Quote:
Originally Posted by sendler
This seems counterintuitive to many people but if you use Pulse n Glide and don't have to step on the brakes very often, adding mass to the vehicle can actually improve the fuel economy.
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My understanding is that:
1. extra mass increases the amount of fuel consumed during acceleration (significant)
2. extra mass increases the amount of fuel consumed while at constant speed (very small due to friction losses-very small amount on level ground)
(Note however, if you factor in normal constant speed cruise control, add in a few hills, gusty wind, etc. constant speed can easily become the opposite of the advantages of pulse and glide and extra weight exacerbates the problem.)
3. However, and here is Sendler's point, when using pulse and glide: the decrease in consumption due to the
extra length of glide
is more significant than the increase during acceleration
.
Also, if you have hills situated such that you cannot capture the potential energy of gravity for later use (because they have a traffic stop at the bottom of the hill for example) then extra mass may be an overall disadvantage because no matter what route you take, you still need to lift the extra mass back up the hill to the starting elevation.
So if your trip:
-Requires Constant speed, such as long highway trip on expressway that traffic or wife require constant speed - keep weight to minimum and use as much driving with load as possible,
-Has hills that it is impossible to take advantage of but require pouring gravity into heat at the brake pads - keep weight to a minimum, BUT
-Allows for significant Pulse and Glide then increased mass allows longer glides (and by association less pulses and less effort by driver), more constant speed, and therefore less fuel used.
Cheers,
Benphyr