The flat plane crankshaft is a unique design used in some high-performance engines. It differs from the traditional cross-plane crankshaft used in most V8 engines, but what is it, and how does it work?
What is a Flat Plane Crank?
The flat plane crankshaft is a design that has all of the connecting rod journals arranged in a flat plane. This means that the crank throws, which connect the connecting rods to the pistons, are all in the same plane, resulting in 180-degree firing intervals. This design is different from the cross-plane crankshaft design, which has the connecting rod journals arranged in a cross pattern, resulting in 90-degree firing intervals.
Who Invented the Flat Plane Crank?
Cadillac introduced a V8 engine with a flat-plane crankshaft in 1923, which was a significant innovation for the time.
The introduction of the flat-plane crankshaft in Cadillac’s V8 engine allowed for an even firing order, which resulted in a smoother and more efficient engine operation. This design was a significant departure from the traditional cross-plane crankshaft used in most V8 engines of the time, which had a firing order that was less evenly spaced.
The flat-plane crankshaft design in the Cadillac V8 engine was a significant advancement in automotive technology, and it helped pave the way for the use of this design in other high-performance engines in the years to come.
How Does a Flat Plane Crank Work?
The flat plane crankshaft design allows for an even firing order, which provides a unique exhaust note and improves the engine’s overall performance. When the engine is running, the cylinders fire in a sequence of 1-8-2-7-4-5-3-6 (for a V8 engine). This even firing order means that each cylinder is firing at an even interval, which results in a smoother engine operation and increased power.
Why Use a Flat Plane Crank?
There are several advantages to using a flat plane crankshaft. One of the most significant advantages is improved engine performance. The even firing order allows for better engine balance, resulting in less vibration and smoother operation. Additionally, the flat plane crankshaft design is lighter than the cross-plane design, which reduces the engine’s overall weight, making it more efficient.
Another advantage of the flat plane crankshaft is that it allows for a higher engine speed. The even firing order means that the engine can rev higher without the risk of harmonic vibrations. This design is ideal for high-performance engines used in racing applications.
What are the Disadvantages of a Flat Plane Crankshaft?
While the flat plane crankshaft design has many advantages, it also has some disadvantages. One of the most significant disadvantages is that it produces more noise and vibration than the cross-plane design. This is because the engine’s firing order is not as evenly spaced as it is with the cross-plane design.
Another disadvantage is that the flat plane crankshaft design is not ideal for low-end torque. The even firing order means that the engine produces less torque at low RPMs. This can be a disadvantage for engines used in applications such as towing or heavy hauling.
Conclusion
The flat plane crankshaft is a unique design that has been used in various high-performance engines for over a century. Its even firing order provides several advantages, including improved engine balance, reduced engine weight, and the ability to rev higher. However, it also has some disadvantages, such as increased noise and vibration and reduced low-end torque. Ultimately, the choice between a flat plane crankshaft and a cross-plane crankshaft comes down to the specific application and the driver’s preferences.
