2011 GM to EPA certification test documents (shows dyno "road load" HP @ 50 mph)

[gone-ot]

Page 32 lists the dyno "road load" HP settings (and HP-equation coefficients!) used to simulate 50 MPH for the various 2011 Cruze and Eco Cruze models:

http://iaspub.epa.gov/otaqpub/displa...d=24271&flag=1

Notice the Eco Cruze shows only 9.3-9.4 HP at 50 MPH!

...similar information is also available on "other" manufacturer's vehicles via EPAs' Document Index System (DIS) website:

Basic Search | Document Index System | US EPA

[cfg83]

Old Tele man -

Cool. I usually assume that 20HP is needed for freeway cruising, but maybe that's an old-drivetrain family-sedan baseline assumption.

The non-Eco 1.8 liter can do 10.1 HP at best, so the Eco uses up to 8% *less* horsepower at 50 MPH.

CarloSW2

[gone-ot]

Carlos, yes, it's really an "eye opener" *IF* the Test Load HP (TLHP) values truly (and accurately) represent the total road load HP required at 50 mph. Note: N/V = engine speed (RPM) at 50 MPH.


Cruze Eco, M6, AR = 3.83:1, P215/55R17 ALS Goodyear, N/V = 30.8, 3312 lbs, TLHP = 9.3; F0 = 23.96, F1 = 0.1143, F2 = 0.01606

Cruze Eco, A6, AR = 3.53:1, P215/55R17 ALS Goodyear, N/V = 34.9, 3434 lbs, TLHP = 10.1; F0 = 26.20, F1 = 0.1554, F2 = 0.01686


Hence, the TLHP equations are something like these:

• _9.3HP = 23.96*(lbf) + 0.1143*(lbf/mph) + 0.01606*(lbf/mph^2) ...so, lbf = 0.388 @ 50 MPH (M6)

• 10.1HP = 26.20*(lbf) + 0.1554*(lbf/mph) + 0.01686*(lbf/mph^2) ...so, lbf = 0.385 @ 50 MPH (A6)

Anybody with an Eco Cruze know if these match-up with the applet we have here?

[RobertSmalls]

Originally Posted by Old Tele man

Hence, the TLHP equations are something like these:

• _9.3HP = 23.96*(lbf) + 0.1143*(lbf/mph) + 0.01606*(lbf/mph^2) ...so, lbf = 0.388 @ 50 MPH (M6)

• 10.1HP = 26.20*(lbf) + 0.1554*(lbf/mph) + 0.01686*(lbf/mph^2) ...so, lbf = 0.385 @ 50 MPH (A6)

Anybody with an Eco Cruze know if these match-up with the applet we have here?

Edit: Nope, the EPA is modeling road load as F=A+Bx+Cx², and we are modeling it as F=A+Cx². Our applet crunches drag area, air density, vehicle mass, etc into two road load coefficients, whereas the EPA has a more sophisticated model.