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      09-28-2013, 03:44 PM   #95
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Originally Posted by mkoesel View Post
Oh, sure, but I am just wondering how much torque we could get from a naturally aspirated 4.5L V8 with a longer stroke. I guess I am wondering if we can calculate that, or is this discussion becoming religion instead of science now?

Regarding, the S55, probably it could never be pushed to 443 ft-lb, right?
Of course it could be "pushed" to 443lb ft. But the Alpina B3 makes 600Nm with "only" a 410hp tune. Indicating it makes torque easier and more torque at a similar, or lower state of tune, than the S55.

If you are looking for a engine that could be compared with the 458 engine I suspect it won't be easy to find anything comparable with a long stroke... It revs to 9000rpm. With a long stroke engine the piston speeds would be astronomical...

A long stroke 4.5l V8 would have to be dramatically different as regards to rev range, cam timing. Parametres that make it very hard to establish whether the difference in torque is down to stroke difference or rpm/state of tune...

Possibly a example of this would be a Ducati 848 engine vs a HD 883:

Ducati 848:
Bore x Stroke: 94 mm 61.2 mm
134 hp (100 kW) @ 10,000 rpm
96.0 Nm @ 8,250 rpm

HD 883:
Bore x Stroke: 76.2 mm x 96.8 mm
53 hp (38.6 kW) @ 6000 rpm
67 Nm @ 4100 rpm

As can be seen here, both engines have comparable volume (848cc vs 883cc), however since the Ducati can rev far higher than the HD it's also possible to make more power and torque. Same issue will be if we should compare a standard 4.5l with the 458.

We cannot compare a 60hp/liter engine with a 158hp/liter engine...

The Honda CBX and Kawasaki Z1300 both featured straigh six engines, one oversquare and the other undersquare.

Kawasaki Z1300 Undersquare:
Bore x Stroke: 62 x 71 mm
120 hp @ 8000 rpm
116 Nm @ 6500 rpm

Honda CBX Oversquare:
Bore x Stroke: 64.5 x 53.4 mm
105 hp @ 9000 rpm
71Nm @ 6500 rpm

Adjusted for volume (1300cc vs 1000cc) the Kawasaki would be at:
92 hp @ 8000rpm
89 Nm @ 6500rpm

At 1000cc the undersquare engine in this example has 13hp less than the oversquare but make 18Nm more than the oversquare engine... Which again falls in line with the N55 B3 vs S55 M3 etc.

There might be other examples that proves the above or makes my point rendered null and void

Last edited by Boss330; 09-28-2013 at 04:07 PM.