What determins the top speed of a car?

Question

Is it gearing and rpms or gearing and hp

What exactly is it?

Answer 1

both really.

The higher the HP the higher the top speed because of the constant power going to the wheels, and the higher the RPM the higher the speed as it allows the engine to rev higher and prosuce more power.

Answer 2

Everything, horsepower, gear ratios, weight, aerodynamics.

Actually most cars to my knowledge are governed. I know for sure on the RX-8, Late 90s Maximas, and a few more cars.

Answer 3

The air drag and weight of a car are major contributes to top speed. This is because horse power is defined as moving a given weight one foot in one minute.

The weight of the car for top speed is not so much how much the car weighs on the scale, but rather how much resistance does it offer to movement. The movement  of one pound one foot is based on dragging the load on dirt. Where a car has wheels.

The designer of a car uses basic machines to overcome this resistance, the tools used are the lever  and wheels. The wheel part is obvious. But the gear box consists of levers in the form of wheels (gears). Another place the lever concept is used is in the wheel diameter itself.

I  had a 1972 Corolla 1600 (in 1972 there  were no rev limiters on this car) 86 hp with 5 speed and I could wind the engine out to 16000 rpm. The top speed was 105,  it just could go no faster. The engine still could turn more RPM's if it had more torque to overcome the air resistance.

Today I have a 1990 Miata also a 1600  (110 HP)  with a 5 speed. I can run at 140 MPH.

The difference in top end comes from the aerodynamic  features and the increased torque available  at a given RPM.

Answer 4

Some cars are limited by the gearing, such as the Saleen S7. It's limited in 6th gear at 6400 rpms. Some cars also don't have enough power to get the car to a higher speed. For instance, the Bugatti Veyron can only go a certain speed because it is aerodynamically, physically, and in terms of power. The car requires such an enormous engine to get to 200 mph, then has to use every bit of it's 1001 hp to get to 253 mph.

I think that it is the power the car has and how aerodynamic it is.  

Answer 5

Also most cars will a governed top speed (programmed into the computer), so when the vehicle hits say 125mph it will not go any faster.

Answer 6

Easiest way to tell: Put your car on a lift and run it up through the gears. You'll never get it to go that fast on the street, but you'll know what its capable of doing.

Answer 7

A combination of power, gearing, and aerodynamics.

Answer 8

Basically it's a question of when the maximum power you can generate is matched to the power required to push the air out of the way.

Now - Power is a strong function of rpm's.  Power goes up steadily as rpm goes up, and then it drops off rapidly when the engine runs out of breath.  As you speed up, there's going to be a point where you either run out of rpms in high gear, or you run out of power in whatever gear you're in.  If you run out of power before the engine develops its max power, then your top speed will be slower.

Gearing has a considerable effect on top speed, because if the car is not geared just right, your max power won't be happening when you run out of power.