Electronic Throttle Deceleration Tips

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

  1. Gageraid

    Gageraid Well-Known Member

    I have not tried without the bug guard yet. That was a purchase I made the first month of owning it. I really like the look of it, and I was under the assumption it wouldn't change mpg. The hood has a few dings from the previous owner that this covers up as well lol.
    I've been searching underneath the Jeep lately for places to maybe fab up some sort of aerodynamic pans or something. I have no skills in that area, though. I know they make a few skid plates for this model, but the owners haven't reported a change in mpg.
     
  2. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    Years ago, I had a convertible, which shares the curse of "bad aero" when the roof is down. And since it was a sunny-day-only cruiser, it rarely moved without the roof squished behind the rear seat. My solution for the bad aero was to drive slower. Drag increases with the square of speed, so knocking 5 or 10 mph off the speedometer helps much more on the high-drag shapes. Even top down, my convertible beat the EPA by 20% on the highway by just driving 50 in a 55 zone instead of trying to keep up with the Joneses as they raced by at 65-70.
     
  3. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    Well, they ARE needed if you need to look cool.
     
  4. RedylC94

    RedylC94 Well-Known Member

    That's right. That's my stategy exactly with my high-drag car, with very similar results.

    If you can simply drive exactly like the original EPA Highway test, you'll beat the EPA's published highway numbers by 28% for 1985-2007 models, and by even more for newer cars.
     
  5. Gageraid

    Gageraid Well-Known Member

    I'm itching to do a mod to help the mpgs a little. So hard to find ideas when no one has the same mindset as I do with it. I think I just need to learn my ScanGauge2 a little better.
    I want to understand engine load better. I rarely hit 99 LOD. If I do, it's at full lock (50mph) on one of the roads that is slightly up hill the whole way.
     
  6. EdwinTheMagnificent

    EdwinTheMagnificent Legend In His Mind

    This is possible ONLY if you have access to E0 fuel. Some of us do not.

    But , yeah. You know and I know that the 81 GLC can totally beat the unadjusted EPA numbers on the highway. But that was a long time ago for me , on fuel that was most likely E0. How does the GLC do on E10 ?
     
  7. Gageraid

    Gageraid Well-Known Member

    I know I'm derailing this thread a little, but I was doing some searching about engine load last night on this site. If I do some testing to figure out what engine load causes "open loop", could using this number help out my driving habits? I still fear I am too LIGHT on the throttle at most times.
    Even thought my mpg isn't that great, I believe it's pretty high for the vehicle combined with my life schedule. I live really close to everything so this Jeep sees way too many cold starts. If my engine is still not up to operating temperatures when I get to work or home from work each night am I wasting gas by backing up in to my driveway as I do everyday?
     
  8. Block heater?
     
  9. Gageraid

    Gageraid Well-Known Member

    Planning on having one by next Winter.
     
  10. Gageraid

    Gageraid Well-Known Member

    Did my open/closed loop test while also display engine load. My testing was done on two different roads, a 35mph and a 55mph one.
    It was harder than I thought it would be to go into open loop. My foot had to be almost all the way down to achieve this. Can someone shed some light and explain what you are seeing here? I can be at 99 engine load and still be in closed loop, but it isn't until my foot is almost all the way down when it finally goes open loop.
    Does this confirm my theory that I should be a bit more heavy on the throttle while getting up to speed?
     
  11. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    You have an automatic transmission - it won't (or shouldn't) go to open loop but instead should downshift a gear. Get too heavy on the pedal and the torque converter won't fully lock. Your Jeep, if you have the V6, has the old 42RLE trans and it's converter is PWM - a fancy acronym meaning the computer can vary slip based on load-vs-throttle-vs-speed.

    You should have a tach in the dash cluster, and you will want to use that to determine throttle setting. The transmission should be upshifting when the tach is around 2000. Once you're in direct drive, you can lean on the throttle and bring the load up over 80%. But keep an eye on the tach... If it starts drifting upward, it means the computer is bleeding off some hydraulic pressure for the converter clutch and you're losing the mechanical link between the engine and driveline.

    You may see 99% engine load when accelerating briskly. But that is not a goal you want to achieve often. You want to use minimal pedal pressure to get the vehicle to move as fast as it needs to, based on speed limits, light timing, weather conditions, and all the other variables. For a real boost in fuel economy, concentrate on shunning the brake pedal. Every time you step on the brake, ask yourself what could have been changed so that you could have avoided having to slow or stop. It could be increasing the buffer, or maybe learning light timing, or even adjusting your route. There will be times when you need to stop, and you do so. But remember that every press of the brake pedal is doing nothing more than using very expensive gasoline energy to grind very expensive brake pads into unsightly black dust on your wheel rims.
     
  12. Gageraid

    Gageraid Well-Known Member

    Thanks for the reply. I know all too well about the brakes. There are many many MANY times I can drive amazing distances without using the brakes. Full lock doesn't occur until 50 mph in this vehicle. 2,000 RPM won't even get me to top gear!
     
  13. RedylC94

    RedylC94 Well-Known Member

    You're correct, sir, about the E10 handicap for most cars. However that should be a small effect, compared to the 0.78 fudge factor EPA used to convert "unadjusted" actual test results to "adjusted" highway numbers. So instead of 28% (100%/0.78-100%), I should've said 24% (0.97×100%/0.78-100%). Anyway, the main point was that beating the published numbers should be easy in any post-'84 car, when one theoretically can match the much higher unadjusted numbers by simply driving like the EPA does.

    As for your question about the '81 GLC and E10, it's quite fond of the stuff. It usually slightly beats its original advertised highway number (45, equivalent to 35.1 "adjusted" as for '85-'07 models) on both long Interstate trips and short local jaunts), burning E10.

    I can't remember the last time I bought E0. With a "dumb" fuel system (i.e., with no closed-loop control of fuel mixture), I suspect switching from E0 to E10 makes very little difference in fuel consumption, as long as it doesn't result in misfiring.
     
    Last edited: Mar 14, 2014
  14. donmk8

    donmk8 Member

    The tires at 55 psi will help but still not roll/coast very far. You may be exceeding the design pressure for the tires when they get hot.
    I have Perelli Scorpion Verde low rolling resistance tires (37 psi) on my 09 Edge, 5400 lbs. I can move it just by leaning on it on level ground.
     

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