Horsepower, CC, pound-feet, cubic inches. These are all common terms in the automotive industry. Horsepower and CC in particular are some of the most mentioned figures in today’s automotive world. Some may wonder, how do you convert horsepower to CC? Can you even convert horsepower to CC?
How about other figures like cubic inches then? That’s what we’re going to discuss in this post. Everything you need to know about engine specs and power output is here. Put your lab coats and science hats on, cause we’re giving you a science lesson!
Horsepower To CC: How To Convert Them?
Converting horsepower to CC is fairly straightforward. One horsepower is equal to somewhere between 14 – 17cc. Yes, there’s no exact equation, and we’ll explain that later on. But if you want to convert them, then this is the best estimate that you have. For this example, let’s take 15 as the middle ground.
So, let’s say you have a 150 horsepower engine. Since one horsepower is equivalent to 15cc, multiply 150 by 15 and you get 2,250cc. On the other hand, let’s say you know the engine is 2,000cc. How much horsepower do you have? Well, divide 2,000 by 15 and you have approximately 133 horsepower.
Simple and straightforward, right? No complicated equations that will turn your brain into mush. Here’s the thing though, horsepower and CC are two completely different units of measurement. Let us explain further:
Horsepower And CC Are Different Units Of Measurement
Horsepower is a unit measurement of power and is the most popular measurement for internal combustion engine power output. Or the more accurate scientific explanation, power is the rate at which work is done. Meanwhile, CC stands for cubic centimeters and is a unit measurement of volume.
CC can be used interchangeably with milliliters (ml). Although you should note that CC is for measuring solid volume, while ml is for measuring fluid volume. Hence why we use cc for engines. But they are the same, 1cc = 1ml. Hence why, for example, you can refer to a 2,000cc engine as a 2.0L engine.
Anyway, since they’re different units of measurement, there’s no exact conversion equation. It’s a bit like converting fluid ounces to pounds; while you can, it’s often an approximation since you need to take the density of the liquid into account.
The same goes with horsepower and CC. A 2,000cc engine doesn’t always equal 133 horsepower. The power output may vary depending on the engine design.
Take the 2,000cc engine in the Honda S2000 as an example. The JDM version of the Honda S2000 makes 247 horsepower. Meanwhile, the USDM version makes slightly less at 237 horsepower. This is because of slight changes in the engine setup.
The bottom line is that they’re different units of measurement, and horsepower and CC are rarely used interchangeably. We’ll explain both horsepower and CC in further detail in the following sections:
A Further Lesson On Horsepower
So, we’ve established that horsepower and CC are two different units of measurement. Now, let’s take a closer look at horsepower. From what it is, its history, and how we measure horsepower.
The Difference Between Horsepower And Torque
We’ll get to the juicy equations right after this. First, let us explain what horsepower is. And we can’t do that without explaining about torque along the way. These two figures go hand in hand and it will be wise to understand the difference between them. There are three terms you need to understand:
- Work is the result of a force over a distance. It’s often referred to as force as well.
- Torque is similar to work, which is a measure of how much a force acting on an object causes the object to rotate. In other words, it’s a measure of rotational motion force. In the context of internal combustion engines, torque is the rotating force produced by the engine’s crankshaft.
- Power is how fast this work is accomplished. The faster it is accomplished, the greater the power.
The video above from Jason Fenske should give a clear explanation of the difference between the two. In the simplest terms possible, torque is how much rotating force an engine’s crankshaft can produce. Meanwhile, power is how fast the crankshaft can rotate.
The Equation For Horsepower
Perhaps, understanding horsepower would be easier by understanding how the concept came about. The formula for horsepower came from James Watt, the inventor of the steam engine.
He chose the term horsepower because horses were commonly used for work and transporting purposes, thus making them a great and clear reference to show what his steam engine was capable of.
Through his equation, Watt deduced that one mill horse can push or pull 32,572lbs of mass (rounded to 33,000lbs) by one foot in one minute. So, one horsepower can push 33,000lbs of mass by one foot in one minute. Here’s the equation:
So, to find horsepower, you’ll need to multiply the force in pounds (F) which is the weight of the mass with the distance in feet (d). Afterward, divide it by the time it takes to travel that distance in minutes (t). And voila! You have the horsepower.
The equation to find a car’s horsepower is slightly different. Since the horsepower output varies depending on the engine speed (RPM or revolutions per minute), you’ll need to add RPM into the equation. So, the formula becomes (Torque x RPM)/5,252.
For example, let’s say you have an engine that makes peak torque of 500lb-ft at 4,000rpm. Multiply the two numbers and you get 2,000,000. Next, divide that number by 5,252 and you arrive at 380 horsepower.
Now, you might be asking, why divide it by 5,252? In a nutshell, it’s because that’s where horsepower and torque figures intersect in the rev range. I’m not an engineer so I’m hardly qualified to explain this, so, I’ll let Jason Fenske explain this one as well:
While this equation is useful, if you want to measure your car’s horsepower, you’re going to have to use a dynamometer, or dyno for short:
Measuring Horsepower With A Dyno
There are two main types of dyno; an engine dyno and a chassis dyno. Carmakers will usually use an engine dyno which measures the amount of power and torque the engine makes at the crankshaft. Then they use the result of this test to put in their brochures.
