Mechanical Performance

• Mechanical Performance
• Introduction
• HORSEPOWER
• TORQUE
• WEIGHT
• Mechanical Performance Grading System ©️
• The Grading System
• Letter Grades
• Explanation of the Relevancy of the Variables
• Horsepower and Torque Explanation
• Weight Explanation
• Conclusion
• ARC Mission Statement

Introduction

Before we dive deep into an automobile’s mechanical performance, it is important to read why we are gathering mechanical performance in the first place. Mechanical performance is one of the two categories for performance. Performance is one of the driving factors for determining a car’s overall quality. Performance is the general measurement of how quickly a vehicle can accelerate, the overall speed of a vehicle, and everything else that occurs between acceleration and maximum drive.

To define all these variables of a car is difficult; however, understanding common performance figures are vital to knowing how vehicles can handle speed. For example, a car noob will have a difficult time understanding how horsepower stacks up against the competition. Questions will arise like “what is a good horsepower number?” or “what is a good 0 to 60 time?”. They could drive a fast car without even knowing because they are most likely used to the cars that they own. Although this could be possible, they are truly clueless about the performance of cars- the initial work to get a car moving, the power exerted to allow the vehicle to climb up the speedometer, and the mass that counteracts the power. Knowing the basics is important; however, the more you know about how cars work, the more knowledge comes from driving.

Back to our original topic of discussion, mechanical performance is the basic performance data of a vehicle’s speed. Dynamometer (dyno) shops specialize in this basic performance data; where they measure three important auto performance figures- horsepower (hp), torque (tq), and weight (lb). Consider these three the trifecta for an automobile’s raw performance. These are the performance figures that come from the push of the gas (and the shifting of the gear for my real care enthusiasts) with minimal to no talent needed. Essentially, straight-line speed depends on horsepower, torque, and weight for the live performance data (which is in the next blog post).

HORSEPOWER

Horsepower, the ‘tell-tale’ performance metric that single-handedly classifies a car’s speed to beginners, is the driving factor of vehicle performance. Horsepower is the rate at which work is done, resulting in the output of a vehicle’s engine. In simple terms, horsepower is the common unit of power that measures a vehicle’s speed once the vehicle is moving.

One mechanical horsepower is equivalent to 33,000 foot-pound force per minute. Don’t let that number blow you away; one horsepower isn’t even strong enough for a lawnmower. It’s the conversions of horsepower that matter most.

The formula for horsepower is as follows:

Where torque is the rotational force that moves the vehicle, the RPMS is the speed of the engine, and the 5252 constant is the net result of horsepower and torque canceling each other out in conversions. This cancelation is called the “5252 RPM cross”. The name originated from the conversion of one horsepower is equal to 33,000 foot-pounds of work in each minute. Next, you balance the equations for velocity and torque. Then, you'll start to see that horsepower will always equate to the torque of a vehicle, multiplied by RPM, and divided by 5,252. If the variables would cancel out, you'll have both torque and horsepower equating to 5,252 rpm. The amount of horsepower that a car produces is usually in it’s higher RPMs (the revolutions per minute that a vehicle’s engine is producing). In other words, the higher the engine’s speed is moving (which is measured in RPMs and displayed on your vehicle’s tachometer), the more horsepower is produced. The more throttle that is applied, the more power your vehicle will exert.

Typically, a car’s horsepower can rank anywhere; needless to say, each car is different. Even past a vehicle’s torque and weight numbers, there are more complex variables that can affect the rate of speed the car will travel. Some vehicles can have over 500 horsepower and still lose to a vehicle with half that amount of horsepower. Although 500 horsepower is typically the standard for high-performance cars, it still depends on the three big numbers of mechanical performance (but is not limited to those numbers).

TORQUE

Horsepower is work and work is speed. If the speed of a vehicle kills the competition; nevertheless, how do we get speed in the first place? That’s where torque, the silent killer, comes into play. Torque is the underlying performance figure of the three metrics. Torque is the rotational force needed for a vehicle to perform work (which is horsepower in the United States). Without torque, an engine will not be able to produce the power. By definition, the torque equation is the rotational counterpart of Newton’s second law of motion.

If:

Then, it is safe to say that:

Force is defined as linear, and torque is defined as rotational. Rotational force is calculated by multiplying the linear force, the distance of the center (axis of rotation) to where the linear force is applied, and the angle between the linear force and the axis of rotation (which is known as theta). Torque is generally measured in Newton-meters (Nm) but is expressed as pound-feet (lb-ft) in the United States.

