[joema]

Originally Posted by swamp2

[LIST]
You are right that an engine only "feels" air density, not altitude but "density altitude" is not a real term.

Density altitude is a real and standard term, and has been used for many years: http://en.wikipedia.org/wiki/Density_altitude

Originally Posted by swamp2

At Sea Level the 335i has about 1.5% more torque than the M3 but is delivered across a much NARROWER rpm band than the M3, NOT A BROADER band.

According to this test: http://www.m3post.com/forums/showthr...highlight=dyno at sea level the 335i peaks at about 8.5% more torque than the M3. Rather than exceeding the M3 torque over a "much narrower" range, it exceeds M3 torque from about 2,200 rpm to 5,600 rpm. IOW the 335i torque is greater than the M3 over the majority of the captured M3 rev range.

Originally Posted by swamp2

Although torque and hp are affected by density the width of the curves is NOT affected.

You're right curve width isn't affected by altitude -- the M3 would still rev to 8,400 rpm, albeit making much less hp and torque. By contrast the 335i would still rev to its redline, making about the same hp and torque as sea level. IOW at altitude, the 335i torque would exceed the M3 over a broader range than at sea level.