Re: fuel consumption carrying weight

Mr.Nice. wrote:

> Is there a simple way of working out an increase in fuel consumption
> by extra weight carried?
>
>
> Regards.
> Mark.(AKA, Mr.Nice.)

No. It depends very much on how and where you drive. For most vehicles the
rolling resistance does not increase significantly with increased load,
provided the tyre pressures are correct for the load, so that the effect of
increased mass is to require more energy to accelerate it. How much more
energy is required depends on the rate of acceleration you ask for. In the
case of a low powered vehicle that you habitually drive at full throttle
anyway, there will be little difference in fuel usage.
Only in very hilly country will the energy required to climb hills be
significant compared to the energy used to accelerate.
JD

On Tue, 16 Nov 2004 06:35:08 +1100, JD wrote:

> Only in very hilly country will the energy required to climb hills
> be significant compared to the energy used to accelerate.

One would assume you are coming down again so very little fuel is used
then compared to going up. I'd say it pretty much balances out which
leaves just the added energy to accelerate the bigger mass.

--
Cheers [email protected]
Dave. pam is missing e-mail

Dave Liquorice wrote:

> On Tue, 16 Nov 2004 06:35:08 +1100, JD wrote:
>
>> Only in very hilly country will the energy required to climb hills
>> be significant compared to the energy used to accelerate.
>
> One would assume you are coming down again so very little fuel is used
> then compared to going up. I'd say it pretty much balances out which
> leaves just the added energy to accelerate the bigger mass.
>
Doesn't work like that - the extra energy you use to increase altitude is
used mainly to heat up your brakes on the way down. Certainly you use less
energy going down, but this does not make up for all or even most of the
extra used in climbing. But you are right, and it has to be very hilly for
the effect to outweigh the acceleration effect. And even then the whole
situation may have changed by, for example, a very winding road that
reduces your speed considerably, thus saving more fuel than the extra used
because of the hills (aerodynamic drag is proportional to the square of the
speed, and is the major component of drag at speeds over about 60kph)
JD
JD

On Tue, 16 Nov 2004 14:05:38 +1100, JD wrote:

> Doesn't work like that - the extra energy you use to increase
> altitude is used mainly to heat up your brakes on the way down.

Come down on your brakes round here and you get brake fade about half
way down... Engine braking is a must. Yes, there will be more energy
going into the brakes but only that from the height loss as you brake
for corners, assuming you are not letting it run away on the
straighter bits. B-) This is a hill that drops around 1500' in about
4 miles.

> But you are right, and it has to be very hilly for the effect to
> outweigh the acceleration effect. And even then the whole situation
> may have changed by, for example, a very winding road that reduces
> your speed considerably, thus saving more fuel than the extra used
> because of the hills (aerodynamic drag is proportional to the square
> of the speed, and is the major component of drag at speeds over
> about 60kph)

I certainly didn't notice any difference in fuel consumption when we
moved up here from the relatively flat south.

--
Cheers [email protected]
Dave. pam is missing e-mail