('14+) Carbon buildup and cleaning on FA20DIT - Subaru Forester Owners Forum
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post #1 of 166 (permalink) Old 03-03-2016, 11:47 AM Thread Starter
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Carbon buildup and cleaning on FA20DIT

Admin note: This is a split off discussion from the following thread: RECALL: select 14'-15' 2.0XT Foresters - ECM update for pre-ignition (Merged Thread)

Update to the update:

Service rep called about 3 or so, stated that the upper engine cleaning seems to have worked, the leakdown now is within spec. Subaru wants them to hold the car overnight and do another leakdown tomorrow when engine is cold to comfirm.

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post #2 of 166 (permalink) Old 03-03-2016, 12:08 PM
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Originally Posted by boomvang View Post
Update to the update:

Service rep called about 3 or so, stated that the upper engine cleaning seems to have worked, the leakdown now is within spec. Subaru wants them to hold the car overnight and do another leakdown tomorrow when engine is cold to comfirm.
Whoa.

I went back and read your old post. 50% leakdown cured by an "upper engine cleaning"? I don't buy it.

I'd ask more questions.


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post #3 of 166 (permalink) Old 03-03-2016, 02:03 PM Thread Starter
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Whoa.

I went back and read your old post. 50% leakdown cured by an "upper engine cleaning"? I don't buy it.

I'd ask more questions.
You bet I will, I am very curious about the definite gas smell in the oil, coupled with the increase in oil level. I will have them smell the oil and see if they agree. I plan on testing the oil, assuming that I am satified with the answers I get.
At least I have a record of this issue, in case it crops up again.
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post #4 of 166 (permalink) Old 03-04-2016, 12:06 AM
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Quote:
Originally Posted by Athens Turbaru View Post
Quote:
Originally Posted by boomvang View Post
Update to the update:

Service rep called about 3 or so, stated that the upper engine cleaning seems to have worked, the leakdown now is within spec. Subaru wants them to hold the car overnight and do another leakdown tomorrow when engine is cold to comfirm.
Whoa.

I went back and read your old post. 50% leakdown cured by an "upper engine cleaning"? I don't buy it.

I'd ask more questions.
Actually this is quite plausible.

Remember DI engines are highly prone to carbon deposits and issues with the vavles. A proper cleaning may be all that is required to pass the leak down.
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post #5 of 166 (permalink) Old 03-04-2016, 08:35 AM
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Exclamation Carbon buildup and cleaning on FA20DIT

Quote:
Originally Posted by Novablue View Post
Actually this is quite plausible.

Remember DI engines are highly prone to carbon deposits and issues with the vavles. A proper cleaning may be all that is required to pass the leak down.
just for my edification, why are DI engines more prone to carbon build up? i would have thought DI systems are more determinate and provide more efficient burns, hence the rationale for switching to DI?

thanks
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post #6 of 166 (permalink) Old 03-04-2016, 10:07 AM
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just for my edification, why are DI engines more prone to carbon build up? i would have thought DI systems are more determinate and provide more efficient burns, hence the rationale for switching to DI?

thanks
With a port injected engine, fuel cleans the back of the intake values. In a DI engine, this no longer happens. That can lead to carbon build up on the back of the valves.
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post #7 of 166 (permalink) Old 03-04-2016, 11:17 AM
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Going 10k+ miles between oil changes on a turbo car, regardless of the quality of synthetic oil you use, sounds like a really bad idea.

Be careful.
I do check the oil levels regularly and send in a sample for a UOA with every change. So far so good. The FXT doesn't get abused, so I'm not concerned at all.

Carbon build-up on the other hand... I wish Toyota with share it's self cleaning D4-S tech with Subaru. IIRC the BRZ with it's Port + Direct injected tech from Toyota will not have carbon build up problems. I think the new Tacomas also have self cleaning injectors...
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post #8 of 166 (permalink) Old 03-04-2016, 12:07 PM
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I do check the oil levels regularly and send in a sample for a UOA with every change. So far so good. The FXT doesn't get abused, so I'm not concerned at all.

Carbon build-up on the other hand... I wish Toyota with share it's self cleaning D4-S tech with Subaru. IIRC the BRZ with it's Port + Direct injected tech from Toyota will not have carbon build up problems. I think the new Tacomas also have self cleaning injectors...
Wow. Since you're getting a sample analyzed each time I can't argue with you. If you stay out of the turbo most of the time, avoiding the thermal shock imposed by it, I guess you can treat it almost like a NA and go 10k miles, but man, that scares me. Glad it works for you.

Do you perform some variation of an Italian Tuneup just prior to changing? It might at least help with carbon buildup.

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post #9 of 166 (permalink) Old 03-04-2016, 10:47 PM
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Quote:
Originally Posted by Novablue View Post
Actually this is quite plausible.

