[Diy_efi] BHP calculations

[Bernd Felsche]

Bruce tapped away at the keyboard with:
[top-post fixed]
> ----- Original Message -----
> From: "Bernd Felsche" <bernie at innovative.iinet.net.au
>> Bruce tapped away at the keyboard with:
>> [top-post fixed]

>> > ----- Original Message -----
>> > From: "Bernd Felsche" <bernie at innovative.iinet.net.au

>> >> Hugh Keir tapped away at the keyboard with:

>> >> > I am working on a spreadsheet to calculate BHP from datalogged
>> >> > information.

>> >> > The basic formula I am working to is:

>> >> > Engine BHP = acceleration BHP + wind drag BHP + transmission loss BHP.

>> >> Don't forget about rolling resistance.

>> > What about the humidity?.

>> Accounted for in aero drag.

>> > Variances in the gravitation pull of the earth?.

>> Accounted for in rolling resistance.

>> > Difference in weight for fuel used during the *event*.

>> In rolling resistance.

>> > Reduction in tire diameter for tire wear.

>> In rolling resistance.

>> > Increase in tire diameter due to heat, as applicable.

>> In rolling resistance.

>> > Variances in ambient O2

>> Aero drag.

> Hahahaha,

> O2 variences have no effect on HP?.   That's interesting.

Aerodynamic drag is largely determined by the density of air. (At
least for bluff-bodied cars.)

> How do you take into count all these changes, in one event?.

Too much to write here:
See Bosch Automotive Handbook - chapter titled "Motor Vehicle
Dynamics" - p338ff in 5th English edition or chapter titled "Dynamik
der Kraftfahrzeuge" - p330ff in 22nd German edition.

>> Rolling resistance accounts for as much as 50% of power requirements
>> at speeds of up to 80kmh (50mph), depending on vehicle aerodynamics
>> and vehicle mass. For light vehicles, the break-even point is closer
>> to 60kmh (37mph).

--
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