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Old 07-20-2010, 03:56 PM   #1
daddyphatsax304
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Join Date: May 2010
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02' WRX Wagon
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Default Stock pistons...cracked ringlands...what next???

I have a 2002 WRX Wagon and my recently purchased car failed a compression test as expected (great deal) so i decided to tear into the motor and find the problem. Cracked ringlands on #4 cylinder piston is what i found...and everything else in the engine looks great...i have yet to get the head inspected but am not expecting it to be damaged...so was wondering what exactly could have caused this and what i can do to prevent it from happening again?!?

My car was purchased w/ a ebay up and down pipe set up...i cant find any manufacturer stamp on either of them...
also has CAI
STI TMIC
Stock Turbo
75k miles on motor...
Everything else is pretty much OEM...
almost certain the car was tuned and it ran really well even w/ the blowed up piston...im guessing the tune was just pushing the car to its limits???


any input would help and thanx in advance!

=)
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Old 07-20-2010, 04:07 PM   #2
erikm
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Knock (detonation) = cracked ringlands
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Old 07-20-2010, 04:29 PM   #3
Concillian
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Which could be caused by one of the following:

1) Consistent use of gas lower octane than premium
2) modding boost higher than stock without proper ECU tuning
3) modding without proper ECU tuning
4) bad or too agressive ECU tuning

If you re-build the engine and take it somewhere reputable that tunes Subarus and ask for a conservative tune your car will run nicely for a long time. I believe P & L is in your area.

It's reasonably common for EJ205 heads to have hairline cracks from the spark plug holes to the valves, presumably caused by overtightening spark plugs. I've never seen a case where these caused issues, but some people feel more comfortable replacing. If staying on stock turbo I don't think I'd worry about them if your heads have them.
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Old 07-20-2010, 07:23 PM   #4
daddyphatsax304
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so yeah from what ive gathered in my reading...the car was probably pushed beyond its capabilities...it seems very quick for having as few mods as it does...i never experienced any detonation in the 2 months ive had the car...alot of misfires and misfire CEL's...but i figured that was caused by the blown piston.

in replacing the piston and rings and getting the head checked out...is there anything else i am missing??

will the car be ok without a tune for a bit or am i risking damage again just by driving it for a little until i can get it tuned??

i was considering an AP or streettuner as well...something that i can upload custom maps with...dont plan on making changes myself...but due to the lack of tuners in this area...i was considering something along those lines.

dont plan on any mods w/ this car for a few yet...next mods will certainly be to the fuel system and hopefully upgrade on the pistons and bearings if any.
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Old 07-20-2010, 10:14 PM   #5
Concillian
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Well, you have to make sure the cracked ringlands didn't score the cylinders when you have the block out. You can replace with stock pistons, with forged as an option depending on future plans. If heads are off, there are tons of options "while they're off" but most are pretty expensive, and won't give much gain on stock turbo.

As for tuning, you have two options:
1) take a trip somewhere like Chicago and get tuned there
2) buy a Tactrix cable, laptop and wideband O2 sensor and use someone like Phatbotti, Euilibrium Tuning, or someone else who does e-tuning via opensource. (Phatbotti and EQ are both NASIOC vendors)

Tactrix is a much cheaper option than AP for mostly the same functionality because it's open-source instead of commercial, like $200 for the cable / adapter plus $2-300 for a wideband, and e-tuning is between $150 and 350 or so.
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Old 07-21-2010, 12:08 AM   #6
Chi_San
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Run 85 octane gasoline at sea level. That'll do it.
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Old 07-21-2010, 07:40 AM   #7
daddyphatsax304
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cool...tactrix was almost my first purchase after buying this car and i decided to wait till i learned a lil more...i didnt think i could flash or upload to the ecu w/ it though

and since i bought this car its only had 93 sunoco ultra in it...but who knows about the joker i got it from.
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Old 07-21-2010, 11:58 AM   #8
daddyphatsax304
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would my oil pump under performing have anything at all to do w/ the plowed piston??

i would think so but im really just trying 2 use logic as i am a scoob noob incase u hadnt noticed...

=)
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Old 07-21-2010, 02:00 PM   #9
Concillian
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Oiling issues usually result in spun rod bearing on these motors. The bearings are on the narrow side, and spun bearing is by far the most common engine failure issue seen in the EJ205s.

2.0L ringlands don't go on the stock turbo unless there's pretty major det issues, there's really very little other explanation. Typically the rods are considered the weakest point for larger turbo big HP. Pistons aren't a strong point, but there are other failure modes more commonly seen in the EJ205.

2.5L ringlands tend to have more issues than 2.0L ringlands. I don't know if this is because you tend to see 2.5L engines at higher HP levels so you see more failures just because people are running cast pistons higher, or if it's due to the design difference in the pistons with lower comp height (distance between pin and top surface) resulting in less area for rings or dish shape allowing more heat into the ring area, or something like that. Also the 2.5L engines have stronger rods, so people are more comfortable pushing them without fear of punching a hole in the block.
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Old 07-21-2010, 02:32 PM   #10
daddyphatsax304
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gotcha...thanx 4 the input...i was well aware of the relationship these motors have w/ the oil pump and the bearings but wasnt sure if that could lead to cracked ringlands or not.
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Old 07-22-2010, 12:54 PM   #11
daddyphatsax304
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Ok so...in inspecting the head of the same side as the blowed piston i noticed the tiny cracks near the spark plug threads that ive read so much about....

they are so small i could not even feel them w/ my finger nail...and ive heard that these are pretty much a non-issue and are very common...

not very nice...
i was planning on repairing the blowed up piston and calling it a day for now...but the more problems i continue to run into the more likely i am to do an all out build on this block

ugh.
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Old 07-22-2010, 12:56 PM   #12
Strider327
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Time for at least a 2.5 Shortblock with forged pistons.
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Old 07-22-2010, 12:58 PM   #13
daddyphatsax304
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Aspen White

Default

Quote:
Originally Posted by Concillian View Post
Which could be caused by one of the following:

1) Consistent use of gas lower octane than premium
2) modding boost higher than stock without proper ECU tuning
3) modding without proper ECU tuning
4) bad or too agressive ECU tuning

If you re-build the engine and take it somewhere reputable that tunes Subarus and ask for a conservative tune your car will run nicely for a long time. I believe P & L is in your area.

It's reasonably common for EJ205 heads to have hairline cracks from the spark plug holes to the valves, presumably caused by overtightening spark plugs. I've never seen a case where these caused issues, but some people feel more comfortable replacing. If staying on stock turbo I don't think I'd worry about them if your heads have them.
i think i read somewhere a few months ago that P&L shut down shop...
may have been another reputable tuner but i recall the thread and im guessing it was P&L
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