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Old 06-24-2020, 09:50 PM   #1
cashrolling
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Default Oil consumption, pistons help, WHAT TO DO????

Ok. I need some input. My car burns about 1 quarter of oil in 1000miles. Alert from that everything is perfectly fine. My mechanic suggested to change pistons to forged ones, stock size drop ins. But after a small research I understand that's a bad idea, that to do it correctly I should take the engine out and rebore the walls to match pistons. My question is, if I instead put back in stock pistons, should I still rebore the walls or I can just drop them in? What should I do?
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Old 06-24-2020, 10:51 PM   #2
blue wrench
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Find another mechanic. It could be a number of things causing your issue but you could atleast start with a compression and leakdown test. Have the cylinders checked out with a boroscope while you're that far but you may need to ultimately have the engine torn down and inspected before throwing parts at it.
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Old 06-24-2020, 11:25 PM   #3
cashrolling
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Quote:
Originally Posted by blue wrench View Post
Find another mechanic. It could be a number of things causing your issue but you could atleast start with a compression and leakdown test. Have the cylinders checked out with a boroscope while you're that far but you may need to ultimately have the engine torn down and inspected before throwing parts at it.
I agree. The Subaru specialist told me he thinks that the Piston rings are causing the oil to go, as we can't see any other place where oil leak. What else should I check? BTW, no smoke coming out of the exhaust
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Old 06-25-2020, 04:03 AM   #4
bobjr94
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What are your power goals, how much boost are you running now ? And how many miles on your motor ?

Yon need to get the heads off before you really know how your cylinders look. If they look good, you might be able to drop in new pistons (stock or forged) with no machine work. If the walls are worn and shiny (but not scratched or gouged) the block should come apart so it can get a quick hone. I have had good luck running a ballhone though them to freshen up a cylinder for a re-ring

If you are over 20lbs maybe go forged, but they aren't as good for daily driving with stock boost levels. In that case I would just reuse the old pistons with new rings.

And there are several places oil can leak, valve seals, turbo, plugged breather lines, bad pcv valve.
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Old 06-25-2020, 09:06 AM   #5
BeastianSTI
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Usually, you'll see some sort of indication of where the oil is going. There are different times of engine operation when you might see the smoke, which can give you an idea of where it's all going.

Some times to check:

- First start up (obvious)
- After the engine comes up to temp
- After running the car, shutting it off for a while, and starting it back up (valve stem seals, possibly turbo seals)
- During spirited driving or right afterward

You could also get one of those flexible cameras and stick it in the spark plug hole of each cylinder to see what the top of the pistons look like. While this isn't a comprehensive diagnostic, if you see one piston is much blacker than the others, it could indicate that the oil rings on that cylinder's piston is fried.

If you're thinking about getting forged pistons, consider whether or not you can afford to let the engine fully warm up before driving it. I wait every time I start my car, but it's not my daily driver anymore.

Should you decide to go the aftermarket piston route, and you aren't planning on shooting for 600hp or anything, you might consider avoiding the 2618 alloy forged piston, and go with a 4032 alloy. The 4032 alloy (e.g. Mahle) has different expansion properties which are closer to the stock piston's expansion rate than the 2618 (e.g. CP piston)
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Old 06-25-2020, 11:56 AM   #6
cashrolling
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Thanks for ur replies. My car is running 472whp, with stock motor and it has 26k kilometers, pretty new. Keep in mind it's a jdm 2013 spec c (ej207). I would drop in forged pistons just for safety, even thou it's been reliable, I have been running that power for over 12k km.most of it track or fast driving. The only time I see some smoke coming out of the exhaust is while revving at 7000rpm with lunch control. Would that be any indication of anything going on?
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