HP/Cubic inch for modern designs

[Bruce Nunnally]

By comparison:

Northstar, Non-VVT FWD: 290 hp 279 CI, 1.04 HP/CI.

Northstar, Non-VVT FWD: 300 hp 279 CI: 1.07 HP/CI

Northstar, VVT RWD: 320 hp, 279 CI, 1.14 HP/CI

Cadillac HFV-6 3.6L VVT 255hp, 217 CI, 1.17 hp/CI

BMW 330i 3L 255hp, 183 CI, 1.39 HP/CI

Acura 270hp 3.2L 196CI 1.37 HP/CI

Lexus i350 3.5L 306hp, 211 CI, 1.45 HP/CI

If the DOHC VVT Northstar in the current RWD STS were as efficient as the 3.5L V6 in the 2006 Lexus I350 the Northstar would produce 404 hp instead of 320 hp.

If it were only as efficient as the BMW, it would produce 387 hp.

The Northstar is NOT limited by the physics of how much hp is possible to be engineered.

The Lexus 3.5L is a ringer btw, as it benefits from direct injection. This is a step function change in fuel injection where the injectors actually inject fuel into the cylinder itself as opposed to into the intake valve tract. The benefit of this technology is lower fuel consumption, and higher output. Rumors I have read suggest that once GM has added direct injection to the 3.6L HFV6 it will produce 300+ hp also, and one would suspect the Northstar will climb up to near 380 hp?

[KevinW]

Please list the practical benefit(s) of optimising solely the high RPM breathing ability of an engine.

[Scotty]

I believe that the more power you can make out of a given displacement the better the gas efficiency will be. This is one reason that I am averaging 19 and 26.

[Bruce Nunnally]

Please list the practical benefit(s) of optimising solely the high RPM breathing ability of an engine.

well, hmmm.

At first I thought you meant, but hey, hp sells but you drive torque. Then I went back to study the C&D engine stats here:

And worked out this HP chart over RPM:

based on the peak torque values at rpm, converted to hp using hp = ( torque x rpm ) / 5252. These are simple linear plots of hp at torque peak to hp at hp peak. Actual engine outputs normally have a curve to them of course.

The CTS 3.6L has more HP at every RPM across the rev band than the BMW 3L.

The Infin and Lexus are harder to extrapolate about, since they are advertisting a very narrow power band.

[JasonA]

In addition, consider when each of these engines was concocted. The FWD Northstar has basically been in place for over a decade unchanged. In 1993, where was Acura or Honda or Bimmer? Not at the level of the Northstar.

When you say the Acura and Toyota are harder to plot since the powerband seems narrow, I think that's what KevinW's point was. My mother in law has a 2004 TL, with the same 270-hp 3.2L. The car screams, but you've gotta have that engine singing, and the car in the right gear. Below about 3000-4000 rpm, you want to downshift to get up into the powerband, even with "VTEC" or whatever that jazz is. Overall, it's a great package, and returns excellent mileage (over 30 on the road), but doesn't feel as responsive on the street as the Northstar for sure (even in the lighter TL body).