Re: what rpm are u guy at in 5th gear with 3.94 final drive at 80mph?with stock 5th (MAC)
Final Drive: 3.39
5th Gear: 0.84
Number of Revolutions of Wheels
3000 rpm/(0.84 *3.39) = 1053.5187263 rpm = 63211.1251 rph
One Revolution distance (for a 225/45 R17 wheel)
Pi * Dia = 3.14 * [ ( 17 * 2.54 * 10 ) + ( 225 * 0.45 ) ] mm = 1.991702 m
( 63211.1251 rph * 1.991702 m/r )/(1000 * 1.6) = 78.686 mph
So at 80 mph, I am doing a tad over 3000 rpms!
Re: what rpm are u guy at in 5th gear with 3.94 final drive at 80mph?with stock 5th (WMTJ)
quote:[HR][/HR]How did you calculate that?[HR][/HR]
I made a Excel Spreadsheet that takes Tire Size, Gearing, Final Drive and RPMs, and spits out a speed. Simple math, and a little geometry. It saves alot of time not having to write out the formulas again and again.
My spreadsheet came out with the same answer pal did with his numbers. (A4 wheels, and stock VR6 tranny)
Re: what rpm are u guy at in 5th gear with 3.94 final drive at 80mph?with stock 5th (Surf Green)
The logic is quite simple- for every engine rpm you calculate the number of wheel revs using gear ratio and final drive and convert that to revs per hour.
Then you calculate the distance the wheel travels in one rev ... Pi*D
Multiply the above two numbers and convert to miles per hour.
Re: what rpm are u guy at in 5th gear with 3.94 final drive at 80mph?with stock 5th (pal)
I asked the same question last week. Go to www.smokemup.com and you will find a calculator for tire size and rpms with different gear ratios. Also make sure you have the right tire size. I had bought my car used and it had 55 series tires that were messing up my rpms. I wish that I had found this out before I bought those new tires.
A forum community dedicated to all Volkswagen owners and enthusiasts. Come join the discussion about performance, builds, modifications, classifieds, troubleshooting, maintenance, new releases, and more!