Meanwhile, a chassis dyno measures horsepower via the car’s wheel by putting it on a set of rollers. Since they measure it from the wheels and not the crankshaft, this means the result is bound to have a lower number. This is due to friction loss in the drivetrain, and a car can lose up to 15% of its crank horsepower.
Chassis dyno is more practical since you don’t have to take out the engine. What you do is put your car on the rollers, tie the car down so that it doesn’t launch off during testing, and you’re good to go. This makes them more popular in the tuning scene.
Both of these dynamometers can be broken down to even more types, but one of the most common ones today is the absorption type. In essence, this type of dyno absorbs the car’s energy and measure them using electronic instruments.
So, which one is better? A chassis dyno is certainly more practical. If you’re trying to determine your car’s overall performance, then a chassis dyno is the way to go. It may also help diagnose issues you’re experiencing with the car.
However, if you’re trying to squeeze every bit of power from your engine, then you’ll have to use an engine dyno. It allows you to be accurate as it measures “true” horsepower at the crank, not at the wheel after it has lost some of those power.
Different “Types” Of Horsepower
When we talk about horsepower, there are actually multiple types. From the section about dynos above, we know that there’s crank and wheel horsepower. Crank horsepower is often referred to as brake horsepower or BHP in the UK. As mentioned, since it’s measured at the crank, the number will always be higher than wheel horsepower since there is no friction loss.
Additionally, there’s also US and metric horsepower. We’re not going to get into the equation, but you should know that metric horsepower is around 1.4% more powerful than SAE horsepower which is what the US use.
The equation to calculate metric horsepower is the same as SAE horsepower. However, the formula converts the values into metric units. So, instead of pounds and feet, it uses kilograms and meters. Hence the slight discrepancy between metric and US horsepower.
As an example, take the original Bugatti Veyron. If you read European publications, you’ll notice that they state the Veyron has 1,001 horsepower. However, American publications will state the Veyron has 987 horsepower. Break out your calculator and you’ll notice there’s a 1.4% discrepancy.
Another example is the McLaren 720S, which has, you guessed it, 720 PS or metric horsepower. However, US publications will write or say it has 710 horsepower because of that slight discrepancy. So, it’s not that carmakers are lying to you. It’s just that somehow even to this day we human beings have not decided on a single universal measuring system.
One last thing note, you’ll often see metric horsepower expressed in PS which stands for pferdestärke which is German for horsepower. Less commonly, it may also be expressed in cavalli vapore (cv). But you’ll rarely see this cv outside of Italian motoring publications.
Horsepower To CC: Understanding Engine Size And Measurements
So, as mentioned, CC stands for cubic centimeters and is a measure of the engine’s displacement. The engine displacement itself is the measure of the cylinders’ total volume that’s swept by the pistons of the engine, excluding the combustion chambers.
There are three common measurements that the industry use for measuring engine displacements: CC, liters, and cubic inches. They all measure engine displacement, but we mostly use CC and liters nowadays. CC gives you a more accurate size, while liters is used for rounding up the CC number and making it easier to read in the brochures.
Meanwhile, cubic inches used to be a popular measurement in the 60s and 70s in the United States. It’s still a popular way of identifying classic muscle car engines because they used to go by cubic inches, but carmakers now use CC and liters in general.
Engines with a larger displacement typically make more power. This is because they can take in more fuel and air and therefore make more powerful combustion, leading to more power.
However, engine size isn’t the only factor. Other factors such as airflow, exhaust system, valve timing, and forced induction (turbocharger or supercharger) that increase air intake can affect the power output. Hence why it’s not common to convert horsepower to CC nor the other way around, because there are other factors in the equation.
Even without the help of a turbocharger, engines of the same size can make different power figures due to things like their bore and stroke and other engine design.
Horsepower To CC: How Do We Measure Engine Displacement?
The bore is the width of the cylinders in the engine. Meanwhile, stroke is the distance the piston travels inside those cylinders. They ultimately decide the size of the engine displacement.
If you have the bore and stroke numbers, you can find out the engine displacement by using the following formula: 0.7854 x Bore x Bore (cm) x Stroke (cm) x Number of Cylinders.
If you want to find out the size in cubic inches, simply convert the bore and stroke size from cm into inches. One (1) centimeter is equivalent to 0.39 inches, and you can use conversion tools to help you convert them quicker.
How Bore And Stroke Affects Power Output
While not as commonly talked about as engine displacement, carmakers still often list their engine’s bore and stroke in their brochures. We tend to gloss over them, but they can actually tell you a lot about an engine’s characteristics.
Now, bore and stroke are so much more than just engine size. The bore and stroke design can change the power characteristics of the engine, and even affect its peak power and torque output.
A car with a larger bore relative to its stroke length will produce more horsepower. This is because there’s more space in the cylinder that allows for bigger valve openings. As a result, the engine can bring more fuel and air into the cylinder resulting in more power.