Remember DI engines are highly prone to carbon deposits and issues with the vavles. A proper cleaning may be all that is required to pass the leak down.
just for my edification, why are DI engines more prone to carbon build up? i would have thought DI systems are more determinate and provide more efficient burns, hence the rationale for switching to DI?

thanks
This was posted on the site before but as they say, a picture is worth a thousand words...

http://forums.nasioc.com/forums/show....php?t=2752551

For what it's worth, we don't know anything yet for sure. But with this recall and a few anecdotal reports of build up, it looks like regular cleanings may be needed.
It's too bad too because Subaru said they designed this system to not have carbon issues.

And as stated in another relpy, normally the fuel washes over the vavles in a more traditional engine. But with DI that doesn't happen and build up can occur. When that carbon finds its way in the cylinder it can cause you issues.

I'm kinda curious about all the DI's out there now. Kia, Toyota, Ford, all the major players are doing DI. But not ever DI engines has known issues. It's worth noting VW (and BMW?) and a few other early DI engines were well known for carbon issues. Some needed cleanings every 10k miles or less or they would not even run!
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post #10 of 166 (permalink) Old 03-05-2016, 09:13 AM
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Not really sure why they went against the dual injection setup that is in the BRZ/FRS....best of both worlds....


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post #11 of 166 (permalink) Old 03-05-2016, 10:40 AM
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Not really sure why they went against the dual injection setup that is in the BRZ/FRS....best of both worlds....
Toyota owns the patent. I believe in the last year or so they have made it freely available to others however.
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post #12 of 166 (permalink) Old 03-05-2016, 07:06 PM
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Revising the Subaru suggested maintenance schedule

Quote:
Originally Posted by Novablue View Post
This was posted on the site before but as they say, a picture is worth a thousand words...

Walnut Blasting - 2015 Subaru WRX, 43k miles - NASIOC

For what it's worth, we don't know anything yet for sure. But with this recall and a few anecdotal reports of build up, it looks like regular cleanings may be needed.
It's too bad too because Subaru said they designed this system to not have carbon issues.

And as stated in another relpy, normally the fuel washes over the vavles in a more traditional engine. But with DI that doesn't happen and build up can occur. When that carbon finds its way in the cylinder it can cause you issues.

I'm kinda curious about all the DI's out there now. Kia, Toyota, Ford, all the major players are doing DI. But not ever DI engines has known issues. It's worth noting VW (and BMW?) and a few other early DI engines were well known for carbon issues. Some needed cleanings every 10k miles or less or they would not even run!
Novablue,

base on the picture of your Link and those 2 links:
FA20D Subaru Engine

https://www.youtube.com/watch?v=PS8riAae_bM

I'd say the 60k miles maintenance should includes an Intake valves cleaning and a Leakdown test along the Sparkplugs replacement.
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post #13 of 166 (permalink) Old 03-05-2016, 11:26 PM
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Originally Posted by valstan View Post
Quote:
Originally Posted by Novablue View Post
This was posted on the site before but as they say, a picture is worth a thousand words...

Walnut Blasting - 2015 Subaru WRX, 43k miles - NASIOC

For what it's worth, we don't know anything yet for sure. But with this recall and a few anecdotal reports of build up, it looks like regular cleanings may be needed.
It's too bad too because Subaru said they designed this system to not have carbon issues.

And as stated in another relpy, normally the fuel washes over the vavles in a more traditional engine. But with DI that doesn't happen and build up can occur. When that carbon finds its way in the cylinder it can cause you issues.

I'm kinda curious about all the DI's out there now. Kia, Toyota, Ford, all the major players are doing DI. But not ever DI engines has known issues. It's worth noting VW (and BMW?) and a few other early DI engines were well known for carbon issues. Some needed cleanings every 10k miles or less or they would not even run!
Novablue,

base on the picture of your Link and those 2 links:
FA20D Subaru Engine

https://www.youtube.com/watch?v=PS8riAae_bM

I'd say the 60k miles maintenance should includes an Intake valves cleaning and a Leakdown test along the Sparkplugs replacement.
I summary:

All DI motors will have carbon issues. No design to date has eliminated the problem. A few designs are doing things to minimize and reduce the problem but it's not eliminated...
Even the Toyota system was mentioned.

So now I'm looking at walnut blasters...


Looks like you can get set up really cheap. $100 at Harbor Frieght. And I'm designing a booth...
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post #14 of 166 (permalink) Old 03-06-2016, 12:04 AM
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@Novablue ....Can I be included....... we can call ourselves "associates in walnut blasting".....

S#....it's what makes a Subaru....A SUBARU!
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post #15 of 166 (permalink) Old 03-06-2016, 03:51 AM
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If your Subie ain't.... running good.... Who you gonna call??... Walnut Blasters!
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