Top Speed Calculation???
Thread Starter
Melting Slicks
Joined: Feb 2000
Posts: 2,109
Likes: 73
From: ATLANTA/HOUSTON
Top Speed Calculation???
Who has the formula to calculate top speed??? I used to have it but can't find it.
I have already gone 181 MPH in my car, with more RPM to go. But I wanted to determine what my car is "capable" of.
Stock tire size
Stock Diff (3.42)
Stock tranny(5th= 0.84)
7200 RPM rev-limit
Cd & power are obviously NOT an issue.
Thx guys.
I have already gone 181 MPH in my car, with more RPM to go. But I wanted to determine what my car is "capable" of.
Stock tire size
Stock Diff (3.42)
Stock tranny(5th= 0.84)
7200 RPM rev-limit
Cd & power are obviously NOT an issue.
Thx guys.
Le Mans Master
Joined: Apr 1999
Posts: 6,129
Likes: 14
From: Vette
Re: Top Speed Calculation??? (DARTH VETTER)
Darth,
7200 rpm would equal 194.9MPH with the variables you specified.
That’s ignoring any possible tire growth and assuming you’ve got enough power at those rpms
Hope this helps :cool:
7200 rpm would equal 194.9MPH with the variables you specified.
That’s ignoring any possible tire growth and assuming you’ve got enough power at those rpms
Hope this helps :cool:
Racer
Joined: Oct 2001
Posts: 396
Likes: 0
From: SAVANNAH GA
Re: Top Speed Calculation??? (DARTH VETTER)
Vetter,
I don't have the calculation but I do have a Physics minor an I would bet you take your peak RPM (7200) divide by 5th gear ratio (0.84) divide again by the diff ratio (3.42).
This should give you 2506.27 RPM of the tire at redline in 5th. I'm not sure the profile on your tire but I know it's an 18" wheel and a 295mm wide. For now I'll assume it's a 35 series tire(295-35-18). We need the diameter so this is the formula: (295mm) * (0.35) * (2) / (25.4) + 18" = 26.13"
To get the circumference: 26.13" * 3.14159 = 82.09"
(conversion factor is 25.4mm/In)
Now we have the distance in inches the car travels for every full rotation of the tire. 82.09" / 12 = 6.84 feet per revolution. At 2506.27 RPM of the rear tire at redline in fifth gear the velocity of the car will be 17,144.87 feet per minute. 17,144.87 / 5,280 (5280ft/mile) = 3.25 miles per minute. 3.25 * 60 (60 minutes in 1 hour) gives you 194.82 mph at 7200 rpm in 5th assuming I got the tire size correct did my math properly and have some clue of what I'm talking about.
If I have the tire size wrong let me know because that will throw things way off. Man you can tell I have some free time. :lol:
[Modified by 96VIPERGTS, 7:15 AM 11/15/2001]
[Modified by 96VIPERGTS, 7:22 AM 11/15/2001]
I don't have the calculation but I do have a Physics minor an I would bet you take your peak RPM (7200) divide by 5th gear ratio (0.84) divide again by the diff ratio (3.42).
This should give you 2506.27 RPM of the tire at redline in 5th. I'm not sure the profile on your tire but I know it's an 18" wheel and a 295mm wide. For now I'll assume it's a 35 series tire(295-35-18). We need the diameter so this is the formula: (295mm) * (0.35) * (2) / (25.4) + 18" = 26.13"
To get the circumference: 26.13" * 3.14159 = 82.09"
(conversion factor is 25.4mm/In)
Now we have the distance in inches the car travels for every full rotation of the tire. 82.09" / 12 = 6.84 feet per revolution. At 2506.27 RPM of the rear tire at redline in fifth gear the velocity of the car will be 17,144.87 feet per minute. 17,144.87 / 5,280 (5280ft/mile) = 3.25 miles per minute. 3.25 * 60 (60 minutes in 1 hour) gives you 194.82 mph at 7200 rpm in 5th assuming I got the tire size correct did my math properly and have some clue of what I'm talking about.
If I have the tire size wrong let me know because that will throw things way off. Man you can tell I have some free time. :lol:
[Modified by 96VIPERGTS, 7:15 AM 11/15/2001]
[Modified by 96VIPERGTS, 7:22 AM 11/15/2001]
Thread Starter
Melting Slicks
Joined: Feb 2000
Posts: 2,109
Likes: 73
From: ATLANTA/HOUSTON
Re: Top Speed Calculation??? (EuG)
EUG- THX, do you have the formula? So I can play with the #'s? Like if I change to a 3.73.
your # is ironic. Off the top of my head, I thought it would be about 194. But I wanted to confirm it.
your # is ironic. Off the top of my head, I thought it would be about 194. But I wanted to confirm it.
Racer
Joined: Oct 2001
Posts: 396
Likes: 0
From: SAVANNAH GA
Re: Top Speed Calculation??? (DARTH VETTER)
Vetter,
I just edited my original post with the corrected tire profile and came up 194 also. Making that kind of power would 6th be an option or is is too long?
I just edited my original post with the corrected tire profile and came up 194 also. Making that kind of power would 6th be an option or is is too long?
Thread Starter
Melting Slicks
Joined: Feb 2000
Posts: 2,109
Likes: 73
From: ATLANTA/HOUSTON
Re: Top Speed Calculation??? (DARTH VETTER)
You must have sent your response right before I did. hehehe
I'm not sure if it'd pull in 6th with the 3.42, But it might with a 3.73 with me spraying the GAS !! :eek: :eek: :cool:
I'm not sure if it'd pull in 6th with the 3.42, But it might with a 3.73 with me spraying the GAS !! :eek: :eek: :cool:
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Drifting
Joined: Jul 2000
Posts: 1,289
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From: Newport Beach, CA, USA
Re: Top Speed Calculation??? (DARTH VETTER)
My guess is 185mph, maybe. You need more ponies to hit 194. (We played with these numbers in figuring what my top speed would be and we were in the 190s with 600hp and an increase in the rev limiter).
