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      04-21-2021, 05:27 PM   #173
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S54 was never based on M54, or S52 US for that matter. It was based on S50B32 euro engine, and the S50 euro engine was an evolutionary engine to the inline 6 used in M1. S14 of E30 M3 was two cylinders "chopped off" of M1's inline 6 for lighter weight. So S55 was the first M engine based on a regular production engine N55.

With regards to S85 and S65, they become quite reliable M engines with the simple rod bearing swap and can last 200K+ miles with occasional track usage, so I am not sure what the fuss is. You should see how many AMG/Audi/Porsche V8 engines are grenaded simply due to a poor oil lubrication and piston clearance design which are not an issue with M cars.

BMW M never bothered with turbo engines until S55 because engineers perceived them as laggy, cheap and unimaginative way to gain horsepower, as high compression naturally aspirated engines are much harder to build correctly and require significant engineering exercise. That approach provided distinct character, performance and fuel efficiency over its competition. The reason S65 is two cylinders off S85 is not because of cost, more because the F1 inspired engine is well designed it can run competitive races for hours, and so did the S65.

Originally Posted by chris719 View Post
It's not financially feasible to design a completely different engine any longer. I mean, it's arguable that it wasn't ever a good idea. S54 and S52 are not that far off of the types of changes we see in S55. S85 and S65 may not have been the wisest decisions. S85 is a great engine, but the character IMO never suited a 5 series, and they blow up at an alarming rate. S65 was more on-target for the car but still not exactly the high point of BMW engine reliability. Probably could have used more low-end torque in such a heavy car but cost forced them to chop 2 cylinders off of S85 and run with it. People love the 1M, and if they had gone the turbo route for S65 I think people would have still been happy with the E9x M3.
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