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XV Crosstrek 2014 Premium 2.0i 6MT
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So, a 2014 port injected engine would have totally different build-up characteristics than a 2018+ GDI. Just saying you can't compare your results with the newer engines.
I just realized when someone else commented on here. You have a 2014 port injected engine. 🤦‍♂️ Sorry but your catch can experience on your Subaru is irrelevant in this case... I would not run a catch can in a port injected engine. Not necessary at all! We can at least agree on that.
So, FB20d and FB20b are apple and oranges but using data from turbocharged engines to confirm your beliefs is ''enough said''? It doesn't matter that my engine is direct or ported injection, that has no effect on the amount of blowby you'll get in the crankcase. I told you that I have one of the FB20b models that has the worst history of oil consumption. Of course the FB20d will be different, but do you really think that after 10 years of selling that engine, Subaru has not only not resolved the issue but evolved their design into letting more blowby gasses through? Comon guys...

On my engine there is a second breather that goes in before the throttle body, hence the existence of dual catch can setups. The intake manifold is harder to inspect but in my case results were the same (clean).

I'm not sure going by a clean throttle body means clean valves.
You are right, there are other causes of carbon build-up that are not related to blowby gasses recirculation. But if everything between your return lines and your valves is clean, then it probably means that this is not a significant source of buildup.

My local subaru shop recommends walnut blasting treatment to remove carbon build-up on DIT engines, you guys should keep your money for that instead.
 

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2022 Crosstrek Premium 6 Speed MT
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123 Posts
So, FB20d and FB20b are apple and oranges but using data from turbocharged engines to confirm your beliefs is ''enough said''? It doesn't matter that my engine is direct or ported injection, that has no effect on the amount of blowby you'll get in the crankcase. I told you that I have one of the FB20b models that has the worst history of oil consumption. Of course the FB20d will be different, but do you really think that after 10 years of selling that engine, Subaru has not only not resolved the issue but evolved their design into letting more blowby gasses through? Comon guys...

On my engine there is a second breather that goes in before the throttle body, hence the existence of dual catch can setups. The intake manifold is harder to inspect but in my case results were the same (clean).


You are right, there are other causes of carbon build-up that are not related to blowby gasses recirculation. But if everything between your return lines and your valves is clean, then it probably means that this is not a significant source of buildup.

My local subaru shop recommends walnut blasting treatment to remove carbon build-up on DIT engines, you guys should keep your money for that instead.
😂😂 Ok we are done here. Not going to argue with you or waste my time. You are entitled to your opinion and it is ok if we disagree. You're not going to convince me otherwise and neither am I so let's call it a truce, shall we?😎
 

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2022 Crosstrek Premium 6 Speed MT
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123 Posts
So, FB20d and FB20b are apple and oranges but using data from turbocharged engines to confirm your beliefs is ''enough said''? It doesn't matter that my engine is direct or ported injection, that has no effect on the amount of blowby you'll get in the crankcase. I told you that I have one of the FB20b models that has the worst history of oil consumption. Of course the FB20d will be different, but do you really think that after 10 years of selling that engine, Subaru has not only not resolved the issue but evolved their design into letting more blowby gasses through? Comon guys...

On my engine there is a second breather that goes in before the throttle body, hence the existence of dual catch can setups. The intake manifold is harder to inspect but in my case results were the same (clean).


You are right, there are other causes of carbon build-up that are not related to blowby gasses recirculation. But if everything between your return lines and your valves is clean, then it probably means that this is not a significant source of buildup.

My local subaru shop recommends walnut blasting treatment to remove carbon build-up on DIT engines, you guys should keep your money for that instead.
I'll revisit this thread in 10 years and 100,000 miles with a photo of my intake valves perfectly clean with no need for the local Subaru shop recommended "walnut blasting". I thought walnut blasting was for cleaning dirty hands, or is that walnut scrub?🤷‍♂️😂
 

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XV Crosstrek 2014 Premium 2.0i 6MT
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220 Posts
Yeah, no problem buddy. 😁

'll revisit this thread in 10 years and 100,000 miles with a photo of my intake valves perfectly clean with no need for the local Subaru shop recommended "walnut blasting".
You're funny 😅 Even if that was possible, you'd have no way of attibuting that result to your catch can, that's scientific reasoning.

But seriously, those worried about carbon buid-up on direct injection engines should look at walnut blasting, the results speak by themselves:
Hand Light Automotive lighting Jaw Automotive tire
 

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Yeah, no problem buddy. 😁


You're funny 😅 Even if that was possible, you'd have no way of attibuting that result to your catch can, that's scientific reasoning.

But seriously, those worried about carbon buid-up on direct injection engines should look at walnut blasting, the results speak by themselves:
View attachment 311209

that looks like a before and after of my titanium coffee cup
 

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2022 Crosstrek Premium 6 Speed MT
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123 Posts
Yeah, no problem buddy. 😁


You're funny 😅 Even if that was possible, you'd have no way of attibuting that result to your catch can, that's scientific reasoning.

