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Old 02-10-2009, 01:18 PM   #5 (permalink)
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Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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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.

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.

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.
Project MPGiata! Mods for getting 50+ MPG from a 1990 Miata
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