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Rod bearing spun!

Engine Building Fundamentals

Relevant Module: Clearances and Tolerances > Engine Bearing Clearances

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Hello all,

I am searching for the cause of the castrophic damage in rod bearings at 1,2 cylinders.

Can be bearing clearnce or just oil pressure or even oil viscosity.

Engine is tsi 2.0 ea888 gen2 out of mk6 gti

Maxpeeding rods, new oem bearings fitted (fresh build) gtx2867r turbo, output 480bhp, 400+torque.

Will post pictures

Attached Files

There have been some reports of the big ends not being honed correctly, and that looks like the bore was a little tight at that point.

Did you check the rod big ends for roundness before using them?

Thank you Gord,

Actually i left the whole process for machine shop, i should ask then.

After the build i did 29 hard pull most was 100-200 km test with no problem.

30th test was from 80 to 260 km at this test engine failed.

Is that still applicable to faulty big end?

The heaviest loading at that point is around TDC and overlap, it may have been cumulative, though, before finally failing.

Forgot to ask before, but something else that can cause issues like that is if the shell wasn't perfectly seated in the bore, with a tiny bit of dirt, or debris, being trapped between it and the cap. It can also be caused by a tiny divot, or dent, in either the cap or shell back, which holds the shell very slightly proud. Sometimes it can be seen as a shiny spot.

Rod shell may be the cause!

The small notch which hold the bearingis not there in the failed bearings!

That's what makes bearing spun.

Attached Files

Looking at it again, I was mistaken in suggesting it was out of round as it looks more like the rod was slightly bent, allowing the side of the big end to rub on the journal cheek. If it had been out of round, I would have expected it to have overheated across the cap width, and it doesn't appear to have occured.

That would make more sense, as the additional heat would expand the big end, reducing the crush on the bearing - which is really what holds the shells in place - and so allow it to spin.

You might find evidence of contact on the other side, near to the beam? If you check the other rods, you may find other evidence of contact, bending or compressive failure with a reduction in the centre to centre lengths.

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