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      04-21-2021, 07:15 PM   #176
kyrix1st
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Quote:
Originally Posted by chris719 View Post
I didn't say S54 was based on M54, but the departure wasn't radical departure or clean-sheet design like the S85 was. You're right that the degree of parts sharing is much higher now obviously.

S65 and S85 are not reliable, period. Throttle actuators, main bearings, rod bearings, S85 vanos... When you have to say "except the rod bearings" you don't have a reliable engine. The main bearings tend to go, too. These are IMO not regular wear items on a street car and this is still a street car.

The fuel efficiency claim is laughable too. There's almost no quicker way to an inefficient engine than to spin it quickly. S85 and S65 get horrific fuel mileage even compared to their contemporaries. I really love S85 and S65, but they are not perfect. Pretending the R&D cost saved by chopping two cylinders off of S85 is not a factor is a bit naive.
I never said high revolution is fuel efficient. Higher compression engines are more fuel efficient. I do not recall RS4 or C63 getting better fuel economy than S65.
You should also re-read what I said about the comparative reliability. There are very few engines that are as strong in motorsport applications as M engines and are reliable at the same time. Throttle actuators should be considered 60-70K wear items, very cheap as well. With engines that see regular OCI (3k-5k km/1yr) there has been little reported cases where the main bearing wear was the main culprit of engine failure; they do wear but at much slower rate than rod bearings. I am referring mostly to S65, S85 did go through a series of revisions over time.
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