N54 failure. 335i

Discussion in 'N54' started by 101duck, Nov 7, 2016.

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  1. 101duck

    101duck Private

    So have a friends car in my garage and it had a weird issue, wasn't at all down on power (or at least didn't seem to be) specs are GTX3576 single turbo, E30 mix, JB4, MHD BMS back end flash, watermeth kit, 6MT, 7" IC etc. Nothing super crazy, just a basic responsive single turbo setup.

    So after a few races one day it developed an issue where it would blow some smoke, tips of the exhaust were oily. Suspected damaged turbo to begin with, so turbo was sent away for testing and came back fine. no dramas with the turbo what so ever. No visible signs of damage on the turbo either.

    So I investigated it a bit more and couldn't find any real faults. Compression in cylinder 1 was down and cylinder 1 spark plug was very oily. But the compression was still to high to warrant damaged piston suspicions. (compression was 150psi cyl 1, 180psi 2-6)

    Got the engine stripped down today and found a very unusual break that I thought I might share with you guys. The car has 80k km on the clock and is a 1 owner AFAIK, always serviced at 5000km, good fuel used, quality parts always fitted.

    First thing I noticed was the wet oil in cylinder 1, the head was coated, the piston was very oily, and once wiped off there was no noticeable damage to the piston top, or the cylinder head, I did notice there was a lot of severe detenation on top of piston number 5 and also evident in the head of that chamber. I can only assume it has a faulty injector and that has caused the detenation in that cylinder alone. as all other cylinders are near on perfect.

    Cylinder 5 Det marks:
    [​IMG]

    Cylinder 1 Oily
    [​IMG]

    Cylinder 1 piston top, oily but no damage:
    [​IMG]

    Damage on cylinder 1 bore:
    [​IMG]

    Piston number 5, clear signs of severe det:
    [​IMG]



    First sign of damage on cylinder 1 I noticed was when the engine was pulled to TDC the piston didn't come all the way up, which I thought was odd but isn't unheard of on some engines. But when inspected cylinder 5 I noticed it came the whole way up, so I knew something was astray.

    Piston number 6 all the way up:
    [​IMG]


    Pulled cyl 1 back up to it's resting point and also noticed it was sitting unlevel, it was approx 20thou down on the back side of the piston, but at least 80thou down on the front side. this is the way the gudgeon pin runs, so I was concerned from this point that either the pin had collapsed or the rod had bent.

    Piston number 1, clearly not at TDC and not running straight:
    [​IMG]

    On to disassembling the bottom end, and all bearings, mains and big ends were perfect, you would expect this engine to have traveled no more than 10,000km it has been kept that clean inside. the bearings look near on new. Infact all the bores (apart from cyl1) looked very healthy also.

    Removed the piston and rod combo from cylinder 1 and found a whole heap of mess. The conrod has bent into an S shape and tilted the head a little, causing the piston to run on a funny angle, pushing the piston skirt into the wall of the cylinder and obviously jamming the oil ring tight on one side and more than likely not touching the other side, hence the excessive oil movement from that cylinder but not to much compression loss.

    This doesn't look super straight:
    [​IMG]

    Piston skirts being mashed up against bore:
    [​IMG]

    Other side:
    [​IMG]

    Rod 1 vs Rod 2:

    [​IMG]

    This is a very odd failure on such a mild setup (considering how far other people have pushed the N54, myself included)
     
  2. 335iHaroon

    335iHaroon Specialist

    Wow this is unusual. Especially on a low mileage mild setup n54.
     
  3. It's quite surprising to see the lack of cylinder wall damage on cyl1. The way the piston looks, I woulda assume there would be a significant amount of wiping on the cylinder walls.
    I would think it would be fair to say that because of the oil getting past the rings, it would only show a slight deviation in compression when testing. Putting oil in the cylinder was what I was taught to do when there is an inclination there is cylinder wall/piston ring issues, and the car out the oil in there for you!
     
