Quote:
Originally Posted by Richbot
Apropos of nothing at all, I happened to tear down a racecar Ford 1.9l that had about 100 hours of flat-out sprint racing time on it last week. The rod bearings looked brand new, and are significantly larger than the ones in the S65 rods. An oversquare motor that only revs to 6000rpm, but still, surprisingly hilarious to put them side-by-side - on one side you have a POS commodity-spec Escort lowest-bidder-supplier engine and the other a high compression high rpm high specific output single-application engine designed from scratch to be a racecar engine platform that costs an order of magnitude and half again more besides to make...wow nice work bmw
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IIRC Honda B-series rod bearings are like 1 mm wider than the S65's, and LS rod bearings are around 50% wider.
I've also heard from people I trust that the wider rod bearings available for S54s cause small but measurable power loss.
I've recently wondered if BMW M was pushing the (lower) limit on rod bearing width in pursuit of compactness/weight/low friction, and maybe the reason for the extraordinarily tight clearances is to help keep the rod stable despite the relatively narrow bearings or something.
But then again, the B7 RS4 has a worse rod/stroke ratio with a comparable redline and output, though it also has slightly lighter rods. Net-net, shouldn't that mean comparable load on the rod bearings? Yet that engine uses slightly
narrower rod bearings than the S65....
Of course I don't know jack about this stuff, so I'd love to hear some informed commentary.