I just bought a new car, nothing incredibly special. And being a nerd, I love creating theoretical calculations based on given data. So, I've been trying to predict the effects on my car under certain scenarios.(adsbygoogle = window.adsbygoogle || []).push({});

I am doing my best to figure out the effects based of equations alone, and not taking my car in for a dyno test. Sadly, I am having difficulty with some equations

I really hope someone out there can help me.

These are the things I would like to determine:

1) If my car is traveling on a flat road at a certain speed, what is the force of the car?

2) If my car is traveling on a flat road at a certain speed, what is the torque that is being generated by the axle shaft?

3) If my car is traveling on an uphill road at a specific angle at a certain speed, what is the force of the car?

4) If my car is traveling on an uphill road at a specific angle at a certain speed, what is the torque that is being generated by the axle shaft?

5) How much torque is being generated by the transmission at a certain engine RPM value?

So far, this is what I have come up with, assuming the engine speed is 3000 RPM and I am only in 1st gear:

Vehicle Speed (MPH) =

(Engine Speed (RPM) x Tire Radius (in)) / (168 x Axle Ratio x Trans Ratio)

Vehicle Speed (MPH) = 21 MPH

Transmission Speed into Axle (RPM) = Engine Speed (RPM) / Trans Ratio

Transmission Speed into Axle (RPM) = 669 RPM

Wheel Speed (RPM) = (Vehicle Speed (MPH) x 5280 x 12) / (60 x PI x Wheel Diameter (in))

Wheel Speed (RPM) = 242 RPM

Axle Shaft Torque to Wheels (lb-ft) =

Trans Torque into Axle (lb-ft) x Axle Ratio

Axle Shaft Torque to Wheels (lb-ft) = ?????????????????????

Trans Torque into Axle (lb-ft) = Engine Torque into Trans (lb-ft) x Trans Ratio

Trans Torque into Axle (lb-ft) = ?????????????????????

(I know the Max Torque at a given RPM value, but I want to find the torque at any RPM value)

Torque of Axle Shaft (lb-ft) = radias of shaft (ft) x Force (lb)

Torque of Axle Shaft (lb-ft) = 0.125 (ft) x ????????????????

Torque of Wheel (lb-ft) = radias of wheel (ft) x Force (lb)

Torque of Wheel (lb-ft) = 1.209 (ft) x ????????????????

From a free body diagram, I have determined the summation of forces in the X and Y direction:

FY = N - mgcos([itex]\vartheta[/itex]) = 0

Fx = F(car) - F(friction) - mgsign([itex]\vartheta[/itex]) = ma

N = mgcos([itex]\vartheta[/itex])

F(friction) = [itex]\mu[/itex]N

F(car) = ?????????????

m = weight of car

These are a few calculations I have determined and a few I am having a problem determining theoretically. I would like to find out these values for any engine RPM value and any given speed.

Here are some specs of my car:

Max Torque: 250 lb-ft @ 4500 RPM

Max Horsepower: 265 HP @ 6250 RPM

Weight: 4078 lb

Axle Ratio: 2.77

Trans Ratio:

1st: 4.484

2nd: 2.872

3rd: 1.842

4th: 1.414

5th: 1.000

6th: 0.742

Rev: 2.882

Wheel Diameter: 29.02 in

Vehicle Performace: 0-60 mph in 7.4 seconds

I'd really appreciate any help anyone can offer.

Thanks!!

Mike

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Simple Calculations for Information on a Car

**Physics Forums | Science Articles, Homework Help, Discussion**