[LINK] Fuel consumption

[Ivan Trundle]

I thought that the torque profile of the engine would have more to do with it than anything else?

Peak engine efficiency occurs when you've got the highest air and fuel mixture driving the pistons with the maximum force (i.e peak cylinder pressure).

But there are lots of other variables which will influence this, such as aerodynamic pressures at different speeds, frontal area, etc.

Also assuming that you're driving on flat ground, staying at constant speed, etc. And that it's not an electric motor we are talking about.

iT

On 26/05/2011, at 9:30 PM, Antony Barry wrote:

> 
> On 26/05/2011, at 8:48 PM, stephen at melbpc.org.au wrote:
> 
>> If a vehicle has an overdrive gear that kicks in at 80 klm/hour, would it 
>> be better for fuel consumption to drive at 75 klm/h and higher revs, or 
>> faster at 85 klm/h but with lower revs?
> 
> 
> 
> The higher the revs the greater the energy loss by friction in the motor. The higher the speed the greater the energy loss due to wind resistance going up as the square of the speed.
> 
> In short - it depends. (80/75)^2 ~ 1.14 so if the loss in the engine was less that 14% going faster is better and visa-versa.
> 
> I drive at 85kmph in 100kmph zones so I potentially cut my fuel usage by 28% and always keep in the highest gear I can. And all the other things, avoid brakes, acceleration etc.
> 
> Tony
> 
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Ivan Trundle
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