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Old 02-10-2009, 01:18 PM   #5 (permalink)
MetroMPG
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Join Date: Nov 2007
Location: 1000 Islands, Ontario, Canada
Posts: 22,373

Blackfly - '98 Geo Metro
Team Metro
Last 3: 70.09 mpg (US)

MPGiata - '90 Mazda Miata
90 day: 52.07 mpg (US)

Winter beater Metro - '00 Chevrolet Metro
90 day: 61.98 mpg (US)

Fancy Metro - '14 Mitsubishi Mirage top spec
90 day: 58.72 mpg (US)

Even Fancier Metro - '14 Mitsubishi Mirage top spec
90 day: 70.75 mpg (US)

Appliance car - '14 Mitsubishi Mirage ES (base)
90 day: 50.04 mpg (US)
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Quote:
Originally Posted by Deezler View Post
You would have to be hardcore about economy to do this.
Sort of like the Suzuki/GM engineers who designed the XFi engine with one compression ring?

Yes, the engine has positive crankcase ventilation back to the intake, so if there is any additional blowby, it's going to get combusted.

Quote:
If you reduce the engine compression sealing ability far enough, you'll end up with lower power and worse economy.
Of course. But again: see the XFi example.

Another potential downside is faster ring wear. Though if I recall, Coyote's experience with these motors is they pretty much require a rebuild at 150k miles regardless of XFi vs. garden variety. At the rate I drive, that means I should set aside some time to tear it down around 2055.

Yet another potential downside someone has pointed out privately to me: the ring spacing may be different between the 2 piston styles, to keep the piston properly aligned in the cylinder vs. thrust angle. If the piston is "unbalanced" it could cause scoring.

Quote:
Your link is dead though so I'm not sure I have the whole story.
Hmm. Works for me. But it's just an abstract. There's really no more useful info than I posted.
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Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
Honda mods: Ecomodding my $800 Honda Fit 5-speed beater
Mitsu mods: 70 MPG in my ecomodded, dirt cheap, 3-cylinder Mirage.
Ecodriving test: Manual vs. automatic transmission MPG showdown



EcoModder
has launched a forum for the efficient new Mitsubishi Mirage
www.MetroMPG.com - fuel efficiency info for Geo Metro owners
www.ForkenSwift.com - electric car conversion on a beer budget
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