How do I calculate the required excavator motor displacement?

Calculating the required excavator motor displacement can be as tricky as finding the perfect coffee-to-water ratio—too little, and your engine’s sluggish; too much, and you risk a wasteful overkill. The key is to balance your hydraulic flow, desired operating speed, and the inherent efficiency of your hydraulic system. In essence, you’re figuring out how much “juice” your motor needs per revolution to power your excavator exactly how you want it to work.

To start, determine the flow rate required by your hydraulic system. This is usually given in liters per minute (LPM) and depends on what your machine is expected to do—whether it’s swinging the boom, digging with precision, or both. Once you have that number, you need to know the motor’s operating speed, usually expressed in revolutions per minute (RPM). The basic idea is that the motor displacement, measured in cubic centimeters (cc) per revolution, is the ratio of the total fluid flow to the motor speed. Think of it as calculating how many milliliters of hydraulic fluid are needed with each turn to achieve the desired movement.

Here’s a simplified way to look at it: if you multiply your required flow (in cc per minute, noting that 1 LPM equals 1,000 cc/min) by a conversion factor, and then divide by the motor’s RPM, you get the theoretical displacement. But hold your horses—there’s more to it. Hydraulic systems aren’t 100 percent efficient; they lose a bit of fluid here and there due to friction and leakage. That’s why you need to account for a volumetric efficiency factor, typically around 85 to 90 percent. This factor ensures that your calculations consider real-world conditions rather than an ideal, frictionless fantasy.

Once you have your basic displacement value, you might need to adjust further based on the specific performance characteristics you’re targeting. Want a smoother, more controlled movement? A slightly higher displacement might be in order. Need more rapid, forceful operation? You might opt for a motor with a lower displacement that pushes the system to work harder, albeit with a little extra wear over time. The choice ultimately depends on the operating conditions and the performance goals of your machine.

Of course, if all of this math feels like decoding an ancient scroll, that’s where the experts step in. At our company, we specialize in high-quality hydraulic components and provide comprehensive support to ensure that every motor meets the precise requirements of your excavator. Our state-of-the-art manufacturing and rigorous testing mean you can trust our motors to deliver the perfect balance of power, efficiency, and durability. We’re always here to help fine-tune the specs to your unique application, ensuring you never have to worry about the math when it comes to keeping your machine running at peak performance.

Curious about what motor displacement is right for your equipment? Contact us today for a personalized consultation and quote. Let’s turn complex calculations into straightforward solutions that keep your excavator moving exactly how you need it to—efficiently and reliably.

Fulian Operation Team

2025.3.21