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HuskerFlex

hypermiling question...

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Lately I've taken to trying to extend my milage a bit...  few questions for you more exprienced folks in this field.

 

Which will be better if you know you are going to have to stop up ahead,

1.  stopping the cruise, and allowing it to idle in gear and slowly loosing speed.

2.  taking it out of gear, and coasting...

 

It seems like the engine idles faster out of gear then in gear... but if going down hill, doesn't pick up as much speed when in gear.

 

Any adivse?

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I like to think I'm a big hypermiler, so allow me to take a stab at this one. First off, the answer to your questions varies largely on several factors:

1) How close are you to the stoplight?

2) How is the traffic around you?

3) What is the weather like?

4) How does the signal work (i.e. actuated (traffic control) or timer control)?

 

What I do is I get to know the lights in an area and how they behave. It's much more difficult to time a light if it is actuated, because you have to be up there to trip it... and if someone from the intersecting road beats you to it... well there you go. So my advice is just slow down a bit, and make the judgement based on the conditions. Usually, if you have 1/3-1/2 mile before the light, you can just turn off cruise and let your car lose 5-10 mph of speed.

 

Another thing I've learned, is to observe the cross walk lights. If they are automated and the light is timer controlled, then you will see a walk signal parallel to the direction of traffic flowing. Your cue that the light is about to turn red is that the hand will begin flashing.

 

The key to hypermiling is minimizing changes in speed. Don't make hard stops, and don't slam on the pedal.

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Leave it in gear and coast. Most engine programs today will cut off cylinders to not use any or little fuel, then when you get slow enough the cylinders come back for a smooth idle. If you put it in neutral all cylinders are back on and the engine has to maintain the idle to run AC, power steering, alternator, etc.

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Leave it in gear and coast. Most engine programs today will cut off cylinders to not use any or little fuel, then when you get slow enough the cylinders come back for a smooth idle. If you put it in neutral all cylinders are back on and the engine has to maintain the idle to run AC, power steering, alternator, etc.

 

Yep - exactly this.  Your best bet is to stay in gear and coast.  The fuel injectors will cut off and you're burning zero fuel.  The absolute best you can do is time the approach so you aren't idling at all...the fuel will be cut off as you coast on approach, then you'll be burning the fuel you would burn anyway when you accelerate away.  The savings come from not idling the engine at a stop, then when you accelerate, at least you aren't starting from 0mph.

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+1 leave in gear and coast.

 

I usually coast so I'm going about 20 mph by the time I reach a stop sign. Any slower and you tick off the person behind you.

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this was what I was thinking...

 

The only time I do the coasting in neutral is on my last mile of my commute.  I turn off the highway (31, east bound on Q).  This is a hilly mile, that is sort of like a "W"...  with each of the hills a bit shorter then the previous.

 

The speed limit is 45 on this road.  If I can turn off of the highway without stopping, it takes little effort going down hill to get to 45.  I can then put in in neutral, and coast.  Going down the first hill, I accellerate to over 45, but this is blead off going up the next hill getting me back to 45 by the peak...  Going down this long next hill gets me up to near 50, giving me the energy to coast most of the way up the next hill to the stop light, getting to about 40 by the peak.

 

That is a full mile of hilly driving, with only 100 yards or so of light down hill accelleration.

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I forgot who told me this, but it has stuck with me for years:

 

There are three ways to avoid a collision. 1) brake, 2) swerve, 3) accelerate.

 

Taking the vehicle out of gear removes the acceleration option.

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Hmm, okay. I figured it was automatic. My advice is simply to make your speed as smooth as possible. If your transmission lurches a bit, the change in your speed is a bit rough. So if you're close enough to the light, just apply a little pressure on the brakes, and then coast the rest of the way.

 

Also make sure to give your transmission enough time to adjust to the lower speed. Don't suddenly apply a lot of pressure to the accelerator pedal... apply it gradually.

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