Racer
Joined: Dec 2000
Posts: 339
Likes: 2
From: West Hartford, CT, USA
Re: Top Speed Calculation??? (DARTH VETTER)
DArth -
I have a simple EXCEL spreadsheet which does the same calcs VIPER did in his post. You can plug in whatever gear/tire/rpm parameters you want and it computes MPH.
I'll be happy to e-mail it to you if you want.
I have a simple EXCEL spreadsheet which does the same calcs VIPER did in his post. You can plug in whatever gear/tire/rpm parameters you want and it computes MPH.
I'll be happy to e-mail it to you if you want.
Le Mans Master
Joined: Jul 2000
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From: Fort Worth Texas
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Melting Slicks
Joined: Feb 2001
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From: DFW TX
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Re: Top Speed Calculation??? (DARTH VETTER)
Here is a good calculator:
http://www.f-body.org/gears/
You can look at swapping in a M6 tranny for your M12 if you want to pull 5th to 200MPH with your 3.42's. Either that or I would look at getting some 3.15 or even 2.73 gears for the top end runs.
The engine is under a very high load at that speed in 5th gear and you really don't want to wind the RPM's out that much if possible. Use your calculations to try and gear the car to hit your desired speed at around 6-6.2K. That way when you're out testing the car with a radar you have not only a higher margin of safety but can pick up a few more RPM's if you're not hitting the speed you want.
-Jeremy
http://www.f-body.org/gears/
You can look at swapping in a M6 tranny for your M12 if you want to pull 5th to 200MPH with your 3.42's. Either that or I would look at getting some 3.15 or even 2.73 gears for the top end runs.
The engine is under a very high load at that speed in 5th gear and you really don't want to wind the RPM's out that much if possible. Use your calculations to try and gear the car to hit your desired speed at around 6-6.2K. That way when you're out testing the car with a radar you have not only a higher margin of safety but can pick up a few more RPM's if you're not hitting the speed you want.
-Jeremy
Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
Re: Top Speed Calculation??? (DARTH VETTER)
I've got another nice calculator, created by Kent Schock, a forum member. I don't know how to post it, but, you can contact Kent, or I can email it to you. It's in *.xls format and it specifically for the C5 trans. i.e.: M6, M12, and A4.
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
[Modified by 2KFRC5, 9:55 AM 11/15/2001]
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
[Modified by 2KFRC5, 9:55 AM 11/15/2001]
Le Mans Master
Joined: Jul 2000
Posts: 7,758
Likes: 0
From: Fort Worth Texas
Cruise-In II Veteran
Cruise-In III Veteran
Re: Top Speed Calculation??? (2KFRC5)
I've got another nice calculator, created by Kent Schock, a forum member. I don't know how to post it, but, you can contact Kent, or I can email it to you. It's in *.xls format and it specifically for the C5 trans. i.e.: M6, M12, and A4.
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
[Modified by 2KFRC5, 9:55 AM 11/15/2001]
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
[Modified by 2KFRC5, 9:55 AM 11/15/2001]
Safety Car
Joined: Nov 2000
Posts: 4,419
Likes: 6
From: Arroyo Grande CA
Re: Top Speed Calculation??? (kewlbrz)
I downloaded that also. It's different from Kent's. They're both nice and obtained the same conclusions, just differently.
[B]Don[?b]
[B]Don[?b]
I've got another nice calculator, created by Kent Schock, a forum member. I don't know how to post it, but, you can contact Kent, or I can email it to you. It's in *.xls format and it specifically for the C5 trans. i.e.: M6, M12, and A4.
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
sounds like the spreadsheet link i posted above.
Just enter your tire size, R.E. ratio and RPM redline. It calculates RPM at speeds upto redline. It's a nice chart. Thanks Kent.
My email: mcmlxiii@eudoramail.com
sounds like the spreadsheet link i posted above.
Le Mans Master
Joined: Aug 2001
Posts: 6,725
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From: Colesville MD
Re: Top Speed Calculation??? (2KFRC5)
Let me throw in my O2. It was stated the cd and power are not an issue. I would disagree. As speed doubles, drag quadruples. This exponential increase becomes harder and harder to overcome. Meaning it takes twice as much power to get half as much gain at those speeds. This is even more of an issue for you frc guys, as your cd is not the .29 of the coupe. I'm no engineer, but STAGED is. Let me see if I can get him in here...
Greg
:cool:
Greg
:cool:
Le Mans Master
Joined: Jul 2000
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From: Fort Worth Texas
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Re: Top Speed Calculation??? (gmatson)
Let me throw in my O2. It was stated the cd and power are not an issue. I would disagree. As speed doubles, drag quadruples. This exponential increase becomes harder and harder to overcome. Meaning it takes twice as much power to get half as much gain at those speeds. This is even more of an issue for you frc guys, as your cd is not the .29 of the coupe. I'm no engineer, but STAGED is. Let me see if I can get him in here...
Greg
:cool:
Greg
:cool:
arguement over... :cheers:
Racer
Joined: Jul 2000
Posts: 275
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From: Point Richmond California
Re: Top Speed Calculation??? (gmatson)
I don't know about HP being a factor for Darth getting to 190+. He makes more power than a STOCK Viper, 911 Turbo, or Ferrari 360 Modena, and they all go 190+. I don't think he'll have a problem, but I haven't looked at his dyno to see how much his hp drops off at those high revs. The FRC still has decent aerodynamics with a CD of 0.31 or 0.32. Better than a Viper GTS which has 0.34, I believe.