CAR FUEL EFFICIENCY & ALTERNATIVE ENERGY

Sunday, April 1, 2007

INERTIA


You gotta have inertia. Whether its in your career. Your passions or hobbies. Self-development. And of course, your automobiles. Well, as far as the cars go you get it without asking. Inertia is all around you. Its central to the physics of your car's gearing system. But taking inertia for granted is not the same as the fun of exploiting it. In my next car decision, whenever that happens, if I don't buy a HEV then at least I hope for a manual shift. It would be a nice break from the rut and a lot more potential to exploit inertia.

Fairly recently I happened to be casually curving through a leisure cruise at a local park moving with the flow at 25mph when it occurred to me. Noticing that at the lower speeds and with some distance from the car ahead fewer full stops were needed even if the car in front stopped intermittently. While the car ahead would sometimes fully stop, with enough distance I could ride out the distance at a slower speed and hope that it would resume its drive without causing a complete loss of inertia. After exiting the park later that day I experimented further on bigger roads. One thing that I noticed almost immediately was that people generally drive hard into a halt probably coming down from 45mph to a stand still within 100 feet. And I am sure all of it would be foot braking (the other option being to use gear braking). Gear breaking is a left-over habit of mine from the good ole manual shift days. Unless I have to reduce speed dramatically I would apply a gear down shift. As my car's automatic transmission has 3rd, 2nd & 1st gear options it allows for more flexibility. I can now, after some practice, bring my 3,200 lbs. vehicle to a full halt from 45mph within 150 feet by using the gear options and a hint of the hand brake right at the end but not a touch on the foot brake. The habit, which my wife finds terribly annoying, also naturally extends the life of the brake pads.

For the purpose of more bang for your petro-buck, the idea is to have to avoid a terribly low speed or a stop at 1st gear so you don't need to build inertia back up. If I spot a red light from afar I will just step off the gas pedal. Most drivers on your tail will know why you are reducing speed albeit a bit early. Some tend to maintain distance while others will move in on your tail with a hint of irritation. But I find that as much as half the time I have employed the tactic I am able to escape the 1st gear and have to re-build up a lot of inertia. Has it helped? Am I getting better MPG? By just looking at the data one can't tell. So much goes into the character of a trip. But by plain logic I don't see why it won't have an impact. I should be improving MPG and buying less brake pads. At 68,000 miles I have had just one change of pads. Now that should reduce fossil fuels usage somewhere.

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