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What is a Flat Plane Crank and Why is it So Loud?

What is a flat plane crank? More importantly, why is it so loud? These are questions that you might be asking yourself, especially if you've ever heard one of these things rev up. If you really want to know more, you can keep reading in order to find out what a flat plane crank really is, what it does and why it makes so much noise. While you're at it, you might also learn why some people consider it superior to its counterpart, the cross plane crankshaft, despite the fact that it can wake someone up from two counties away.

What Is It?

In short, it is a crankshaft that makes it part of an automobile engine. The crankshaft is important in any car because it is one of the major moving components that allows the pistons to fire in sequence as they were designed to do. Without it, the engine would essentially cease to function. Furthermore, it is the crankshaft that allows a car's engine to rev up to a particular RPM. This in turn has a direct impact on not only how fast the car is able to run, but how quickly it's able to accelerate. Of course, there are other factors involved as well. When it comes to something as complex as an automobile, there are a lot of moving parts that have to be considered such as the pistons themselves, the transmission, so on and so forth. However, nothing would be able to function properly if not for the crankshaft. That is precisely why it's so important that the proper crankshaft be used and that it not be abused beyond its ability to function.

The Differences In The Two Crankshafts

There are two main types of crankshafts, the flat plane crank and the cross plane crank. The two are quite different in the way they operate. The flat plane crank fires the cylinders in a flat line, or plane, hence its name. Conversely, the cross plane crank fires cylinders across from each other, going in something of a zigzag pattern. For example, a cross plane crank is designed to fire in sequence. Therefore, you have pistons firing from the first to the last cylinder in an engine, regardless of where the cylinders are located. A flat plane crank, on the other hand, will fire all cylinders on one side of the engine and then all cylinders on the other side of the engine. Obviously, this makes it necessary for the flat plane crank to have a lot more moving parts. It also has a great deal more vibration associated with it then does the cross plane crank. As such, it has a tendency to make a lot more noise, but that extra noise isn't only because of the added vibration.

Why Is It So Loud?

The biggest reason that a flat-plane crank makes so much noise is because it allows the engine to rev up much higher than the cross plane crank. Engine designers that really want to get the most out of a performance engine may choose to use a flat-plane crank because it's capable of getting the engine RPMs up much higher than a cross plane crank ever could. The difference in the engine RPM goes back to the way the two different crankshafts fire the cylinders. The ability to rev the engine up to a faster speed is directly tied to the way that the cylinders are fired. Since the flat plane crank isn't forced to perform in a zigzag pattern, it's able to get right to the point and fire each cylinder in rapid succession. This in turn means that the engine itself is turning at a much higher RPM. This higher RPM also means that the crankshaft is making more noise, as is the engine itself and virtually every component associated with it. When you put all of that together, it makes a considerable amount of noise that is capable of driving even the sanest of individuals completely crazy.

A Dying Breed

Because of the excessive noise associated with the flat plane crank, it is very rarely used on automobiles that are manufactured today. In fact, it's almost impossible to find one on a street-legal automobile manufactured in recent years. In order to get your hands on one, you almost have to look into high performance cars that are designed specifically for the racetrack. Conversely, you might be able to find one that has been installed as an aftermarket part on a high performance engine. Keep in mind, a lot of work goes into changing the style of crankshaft on an engine. It's not as simple as just replacing one with the other. Done properly, it can get the right engine running, and running fast. However, you have to have some solid knowledge about automobile engines in order to pull it off successfully.

More Noise Means More Power

At the end of the day, more noise often means more power. Stop and think about it. Have you ever been to a racetrack and thought that it was quiet? High performance cars that are capable of running at extremely high speeds have a tendency to be exceptionally loud. Part of that is due to the different engine components, including the crankshaft. If you really want more power, the flat plane crank is an excellent way to get it, but you might pay for it when it comes to being able to hear well after you’ve listened to one for a few years. Now that you know more about what a flat plane crank is and why it's so noisy, you know why it's largely been phased out when it comes to street legal automobiles. Not only do people not want to hear the noise when they're driving (or when a car is running through the streets of their neighborhood), many municipalities have guidelines against loud vehicles. Therefore, this particular type of crankshaft became largely unpopular for any vehicle that wasn't designed for high performance. There is no doubt that the flat plane crank will get you where you want to go quickly and efficiently. The thing is, everyone else will hear you coming.

Benjamin Smith

Written by Benjamin Smith

Benjamin Smith is one of the managing editors of Moneyinc. Ben's been focusing on the auto and motorcycle sector since 2005. He's written over 1000 articles in the space and continues to learn about it each day. His favorite car is "any Bugatti" and he's a die hard Harley Davidson fan.

Read more posts by Benjamin Smith

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