Calculating RPM vs Speed for 6speed S4.... (Help, I screwed up something)
12-28-2001, 10:52 AM
#1
AudiWorld Expert
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Calculating RPM vs Speed for 6speed S4.... (Help, I screwed up something)
gearing info:
1st - 3.500
2nd - 1.889
3rd - 1.231
4th - 0.967
5th - 0.806
6th - 0.684
Reverse - 3.455
Final - 4.111
Tire Size = 225/45R17
Circumference = Pi * Diameter
Ideal Diameter = 17" + 2(225mm*0.45) = 24.97"
Ideal Circumference = 78.45"
63360 inches = 1 mile
60 min = 1 hr
To find Speed
Given RPM & Gear
Speed = RPM * 60min/1hr * 78.45"/rev * 1mi/63360" / (GearRatio * 4.111)
To find RPM
Given Speed & Gear
RPM = (Speed * GearRatio * 4.111) / (60min/1hr * 78.45"/rev * 1mi/63360")
1st - 3.500
2nd - 1.889
3rd - 1.231
4th - 0.967
5th - 0.806
6th - 0.684
Reverse - 3.455
Final - 4.111
Tire Size = 225/45R17
Circumference = Pi * Diameter
Ideal Diameter = 17" + 2(225mm*0.45) = 24.97"
Ideal Circumference = 78.45"
63360 inches = 1 mile
60 min = 1 hr
To find Speed
Given RPM & Gear
Speed = RPM * 60min/1hr * 78.45"/rev * 1mi/63360" / (GearRatio * 4.111)
To find RPM
Given Speed & Gear
RPM = (Speed * GearRatio * 4.111) / (60min/1hr * 78.45"/rev * 1mi/63360")
12-28-2001, 03:17 PM
#4
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Hey, looks like i was wrong
Comin home from work today cruisin at 80 in 6th, double clutched down into 3rd.. car reved up to 5400 (I think) got on the throttle and rode up to 6800 to a speed of 96 or soo..
Tried 2nd.. right 60 mph or so, hit the rev limiter.
Thanks, Sorry for wasting your time
Tried 2nd.. right 60 mph or so, hit the rev limiter.
Thanks, Sorry for wasting your time
12-28-2001, 05:08 PM
#5
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I should just put these up on a page somewhere...
MIND YOU THESE ARE ALL "THEORETICAL" assuming you had the horsepower to overcome the drag :-)
<img src="http://www.taner.net/s4/s4-chipped.png">
<img src="http://www.taner.net/s4/s4-tip.png">
<img src="http://www.taner.net/s4/a6_42.png">
AND for fun...
<img src="http://www.taner.net/s4/E46_M3.png">
<img src="http://www.taner.net/s4/s4-chipped.png">
<img src="http://www.taner.net/s4/s4-tip.png">
<img src="http://www.taner.net/s4/a6_42.png">
AND for fun...
<img src="http://www.taner.net/s4/E46_M3.png">
12-28-2001, 06:37 PM
#6
when you say ideal diameter, are you just saying this
or did you go through, take measurements and calculate this. And what is it ideal for? I was actually thinking about figuring out the ideal total wheel/tire diameter for best 1/4 and 0-60 times.
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01-02-2002, 05:23 AM
#8
AudiWorld Expert
Thread Starter
I'm saying that based on the tire size (225/45R17), I calculated the circumference...
and thus the distance the car travels for one rotation of the axle. This # is "ideal" because not all tires with the same size markings are actually the same size and also depending on air pressure and just the fact that the tire is on an actual circle when rotating means that it may or may not travel the calculated circumference distance for one revolution. If you compare these calculated numbers to what actually shows on the speedo, you may see a discrepancey because the engineers that calibarated the speedo used a different value for the distance traveled for one revolution (if indeed they did)
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