  4. OP, did you check the oil pump?
     
  5. Tony@VargasTurboTech

    [email protected] Sergeant Vendor

    Its not actually odd at all. 95% of the N54's we tear down have bent rods even at reasonable power levels. Usually 3-4 holes are all slightly bent. Stock rods are not as strong as people think they are. This honestly looks like a typical N54 failure, have him get a good set of .05 over bore pistons, and some rods, have the block bored for the oversize pistons, and he will be good to go.
     
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  6. Tony, is it usually bank 2 that you see these bent rods on? Do you always see signs of detonation? How did the oil pumps look?
     
  7. Tony@VargasTurboTech

    [email protected] Sergeant Vendor

    Honestly, no real data that shows one bank is more likely to bend rods than the other. Its the ability of these motors to make so much TQ so quickly that bends them. When doing testing on the built bottom end GC MT car, we see 720WTQ or so by 4400 RPM, Lites do it even quicker. This is very hard on rods, and you can bend them without even realizing it. If you want to play nice with a stock motor, limit your tq down low. 768_721_734_7600.jpg
     
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  8. Oh wow, that is interesting. My buddy's engine's cylinder 1 went on him as well. We're not sure what the failure is quite yet as the motor is still sealed, but his compression is down too. We think it is just a simple ring failure from running really lean when his port failed.
     
  9. Tony@VargasTurboTech

    [email protected] Sergeant Vendor

    The most common of all the failures is the broken ringland, you will see a hit in compression, and the engine will have a slight lope at idle. We realized the rods were bending when we pulled down 3-4 motors with broken ringlands, and found bent rods in all of them. Who knows how long the rods were actually bent... Typical ring land failure attached. These pieces usually stay in place, and just bleed boost past the rings. If you continue the drive the car hard, they will dislodge, pressurize the crankcase, and ruin the block most likely. The motor should stopped being run immediately after a ring land failure is suspected. IMG_8192.JPG IMG_8193.JPG IMG_8194.JPG IMG_8195.JPG
     
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  10. DR-JEKL

    DR-JEKL Lurker

    22
    Damn any update on this one Duck??
     
  11. 101duck

    101duck Private

    forged pistons and rods and a full rebuild. stock head :)

    nothing fancy, just some reliability.
     
  12. doublespaces

    doublespaces Administrator

    AZ
    2009 E93 335i
    When do you go back to the strip?
     
  13. Abacus38

    Abacus38 Corporal

    190
    Tampa/Orlando, FL
    2007 Ti Ag 335i
    Yeah as others stated and what I've stated in past. When Hitting that much TQ down low you risk bending the stock rods. Similar to the reason you don't spray nitrous at low rpms
     
  14. doublespaces

    doublespaces Administrator

    AZ
    2009 E93 335i
    Pshh, I spray on startup
     
  15. 101duck

    101duck Private

    When its not 45degrees every day. (Real temp not f)

    So bloody hot. Cbf even looking at my car let alone driving or racing it
     
  16. R.G.

    R.G. Sergeant

    352
    Henderson, NV
    E92 N54, F02 N54
    Nice autopsy documentation Duck. Mucho appreciate the contribution.
     
  17. Twisted Tuning

    Twisted Tuning Sergeant Vendor

    397

    been saying this for a while
     
  18. Abacus38

    Abacus38 Corporal

    190
    Tampa/Orlando, FL
    2007 Ti Ag 335i
    But when will people start to listen? I love the N54 but it seems like we are always doing stuff backwards lol
     
  19. Twisted Tuning

    Twisted Tuning Sergeant Vendor

    397
    Facts, lol
     
  20. frmtl2_335i

    frmtl2_335i New Member

    9
    Same thing happened to me, on cyl 3. Detonation that cylinder, puffs of smoke after pulls, little compression lost compared to the rest. Oily valves and oil down the manifold runner (#3).
     

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