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  • AAN Engine Damage

    I have an 92’ UrS4 with the following mods: HX35, NM exhaust cam, 450cc Injectors (Stock FPR), 90mm exhaust pipe, big FMIC (76mm pipes).
    Other than that, its mostly stock. The car has 305kkm. I’m using 10W60 oil.
    I’m running motronic with prjmod. Boost was 1.75bar up to 6K rpm and than drop to 1.60bar to redline (7250rpm).

    After some hard pulls on the highway, I started to ear some very light knocking noise from the engine when on low load. Checked the oil pressure and the needdle was bouncing heavly. Shuttered the engine down imidiatly and never started it again.
    Removed the oil pan, after a quick inspection I realize that have spun the bearings on connecting rod number 5.
    Never seen oil temps over 130ºC.

    Never had any codes related with knock or had knock on Winlog when mapping / testing. Target AFR was 12.8, checked with innovate wideband.

    What do you guys think that could cause the failure? Low oil pressure? Unexpected Knock? Or just metal fatigue?
    I’m investigating this further before doing engine rebuild.
    Thanks in advance!
    92' UrS4 2.2T
    89' 80 Quattro 2.3 20v
    93' 80 1.9 TDI
    92' 100 2.5 TDI
    99' Cabriolet 1.9 TDI

  • #2
    If you never had knock, are you sure the knock control is working?
    Other than that - cylinder number 5 is not the most knock prone. So I would rule out any kind of mapping issue. If you had a problem with the mapping, you would first always damage cylinder 3 or 4.
    Excessive knock you will see if you remove the piston, you can easily check marks. If there are clear knock marks, then you should definitely flow test the injectors to make sure that this cylinder is not starved of fuel.

    Other than that, are you sure all the tolerances were to spec when the engine was assembled? Or was it never disassembled? Was the oil pressure ok? And so on...
    http://tuner.ee - http://www.facebook.com/tuner.ee

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    • #3
      0.87 seems a lean target AFR on full load. I would guess knock has hammered out the shells. Since the bottom end needs stripping now I guess you will find out soon enough
      Knock damage looks like the piston has been sand blasted.
      Panthero Coupé quattro 20vt
      Indigo ABY coupé
      Imola B6 S4 Avant

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      • #4
        prj
        I have this car from about 10 years now. As far I know, this engine never was disassembled, but cant be 100% sure.
        The oil pressure, when hot, the minimum was above 1.5bar and almost 5.0bar max (didnt reach).
        The injector are Bosch genuine 0280155968, bought new and have done about 3kkm.
        I have seen some knock on low load, nothing major. Anyway, I cant be sure the the knock control is working properly.
        I was looking into some logs i have done, and found something odd in one pull at 3rd and 4th gear. On 4th gear, the knock gone crazy! Thats the only one that happend. Its the log attached

        Error404

        My bad, the target AFR is 11.8, just mistype, as you can see in the log.
        The actual AFR is "MAF_T"
        I guess that I need to find the time to strip the engine.
        92' UrS4 2.2T
        89' 80 Quattro 2.3 20v
        93' 80 1.9 TDI
        92' 100 2.5 TDI
        99' Cabriolet 1.9 TDI

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        • #5
          I don't see anything "crazy". The tuning looks good to me. Whatever happened did not happen because of the tuning.
          Can be also that engine is just worn, or maybe your prior experiments bent the rods a bit.

          You need to take the crankshaft out, check it for straightness, grind it to repair specification, fit new shells, fit H-beam connecting rods and put it all back together at the very minimum.

          You can also inspect the oil channels for any debris, but whatever happened it is definitely not the tuning responsible for it - it looks pretty good to me. Boost is not overspiking, actual AFR maybe could be a little better but really nothing out of the ordinary.
          http://tuner.ee - http://www.facebook.com/tuner.ee

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          • #6
            Thanks for your time!
            Going to disassemble the engine when I find the free time and take the measurements.
            I will post the developments here and maybe start a project thread.
            92' UrS4 2.2T
            89' 80 Quattro 2.3 20v
            93' 80 1.9 TDI
            92' 100 2.5 TDI
            99' Cabriolet 1.9 TDI

            Comment

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