Quote:
Originally Posted by mkoesel
Note that the V8 in the 458 is also an exemption as it makes more torque per liter than any other engine currently on the market.
If we go the route of subjectivity and look just at the "normal" non-performance cars out there with typical engines, I think we may indeed see a tendency for the under square engines to show slightly higher peak torque and at a slightly lower RPM than those with over square geometry. But, we are talking about an M engine here. Plus as swamp notes, road car engines are all so close to square, relatively speaking, that there is little variation in geometry to begin with.
For the record I still haven't been able come up with a truly compelling reason which is why I remain skeptical.  |
Just a question; You remain sceptical about the info that claims 89,6mm bore and 80mm stroke? (Which I also have said needs to be confirmed). So I also have a bit of sceptisism towards that
However I believe that the reasoning might be twofold (and this is just my private thoughts):
1: An oversquare engine will have better ability to produce torque higher in the RPM range and an undersquare engine will in the lower RPM range. Producing torque higher in the RPM range will yield more power. Low cost, durability, reliability, overall efficiency favor long stroke low RPM engines.
High specific output, power to weight favor bigger bore high RPM engines.
2: A new block with larger bore spacing allows for larger bore in future versions of the S55. The short 80mm stroke also leaves plenty of room for longer stroke.
In short, the S55
could form the basis of a new generation of M engines, from the 3l M3/M4 to a 3,6-3,8l (for example with a 3,8l - 94mm bore and 91mm stroke) M5/M6 engine. All possible to accomodate within the S55 block, but not realistically in the N55 (you would need a 98mm stroke to get 3,7l from the N55).