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Old 01-18-2008, 06:21 PM   #8 (permalink)
Coyote X
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Join Date: Dec 2007
Location: Southen West Virginia
Posts: 654

Metro XFi - '93 Geo Metro XFi Convertible
90 day: 62.17 mpg (US)

DR650SE - '07 Suzuki DR650SE
90 day: 55.26 mpg (US)
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If you have shaved the head the cam is now retarded from it's stock location. On a metro it is about 1 degree per 0.020 shaved. It should be similar on any over head cam inline engine. I would say to increase your low end, advance it a few degrees past stock. If you can get an adjustable cam gear that would be perfect to figure out where it is best at. The more advanced the cam the more it favors the bottom end. Up to a point anyway ~5-10 degrees advanced on a standard metro cam is good but on your car I have no idea.

If you have the stock cat on the exhaust it probably isn't really affecting it that much. If the cat is gone having a bit of back pressure will help the bottom end out. Maybe just crimp a pipe so it is reduced by maybe 1/4 of it's flow. The farther away from the engine the restriction is the less effect it will have and the bigger it will need to be so try and get it reasonably close.

Also weight reduction is always a good thing so consider if you really need all the stuff that is in the car now and take out what you don't.

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