At Dynomite Performance, we strive to provide the most accurate performance testing for vehicles, which is why we use an inertia-based chassis dyno. In this article, we’ll explain how our DynoJet model 224x dynamometer works and how it calculates performance data.

What is an Inertia-Based Chassis Dyno?

An inertia-based chassis dyno is a tool used to measure a vehicle’s power output, primarily focusing on torque and horsepower. Unlike other types dynos, which may use electric or hydraulic braking systems, the inertia dyno relies on the physical principle of inertia to measure a vehicle’s performance.

The key component is a large, precisely weighted drum that the vehicle’s wheels turn. The dyno records how fast the drum accelerates when the vehicle is driven at full throttle. The rate of acceleration of the drum is then used to calculate the power output of the vehicle.

How Does It Work?

1. Vehicle Setup The vehicle is positioned on the dyno with the drive wheels resting on a large drum. The vehicle is strapped down securely to ensure it remains stationary, and the wheels are placed in contact and parallel with the roller.
2. Acceleration of the Drum As the vehicle accelerates, the wheels turn the drum. The drum’s mass creates inertia, resisting acceleration. The faster the vehicle’s wheels spin, the faster the drum rotates. Sensors on the dyno track the rate of acceleration, providing the first crucial piece of data for power calculations.
3. Data Recording As the engine reaches higher RPMs, the dyno records the change in the drum’s speed over time. This change is important because it correlates directly with the vehicle’s ability to overcome the drum’s inertia. The system collects real-time data on the drum’s rotational speed and vehicle RPM.
4. Calculating Power and Torque The dyno software uses the known mass of the drum and the recorded acceleration to calculate the engine’s power output. The basic formula used to determine horsepower is:

Torque is calculated using a different formula that takes into account the rotational speed (RPM) of the drum:

These formulas help determine the vehicle’s torque and horsepower across the RPM range, providing insights into its performance under different driving conditions.

Why Use an Inertia-Based Dyno?

Inertia dynos are particularly useful because they simulate real-world driving conditions, where a vehicle must overcome mass (in this case, the drum) to accelerate. Since the drum’s weight is constant and known, inertia-based dynos offer highly repeatable and accurate results, making them ideal for testing modifications, tuning, or performance benchmarking.

At Dynomite Performance, our dyno provides a reliable and efficient way to measure your vehicle’s power and provide us with the tool needed to tune your vehicle effectively. Whether you’re looking to test new performance modifications or establish baseline figures, the accurate, real-world data captured by the inertia-based dyno ensures you know exactly how your vehicle performs on the road.