engine off coasting

Discussion in 'Fuel Economy' started by schuylkill, Aug 3, 2014.

  1. schuylkill

    schuylkill Well-Known Member

    In order not to get off topic on the tread this quote by Andrew came from I thought I would see if it has its own life. Assuming this is true what are the particulars others use here in "urban" speed engine off gliding. I find that on my commute, I would need to be keying off very frequently in order to do this. I am exploring an alternative route for my commute home which I sometimes use, but not until this last run did I try to optimize engine off glides and it was not too bad with the heavy Friday traffic, a lower speed and less congested drive. And is it worth engine off on long glides on the highway? Why not if it helps at all? If it is to save on wear on the drive train then I have better luck with my bump starts at highway speeds than urban speeds, smoother starts, hardly noticeable.
     
  2. 08EscapeHybrid

    08EscapeHybrid Moderator

    First of all, let me just mention for those that may not be familiar with the procedure, that one should not do an engine off coast unless your vehicle is flat towable. Otherwise, your transmission will be turning but the transmission pump would not be, and this can cause premature wear and possibly a failure of the transmission itself.

    Because of this I generally don't do it in my vehicles. I do however turn off the engine when sitting at lights. That helps a lot when driving my pickup truck in the city.
     
  3. phoebeisis

    phoebeisis Well-Known Member

    Right-
    Engine off at LIGHTS- safe for ALL vehicles.
    Engine off gliding-check your owners manual-
    and maybe not a great idea if you have a newish car-still in warranty
    especially one with ONBOARD long memory that the service techs can access.

    I do engine off glide one of my vehicles but never do it with the 1998 Suburban
    1) Because it requires you devote ALL your attention to it-so it wears me out
    2)It requires "co-ordination" which over time you certainly develop
    3) 98 Suburban has crummy-ish OEM brakes which aren't improved by losing some "boost"
    4) When I tried it-my power steering-almost immediately "lost boost" so I went from the usual waaaay over boosted steering to VERY heavy steering-seemingly instantly
    5) GM to their credit- "somehow" effectively disconnects the transmission from the motor rear end when you lift completely off the gas at 35-40 mph- you get absolutely ZERO engine braking if you are in top gear under 45 mph and lift off completely
    You don't have to fumble around and put it in N
    GMs motor on coast BEAUTIFULLY- well the trucks do-??

    On the other hand-motor off Pulse and glide would probably boost my "at temp city mpg"from 16-17 mpg to 20-22 mpg-
    It uses .6 gph or mile while idling-and when you lift off it doesn't immediately drop to .6gph- so mpg would dramatically IMPROVE if I was up to motor off P&G

    Yeah Motor off P&G might improve my city mpg by 25-40% over motor on P&G with shut down at lights or long stops of any sort
    Long meaning projected to be more than 30 seconds.

    My other car I regularly motor off glide shut down at lights
    It is simple to do since Toyota does it for me
     
  4. timw4mail

    timw4mail Well-Known Member

    It seems like Engine-on coasting is nearly as good, and a lot easer/safer to do. Not to mention you don't have the problem with power steering and brakes, and it doesn't kill your transmission.
     
  5. ksstathead

    ksstathead Moderator

    For certain vehicles ICE-ON is the only option.
    For certain vehicles and conditions, ICE-ON is nearly as good.

    But in general, if your vehicle is flat-towable and bump-startable, ICE-ON is nowhere near as good as ICE-OFF.
     
  6. phoebeisis

    phoebeisis Well-Known Member

    Yeah-ICE off-easily 25% better FE
    When gliding my car uses .7gph
    Every 9 minutes of that saves .1 gallon
    a 7 mile city trip could easily have 9 minutes of gliding-
    Instead of using .5 gallons 14 mpg
    I could use .4gallons 17.5mpg
    Yeah motor off works-but it takes sooo much concentration and the brakes power steering
    I don't do it with the Suburban
    I do it constantly with the Prius-(with "a little" help from Toyota)
     
  7. some_other_dave

    some_other_dave Well-Known Member

    EOC is more use at lower speeds. At high speeds, you bleed off speed more quickly, so your engine-off times are much shorter. At low city-type speeds, you can coast for a lot longer time. And if you're doing that with the engine off, that's more savings.

    -soD
     
  8. ksstathead

    ksstathead Moderator

    I don't P&G on the highway unless deserted because of wind resistance, except for opportunities where I need to slow anyway... So I think of it mostly as a city technique.

    On the highway, I'm already 20+ mph slower than most, so P&G only compounds that delta at the low end.
     
  9. RedylC94

    RedylC94 Well-Known Member

    You flatlanders just need some nice, long downhills on your highways.
     
  10. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    We do actually have some. Only thing is , you can't tell it's downhill or uphill unless you're looking at your Scangauge.
     
  11. RoadWarrior222

    RoadWarrior222 rockit serjun

    I gots a couple that are so steep that you don't need engine off, because you're gaining speed with your foot off the gas and your motor in fuel cut. Thankfully only about half a mile worth each though, because you pay it back twice on the way back.

    (Sure, you could gain MORE speed, but nobody needs to be going 100mph with only one pedal application left in the brakes)
     
  12. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    I can count the number of times I need to be going 100 MPH on the thumbs of one foot.
     
  13. 08EscapeHybrid

    08EscapeHybrid Moderator

    I've done it (over 100 MPH) before...

    Chevy Caprice with police package,

    E450 Super Duty with ambulance package

    International DT4700 Low Profile with ambulance package.

    1980 Pontiac Bonneville Safari with dumbass 16 y/o driver package.
     
    Last edited: Aug 7, 2014
  14. schuylkill

    schuylkill Well-Known Member

    When I was a kid my neighbor buddy was a few years older and a volunteer fire fighter and drove like a maniac. He took me for a ride in his Camaro and got up to 100+. I was on the floor behind the seat scared to death. This was out in the Pine Barrens in New Jersey, desolate and dark. I get uncomfortable today getting up to highway speeds sometimes. You learn to slow down and it's the new normal. There is one hill I sometimes zoom down, bump start to slow down and brake, but it's a long run.
     
  15. RedylC94

    RedylC94 Well-Known Member

    Yup, those downhills that are so steep you have to brake (including "engine braking") to be safe are big energy-wasters, especially when there's a stop sign at the bottom.

    On another hand, long, gentle downhills are also frustrating when I could coast down them, but only at a speed a lot slower than everybody behind me wants to go. That's the circumstance in which a super-high gear ratio would be most useful.

    Grades just steep enough you can coast down at about the same speed you'd choose to travel on the level are best!
     
  16. RoadWarrior222

    RoadWarrior222 rockit serjun

    Got one of those in the city, I can maintain a nice 30mph down all the way.... traffic usually has other ideas.
     

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