Horse calculators can help you figure out how much horsepower will reach a certain figure of maximum speed with your car. However, before we begin to calculate the amount of horsepower, you need to achieve a certain goal with maximum speed, let's first consider some factors affecting the maximum speed of your car or vehicle.
In general, the maximum speed is a physically balance point between all forces acting on your car. When the total amount of forces moving the car forward is exactly equal to the total amount of forces holding it back, the car can no longer increase its speed and reaches its maximum speed in steady state.
At the same time, we divided the maximum speed equation into two main factors, which are:
Power: horsepower
Resistance: presented in drag mode
Destroying it even further:
Factors affecting how much your car has behind you are related to:
- The total raw horsepower you must work with
- The ultimate gear of your car, which combines the transmission coefficient, the differential ratio of the final gear and the wheel and tire diameter
And factors affecting how much resistance your car has against it are related to:
- The aerodynamic profile of the car, which is summed with one number, called the drag coefficient, which summarizes the various parameters, such as:
- Frontal area of the car (which determines how well the car penetrates through the wall of air ahead)
- The height of the car or the ground clearance, which determines the parts of the air flow that are split and locked both along the roof line of the car and under the belly on the vehicle
- The side profile of the car, which determines how the air is evacuated after it passes, under and around the car, and determines the characteristics of the low pressure zone behind the rear window or the rear bumper of the car. This zone is always effectively sucking the car back and should be kept to a minimum.
- In addition to aerodynamic drag coefficients, there are also mechanical drag arising from the rotation of a high-speed engine, in a gearbox, wheel and tire, a heavy shaft and axle (especially on cars with four wheels, for example) and so on.
Studies have shown that (and some racing classes, such as Formula 1, pragmatically confirmed this) that after a point of about 100 miles per hour the mechanical drag coefficients become less significant when the maximum vehicle speed is reached.
At these speeds, aerodynamic resistance is the main resistive force in determining the characteristics of a car, so in sports, such as Formula 1, vehicles with a similar engine differ significantly in performance, based on which car has the correct aerodynamic setting for the best combination of maximum speed, and also aerodynamic thrust (pressing force) during high-speed turning. For comparison, a lower racing speed class, for example, auto-shifting (limited by track design to about 80 miles per hour for the fastest cars), you will find that usually the most productive cars are the best mechanical traction (coming from proper suspension settings and good traction tires) without real dynamic effects emanating from the aerodynamic design.
Having said that, taking advantage of the maximum speed by changing the retention rate of your car can be a costly process with ever-decreasing returns. After the first set of basic configurations has been exhausted, for example ...
- Lower vehicle height to reduce turbulence under the car
- Installing an aftermarket front bumper with an integrated air divider or expanding the factory bumper with an air splitter added to increase the percentage of air flow over the car
- Use of lower profile limbs on a vehicle, such as lower profile mirrors or rear spoilers with a less aggressive angle (to ensure a better balance between dragging and dragging down)
- The underside panels of the car to give a smooth lower belly, which helps to accelerate the air under the car and reduce the turbulence below. (You'll find manufacturers like Mercedes do it on their lowest level compact cars to improve stability and mileage.)
- Using the rear or rear bumper with a built-in rear diffuser, improve the transition of the two airflows from the top and bottom of the car, causing the rear bumper, and preventing the car from being sucked outside the bumper under low pressure.
- Cut off the top of the car and lowered the height of the roof in relation to the hood and trunk (think about the height of the roof on the Corvette vs on a jeep to better understand why it works)
- Use strategically placed air vents in the hood, front and rear fenders to facilitate air flow through certain high pressure zones (for example, under the hood or in manholes) to reduce pressure in these areas and help increase air flow through the vehicle
... as soon as this list of changes has been exhausted, you will find that the drag coefficient can actually drop by 30%. However, the maximum speed is associated with dragging as follows:
Capacity for air resistance overlap = fA x Cd x 0.00256 x mph cube / 375
Pay attention to this equation that the cube of maximum speed is related to the resistance coefficient of Cd, so a change in the resistance coefficient from a typical 0.45 to a sportier 0.30 (decrease by 30%) only leads to an increase of 12% in your actual maximum speed (t . e. from the maximum speed of 100 to 112 miles per hour)
This is a significant gain, but to do something as significant as doubling the maximum speed, you will still begin to increase your overall power level. It was a realization that was quickly apparent to Volkswagen designers working on the 1100hp Bugatti Veryron, and probably this was the reason they had to use so much energy to reach their maximum speed at 400 km / h.
Therefore, returning to this equation outlined above, we know that if a car is limited to a limited speed at its maximum speed (then we have more gears to accelerate or where we reach our maximum speed in top gear much earlier than the red line), then we know that increasing engine power to use the remaining range of revolutions (or gear ratios) is a very practical way to increase the maximum speed of a car.
In a practical sense, even if the drag coefficient is not known on the car in question, you can calculate how much energy is required to reach a certain maximum speed target by comparing your current power levels and maximum speed with your target peak speed. Thus, using the equation below (obtained from the general equation above), we obtain:
New horsepower = old horsepower * (new maximum speed / old maximum speed) ^ cubed
A practical example close to home for me is 320 horsepower 3000GT VR4. This two-cylinder turbocharged car has an excellent aerodynamic shape and is capable of reaching a maximum speed of 160 miles on the 5th gear at 6000 rpm at 1000 rpm in order to go on this gear and the whole unused sixth gear.
The availability of the car is obviously limited (and not limited by the limitation of transmissions or limited movement) at its maximum speed, some of the enthusiasts went further to modify this car and smash the barrier 200 miles per hour.
Applying the formula above:
New horsepower = 320 hp * (200 miles per hour / 160 miles per hour) ^ 3
New horsepower = 625 horsepower
So this suggests that to achieve a maximum speed of 200 miles per hour in the 3000GT VR4, we know that we will need at least 625 horsepower (assuming that we have enough gear and rpms to increase the wheel speed by 200/160 or 25%, still working under the red increase in the number of revolutions of the car).
As a last note, it may seem insane to try to double the power of your car and reach a maximum speed that surpasses any speed limit you will ever encounter on a regular road:
1. There are certain platforms, such as the Chevy Corvette, Mitsubishi 3000GT, Toyota Supra ..., etc., where doubling or tripling the power levels on these iconic sports cars is not only a common practice, but also reliably cheap ($ 7,000 US for 3000GT using Dynamic Racing “Diablo Killer” update package)
2. There are also sanctioned racing classes that allow enthusiasts to race their cars on top speed tests, as well as standing mile acceleration tests. These are very exciting and challenging racing classes that attract only the most dedicated enthusiasts to extract every ounce of aerodynamic design, horsepower, thrust, equipment, stability and durability from their cars and become more of a racing cult or addiction that is hard to break.
