Anyone know how 2 calculate speed at a given distance based on horsepower and weight?

crazya_22 · 06-04-2009, 11:46 PM

I exhausted the search button and can't find any thing so I figure one of you may be able to help.

Example: If a car weighing 3,000 lbs with an output of 140 horsepower accelerates under full throttle from a stop to a distance of 300 feet at what speed will they be traveling?

I know this could get very complicated with torque, hp, power bands, driver mod, tires, etc, but I am simply looking for a formula utilizing only the given knowledge.

Thanks in advance guys.

Sh0cker · 06-05-2009, 08:31 AM

Here's what I think:

You don't have enough info because you need the RPM of the wheel if you're measuring hp at the wheel
Tq = 5250 * hp / RPM
If you measure torque directly you can skip this step and assume constant torque (totally unrealistic):

Then
F = Tq / (wheel radius)

Then
a = F / m

And
(distance) = 0.5 * a * t^2

Solve for time and put into
v = a * t

Make sure your units are consistent (i.e. lbf vs. lbm)

I took my PE exam last month and already forgot most of the stuff...but the bottom line is you don't have enough info.

TheAcAvenger · 06-05-2009, 09:29 AM

Choice D: Not enough information.

You'd need friction coefficients and drag coeffiecients, and a dyno so we actually knew how much power you were putting to the wheels per rpm.

200Duece · 06-05-2009, 11:06 AM

drive ratio's and tire size

crazya_22 · 06-06-2009, 12:04 PM

I believe this link will have all of the necessary information, I cannot put the car on a dyno because I do not have one. I am curious because the rate at which this car can accelerate is pertinent to a legal issue, and before I pay an expert to make an evaluation I would like a ball park figure. The car is an automatic so the top set of gear ratios is correct.

*Note add 500 pounds to the weight of the car for passengers/cargo.

http://lasvegascars.vehix.com/invent...5F00000002372F

Thanks.

thread killer · 06-06-2009, 12:52 PM

so go to the track. fixed.

The HACK · 06-06-2009, 01:50 PM

Here's one that calculates the 1/4 mile trap time.

http://robrobinette.com/et.htm

crazya_22 · 06-06-2009, 07:40 PM

Quote:

Originally Posted by thread killer

so go to the track. fixed.

I cannot go to the track because I do not have the car. it was totaled in an accident five years ago.

thread killer · 06-06-2009, 08:13 PM

well then your shoot outta luck then arnt ya.

crazya_22 · 06-11-2009, 05:54 PM

Quote:

Originally Posted by thread killer

well then your shoot outta luck then arnt ya.

Congrats, you have officially lived up to your moniker I hope your proud of yourself.

thread killer · 06-11-2009, 10:30 PM

no boss, you mucked up your own thread by asking a question that CANT be answered with the statement you provided.

example:

"hey guys, could you tell me how fast a tire RPM is when it goes at 60 mph"

what are we talking about here? a 235/45/17 or a 38x15.50x15 super swamper?
your ]missing[ something.

and just a *wild* guess with a chevy cavalier with a quad4 and a auto...... 17-18ish in the quarter.
300 feet i would *estimate* about 35-45 mph. a 17ish 1/4 would be about 60ish MPH in the 1/8th......

