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Thread: MPG w/ Fat Tires and an ECU Tweak

  1. #1
    Still Plays With Cars Loren's Avatar
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    MPG w/ Fat Tires and an ECU Tweak

    Just thought I'd throw this out there.

    I've modded the heck out of the suspension of this car. That doesn't affect fuel economy much, other than I can confidently take turns faster than I should with zero drama... thus slowing down less. The big killer for me is the 195/50 "max performance summer tires" that I have on the car (Dunlop Direzza ZIII), which are decidedly non eco-friendly.

    My latest mod was an ECU tweak (add-on, OBD plug-in thingy) that has advanced ignition timing, and made the throttle a lot more sensitive. But, I don't think this has affected fuel economy at all... as long as I keep my foot out of it. Oh, and I'm also running 91 or 93 octane. Have been forever just in an effort to get the ECU to learn to keep the timing more advanced. And now that I've got a "tuner" that's forcing it to be more advanced, I "need" to run that octane.

    So... Typical running around town, I'll see 32 mpg on short trips. Maybe 34-36 on a longer trip... maybe even 40-42 if it's a particularly long trip and I hit the lights just right. That's in "typical" suburban/urban traffic, driving "mostly economically", but not "hypermiling".

    Decided to do a brief (maybe 10 miles?) post-lunch, casual economy run this afternoon. I reset the MPG with the car warmed up and while sitting at a light. I was pretty lucky with the traffic lights, and took a very light-traffic and low-speed route that kept me between 30 and 40 most of the time. I never turned off the AC, and never cut the engine. Neutral coasted for long flat or downhill stretches. DFCO when coming to a stop. Gentle/moderate acceleration. Shifted no higher than 3k and babied the throttle in top gear, never cruising below about 1800-2000.

    Net result for this trip: 46.3 mpg.

    Add 1.3% for tire size difference = 46.9 mpg

    I'm still disappointed that it's SO HARD to get 50 mpg in this car without getting into serious hypermiling. (EOC, extreme coast-downs, etc) I could get my manual trans Yaris (with the same tire/wheel package) to 50+ with nothing but DFCO... perhaps not "easily", but "regularly". And the Versa that I used for a DE car with it's awful CVT... it would do 47-48 EASY, and hit 50+ on occasion if I used neutral coasting.

    So... yeah, if I kept the stock narrow eco tires and ran without the AC... I'd probably hit 50-52 pretty easily. And that's good. But, for what this car is supposed to be, it seems that cars like the Yaris and Versa are capable of the same trick (50 mpg) without quite as much work.

    I just have to remind myself that no matter how I drive my Mirage, I'm still getting AT LEAST 30% better fuel economy than the typical cars and SUV's around me.

    One thing I will say about the Mirage is that it recovers its average MPG from a cold start better than anything else. The Yaris and Versa would make a cold-start trek from my driveway to the main road (25 mph, about 3/4 mile, two stops) and see maybe 12-14 mpg. The Mirage will regularly be at 21+ in that distance. Much better management of cold-start fuel. But, it loses HARD on acceleration. To get that little 1.2 to motivate, it uses some fuel.

    My love/hate relationship with the Mirage continues.

    But, it's still fun to show up at an autocross and beat 1/2 to 2/3 of everyone there in a car with 74 horsepower. (and get an easy 40+ mpg on the way home with delightful air conditioning and Bluetooth audio)


    Simplify and add lightness.

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    Moderator Eggman's Avatar
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    Quote Originally Posted by Loren View Post
    Shifted no higher than 3k
    Try shifting at or below 2000 RPMs.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Still Plays With Cars Loren's Avatar
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    Not in the traffic that I have to drive in.

    Plus, I really don't like to lug the engine that much.

    If I'm hypermiling (or close to it), I'm usually shifting between about 2400-2600. I just don't let it get up to 3000. I think throttle position is more important than absolute revs. If I'm shifting sooner, but mashing the gas harder, I'm not going to see any benefit over lighter throttle and letting it rev.
    Simplify and add lightness.

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    Moderator Eggman's Avatar
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    So you won't even try? You might be surprised.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Senior Member Top_Fuel's Avatar
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    I just got back from visiting the area where Loren lives near Tampa. He's got a couple of things working against him for sure.

    The first is having to run the AC all the time. The second is the traffic. It's pretty busy down there...and it's not even the congested time of year yet! I know I would have a hard time taking my car down there and duplicating my current mileage where he lives in those conditions.

    These little engines apparently use a lot of fuel under load...whether it's accelerating, driving the AC compressor, or trying to do both at the same time

    I have often wondered if an engine with a little more hp/torque could actually pull off better fuel economy because it wouldn't be so taxed under these conditions. And it might be able to move the car more efficiently with a steeper overdrive gear.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)


  7. #6
    Still Plays With Cars Loren's Avatar
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    Quote Originally Posted by Top_Fuel View Post
    I have often wondered if an engine with a little more hp/torque could actually pull off better fuel economy because it wouldn't be so taxed under these conditions. And it might be able to move the car more efficiently with a steeper overdrive gear.
    I believe that is the case.

    I drove a BMW Z4 3.0si for a couple years. Economy wasn't great around town because it was WAY too easy to just mash the gas and go. Just casually cruising through 1st, 2nd and 3rd would put you at 60-70 mph without even realizing it. 300 ft/lbs of torque will do that.

