Undersquare, Square, Oversquare ~ pros/cons?

[Jazzbass 1]

As I understand it, an oversquare engine (bore>stroke) can rev higher, but exhibits less torque than an undersquare (bore<stroke) one of equivalent displacement. Thus oversquare motors are sometimes considered as sporty engines (and longer lasting) and undersquare as workhorses (and faster to wear out).

My car has a square engine (bore=stroke=84mm) M52B28. Is this a sort of compromise solution between the two, or are there other advantages/reasons why BMW chose a square configuration?

Are the S designated motors oversquare?

Obviously, I am not a mechanic and my understanding is therefore suitably limited in such esoteric matters.

[cainchapman 0]

I would agree with the basic assumption. Oversquare = revs & kW, undersquare = torque.

However, it's generally rpm that wrecks the motor, not torque.

Soory, got to go and drink with Firemen. Back in a day or so.

Ciao

[westy 614]

Long stroke = high piston speed,hence high wear rate.For the same RPM the piston has further to travel.

If you limit the RPM the wearrate evens out I guess.

Generally speaking a short stoke engine will build RPM faster than a long stroke engine,but I assume its relative to the bore size also.

As an interesting sidenote(to me anyway)an inline engine will produce more torque earlier in the rev range than a Ved engine.

I get right into this sh*t,if anyone else has more info lets hear it.

[Jazzbass 1]

Yes, I'd read that about an inline being more efficient.

Apparently it is to do with fewer moving parts?

More bits in motion means more mechanical losses.

So, back to the question, is a square engine a compromise between revs and torque, or is there a better reason?