Im 16 and pretty bored. I've been doing the math and I'm trying to see the absolute top speed, with out any variables.

lets say : 7000RPM, 27.6inch tall tires, 3rd gear 700R4, 3:08 rear

7000 RPM > 3rd gear - 1.00:1 > 7000 RPM > Rear - 3.08:1 > 2273 RPM at Tires

Circumference of tire ( 3.14[pi] x 27.6[diameter] ) = 86.664 rounded to 86.67in

then

Circumference[86.67] x RPM at tires[2273] = 197,000.91in per minute

Then convert inch to feet

197,000.91in / 12 = 16,416.7425ft rounded to 16,416.74ft

Then convert feet to miles

16,416.74ft / 5280 = 3.10923106miles rounded to 3.11miles

So now we have 3.11miles per minute, convert to hours now

3.11mile x 60 (60minutes in a hour) = 186.6mph

186.6mph is that correct? Not counting anything like weight/air drag or anything, in the perfect world.

Now if thats correct can someone help me make it more realistic by adding real world things like air resistance and what not? Is there any performance loss anywhere in the car? (like clutches or something?)

 

Your maximum speed based on the data you provided is correct as far as ignoring physics goes, yes. Looking for actual top speed is a bit harder, it takes into account the coefficient of drag, vehicle frontal area and horsepower. The lower the first two and the higher the last one, the faster you'll go. My 84 Z28 would do 128 mph with my 305. It had (just guessing) about 160-170 horsepower. I might be wrong, but I think the firebirds drag coefficient is a little lower than the camaro.

 

Say the drag coefficient is .333 (thats what I found for a 82 firebird)

How would I calculated that in?

 

I don't know anything about the drag coefficient, but I doubt if the torque converter will let you lock it up since you're also going to be WOT. I'd use a 1.1:1 transmission gear to factor in the 10% slip the converter will probably have, but depending on the car/converter it could actually slip anywhere from 5%-20% in the real world. You should probably try searching for automotive calculations or calculators. I know I use 2-3 different ones all of the time, one being the rpm/gear/tire calculation you did above.

 

You also need to know air density.

 

How would I do that?

 

https://webdisk.ucalgary.ca/~jmknopp...eed%20calc.xls

This spreadsheet calculates it for you (your above mentioned variables). To help you pick gearing etc.

Once you get into the tricky stuff involving HP needed to push the air - then you're on your own. Too many variables to properly model unless you're paid to do it, and you have the right software

 

Alright, I am really bored and my math needed tuning up. Here it goes (values used for an IROC) - aerodynamic top speed w/ 300 hp:

Frontal area, I am using from the main page of 24 square feet (2.23 square meters). Coeffeicient of drag will be .34. Engine power will be set at 300 hp. Air density will be at sea level (1.225 kg/m^3).

What we know:
Fa = 2.23 m^2
Cd = 0.34
P = 223800W (746W per horsepower, 300 hp)
Density = 1.225 kg/m^3
1N = Kg * (m/s^2)
1W= N * (m/s)

V = [(2P) / (Density*Fa*Cd)]^(1/3)

V = [(2*223800 Kg m/s^2 * m/s)/(1.225 Kg/m^3)*(2.23 m^2)*(0.34)]^(1/3)

V = 78.4 m/s
V = 175.4 mph