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Old 11-28-2007, 04:04 PM   This thread is in the EcoModder Project Library | #1 (permalink)
MetroMPG
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Location: 1000 Islands, Ontario, Canada
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Blackfly - '98 Geo Metro
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Metro taller transmission swap thread: +5% efficiency gain (taller final drive)

(Originally written: 05-29-2006)

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Motivated by SVOBoy's transmission swap...

Exactly when I would make the time to do this, I don't know. I already have too many projects stacked up in a holding pattern over the airport.

But, I figure: start this thread and maybe it'll motivate me or someone else.



There it is - transmission from a 4-cylinder (non-GT) Suzukiclone. Same housing and gear ratios as the 3-cylinder version, just a taller final drive:

1998 Metro/Firefly 1.0 L:
1st = 3.416
2nd = 1.894
3rd = 1.280
4th = 0.914
5th = 0.757
Final = 4.39

1989-1994 Swift 1.3L SOHC 5-speed:
1st = 3.416
2nd = 1.894
3rd = 1.280
4th = 0.914
5th = 0.757
final = 3.523

gear ... mph ... ratio ... rpm @ 4.39 calculated (observed) ... rpm @ 3.523

2 ... 40.4 ... 1.894 ... 4959 (5175) ... 4157
3 ... 40.4 ... 1.280 ... 3351 (3495) ... 2809
4 ... 40.4 ... 0.914 ... 2393 (2500) ... 2006
5 ... 40.4 ... 0.757 ... 1982 (2080) ... 1591

Engine RPM figures are calculated from this site:
http://wildcatent.freeyellow.com/zookmods/calc.htm
using outside tire diameter of 22.764 inches, calculated here:
http://www.net-comber.com/tirecalc.html

(Observed RPM) may not be reliable because it's hard to get a figure off the ScanGauge - digital tachs suck, especially when the numbers move around.

Works out to a caculated 391 rpm drop going from the stock 4.39 final drive to 3.523 in 5th gear at 40.4 mph

There was an observed 420 rpm drop on the stock 4.39 when shifting from 4th to 5th @ 40.4 mph.

The mini experiment showed a 8.9 mpg/18.9% improvement in FE from that 420 rpm drop at that speed.

Something to think about anyway.

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