Lower the idle of a car such that the engine dies when you take your foot off the gas. Yes, you'll have to start the thing again at every stop light, but it should save a significant amount of gas over time.

Ok, maybe it's not ideal for stop-and-go traffic. Perhaps an engine that auto-starts when you push the gas pedal?
-- Worldgineer, Jul 21 2006

Found this that you might find interesting http://www.freshpat...ptan20050197235.php
"Foot controlled engine start and stop system for conversion of an off-road utility vehicle for use as a golf cart" [half, Jul 21 2006]

Citroen C2 and C3 http://www.citroen....ails.asp?page=page1
Well baked. Sorry this link is PR puff, but you get the idea. Apparently it uses the alternator as the starter. [Gordon Comstock, Jul 24 2006]

This was part of the plan when the 42 volt automotive electrical systems were being talked about so much. Due to the higher voltage, more power could be delivered through the starter circuits to the starting motors which could in turn have a higher power output than the current crop of measly 12 volt systems. In fact, some of what I read indicated the starter motor would be able to provide the initial propulsion.

I think there are existing golf/utility carts that operate this way.

Given that the boost for power steering and power brakes are quite often derived from the running engine, it would be difficult to do as a retrofit. You could take pulses from the speedo or ABS to prevent the car from shutting off while it's rolling.

I think it's a fine plan that I think might be realized as a side effect of the push toward electric cars. The electrically driven accessories, e.g. air conditioning and power steering, should become more commonplace.
-- half, Jul 21 2006


I knew that about the 42 volt system. But it seems that even with 12 volts this could work reasonably well. My car starts very quickly - certainly fast enough for a stop light.
-- Worldgineer, Jul 21 2006


Prius does this. So do even the "mild" hybrids from GM
-- Galbinus_Caeli, Jul 21 2006


This is not a new idea. I heard that turning off the engine is only effective if the vehicle is to be stoped for more than two minutes.
-- BJS, Jul 22 2006


Hybrids all do this.

I was shocked the other day when I saw a Modern Marvels show about trucks. They were talking about electric trucks built in the 20s!
-- theircompetitor, Jul 22 2006


I've heard widely varying figures for how much gas is used starting the engine--everything from 10 minutes idling to only 30 seconds. Hard to know what to trust.
-- 5th Earth, Jul 22 2006


A warm engine doesn't need much fuel to start at all. Even when the engine is still cold I can't imagine the start taking more fuel then a minute of idling.

You can verify this by using the OBD2 port to watch how much fuel is being used for idling or starting, either by reading fuel flow directly or by reading the injector timing.
-- jmvw, Jul 23 2006


Hmnmm why not just turn it off at the lights...
-- madness, Jul 24 2006


If you travel in countries where fuel is expensive, you'll see the drivers conserve energy by all sorts of means, including not idling when stopped, even in traffic; turning lights off at night when in areas lit by city street lights, and, of course, not running air conditioning any time ever.
-- DrCurry, Jul 24 2006


The "energy loss" ie idling must exceed 30 seconds to equal power saved probably comes from the electricity needed to start the vehicle. If resuming motion is done with a hydraulic accumulator powered by the brakes then this wouldnt apply.
-- Kirkmcloren, Aug 14 2006



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