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They call me the destroyer of piston #4 (Rebuild time)


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Well the story goes around april of 2012 my car was having some knock and oil consumption issues. Turns out piston #4 had 4 chunks of ringland broken off and piston #2 had a hige chunk that broke off. So a new 2012 ej257 block was put it. So the car was back up and running around the end of July. I was under the impression that these were good for ~375whp or so. I was at about 250whp using equal length headers (The saver of cylinder #4 yay....or so I thought). It ran good after the break in. It was noticably faster than the last block (Just basic stage 2+ headers/ebc). Now its the end of October, 3900 miles later (1200 of which were break in miles) And here we go again. Have knock and oil all over the place. Compression test shows 60psi in #4 and 150 in the rest. Leak down for #4 shows 80 percent leakage through oil cap. YAY! Tore it down and would you look at that piston #4 has 3-4 chunks broken. Its still so new the coating on the side of the pistons still look perfect.
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http://i622.photobucket.com/albums/tt307/fibtlcivic/enginelift_zpse4d38c3d.jpg

http://i622.photobucket.com/albums/tt307/fibtlcivic/boom_zpsa6ab35bf.jpg

http://i622.photobucket.com/albums/tt307/fibtlcivic/stand_zps3b23534b.jpg

http://i622.photobucket.com/albums/tt307/fibtlcivic/engine_zpse3fd9a40.jpg

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Got some oil just chillin on top of the block.

http://i622.photobucket.com/albums/tt307/fibtlcivic/oil_zpsf652b678.jpg

Heres the number 4 piston

http://i622.photobucket.com/albums/tt307/fibtlcivic/piston2_zps8d4b98ce.jpg

http://i622.photobucket.com/albums/tt307/fibtlcivic/piston1_zps8e772c25.jpg

Lifted Yo!

http://i622.photobucket.com/albums/tt307/fibtlcivic/lift_zps2d8fb068.jpg

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Did the whole motor pull and tear down in 1 day I was proud of myself (first time ever pulling/ tearing down a subaru motor). Motor pulled in 3 hours and 15 minutes. The only part I messed up on was when I pulled the drivers side head off I didnt know the valve bucket shims just fall out so they all made a nice splash into my coolant/oil bucket. Going to have to check for the clearances on those. Does anyone know the clearance on those to the cam for the exhaust side?? Is it something like .25mm or .20mm?

 

Another question. There where some metal shavings in the oil which most likely came from the ringlands. If all the bearings look good should I worry about replacing those?

What about the oil cooler?

 

Next the cylinder walls all look to be in good condition. Im looking at getting CP forged pistons. Id imagine the best route would be to get the 99.75mm pistons for a small bore and rehone over the oem sized ones just to be safe? If I do get a larger piston do I need to get a different headgasket other than stock?

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So as of right now my list for rebuild is:

 

CP Forged Pistons 99.75mm (.25mm over)

05-06 Legacy GT full gasket kit

Gates racing kevlar timing belt kit

OEM NGK sparkplugs

ARP headstuds (Input on if these are really necissary would be appriciated)

ACL rod/crank bearings if the oem ones are torn up.

And of course machine work

Would throwing a lightweight crank pulley on be a good idea? My oem one is all rusty and looks like poop.

 

Am I missing anything for the basic rebuild? Anything else that I should look at while im in the motor? Ill definently look at the pick up tube again to see she looks.

 

My goal is only around the 350whp mark so im not going for anything crazy. And maybe in the future e85 on the same turbo (looking at a blouch 20g).

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Wow, yet another ej257 bites the dust. Sorry to see that.

 

The LWCP would be ok but I'm not sure its worth it.

 

Yes, the ARP studs are worth it, mine has them as well.

 

Let the machine shop measure the block before you order pistons. You may be able to buy the stock size.

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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LWCP depends on what flywheel setup are you using. IME the LWCP is only good on a DMFW or OEM SMFW. Once you get into aftermarket LWFW the LWCP is more of a detriment on a DD than a plus. Taking too much weight off the rotating assembly is not a plus in a 3500lb+ car IMO.

 

FWIW, I took my LWCP off and sold it. I suppose I could have put it on the OBXT instead of the LGT but I'd rather just swap to a SMFW setup when the inevitable clutch swap comes.

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May be it was a bad piston from the factory...I'm sure you've read the disscussion in my "got some new stuff for engine R&R" thread a few day's ago.

 

;)

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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Yeah, it's become pretty clear as of late that the stock pistons are generally no bueno, but at only 250whp that's not a huge concern.

 

Either way, asking about who tuned the car is an extremely relevant question here.

"Bullet-proof" your OEM TMIC! <<Buy your kit here>>

 

Not currently in stock :(

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Yeah, it's become pretty clear as of late that the stock pistons are generally no bueno, but at only 250whp that's not a huge concern.