    But, due to its gearing and excellent use of VVT and DBW, I could return 30+ mpg on the highway with that car... cruising 80-85. All day long.

    Try cruising 80 in the Mirage. (especially with wide performance tires) You're not going to do much better than 32 mpg.

    I think that's why the 1.5 Yaris and the 1.6 Versa are easier to get MPG out of. They have significantly more usable torque than the Mirage. Comparitavely, they have about 15% more weight... and 40% more power/torque.

    And you're right. Urban Florida isn't great for eco driving. It's pretty flat. Not a lot of hills to work with in most places. If you're not lucking into overpass situations followed by a green light, you're pretty much flat-cruising. And there's usually too much traffic to get away with any significant "pulse and glide" without pissing people off.
    Simplify and add lightness.

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    Moderator Eggman's Avatar
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    Quote Originally Posted by Loren View Post
    I believe that is the case.

    I drove a BMW Z4 3.0si for a couple years. Economy wasn't great around town because it was WAY too easy to just mash the gas and go. Just casually cruising through 1st, 2nd and 3rd would put you at 60-70 mph without even realizing it. 300 ft/lbs of torque will do that.

    But, due to its gearing and excellent use of VVT and DBW, I could return 30+ mpg on the highway with that car... cruising 80-85. All day long.

    Try cruising 80 in the Mirage. (especially with wide performance tires) You're not going to do much better than 32 mpg.

    I think that's why the 1.5 Yaris and the 1.6 Versa are easier to get MPG out of. They have significantly more usable torque than the Mirage. Comparitavely, they have about 15% more weight... and 40% more power/torque.

    And you're right. Urban Florida isn't great for eco driving. It's pretty flat. Not a lot of hills to work with in most places. If you're not lucking into overpass situations followed by a green light, you're pretty much flat-cruising. And there's usually too much traffic to get away with any significant "pulse and glide" without pissing people off.
    The Mirage is often referred to as a City Car. It can work well on highways, but it's design tends to favor urban traffic.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Speed kills mpg in any car.

    Quote Originally Posted by Eggman View Post
    The Mirage is often referred to as a City Car. It can work well on highways, but it's design tends to favor urban traffic.
    Even the Toyota Prius does better in the city than the highway. Checking some Prius reviews, owners aren't getting much better than 50 mpg when their cars are pushed at higher speeds. The newer Prius seems to be doing better than the earlier models.

    My 2017 Mirage ES (manual) always gets 40-50 mpg regardless of where I go. During the winter months, I would say it was doing around 40-44 mpg on average. This summer it seems to be doing about 5 mpg better than that overall. When I drove to North Dakota earlier this summer, I was doing 75-80 mph on the interstate with the A/C on. Under those conditions, it dropped to about 42-43 mpg. I don't remember fighting any strong winds on that trip, & that may have helped, too.

    I just drive normal in my opinion. I keep my tires inflated to approximately 40-42 psi, but I do that with any vehicle I own (a few pounds under the maximum psi). I never look at the odometer for MPG readings, because I don't have much faith in them. I just use the calculator on my smart phone & do the math when I fill up each time. My Mirage turned over 15,000 miles this week, & I have never been under 40 mpg on any tank of gas. I live in rural southwest Wisconsin. I don't have to fight traffic much. Getting behind a school bus would be the extent of my frustration.

    I took a trip to Lake Superior a couple weeks ago. That involved a different combination of highway driving (some 4-lane & 2-lane). I averaged about 46-48 mpg on that trip. That was with two people & a car full of luggage, coolers, & stuff.

    Just looking at Toyota Prius as a comparison, the older models didn't do much better than my Mirage when driving at higher highway speeds. You could probably buy two discounted Mirages for the price of one Prius.

    Speed is a killer for mpg on any car. That's why we had 55 mph speed limited implemented in 1974 (until 1995) after the great oil crisis of 1973. I think the Mirage is a nice package for the money. Creating a car that is affordable, reliable, and very economical is probably more of a challenge than creating an expensive vehicle of any sort. I really like the Mirage as is. If it was more like the Yaris or Fit, I would buy a Yaris or Fit. If Mitsubishi marketed the Mirage better (lowered the MSRP rather than their confusing gimmick discount deals), the value of the Mirage would be seen by more consumers/critics.

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  12. #9
    Still Plays With Cars Loren's Avatar
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    One "benefit" of the low power in the Mirage, it means that pretty much ANYBODY is going to get good fuel economy out of it. If you have more power, the average driver is going to USE that power and not get max fuel economy. I haven't really tried it, but you could probably drive the Mirage nearly flat out everywhere and still return 28-32 mpg average. Something like a Fit or Versa, that would get you into the low 20's easily.

    I wish I could get accurate full-tank mileage, but since I generally do at least one autocross on each tank of fuel... it throws my tank averages WAY off. (my trip average during a typical autocross session is usually less than 12 mpg... and the drive home is almost always 46ish) So, I just watch the in-dash display for trip MPG's when I feel like playing the hypermiling game.
    Simplify and add lightness.

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    Yeah trust me if you go flat out all the time you will get a consistent 16mpg...I did that when I first got my liscesnse, fun, but super wasteful :')


        __________________________________________

        click to view fuel log View my fuel log 2017 Mirage ES 1.2 manual: 37.4 mpg (US) ... 15.9 km/L ... 6.3 L/100 km ... 44.9 mpg (Imp)


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