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Old 08-25-2008, 11:39 PM   #51 (permalink)
bbjsw10
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Join Date: Jul 2008
Location: Findlay,OH
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bbjsw10 - '91 Geo Metro Xfi
90 day: 51.06 mpg (US)
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I have started accelerating differently, I was taking off at 10in. hg. now I have began to take on in first shift to second at like 5 mph, and 2nd-4th about 4-5in. hg.

I have an A/Fuel ratio gauge and at this position of throttle it stays a lil more on the lean side.(I have been listening for spark knock none what so ever) If I give it any more throttle than this it goes into opem loop and stays pegged at rich. It kinda has a little sweet spot right there at about 40-50% throttle, it is a very small area I have to watch A/F gauge very closely or it goes rich. I can't move my foot more than 1/8" or I lose this spot. I also must shift about 2200-2500 rpm to stay in this fuel reading. Maybe it is the Xfi ecu has a different map.

This should in theory reduce my pumping loss of the engine by not "bogging" it down at the lower throttle position. I guess only time will tell on this method I hope it does do what I am thinking it will. Another added benefit of this is that I reach cruising speed in 5th about 5-10 seconds sooner, which is probably the most efficient speed for this car 35mph in 5th.

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