But seriously, those worried about carbon buid-up on direct injection engines should look at walnut blasting, the results speak by themselves:
View attachment 311209
😂 Pretty sure a catch can will be somewhere in between a walnut blast and nothing. I'm good with the $200 spent for the "in between"
that looks like a before and after of my titanium coffee cup
😂Or my hands before and after doing an "in frame" rebuild on an MTU Diesel engine.😂
 

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2022 Crosstrek Premium 6 Speed MT
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Don't the 2021+ 2.5's already come with an OEM version of an oil catch can?
Stop the Video @ 0:31
Please correct me if I am making the wrong assumption.
I don't believe that is correct information that it is an air oil separator. You can't believe everything you see on YouTube. I have a catch can installed in my '22 Crosstrek with a 2.0 and I get a couple ounces of smelly oil residue liquid every 1500 miles. When I installed the catch can at about 100 miles on the odometer, the line from the PCV to the intake already had oil fluid into it. If an air oil separator came stock from the factory, I'm pretty sure this line should be dry. Hopefully others will chime in here.
 

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2022 Crosstrek Premium 6 Speed MT
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No that's not an AOS. It doesn't have a drain, so if it was, it would just fill up and eventually run into the throttle anyways.
That's why I like the catch can on my 2022 Crosstrek. I empty out 2oz or so of nasty smelling oil/fuel liquid every 1000 miles or so that doesn't go in the intake.👍 I'm going to pull the intake manifold at 15000 and see how well my catch can is working. Lots of differing opinions/controversy on this one for sure.
 

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2022 Crosstrek Limited
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140 Posts
Did the install of a catch can void your warranty on a 2022 Subaru?
I have one rolling around in the trunk of the XJR. But cleaned the intercoolers two months ago and there was only a little oil and no dreaded sludge. Was hoping to keep the intercoolers clean and keep oil out of the cats.
 

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Did the install of a catch can void your warranty on a 2022 Subaru?
I have one rolling around in the trunk of the XJR. But cleaned the intercoolers two months ago and there was only a little oil and no dreaded sludge. Was hoping to keep the intercoolers clean and keep oil out of the cats.
I have no clue but I will return it back to stock if I ever need warranty work. Otherwise my Crosstrek will never see the inside of a Stealership service department! I do all my own maintenance and repairs.
 

· Butchin' Moderator
2018 Orange Subaru Crosstrek Limited
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Something occurs to me here. Stepping away from the question of intake valves for a moment. If DI forces all the cleaning agents into the cylinder (at a higher pressure as well?) then wouldn't the expectation be that DI engines would have cleaner combustion chambers than others without this feature? Has anyone here actually been forced to repair their heads due to carbon fouling of the intake valves and recorded this? Frankly it seems plausible that the material entering the engine through the PCV valve would certainly be "dirty." I'm unaware of how much blowby is re burned by modern PCV systems.
 

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Something occurs to me here. Stepping away from the question of intake valves for a moment. If DI forces all the cleaning agents into the cylinder (at a higher pressure as well?) then wouldn't the expectation be that DI engines would have cleaner combustion chambers than others without this feature? Has anyone here actually been forced to repair their heads due to carbon fouling of the intake valves and recorded this? Frankly it seems plausible that the material entering the engine through the PCV valve would certainly be "dirty." I'm unaware of how much blowby is re burned by modern PCV systems.
I believe you are right that DI combustion chamber is cleaner, but the intake valve problem may cause performance issue when it has thick deposit. I suspect the Subaru boxer has stronger oil pump that may affect the amount of blowby since I can see more oil comes out from oil cap when the engine is on compared to my other cars.
 

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I'm wondering how my intake valves will get any build up at all on the back side of valves with me having installed a catch can as soon as I took delivery. Isn't only fresh air from the intake going to the valves? It appears as though my catch can is stopping 100% of the oil residue going into the intake. I have checked the line going from the catch can to the intake and it is and has always been bone dry. As I mentioned before, the liquid I drain from the catch can every 1-1500 miles is a nasty smelling fuel/oil mixture. I'm glad this liquid is not going into my intake!
Drinkware Liquid Food storage containers Drinking water Mason jar
 

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There’s also EGR (exhaust gas recirculation.) Soot and carbon can get on the back side of the intake valves from that as well.

I’ve also heard that oil seeping through the valve guides can cause carbon buildup as well.

Anyway, from my experience with VWs, catch cans may help a bit, but they’re not a 100% solution.
 

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2022 Crosstrek Premium 6 Speed MT
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There’s also EGR (exhaust gas recirculation.) Soot and carbon can get on the back side of the intake valves from that as well.

I’ve also heard that oil seeping through the valve guides can cause carbon buildup as well.

Anyway, from my experience with VWs, catch cans may help a bit, but they’re not a 100% solution.
Ah yeah I forgot about the EGR! I need to do an EGR delete now. Lol EGRs are definitely dirty!
 

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I'm wondering how my intake valves will get any build up at all on the back side of valves with me having installed a catch can as soon as I took delivery. Isn't only fresh air from the intake going to the valves? It appears as though my catch can is stopping 100% of the oil residue going into the intake. I have checked the line going from the catch can to the intake and it is and has always been bone dry. As I mentioned before, the liquid I drain from the catch can every 1-1500 miles is a nasty smelling fuel/oil mixture. I'm glad this liquid is not going into my intake!
View attachment 312180
Dream on. There is zero evidence that catch cans do anything.
Two things known to work are walnut blasting and intake jvalve solvents like CRC. I do that every 7/8 K miles to both my foresters and at 50K miles I am having the walnut shell blasting done.
 
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