The more torque a vehicle has, the easier it will be for an engine to produce its maximum amount of horsepower. For example, in gasoline (petrol) vehicles, torque is found to produce the highest quantities in the lower range of RPMs in a given engine while horsepower is found to produce the highest quantities in the higher RPMs. The relationship goes back to the common principle; torque is the force that gets the wheels moving and horsepower is the speed at which the car moves.

That’s also why torque is important for towing. Imagine having all of this power, but the 3000-pound trailer you are towing cannot move. The car’s wheels will spin, and the car will even move. While the vehicle is making all of this power, the driving force (or the rotational force that is pulling the added weight) is not present, resulting in the trailer stagnancy. Although you will not be towing anything during a drag race, the vehicle is still hauling the gross weight (the curb weight of the vehicle plus any other weight that does not come with the vehicle). Take note of a slightly different example, an electric vehicle. They are in a different class than gasoline vehicles because their maximum torque is used throughout the whole RPM band. Maximum torque starts at nearly zero RPMs and decreases as speed increases. In short, without torque, horsepower is useless.

Usually, torque can range all over the place (just like horsepower). It strictly depends on a vehicle’s use and engine build. For example, some production pickup trucks are equipped with turbo-diesel engines, which are superior torque engines, that have over 1000 lb. Some turbo-powered gasoline engines have more torque than horsepower. Generally speaking, torque is essential for towing, less critical for top-speed, but still crucial for overall speed.

WEIGHT

With the two driving forces of a car established, it’s time to focus on why the driving forces exist. The mass of a vehicle comes in all different types of forms, usually as either:

1. Pound (lb) or
2. Kilogram (kg)

Pounds (lb) is the weight figure used to determine a vehicle’s total mass in the United States:

$1lb=2.2kg$ or $0.4545lbs=1kg$

By definition, a vehicle’s weight is a measurement of how much the car has to carry. There are three types of weight figures: dry weight, curb weight, and gross weight.

1. Dry Weight is the vehicle’s minimum weight. This would include every part of the vehicle, excluding any operating fluids and any cargo, equipment, or passengers in the car. The dry weight is often used in showrooms or pre-production factories and cannot be operated. The term is used loosely with ‘shipping weight’ because factories transport brand-new vehicles without any type of fluids. This helps preserve the new life of the vehicle. Dry weight is also used in performance figures like general weight and weight-included formulas because a lighter vehicle appeals to a majority of the general public.
2. Curb Weight is the vehicle’s operating weight without anything else inside of the vehicle. The car would include its standard equipment and optional packages as well as its operating fluids. Fluids would include a full fuel tank, motor oil, transmission oil, brake fluid, coolant, air conditioning refrigerant, and battery. Consider curb weight as the standard for an operating vehicle; it has all of the required needs to drive but doesn't have the actual driver or cargo to go with it. Curb weight is the most common form of weight used by manufacturers because it is unanimously the most accurate.
3. Gross Weight is the heaviest of the three-vehicle weights. It is used for country regulations and certain car owners to see the standard of how much weight the vehicle could carry. Regulators use it as a measurement because of city restrictions and licensing requirements. Certain car owners reference this weight for the reason of towing capacity. Gross weight includes everything that the curb weight includes plus passengers, cargo, and additional aftermarket accessories. It includes everything besides the vehicle’s external towing measures (which is known as gross combined weight).

Focusing on the vehicle’s curb weight, it is the most accurate dividing force against the vehicle’s horsepower and torque. When a vehicle moves, weight slows it down. When a vehicle is halted, that is the weight pulling down the vehicle. Horsepower and torque versus weight are indirectly related, thus always being contrasted. The weight does add a performance benefit; however, the benefit does not relate to mechanical performance. Going off subject, the weight helps improve grip. This will allow the vehicle to put more pressure on the wheels, thus making the vehicle’s tires spin less.

Unlike the first two mechanical performance categories, a lower weight is generally better. The weight is too low if the vehicle cannot get traction to the tires, and is too high if the vehicle doesn’t move quick enough (according to its live performance). Finding a balance is always important, but a lower weight means more advantages in performance.

Mechanical Performance Grading System ©️

One particular metric does not dictate a car’s superiority over another car. For example, the horsepower of one vehicle doesn’t deem the vehicle to be faster than the other vehicle that’s in comparison. While there are plenty of factors that can play into each vehicle’s performance metric, it is essential to know the baseline of each system. The mechanical performance grading system is fundamental to classifying a car’s superiority over the next one. Grading systems can vary, however, this is one of the few that objectifies each performance metric.

