Split Piston - Engine tear-down! LOT's of Pics Inside

stashtrey · 10-18-2015, 09:32 AM

Some of you may have seen my thread about my #2 piston cracking and my subsequent engine swap nightmare.

I finally got the engine home last week and on a stand to begin pulling it apart for inspection. I replaced the motor as there was an assumption that they cylinder wall would be damaged. Well... it appears to have come out unscathed. Very odd failure of the piston.

As you can see from the photos... the piston cracked all the way down each side to the bottom outer edge on each side. Interestingly enough, the rings were undamaged and the cylinder wall looks as it should and as all the others.

The head looks good as well!

Plans previously were to part it out and try to recoup as much $$ to offset the large hole in my wallet after the swap. Now I need to rethink my strategy given this new discovery.

Pretty fun tearing the motor apart! Very cool to have a full scale model of the exact motor in my car... sitting on a stand in my garage!

Enjoy the pics and I look forward to expert opinions and suggestions on what YOU would do in this situation.

Cheers!

noorj · 10-18-2015, 10:57 AM

preignition is a nasty thing

Miller335 · 10-18-2015, 12:13 PM

Quote:

Originally Posted by noorj

preignition is a nasty thing

I doubt the piston itself was the weak link if that was the cause.

stanlalee · 10-18-2015, 06:14 PM

That just looks like a faulty piston not up to the task (well faulty for 400+ whp use lol). Way too clean/non-destructive for detonation failure.

apme123 · 10-18-2015, 11:13 PM

Quote:

Originally Posted by stashtrey

Some of you may have seen my thread about my #2 piston cracking and my subsequent engine swap nightmare.

I finally got the engine home last week and on a stand to begin pulling it apart for inspection. I replaced the motor as there was an assumption that they cylinder wall would be damaged. Well... it appears to have come out unscathed. Very odd failure of the piston.

As you can see from the photos... the piston cracked all the way down each side to the bottom outer edge on each side. Interestingly enough, the rings were undamaged and the cylinder wall looks as it should and as all the others.

The head looks good as well!

Plans previously were to part it out and try to recoup as much $$ to offset the large hole in my wallet after the swap. Now I need to rethink my strategy given this new discovery.

Pretty fun tearing the motor apart! Very cool to have a full scale model of the exact motor in my car... sitting on a stand in my garage!

Enjoy the pics and I look forward to expert opinions and suggestions on what YOU would do in this situation.

Cheers!

Just looks like it was a casting defect that made it split, I don't see any pre detonation on top. It looks like the block and head could be salvaged, I would rebuild and sell it.

KiwiRD · 10-19-2015, 02:41 PM

Now take that thing to a metallurgist and ask if it's forged.........

wgknestrick · 10-19-2015, 03:13 PM

cracked piston = forged?

theweebabySeamus · 10-19-2015, 03:15 PM

Replace piston (or all pistons), reassemble.

KiwiRD · 10-19-2015, 03:18 PM

Quote:

Originally Posted by wgknestrick

cracked piston = forged?

That's kind of what I was getting at

noorj · 10-19-2015, 07:31 PM

preignition causes a disruption in the boundary layer, which then causes extremely high surfaces temp on the piston and reduced surface strength and a fracture at the center of the piston. if it were a casting defect it would have failed after a very few amount of miles

332ijunkie · 10-19-2015, 08:40 PM

I see casting/manufacturing defects surface after 100k somewhat often. Have replaced a few single valve springs on a number of BMW engines. Just 1 spring randomly decides to break, rest are perfectly fine for another 200k, that looks to be the case here.

derryck · 10-20-2015, 07:52 AM

That'll buff out...

stashtrey · 10-20-2015, 10:46 AM

Quote:

Originally Posted by derryck

That'll buff out...

Lmao!

dreyo27 · 10-20-2015, 02:41 PM

seems like the perfect time to build the engine with lower CP forged pistons.

stashtrey · 10-20-2015, 08:22 PM

Pulled the wrist pin and snapped some pics of the crack from the inside. Really hard to believe it held together like that considering all the heat and violent motion inside.

Miller335 · 10-20-2015, 08:45 PM

That's some craziness.
Thanks for sharing pics.

so?confused · 10-20-2015, 08:50 PM

no damage to cylinder wall?

Fred_Boosted · 10-20-2015, 09:11 PM

Very nice photo sharing there. Put forged rod and piston in and lower the compression ratio for some hybrid turbo or single turbo fun?

stashtrey · 10-20-2015, 09:58 PM

Quote:

Originally Posted by so?confused

no damage to cylinder wall?

No damage at all. Pics of cylinder in OP....all the machining lines are there and undisturbed. Crazy, eh!?

Jaronbwall · 10-22-2015, 08:44 AM

It surprised me how thin the spacing is between the cylinder walls.
Are you going to build the motor now with forged components?

