The Basics of Chassis Dynos Testing

Over the past 10 years, chassis dyno testing has grown nationwide, giving the public the opportunity to evaluate engine performance and compare the results with other vehicles. It’s an exciting prospect for car enthusiasts everywhere, but it helps to understand the process a bit.

It’s important to understand that the type of dyno in your car and the method of chassis dyno testing significantly affects your results. The basic types of chassis dyno can be divided into three groups: water-brake or hydraulic dynos, electric dynos and inertia dynos. An inertia dyno is perfect for full-throttle acceleration runs—and that’s pretty much it, though the more modern load-bearing hydraulic and electric dynos can do constant speed pulls, step tests and part-throttle testing in such a sophisticated modern way that full road-load simulations can be conducted right on the dyno.

One of the most widely used forms of chassis dyno testing is the inertia dynos—many car enthusiasts wonder how this method of testing works. Here are the basics—inertia dynos only works when the car is accelerating. It evaluates horsepower by analyzing the dyno drum's acceleration rate with specialized computer software and an accelerometer, and uses heavy roller drums of known mass rotating on bearings that they are mounted on.

The car is positioned on the dyno with the drive wheels sitting on the rollers, placed in gear and then accelerated at wide-open throttle. As you can imagine, it takes some time and force for the tires to accelerate the weighted rollers. The software monitors roller velocity and acceleration time, while estimating the power of the rear wheels. The software then measures the power and gear-compensated engine torque against engine rpm.

There is a lot more to this growing mode of testing, but this should give you a basic understanding for when you are ready to compare your engine to your buddy’s.

img credit: sierrainstruments.com