What is the main determinant of top speed, Horsepower or Torque?
I would guess torque since the drag pushes against your vehicle and having more hits per revolution on the crank would keep you moving forward..?...

Also is there a formula to calculate top speed? Drag co effecient of a 93-97 camaro is .35 or so isnt it?

 

I don't know what the formula is, but there's a lot more to it than engine power.

Gearing plays a big role in top speed, possibly as much or even more than engine power.

Second thing is aerodynamics.

Then the combination of the three. Does your top gear/final drive combination have enough torque multiplication to pull through the aerodynamic resistance of the body at a given speed and engine RPM? Will your top gear be able to pull through the resistance all the way to the redline or only to a certain point in the powerband?

 

Max speed occurs when power available = power required (drag, friction, etc), so the answer is "power". You are on the right track, however, because power is just torque AND rpm, or the rate at which the torque is applied.

I have an old computer program which is pretty effective in predicting performance. Using the .35 Cd, and a fairly stock LS-1 (free mods, maybe a cat-back, etc), max speed is 155-160. The math is tedious to do by hand, as nothing is very linear.

Interestingly, the best gearing (with 275/40-17's) is 5th gear and 3.73's. It puts the engine @ 5500 or so. Fortunately the stock LS1 hp curve is fairly flat from 4500-6000, so 3.23's only lose a couple of mph, even though you lose about 1000 rpm.

 

there are numerous online calculators that let you start with the drag coefficient of a particular car and input things like power and torque.... i'd link for ya but.... its really easy just go to google

 

i went to one of the top speed calculators and tried it out... It didnt factor in Drag or my cars toque/hp... Used tire size, gear ratio of tranny and final gear drive ratio... My car goes like 190mph.

actual would be Maybe around 175mph..

 

that was just a gear calculator... hell, if I could hit redline in 6th it would be like 250mph... doesnt mean she'll go that fast

 

Sorry to burst your bubble, but with 318 RWHP, you'd need a 20-30 mph tailwind to get 175!

A C5 Vette, with a .29-.30 Cd and a little less frontal area(The other big factor in producing drag) doesn't quite get to 175 in Z06 form.

The difference in power req'd to go 175 over 160 is about 30% or something around 415 RWHP in your car.

My $.02

 

Dont worry you didnt hurt my feelings.. Im not sure of the top speed thats why i had the Maybe in there.. Just trying to get a better idea of what it can actually do. 158mph is stock for an LT1 and ive had her up to 148mph and still pulling. I had to let off because I felt the stock drive shaft reach its critical limit.

 

There is a rule of thumb that lets you make some surprisingly accurate estimates.

For every 10% increase in speed you need about 1/3 more power.

So, starting with your engine's known horsepower and top speed, begin making the calculations with the assumption that at top speed your engine is making it's top horsepower.

 

if all the other limits are set aside, and only your torque numbers are put against the wind resistance, you'll know how fast your car can go.

assuming there's no wind, your car will go up to the point where TQ is equal to wind pressure.

 

Here is the Coefficient of drag formula for you.

Cd= (Drag) / (0.5*density*(Velocity Squared)*Frontal Area)

Rearange that to get

Velocity Squared= Drag / 0.5*Density*Frontal Area

When Engine Power=Drag + Rolling Resistance. You have top speed.

 

FYI my appr. 310 rwhp. car w. 3.73 rear, can do 145 mph on 6-th gear.