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Old 09-29-2014, 08:17 PM   #1 (permalink)
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Blackfly - '98 Geo Metro
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Last 3: 70.09 mpg (US)

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15 mods = 15% MPG improvement: A-B test, 2007 Honda Civic 1.8L, 5-speed

Some of you may have seen the thread where I was hunting for a winter car to give the Firefly/Metro a break. I ended up getting a good deal on a 2007 Honda Civic LX (1.8L, 5-speed manual):

Since I got it, I've been busy ecomodding it, getting it ready to put in active duty next month.

Before I began modding, I ran a set of baseline speed vs. MPG runs (2-way averages from 70 through 100 km/h). Yesterday, I repeated the speed/MPG runs with all the mods in place (same flat test road, similar ambient temperature).

The mods:
  • Increased tire pressure
  • 6.5% taller gearing (owing to taller winter tires -- 65 vs. 55 series)
  • Reduced tire/fender gap (due to taller tires and slightly greater wheel offset)
  • 100% smooth wheel covers (coroplast)
  • Civic hybrid style decklid spoiler (CAD ... cardboard... version)
  • Civic hybrid style rear wheel spats (coro)
  • Full upper grille block
  • Partial lower grille block (with pop-out section if it gets warm)
  • Licence plate relocation (better aero than the stock bracket)
  • Daytime running lights switch (DRL's off when not needed)
  • Passenger side mirror delete
  • Driver side mirror folded (highway), with convex mirror mounted on trailing edge
  • 1 wiper delete
  • Vertical spoilers on the rear bumper corners
  • Big @$$ air dam (which scrapes now & again)

A-B test results ...

(UPDATE: the chart below has been updated with calibrated fuel consumption numbers. Original chart was based on a ScanGauge with default fuel offset settings.)

That's an average of 15.1% better MPG than stock.

Thoughts/observations ...

- Take this with an appropriately sized grain of salt. It's not a proper "good as possible" A-B-A test under the same day/conditions. I'm not planning to remove/reinstall this set of mods to do an A-B-A.

- That said, I actually ran the "B" 80 km/h pair twice (repeated it at the end), and the 2nd pair of runs produced the same numbers.

- Those MPG figures honestly seem too good to be true: with all the mods in place, the ScanGauge reported 64 mpg (US) at 80 km/h (50 mph). Unmodified, it showed 55.9 mpg at that speed. I'll just have to wait for a fill-up to calibrate the gauge and see how close to (or far from) reality it is. I'll come back and fix the graph if it turns out these numbers are way off. ... UPDATE ... calbration done and the chart above has been updated.

- Though I would think the relative/percent change should hold, regardless of whether the gauge is calibrated or not.

Coming up: I'm going to post a bunch of pics of the mods. See the project thread for some detailed pics of how some of them were made:

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Latest mods test: 15 mods = 15% MPG improvement: A-B test, 2007 Honda Civic 1.8L, 5-speed
Ecodriving test:
Manual vs. automatic transmission MPG showdown: Nissan Micra 1.6L

has launched a forum for the efficient new Mitsubishi Mirage - fuel efficiency info for Geo Metro owners - electric car conversion on a beer budget
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