Originally Posted by CarFan
I am simply unconvinced that the variation levels in output are so substantial that this explain 20 versus 28. Far too expensive a way to determine which engines are supplied and if true it likely means that a significant number of engines go over 300 hp and others can't even get 150. That's a severe design flaw and of the many things known about BMW engines, being under-engineered is not one of their characteristics.
Not to mention impossible if the laws of physics are to hold.
You are just burning fuel in a chamber, unless there is something wrong with the air input, friction is the only other thing that can eliminate from performance. If you had any siginificant friction causing this, the part would wear out and break. I mean it's not really possible unless something is malfunctioning.