 

Either way, asking about who tuned the car is an extremely relevant question here.

 

I know, I just didn't want to sound like I was trying to place blame. But the question had to asked.

 

I would hope by now all Tuners know of the issue with #4 MAP.

 

Here's a post from my Tuner.

 

http://legacygt.com/forums/showthread.php/dangerous-cylinder-trims-5th-gen-lgts-193842.html

305,600miles 5/2012 ej257 short block, 8/2011 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. (SOLD).  CHECK your oil, these cars use it.

 

Engine Build - Click Here

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#4 map? what does that even mean?

 

stock tunes have 1 to 2* of advance set for cyl 2 and 4 above the base timing and advance tables, 4 is closest to the knock sensor, so subaru said, rather than all 4 knocking to trigger the sensor we'll advance timing in cyl 2 and 4 so the knock sensor hears it and pulls timing for all 4 cyl across the board. subaru designated 2 and 4 to "take one for the team". So inr eality, if you're going to knock, it's bound to be 2 or 4 first, that contributes to the failure of cyl 4 in these engines.

 

NOW

 

most competent tuners will zero these tables out so cyl 2 and 4 do not knock ahead of the rest(even at higher than stock boost where it can lead to damage). this is -ok- since tuners are monitoring knock and tuning for a proper and safe AFR, and appropriate timing and boost based on mods. a safe and conservative tune should not have issues with detonation unless something mechanical occurred to lean out the engine or cause bad knock (boost cut set too high? prolonged bad gas? or lower than 91 oct?) I know of many people running 350+whp on stock ej257's with quality tunes. You're playing with fire with these new shortblocks, they do not take knock very well and you must be careful and considerate of knock events.

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I got my car tuned from infamous both times. There was no knock that i logged.

 

I have a single mass oem flywheel at the moment. Ive heard some horror stories of the oem ones falling apart. So itd be more for safety.

 

And the broken ringlands were in the same spot pretty much. The top (crown i believe its called) is perfect but the 2 after are broken. Isnt it usually the top that breaks?

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Doubt it's the tuner then, lol. The stock pistons are just proving to be cruddy. If you have to do a tear down of any kind it seems that dropping in pistons is a good idea, especially if you are going to be modding at all.

"Bullet-proof" your OEM TMIC! <<Buy your kit here>>

 

Not currently in stock :(

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And to respond to the last one 91 octane was always used. And boost was set to 18.5psi but was only hitting about 14-15 in first and second and ~17 in 3rd-5th. Of course at the 3000 rpm range it hit 18.5. Im assuming this was due to the raised compression 8.2 up to 8.7.
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The ringland below the compression ring is what usually cracks. if that cracks and the engine keeps knocking, it will crack more lands and maybe even the crown. i notice in your other threads that even after you put in the new shortblock you were still knocking, and dropping WGDC. maybe you have a clogged injector or failing fuel pump causing leaning and knocking.....

 

i also noticed that you boosted to 25psi at one point :lol:

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one thing that disturbs myself and a few other tuners is that sometimes the knock sensor listening range is not widened when running higher power. this means the ecu will not detect knock when in fact the engine is knocking, and its usually up in the higher g/r load ranges where knock is deadly. knock is what killed his pistons, both on previous short block and on current. No two ways about it. there's really no other reason, it's now about finding out why it knocked.

 

my question is, and will be the kicker. was the same tune (map) used on both engines? Also, fun fact of the day, COMMONLY when an injector is failing there are misfires here or there. I suppose it could be possible that the injector is failing in some crazy way to lean that cyl out, but again, you'd probably have some misfires here or there and/or the knock sensor would pick up knock. the fuel pump may be problematic and they usually cause a lean out condition in higher rpm/loads, however if the listening ranges aren't appropriate in the higher loads/rpms, a failing pump will cause serious det and the ecu won't be listening for knock, thus your engine will continue to det itself to pieces and the ecu won't know about it.

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one thing that disturbs myself and a few other tuners is that sometimes the knock sensor listening range is not widened when running higher power. this means the ecu will not detect knock when in fact the engine is knocking, and its usually up in the higher g/r load ranges where knock is deadly. knock is what killed his pistons, both on previous short block and on current. No two ways about it. there's really no other reason, it's now about finding out why it knocked.

 

my question is, and will be the kicker. was the same tune (map) used on both engines? Also, fun fact of the day, COMMONLY when an injector is failing there are misfires here or there. I suppose it could be possible that the injector is failing in some crazy way to lean that cyl out, but again, you'd probably have some misfires here or there and/or the knock sensor would pick up knock. the fuel pump may be problematic and they usually cause a lean out condition in higher rpm/loads, however if the listening ranges aren't appropriate in the higher loads/rpms, a failing pump will cause serious det and the ecu won't be listening for knock, thus your engine will continue to det itself to pieces and the ecu won't know about it.

 

:whore:

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