06-04-2009, 11:46 PM	#1
crazya_22 Q 0 Rep 44 Posts Drives: 335i Join Date: Sep 2008 Location: Vegas iTrader: (0)	Anyone know how 2 calculate speed at a given distance based on horsepower and weight? I exhausted the search button and can't find any thing so I figure one of you may be able to help. Example: If a car weighing 3,000 lbs with an output of 140 horsepower accelerates under full throttle from a stop to a distance of 300 feet at what speed will they be traveling? I know this could get very complicated with torque, hp, power bands, driver mod, tires, etc, but I am simply looking for a formula utilizing only the given knowledge. Thanks in advance guys. __________________ Drives: 335i very slowly
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06-05-2009, 08:31 AM	#2
Sh0cker n00b 5 Rep 178 Posts Drives: 335i Join Date: Jul 2008 Location: NJ iTrader: (9)	Here's what I think: You don't have enough info because you need the RPM of the wheel if you're measuring hp at the wheel Tq = 5250 * hp / RPM If you measure torque directly you can skip this step and assume constant torque (totally unrealistic): Then F = Tq / (wheel radius) Then a = F / m And (distance) = 0.5 * a * t^2 Solve for time and put into v = a * t Make sure your units are consistent (i.e. lbf vs. lbm) I took my PE exam last month and already forgot most of the stuff...but the bottom line is you don't have enough info. __________________ His: 08 E92 335i (sold), 99 Corolla beater car Hers: 09 Tiguan Previous: 09 e93 328i, 04 WRX, 07 S40, 03 E46 330xi, 04 F4i, 04 EX250
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06-05-2009, 09:29 AM	#3
TheAcAvenger Brigadier General 133 Rep 3,132 Posts Drives: 2018 R35 GTR / 2007 E92 335i Join Date: Apr 2006 Location: 757 > Nova > Denver iTrader: (1)	Choice D: Not enough information. You'd need friction coefficients and drag coeffiecients, and a dyno so we actually knew how much power you were putting to the wheels per rpm. __________________ 2018 R35 GT-R Cicio800 \| 2007 E92 335i - RB Turbos, TC Kline DA Coils, HPA M3 Suspension, Quaife LSD, Stoptech BBK, JB4, FuelIT, AR Downpipes, RDSport Quads, Stett OC, Helix IC, Volk TE-37, Vorsteiner V-35, OSS Headlights \| Retired - 2015 F82 M4
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06-05-2009, 11:06 AM	#4
200Duece Colonel 45 Rep 2,575 Posts Drives: '73 2002,'18 X5 35d,'17 328d T Join Date: Jan 2007 Location: A Whale's Vagina, Ca iTrader: (5)	drive ratio's and tire size __________________ 1988 E28 535is Euro Conversion --- sold 2009 E90 335 6MT --- sold 2003 E39 540iT Msport --- sold
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06-06-2009, 12:04 PM	#5
crazya_22 Q 0 Rep 44 Posts Drives: 335i Join Date: Sep 2008 Location: Vegas iTrader: (0)	I believe this link will have all of the necessary information, I cannot put the car on a dyno because I do not have one. I am curious because the rate at which this car can accelerate is pertinent to a legal issue, and before I pay an expert to make an evaluation I would like a ball park figure. The car is an automatic so the top set of gear ratios is correct. *Note add 500 pounds to the weight of the car for passengers/cargo. http://lasvegascars.vehix.com/invent...5F00000002372F Thanks. __________________ Drives: 335i very slowly
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06-06-2009, 12:52 PM	#6
thread killer Banned 14 Rep 472 Posts Drives: faster then your car Join Date: Nov 2008 Location: pulling away iTrader: (3)	so go to the track. fixed.
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06-06-2009, 01:50 PM	#7
The HACK Midlife Crises Racing Silent but Deadly Class 1834 Rep 5,337 Posts Drives: 2006 MZ4C, 2021 Tesla Model 3 Join Date: Oct 2007 Location: Welcome to Jamaica have a nice day iTrader: (1)	Here's one that calculates the 1/4 mile trap time. http://robrobinette.com/et.htm
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06-06-2009, 08:13 PM	#9
thread killer Banned 14 Rep 472 Posts Drives: faster then your car Join Date: Nov 2008 Location: pulling away iTrader: (3)	well then your shoot outta luck then arnt ya.
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06-11-2009, 10:30 PM	#11
thread killer Banned 14 Rep 472 Posts Drives: faster then your car Join Date: Nov 2008 Location: pulling away iTrader: (3)	no boss, you mucked up your own thread by asking a question that CANT be answered with the statement you provided. example: "hey guys, could you tell me how fast a tire RPM is when it goes at 60 mph" what are we talking about here? a 235/45/17 or a 38x15.50x15 super swamper? your ]missing[ something. and just a wild guess with a chevy cavalier with a quad4 and a auto...... 17-18ish in the quarter. 300 feet i would estimate about 35-45 mph. a 17ish 1/4 would be about 60ish MPH in the 1/8th......
	Appreciate 0 Quote

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