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Old 09-18-2017, 01:38 PM   #1 (permalink)
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.8 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 73.57 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)
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"MPGiata" modding thread: aiming for 50 MPG with a 1990 Miata

You may have already seen my initial Miata thread, which documents the saga of buying and repairing this fun old turd bucket to make it road legal. Time for a fresh thread that focuses on the ecomodding!

The car:
  • 1990 Mazda Miata MX-5
  • Engine/trans: 1.6L (116 hp), 5-speed
  • Drag coefficient (random search result): 0.38 top up; 0.40 top down
  • Frontal area:
  • Curb weight: ~2k lbs, depending on options
  • Odometer: 216k kilometres (134k miles)

MPG potential:

EPA says: 22 city / 28 highway / 24 combined

AntiochOG did a 50 mpg fill using pulse & glide (but P&G is not my plan): 50 mpg! (1990 Mazda Miata)

The top 3 Miatas in EM's garage:
Fuelly shows a couple hundred owners of the early 1.6L cars are averaging 27 mpg US. Half a dozen owners of the 1.6L "NA" model report averages of 40-45 mpg.

The goal:

50 MPG (US) / 4.7 L/100 km, in my typical summer driving environment:
  • relaxed cruising, almost always taking the scenic route or back roads;
  • but fun DWB ("driving without brakes") in the twisties!
  • 80 km/h (50 mph) max. posted limit most roads
  • primary driving techniqe = driving with load (when not affecting traffic)
  • but also engine-off coasting toward some turns & stops, or on steep enough descents that allow me to keep speed.
  • top will be down most of the time (despite worse aero), since that's one of the main reasons I got it!

Results so far:
1) 37.5 mpg US = 6.1 L/100 km: first fill last year, cool autumn driving (10-15 C = 50-60 F) with no mods other than tire pressure;

2) 43.6 mpg US = 5.3 L/100 km: 2nd fill (1st fill of this year); warm summer driving with some mods in place;

3) 44.2 mpg US = 5.2 L/100 km: warm summer driving with even more mods in place;

4) 49.9 mpg US = 4.7 L/100 km: so close! Continuing ideal warm weather, still more mods!

5) 51.0 mpg US = 4.6 L/100 km: Success!! 2/3 ideal warm weather, still more mods.

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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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