Electronic Throttle Deceleration Tips

Discussion in 'Fuel Economy' started by Gageraid, Mar 8, 2014.

  1. Gageraid

    Gageraid Well-Known Member

    Good day, all.
    I hope this question can be answered. Please keep in mind I drive a really heavy 4,200 pound Jeep that can easily come to a stop when you let off the accelerator. Coasting is a joke.
    Here's my dilemma. When I am coming down a hill or just on a flat road, I obviously know to try to coast as far as possible, but I'm wondering if there is a better way for me.
    Is it beneficial for me to be every so slightly touching the throttle under these circumstances?
    I attached a picture. From traveling right to left (popular road I drive down), the blue line is as far as I can coast without applying the gas. Without my right foot, it'll be at about 25mph at this area. Max speed down the hill is 42mph. That light is red 60 percent of the time.
    To simplify my question, can I gain mpg by being on the electronic throttle slightly instead of trying to coast as far as possible just to apply the gas again to regain speed? Thanks in advance.
    [​IMG]
     
  2. seftonm

    seftonm Veteran Staff Member

    Are you coasting in gear or in neutral? I would say the best way to go down the hill would be in neutral. That avoids some of the drag and engine braking and you should coast a bit farther. Then put it in gear to get back up to speed, or if you need to brake then put it in gear to take advantage of fuel cut.
     
  3. Gageraid

    Gageraid Well-Known Member

    Everything is done in gear. Been trying to brew up some questions to help my mpg because it seems I've finally reached my limit with how high I can go.
    My last car was carbureted, so I'm sure you can imagine how weird it is for me to drive a vehicle with electronic throttle. The vehicle is so heavy that is slows down so much as if you were on the brakes in a regular car. Get a lot of weird looks when I coast to a stop because it's rare that I need the brakes.
     
  4. seftonm

    seftonm Veteran Staff Member

    Try coasting in neutral next time, you may get a much longer glide out of it. My rule of thumb is coast in neutral unless you need your brakes to slow down. If you need to slow down, brake while you're in gear. What are your tire pressures at? That may be really slowing you down too. Though I bet the tires that Jeeps come with may not be the best for rolling resistance to begin with :p
     
  5. Gageraid

    Gageraid Well-Known Member

    Can't tell a difference in neutral, but I could give it another shot.
    Tires are at 55 psi I believe. I should remember, I just checked last week.
     
  6. Gageraid

    Gageraid Well-Known Member

    I finally found the re-calibration process for my electronic throttle body. Only took a year of researching to find it. Not sure if it's factual or not, but I did it.
    Went for a test drive and it felt different. Hopefully I found some extra mpgs here, and not the placebo effect. Chrysler and their secrets.
     
  7. ILAveo

    ILAveo Well-Known Member

    My response to this is that I would check for a dragging brake (or bad wheel bearings?) if you can't tell a difference in N.

    It's the time of year to have seized e-brake cables..
     
  8. Gageraid

    Gageraid Well-Known Member

    I have brand new wheel bearings and I use my e-brake every single day and know it's working.
    Seriously a 4,200 pound vehicle with a 4 speed auto isn't going to coast far. Like I said, I'll try again in neutral, but I don't remember a difference.
     
  9. seftonm

    seftonm Veteran Staff Member

    Number of gears in the transmission shouldn't make a difference in neutral. The aerodynamics are probably a much bigger factor than the weight. We drove an A7 TDI quattro cross-country last year; it weighs 4200 lbs empty and we had 4 adults and gear in it. It coasted fine, much better in neutral than in gear.
     
  10. Gageraid

    Gageraid Well-Known Member

    Yeah. Not sure if you've ever seen my Jeep, but it's far from aerodynamic.

    [​IMG]
     
  11. RedylC94

    RedylC94 Well-Known Member

    Weight doesn't explain not coasting well. In fact, the more weight you have in proportion to the total of tire rolling resistance (which is roughly proportional to weight) plus aerodynamic resistance (which isn't), the farther you can coast. Assuming the brakes and tires are OK, high aero drag is probably your biggest handicap.

    LOW weight in proportion to aero drag is why my car (or a motorcycle or bicycle) does not coast as far or fast as most cars.
     
  12. Gageraid

    Gageraid Well-Known Member

    May be I'm wording how I feel about the coasting wrong. It obviously can coast, but the speed drops as if you were on the brakes in a normal car.
    It is not uncommon for me to drive from Point A to Point B all the way across town and only use my brakes once to park (assuming I caught all the lights).
     
  13. ILAveo

    ILAveo Well-Known Member

    I'm sure that your jeep is more aero than the GMC 3500 with aftermarket side tool boxes and liftgate that I drive at work. ;)

    When I've had cars/trucks not coasting differently in neutral it pretty much has always meant that something is dragging. Neutral coasting is my first diagnostic for MPG issues.

    I'd be checking for hot brakes after driving without using them. Could be a sticky caliper or bad adjuster.
     
  14. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    You guys used neutral ? The Cool Kids in the A6 DWL in gear. Well , I don't know about Wayne ; I was usually sleeping while he was driving.
     
  15. Gageraid

    Gageraid Well-Known Member

    I'm not worried about anything being wrong with it. I get better MPG than 90 percent of people I talk to with the same vehicle on the forums. It could be better in neutral, but to such a small extent that would not be felt is all I'm saying.
    Drive a newer body style Jeep Liberty (2008-2012) and it'll feel much different than anything you've driven before.

    Another update on the throttle calibration, she seems to be running extra strong. I'm convinced it worked.
     
  16. seftonm

    seftonm Veteran Staff Member

    Maybe that's why we always flew by you going downhill ;)
     
  17. worthywads

    worthywads Don't Feel Like Satan, I am to AAA

    My wife's Honda Element is quite a brick at speed too. I throw it in neutral coming down hills I would normally pick up speed on with the Tacoma and it just dies losing speed or staying the same. Wind resistance is the problem.

    Have you tried without the bug guard. We had 1 on the Element after hearing reports of bugs and rocks hitting the windshield. After 6 years decided to go without and picked up minimum 1 mpg.
     
  18. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    The final numbers speak for themselves. But we did have a "ringer" in our car, too.
     
  19. CPLTECH

    CPLTECH Well-Known Member

    In the picture I focused on the tires. Apparently, those are needed for your location? I recall a purchase of a used 85 S10 with similar tires. It would not roll down a hill. Put some passenger tires on it and it was a world of difference, yet handled the weight. On my 2006 PathFinder, I stay away from LT tires for that reason. MPG matters to me more than macho.

    As others stated, pump the tires up. ~45psi works out well for my vehicle.
     
  20. Gageraid

    Gageraid Well-Known Member

    Almost done with this tank which is showing me no noticeable change in mpg with these tires.
    Those tires were installed a few weeks ago. The stock tires were really dangerous.
    Gonna focus a lot on these next few tanks especially if this throttle re-calibration actually worked, which seat of the pants is telling me yes.
     

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