The gist of the mechanical performance grading system is simple; to rate a vehicle’s given performance. Since there isn’t a clear number established in the automotive industry, the AutoReportCard decided to formulate each metric according to any given industry standard. The numbers are an estimate of what the majority of owners would feel is comfortable; though, one person’s comfort with a specific metric will vary to another person’s. For illustration purposes, 4000 lbs. is roughly the industry average for a vehicle produced in America. Although this is average, people may have never driven a car over 3500 lbs. Overall, the system considers a vehicle’s horsepower, torque, or weight and compares them to industry standards. Please note that the grading system takes into account one of the three metrics at a time.

The Grading System

The grading system itself consists of 20 letter grades. Each letter grade consists of a range of numbers. Similar (but different) to a school grade, there are added measures to ensure the inclusion of all vehicles and their performance characteristics- from the 70 horsepower Smart Fortwo to the monstrous Bugatti Chiron. The vehicles seen on this list are typically the ones that were produced in the 21st century (there are some exceptions because of models that started production in the late 1990s).

The grading system is demonstrated below:

The following table describes the letters for the grading system:

Letter Grades

* Upper boundary of the outstanding scores can be broken. It is to be known that this is where the scale stops.

Explanation of the Relevancy of the Variables

Horsepower and Torque Explanation

Horsepower, which is a unit of power, is the industry standard for measuring a vehicle’s primary performance capabilities. Torque, which is the force needed for horsepower, is the automotive industry standard of a vehicle’s performance capabilities. These two combine to be the needs of automotive performance. Without either one, the vehicle will not perform well in any event (whether it’s in straight-line or other racing purposes). Therefore, both of these metrics are placed on the same scale. There are three different scales used for these two performance metrics- stock, track, and drag. The “stock” scale is meant to calculate the horsepower or torque of a stock vehicle and is scalable to hold up to 1000 horsepower or lb/ft of torque. The “track” scale is a means to calculate the horsepower or torque of a vehicle in a track setting (excluding the drag strip) and also classifies modified vehicles. It is scalable up to 1500 horsepower or lb/ft of torque. The “drag” scale is meant to calculate the horsepower or the torque of a vehicle ready for the drag strip. It is scalable to 2000 horsepower or lb/ft of torque. All scales represent a vast majority of vehicles; however, there are a couple of exceptions to note. There are stock vehicles that have more than 1000 horsepower or 1000 lb/ft of torque. There are also track cars that have more than 1500 horsepower or lb/ft of torque, and drag cars that have more than 2000 horsepower or lb/ft of torque. These exceptions are classified as “O” because the grade can extend to infinity.

Attached below is the grading systems for stock, track, and drag cars:

Weight Explanation

Weight is a mass figure that is known for its characteristics of force on a vehicle through gravity. Weight goes against horsepower; which is the reason for its negative correlation graph. The heavier a car, the more torque, and horsepower is needed to reach a satisfactory speed. For example, a car that weighs 5000lbs with 500 horsepower and 500 lb/ft of torque doesn’t have the same mechanical performance as a vehicle that’s half the weight with the same amount of horsepower and torque. There is one scale for weight, which puts an advantage for lighter vehicles. Although lighter vehicles will have grip issues (in comparison to heavier vehicles) in terms of straight-line driving; predominantly, lighter vehicles do not need as much power or force to reach their maximum capabilities. The scale breaks down the vast majority of vehicles, from stock cars to track and drags cars. The scale goes as low as 1540lbs and as high as 7375lbs. There are instances that vehicles are more or less than the scale’s extremities. In these cases, the hyper-extreme numbers are considered to still count in the minimum/maximum range. For instance, the “O” and “Z” grades are the extreme cases, and anything past their limits is still classified as those grades.

Attached below is the grading system for weight:

Conclusion

With mechanical performance, we can figure out a vehicle’s pure performance characteristics just off of the realm of three numbers: horsepower, torque, and weight (lbs). Although the formula is still in its testing stages, it is important to note that the formula has come a long way. At the AutoReportCard, we are striving to add another dimension of weighting scales for grades. We are also looking to patent the official formula; for the knowledge that it’s worth, the secret formula can be used in a wide variety of applications. As it stands, we are looking forward to developing the mechanical performance formula.

ARC Mission Statement

The AutoReportCard’s mission is simple- strive for evaluating with quality, while objectifying everything to separate the best and the worst qualities of an automobile.