How do I to calculate engine rpm in 5th gear?
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Senior Member
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Joined: Oct 2004
Posts: 608
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From: Pelham, NH
Car: 91 B4C, 17 C7 GS, 16 Denali DMax
Engine: LS3, LS3, LML
Axle/Gears: 3.23, 3.42, 3.23
How do I to calculate engine rpm in 5th gear?
I am trying to calculate the rpm I will pull in 5th gear at any given speed.
For example my proposed setup will be as follows:
5th ratio = 0.68
Rear end ratio = 3.23
Tire diameter = 25.7 (245/50 16)
Target highway speed = 75mph
Can anyone provide a link or the calculation so I can adjust for different rear end ratios?
Thanks!
For example my proposed setup will be as follows:
5th ratio = 0.68
Rear end ratio = 3.23
Tire diameter = 25.7 (245/50 16)
Target highway speed = 75mph
Can anyone provide a link or the calculation so I can adjust for different rear end ratios?
Thanks!
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Joined: Oct 2003
Posts: 428
Likes: 5
From: Buffalo, NY
Car: 1987 Camaro IROC-Z28
Engine: TPI 350ci L98
Transmission: T56 - Hurst Shifter
Axle/Gears: BW - 3.70
Go here:
CamaroZ28.Com - FULL THROTTLE INTERNET
Click on RPM and MPH Calculation.
There may be a calculator on this site too.
CamaroZ28.Com - FULL THROTTLE INTERNET
Click on RPM and MPH Calculation.
There may be a calculator on this site too.
Supreme Member
Joined: Aug 2005
Posts: 3,004
Likes: 4
From: Yellowknife, NWT, Canada
Car: 84 Z28
Engine: 357
Transmission: TH-350C
Axle/Gears: 3.43
whats wrong with this?
https://www.thirdgen.org/calculations
Your looking at just over 1000rpm with that combo.
https://www.thirdgen.org/calculations
Your looking at just over 1000rpm with that combo.
Thread Starter
Senior Member
iTrader: (5)
Joined: Oct 2004
Posts: 608
Likes: 0
From: Pelham, NH
Car: 91 B4C, 17 C7 GS, 16 Denali DMax
Engine: LS3, LS3, LML
Axle/Gears: 3.23, 3.42, 3.23
One or both of them is wrong.
The one you linked to here on TGO says I will turn 1076rpms (which I think is low).
The one on CamaroZ28.com says I will turn 2155rpm which seems more realistic to me.
Although the one from TGO is almost exactly half of what I calculated on CamaroZ28.com.
The one you linked to here on TGO says I will turn 1076rpms (which I think is low).
The one on CamaroZ28.com says I will turn 2155rpm which seems more realistic to me.
Although the one from TGO is almost exactly half of what I calculated on CamaroZ28.com.
Member
iTrader: (2)
Joined: Oct 2003
Posts: 428
Likes: 5
From: Buffalo, NY
Car: 1987 Camaro IROC-Z28
Engine: TPI 350ci L98
Transmission: T56 - Hurst Shifter
Axle/Gears: BW - 3.70
Well both calculators work correctly. You just put in the wrong number on the one on thirdgen which is why I recommend you use the other calculator.
The diameter of a tire or circle is twice the radius. The calculator on thirdgen is looking for the radius of the tire not the diameter. So take your tire diameter(25.7) and divide it by 2 to get the radius(12.85). Put that number into the thirdgen calculator to get the RPM of 2153, the same as on camaroZ28.
Here is another calculator that I like the best since it gives you all of your MPH & RPM for each gear.
http://www.f-body.org/gears/
The diameter of a tire or circle is twice the radius. The calculator on thirdgen is looking for the radius of the tire not the diameter. So take your tire diameter(25.7) and divide it by 2 to get the radius(12.85). Put that number into the thirdgen calculator to get the RPM of 2153, the same as on camaroZ28.
Here is another calculator that I like the best since it gives you all of your MPH & RPM for each gear.
http://www.f-body.org/gears/
Supreme Member
Joined: Aug 2005
Posts: 3,004
Likes: 4
From: Yellowknife, NWT, Canada
Car: 84 Z28
Engine: 357
Transmission: TH-350C
Axle/Gears: 3.43
haha, i overlooked that part. one is radius the other is diameter.
BTW vbmike, the last time i checked diameter was 3.14x the radius
BTW vbmike, the last time i checked diameter was 3.14x the radius
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