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Formula for R.P.M

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Old 04-14-2004, 09:58 PM
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Perfomer
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Default Formula for R.P.M

I am putting 4.88 gears , currently running 3.73 , Does anyone know the formula to show what rpm the motor will turn in the 1/8 mile? any help would be apprecated Thanks Dwight
Old 04-14-2004, 10:42 PM
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bence13_33
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Default Re: Formula for R.P.M (Perfomer)

You need to know your tire height, rear end gear ratio and your gear ratios in your transmission. There is a calculator located at http://www.smokemup.com . If you don't mind me asking....why the 4.88 gears, do you run strictly 1/8 mile with your car or is it a high winding motor?
Old 04-14-2004, 11:34 PM
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Default Re: Formula for R.P.M (Perfomer)

I am putting 4.88 gears , currently running 3.73 , Does anyone know the formula to show what rpm the motor will turn in the 1/8 mile? any help would be apprecated Thanks Dwight
redline? How fast are you planning on going in the 1/8th?

If you are simply comparing 3.73 to 4.88 I think you just take the ratio of the 2 ratios, ie 4.88 divided by 3.73 = 1.308, so at any point, at any speed your engine will be turning 1.308 times faster for a given speed.

So, if with the 3.73 you are turning 5000 rpm, at that same speed (in the same gear) you will be turning 6541 rpm with 4.88 gears.


[Modified by MNJack, 11:38 PM 4/14/2004]
Old 04-14-2004, 11:52 PM
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Default Re: Formula for R.P.M (Perfomer)

If you're running an automatic transmission, you may want to contact TCI or B&M about a torque converter recommendation with your new gearing.


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Old 04-16-2004, 10:38 PM
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Perfomer
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Default Re: Formula for R.P.M (bence13_33)

Thanks for the info , I am running 1/8 mile only with the 3.73s Igo thru the lights at 4800 rpm 6.78 et at 101 mph. I think that with 4.88 will put me at 6100 thru the lights and pick up the et by a couple tenths. I am running a 327 with a 501 lift crane cam 9.5 compression and a 175 shot nitrous , 60ft times are 1.45 . I found a formula at richmond gears

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