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post #1 of 2 (permalink) Old 10-27-06, 05:33 AM Thread Starter
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Age: 31
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hey guys just woundering if someone could help me with a gearbox calculation
i have ef I6 with a T5 and 3:45 diff gears what speed em i doing at 5,900rpms?

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post #2 of 2 (permalink) Old 11-25-06, 05:55 AM
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Re: help

from: Speed versus RPM calculator

the formula relating road speed and engine rpm is

mph = (rpm * cir) / (gear * final * 88)

where rpm = engine rpm
cir = tire cicumference, in feet
gear = gear ratio of your car
final = final drive ratio of your car
88 = combines several conversion factors

for example, the audi 90 quattro (R&T, december 1987). its tires are 195/60VR-14,so our calculated circumference works out to be 72.92 inches or 6.08 feet. its final drive is 4.11:1, its 5th gear is 0.79:1, so their product is 3.25 and the rest is a quick calculation away:

mph = (rpm * 6.08) / (3.25 * 88) = 0.0213 rpm

so, for instance, the audi will do 21.3 mph for every 1000 rpm in 5th gear.
and thanks to google's calculator

1 mile = 1.609344 kilometers
Its fun to sit down and work out your cars max speed (if air resistance and power werent an issue).

95 EF

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