500hp

[SR71]

The 458 makes 560hp from 4.5 litres for 125hp/litre.

Assuming a B7 revs to 9000rpm the difference in piston speeds between a 458 and B7 would be 24.3m/s versus 27.8m/s....doesn't seem like much.

But the loads on the piston are proportional to acceleration and in the B7 would be greater by ~14% courtesy of the stroke.

I'm not sure why the B7 has such a long stroke?

[PetrolDave]

Just seen this on Audizine http://www.audizine.com/forum/showthrea ... -switching!

[ArthurPE]

The 458 makes 560hp from 4.5 litres for 125hp/litre.

Assuming a B7 revs to 9000rpm the difference in piston speeds between a 458 and B7 would be 24.3m/s versus 27.8m/s....doesn't seem like much.

But the loads on the piston are proportional to acceleration and in the B7 would be greater by ~14% courtesy of the stroke.

I'm not sure why the B7 has such a long stroke?

loads are ~ to a
but a ~ v squared
so loads >30% higher

long stroke = more torque over time (rpm in this case)
hence 90% peak from 2500 to redline

[Gardus@Supersprint]

The 458 is flat crank too...

[MoRS6+]

Ah damn, only 485bhp but close to 500:

http://www.pistonheads.com/sales/1985510.htm

[RS4Molar]

Ah damn, only 485bhp but close to 500:

http://www.pistonheads.com/sales/1985510.htm

wouldn't beleive that at all!!!!!!!

[adsgreen]

Flat plane crank does give a more balanced (so no need for counter weights) and high reving engine - key for NA power.

However, a long stroke implies small bore - this gives lower down torque but also smaller packaging. If you were to put short stroke engine in the front then it would need bigger bores for the same displacement dramamtically increasing the dimensions of the engine. With mid mounted this isn't so much of a problem as you can bin the rear seats but for front engined this hits the handling (in weight distribution and polar inertia).

As with most things, it's a compromise.

[RS4Molar]

absolutely correct