Coasting vs. Engine Braking

[caveatipse]

No, but in my Yaris, during engine braking, the fuel injectors SHUT OFF. that is my point lol.

[skewbe]

Most cars work that way these days.

Do you understand that you cannot coast as far with the engine engaged?

[caveatipse]

Originally Posted by skewbe

Most cars work that way these days.

Do you understand that you cannot coast as far with the engine engaged?

Yes I understand. I am measuring from the point I decide to decelerate, to the point of the complete stop.

[GasSavers_mattW]

Just consider the a situation where EOC is not an option and a traffic light ahead of you turns red. If the car is put in neutral the energy you used to accelerate to that speed is dissipated by the brakes (wasted) and the engine runs at its no load idle. If the car is left in gear then the energy you used to accelerate to that speed is dissipated within the engine friction/pumping losses etc (also wasted) but the engine isn't using any fuel. What the hard core FE guys are saying is that there is a third and better option where you turn off the engine while still moving (car in neutral) and use the brakes to slow down, the advantage being that at the traffic light you continue to use no fuel whereas with the engine braking you would start to use fuel again at <1000rpm.

So if you are going to stop anyway use EOC, if not the next best is to use engine braking, if not that then use a neutral coast.

[skewbe]

Also, if you can adopt EOC, at the sudden red light, or any stop that you mistime, you will not have reason to restart the engine until it is time to move again. A lot of fuel is wasted idiling at stops, and it can mage a big difference in you mpg numbers.

[JanGeo]

Not in a Scion / Toyota VVTi engine - when it starts up again it will be burning more fuel than it would have running at a stop light for 1 minute. And that is if it starts without a lot of cranking. Better off keeping the engine running - remember it only burns .1gph when warmed up which comes out to 0.5 cents per minute - definately not worth the wear and tear on the ignition switch - starter - battery etc in the winter time. Steering is powered by the engine and believe me - you can't turn quickly without it in fact just turning into a parking space is almost impossible while coasting with the engine off - the steering is not designed to be turned without the pump running.

[skewbe]

What is that one minute figure based on? Most of what I've seen is 5 to 10 seconds.

Are you using a kill switch or the key (and resetting the ecu)?

[JanGeo]

Originally Posted by skewbe

What is that one minute figure based on? Most of what I've seen is 5 to 10 seconds.

Cost of gas at $3 a gallon and 0.1gph burn rate. A restart burns 0.4-0.5 gph for more than 30 seconds. Plus in 18k of driving I can count on one hand the number of times the engine fired up after 1 compression cycle of a cylinder and several times I cranked and let go the key and had to crank again a lot more to start. Just better to keep everything running and warmed up.

[skewbe]

Ideally you would not be sitting there for 30 seconds idiling, but you would start the engine and go.

[Mighty Mira]

Originally Posted by skewbe

Are you using a kill switch or the key (and resetting the ecu)?

What's the difference? Also, is there any difference if you are going virtually straight from restart to in gear acceleration?