10-18-2015, 09:32 AM	#1
stashtrey Lieutenant Colonel 294 Rep 1,834 Posts Drives: 08 E90 335xi TiAg Join Date: Dec 2012 Location: Sacramento, CA iTrader: (8) Garage List 2008 E90 335xi Sedan [0.00]	Split Piston - Engine tear-down! LOT's of Pics Inside Some of you may have seen my thread about my #2 piston cracking and my subsequent engine swap nightmare. I finally got the engine home last week and on a stand to begin pulling it apart for inspection. I replaced the motor as there was an assumption that they cylinder wall would be damaged. Well... it appears to have come out unscathed. Very odd failure of the piston. As you can see from the photos... the piston cracked all the way down each side to the bottom outer edge on each side. Interestingly enough, the rings were undamaged and the cylinder wall looks as it should and as all the others. The head looks good as well! Plans previously were to part it out and try to recoup as much $$ to offset the large hole in my wallet after the swap. Now I need to rethink my strategy given this new discovery. Pretty fun tearing the motor apart! Very cool to have a full scale model of the exact motor in my car... sitting on a stand in my garage! Enjoy the pics and I look forward to expert opinions and suggestions on what YOU would do in this situation. Cheers! Attached Images __________________ E90 2008 335xi - TiAg - AMS FMIC - BMW PE - BMS OCC - ER CP - KW V3 - Vorshlag Camber Plates - AG M359 18" PSS - Alpina Flash - RB PCV Valvle - AFE Intake - Walbro LPFP
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10-18-2015, 10:57 AM	#2
noorj calibrator 12 Rep 80 Posts Drives: 2007 E92 335i Join Date: May 2014 Location: Detroit iTrader: (1)	preignition is a nasty thing Last edited by noorj; 10-18-2015 at 11:18 AM..
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10-18-2015, 06:14 PM	#4
stanlalee Major 261 Rep 1,093 Posts Drives: 07' E92 335i manual Join Date: Oct 2013 Location: Newport News, Va iTrader: (0)	That just looks like a faulty piston not up to the task (well faulty for 400+ whp use lol). Way too clean/non-destructive for detonation failure.
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10-19-2015, 02:41 PM	#6
KiwiRD Captain 152 Rep 645 Posts Drives: 2007 E90 335i M Sport 6MT Join Date: Nov 2014 Location: Auckland, New Zealand iTrader: (0)	Now take that thing to a metallurgist and ask if it's forged.........
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10-19-2015, 03:13 PM	#7
wgknestrick Private First Class 43 Rep 133 Posts Drives: 2011 335 xdrive Join Date: Dec 2014 Location: Lancaster PA iTrader: (0)	cracked piston = forged?
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10-19-2015, 03:15 PM	#8
theweebabySeamus Captain 376 Rep 902 Posts Drives: M3 Join Date: Jul 2014 Location: Bay Area iTrader: (1)	Replace piston (or all pistons), reassemble.
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10-19-2015, 07:31 PM	#10
noorj calibrator 12 Rep 80 Posts Drives: 2007 E92 335i Join Date: May 2014 Location: Detroit iTrader: (1)	preignition causes a disruption in the boundary layer, which then causes extremely high surfaces temp on the piston and reduced surface strength and a fracture at the center of the piston. if it were a casting defect it would have failed after a very few amount of miles
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10-19-2015, 08:40 PM	#11
332ijunkie 65 Rep 174 Posts Drives: 08 335i, 87 M52 E30, M52 E36 Join Date: Jul 2013 Location: Atlanta GA iTrader: (0)	I see casting/manufacturing defects surface after 100k somewhat often. Have replaced a few single valve springs on a number of BMW engines. Just 1 spring randomly decides to break, rest are perfectly fine for another 200k, that looks to be the case here.
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10-20-2015, 07:52 AM	#12
derryck Captain 57 Rep 879 Posts Drives: 2009 335 Coupe Join Date: Apr 2007 Location: Florida iTrader: (4)	That'll buff out...
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10-20-2015, 02:41 PM	#14
dreyo27 First Lieutenant 92 Rep 322 Posts Drives: 2007 335i e92 Join Date: Aug 2015 Location: Sacramento CA iTrader: (3)	seems like the perfect time to build the engine with lower CP forged pistons.
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10-20-2015, 08:22 PM	#15
stashtrey Lieutenant Colonel 294 Rep 1,834 Posts Drives: 08 E90 335xi TiAg Join Date: Dec 2012 Location: Sacramento, CA iTrader: (8) Garage List 2008 E90 335xi Sedan [0.00]	Pulled the wrist pin and snapped some pics of the crack from the inside. Really hard to believe it held together like that considering all the heat and violent motion inside. Attached Images
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10-20-2015, 08:45 PM	#16
Miller335 Colonel 291 Rep 2,189 Posts Drives: 2007 E92 Join Date: Oct 2013 Location: Portland, OR iTrader: (0)	That's some craziness. Thanks for sharing pics. __________________ 2007 E92 335 6MT w/335is clutch FBO MHD E60 Wedge map 49k miles
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10-20-2015, 08:50 PM	#17
so?confused jr 22 Rep 555 Posts Drives: 335i Join Date: Apr 2007 Location: new rochelle iTrader: (2)	no damage to cylinder wall?
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10-20-2015, 09:11 PM	#18
Fred_Boosted Captain 90 Rep 632 Posts Drives: 335i Join Date: Nov 2011 Location: USA iTrader: (1) Garage List 2010 BMW 335i [8.00]	Very nice photo sharing there. Put forged rod and piston in and lower the compression ratio for some hybrid turbo or single turbo fun?
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10-22-2015, 08:44 AM	#20
Jaronbwall Driving cars and riding bikes really fast 285 Rep 1,002 Posts Drives: 2009 335i Join Date: Sep 2014 Location: Indianapolis iTrader: (0)	It surprised me how thin the spacing is between the cylinder walls. Are you going to build the motor now with forged components? __________________ 335i, sport pkg, 3 pedals, Blacked out, LED markers, OZ Ultraleggera wheels, Firestone Indy 500s, x-pipe, vibrant 1792, PE mod MHD stage 2+, BMS DPs, ARM charge pipe, Tial BOV, ARM FMIC, dual cone, CSF radiator, M3 control arms, sways, HAWK pads. https://www.strava.com/athletes/8309149 Follow me on Strava
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