about but in a different post. Initially when I heard about the oil dilution in the L15B7 I told myself I wasn't going to buy the car. I eventually found out that this was a concern in all direct injection motors and decided to put my faith in Honda a little bit. There is actually a bunch of legitimate, peer reviewed literature on this topic if you search for it on Google scholar.

I had basically already planned on doing what you're suggesting in a few ways. I plan on changing the oil at 30-40% life just to keep it extra fresh and using whatever the best oil my research tells me. It takes so little oil that there's no reason to ever cheap out on it, which I don't even do in my trucks anyway.

I read that in these engines, some of the conditions in which oil dilution is encouraged are cold starts and driving before reaching operating temperature. Also excessive idling and excessive engine breaking. What I've been doing is starting it and waiting for it to idle down when it enters the "closed loop," which I have to look up again because I forgot what that even means. Then I drive it easily, short shifting until operating temperature. Also it's going to be garaged all winter because I wouldn't drive a car in Michigan, in the snow so cold weather isn't a concern.

Out of curiosity, what oil would you guys suggest? I've read that the reason direct injected motors use such thin oil is because it allows the engine to reach operating temperature faster. It calls for 0w20 but I've also seen a few people say that Honda is, in some places, recommending running 0w16 to get it up to operating temperature even faster. Idk about doing that though unless I flat out confirm it.
 

Hollywoo0220

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That is something that I was also going to ask about but in a different post. Initially when I heard about the oil dilution in the L15B7 I told myself I wasn't going to buy the car. I eventually found out that this was a concern in all direct injection motors and decided to put my faith in Honda a little bit. There is actually a bunch of legitimate, peer reviewed literature on this topic if you search for it on Google scholar.

I had basically already planned on doing what you're suggesting in a few ways. I plan on changing the oil at 30-40% life just to keep it extra fresh and using whatever the best oil my research tells me. It takes so little oil that there's no reason to ever cheap out on it, which I don't even do in my trucks anyway.

I read that in these engines, some of the conditions in which oil dilution is encouraged are cold starts and driving before reaching operating temperature. Also excessive idling and excessive engine breaking. What I've been doing is starting it and waiting for it to idle down when it enters the "closed loop," which I have to look up again because I forgot what that even means. Then I drive it easily, short shifting until operating temperature. Also it's going to be garaged all winter because I wouldn't drive a car in Michigan, in the snow so cold weather isn't a concern.

Out of curiosity, what oil would you guys suggest? I've read that the reason direct injected motors use such thin oil is because it allows the engine to reach operating temperature faster. It calls for 0w20 but I've also seen a few people say that Honda is, in some places, recommending running 0w16 to get it up to operating temperature even faster. Idk about doing that though unless I flat out confirm it.
I would recommend Pennzoil Platinum. Keep with the recommended 0W-20. It has a high detergent/dispersant additive - higher than Mobile 1.
you will notice that it gets just a smidge darker quicker than some others, but that just is proof in the “pudding” that displays its ability to suspend carbon contaminates.
 

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GDI carbon buildup only happens with irresponsible operation and ownership. Drive the car hard enough or, I don’t know, man up and take it to the track and this issue will be nonexistent.
 
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indiMjc

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GDI carbon buildup only happens with irresponsible operation and ownership. Drive the car hard enough or, I don’t know, man up and take it to the track and this issue will be nonexistent.
I actually do shift at higher rpms in this car than my truck and honestly, as much as I try to not beat on my stuff, the car is just too fun to always drive slow anyway lol. I don't really red line it all that often but the power drops off before redline anyway. It definitely makes me drive quite a bit differently.
 

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If you do beat on the car a bit and plan to tune, I'd recommend 5w-30. I'm using AMSOIL myself and love the product. Even their cheapest oil is better than factory fill and I usually do 10k km on an oil change. It does smell of fuel at that point but the car usually shows 40-50% oil wear.

Reason for 5w-30 is that's what is recommended in Euro cars and lighter weight oil is ONLY used to give better fuel efficiency, even if it's about 0.01% better, car manufaturers do everything to keep above the fuel efficiency bar they have to make. 0W-20 is NOT good for engine longevity and does a poor job at preventing detonation since it's so light. I also noticed the engine runs a bit smoother at all rpms since the switch, especially past 5k doesn't sound as tinny as it did with the OEM oil. 5W-30 is only slightly thicker than stock so it won't affect oil distribution or anything.
 

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You might want to consider the fact that your alteration of adding the catch can has created what is being caught in it. A self fulfilling prophecy. You have altered the design implemented by the Honda engineers.
This is definitely it IMO. The can is colder than the engine, so it's causing vapors to condense.
 

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I also made a lot of searching about these engines.
-Don't buy regular fuel, I'm buying Premium. 3rd party companies says detergent percentage more in Premium fuel.
-Warm up your engine at least 10-15 minutes. Even summer times I'm doing it.
-Change your oil regularly. I mean when my oil life is %30-40 I go for oil change.
- yes I also checked everywhere our engines doesn't really need oil catch can.

I'm sure there is members on forum who has over 70-80k miles on their cars. So maybe they can reply better than me. My car has 43k.
 

turbociv910

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You might want to consider the fact that your alteration of adding the catch can has created what is being caught in it. A self fulfilling prophecy. You have altered the design implemented by the Honda engineers.
Also honda - They arent going to drain this every 2500 miles, just stick it back in there and we can charge them to clean it up after 30k miles
 

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