Quote:
Originally Posted by JCL
Interesting calculation. I'd use 80% for the alternator, less 10% on the belt drive.
But if it means 1.5 hp, that is about 5% of the 30 or so hp required to maintain steady state cruising speeds. That's measurable.
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OK, for the 4.6is at 70mph and -5C (winter), I get 41.2HP including air drag and rolling resistance. I guessed .015 for winter tire rolling resistance and an optomistic 80% drivetrain efficiency. Have no idea what the engine efficiency is, so stuck with the default of .22, possibly higher on the 4.6?
Used this calculator: Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
And used 4.6is data from here: BMW X5 4.6is E53 (2001) - technical specifications - maximum power, maximum torque, fuel consumption - urban/extra urban/combined, maximum speed, acceleration, weight, dimensions, engine, suspension, rims/wheels, tyres, brakes, transmission/gear box,
Still, that's 3.5% going to just seat heating. I plugged in a parasitic load of 800W and it lowered the guesstimated gas mileage from 13.2 to 12.8mpg.
Interesting to see that the difference between -5C and +25C is 8HP because of the lesser air density and lower rolling resistance (summer vs winter tires).
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Olympic Peninsula, WA, USA
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2005 Mini Cooper 100k, British Racing Green/Silver-Black
04/2002 4.6is 140k, Silver/Black-Alcantara *FOR SALE*
1989 325iX 270k, Diamond Black/Black
1984 318i 370k *SOLD* (First Bimmer)
Honorable Mentions: '71 2002, '87 325, '90 325ic, '92 525it, '93 325i, '94 530i
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