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      09-26-2013, 04:46 AM   #19

Drives: No BMW for now
Join Date: Jun 2006
Location: Canton, MI

iTrader: (1)

Originally Posted by Boss330 View Post
Good points.
Thank you.

On a NA engine they wanted the longest stroke possible to gain some torque fro driveability, hence why the old engines had a fairly long stroke.
But, torque changes achieved solely by adjusting bore and stroke at a specific fixed displacement are of minimal significance in the overall picture. With so many other factors affecting the engine's output characteristics, attacking the bore dimensions simply to achieve a torque increase is not cost effective in general.

On the S55 the FI takes care of the torque deficite present in a short stroke engine. You can have your cake and eat it Both short stroke and high torque
I am not so convinced. I disbelieve that if we built a 3.2L naturally aspirated I6 engine using the 89.6mm of the S55 at 360hp (a power figure which BMW did reach in the CSL), that there would be any valid claims of a torque issue. Such claims would boil down to the same rhetoric we endure with respect to the S65 and S85. And speaking of that, what happened to this under-square, high revving alleged high torque design of the S54 once they got ahold of the 98mm bore spacing? Surely we cannot honestly believe the huge increase in bore and huge decrease in stroke was all done at the expense of a supposedly superior higher torque design of the past I6, all while the ability to reverse the bore dimensions to over-square just happened to conveniently and coincidentally present itself.

Color me a very deep shade of skeptical.

Getting back to the S55, I accept that the new spray on lining allows for a larger bore. But I still think the bore center must be greater than 91 mm now and I am very eager to know if this is the case.
Appreciate 0