Meanwhile, a longer stroke relative to the bore width will produce more torque in low RPMs. This is because it has a smaller room for the valve opening, which results in less air-fuel mixture and quicker combustion at low RPMs.
While this creates more torque down low, a longer stroke will result in higher piston speeds. This increases the inertia of the connecting rods (conrod), which could tear the connection apart.
As a result, engines with a longer stroke tend to have a lower maximum RPM to prevent the conrod from tearing. Since horsepower depends on how fast the engine can rev, this type of engine usually has a lower horsepower output.
You’ll often find that diesel and industrial engines often have a longer stroke relative to their bore width. An example of a car with a much larger bore width than its stroke length are Formula 1 cars. Their cylinders are very wide, while the stroke is much shorter which allows them to rev much faster.
Horsepower To CC: Questions And Answers
Got any more questions about engine power and sizes? We try to answer as many as possible below:
How To Convert Horsepower To Kilowatt?
Another common unit of measurement of power is Kilowatt (kW). While this is the EU’s standard of measurement, the vast majority of European carmakers use horsepower, albeit the metric horsepower rather than SAE. Australia is one of the few countries that regularly use this unit of power measurement.
Anyway, 1 horsepower is equal to around 0.74 kilowatts. So, if you want to convert it, simply multiply the horsepower figure by 0.74. So, if an engine has 400 horsepower, this means it has 296kW of power.
Meanwhile, to convert kilowatt into horsepower, multiply the kilowatt figure by 1.34. As an example, a 400kW means it has 536 horsepower. Unlike horsepower to CC, they’re straightforward since they’re the same type of unit of measurement.
How Do I Convert LB-FT Into N⋅m?
In the metric system, a more popular measurement of torque is the Newton meter (N⋅m or Nm). Despite its name, it was not introduced by Isaac Newton himself, but rather by Richard Salter.
Newton-meter measures torque as well, which is force over a distance. But rather than using pounds and feet, it uses kilograms and meters. Anyway, 1lb-ft is equivalent to 1.3558Nm. So, a car with 300lb-ft of torque has around 406 of torque when measured in Newton meter.
If you’re converting the other way around, 1Nm is equivalent to 0.738lb-ft of torque. As an example, a car with 300Nm of torque has 221 torque when measured in lb-ft. If you don’t feel like remembering this conversion rate and breaking out your calculator, there are plenty of online conversion tools you can use.
Why Don’t Carmakers Use Cubic Inches Anymore?
It’s mostly because US carmakers were the only ones using cubic inches to measure engine displacement. Every other carmaker – even when they bring their car to the US – uses the metric system which is either CC or liters.
Over time, consumers – in the US and globally – have gotten used to using CC and liters. To ensure they remain competitive and to reduce the chances of conversion errors, US carmakers decided to use the metric system as well. They started adopting it in the late 80s, and since then cubic inches has fallen out of fashion.
Why Is Crank Horsepower Called “Brake” Horsepower?
It does sound misleading, doesn’t it? You would think that brake horsepower somehow relates to the car’s braking force. However, the name simply came from a technique to measure power.
Older engine dynamometers connect the engine to a large drum with an internal water brake, which measures the resisting braking force produced when opposing the rotation of an engine’s crankshaft. Hence the name brake horsepower.
Now, the US doesn’t typically use brake horsepower or BHP and will simply refer to it as crank horsepower. BHP is more commonly used in the UK. However, UK brake horsepower figures will almost certainly be lower than US crank horsepower figures.
This is because US carmakers typically test crank horsepower without the engine’s ancillaries such as the alternator and power steering. Meanwhile, UK carmakers will often attach these during testing. Since these ancillaries will consume power from the engine, the BHP figure will almost certainly be lower.
How Much Does A Dyno Cost?
All this talk about horsepower and torque probably got you thinking of doing a dyno. Of course, this isn’t necessary if your car is bog-standard unless you have strong reason to believe that your car’s manufacturer is lying about the power figures.
Anyway, a dyno run typically starts at around $150 per hour. Of course, the main purpose of a dyno is to tune your engine. The dyno can help detect problem areas, and you can tune various aspects (such as fuel and air mixture and ignition timing) and see if it improves.
This will take the better part of the day. Meaning your initial cost for the dyno will be around $450 for a half-day and $650 for a full day. This doesn’t include the cost of tuning the engine itself.
It sounds expensive, but if you’ve made major performance modifications to your engine, you definitely want to dyno tune your car. It will help detect problem areas, maximize your power output, as well as minimize wear and tear to your engine.
Horsepower To CC: In Conclusion…
To summarize, one (1) horsepower is equivalent to about 14 – 17cc. However, as we’ve countlessly repeated in this post, they are different units of measurement and therefore are not used interchangeably.
Horsepower is a measurement of the engine’s power output. Meanwhile, CC stands for cubic centimeters and is a measurement of the engine’s size. Specifically, the engine’s cylinders’ displacement.
While engine size can affect power output, many other factors can affect the engine’s power output. These factors include the valve openings, camshaft design, ignition timing, and bore and stroke size amongst other things. When you consider this, it makes no sense to convert horsepower to CC or the other way around.
Hopefully, this has been a helpful guide to engine power and size measurement!
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