how we built
a chassis dyno
Building the chassis dyno
We chose to build an in-floor chassis dyno rather than a more vibration-prone floor-top system to ensure the platform would be stable enough to produce valid, reliable data. The final product is a chassis dyno capable of testing everything from a 300cc motorcycle to a 14L tractor-trailer. If it can fit through the door, we can test it!
We chose Timken roller bearings for their ability to withstand high speeds for extended periods. These bearings have a life expectancy of 2 years when running 24/7 @ 160km/h and are capable of reaching 8,000 RPM. We chose Timkin SAF cast-steel pillow block housings because of their ability to bear high loads and resist contamination from debris falling into the pit.
We sourced a 2,500 lb. industrial precision roller that’s round to within 0.000001 of an inch, creates 2,278 foot-pounds of inertia and can support a 10-ton vehicle. To ensure a stable platform, we capped off our roller with ½” diamond plating set on 3” steel framing.
Dyno testing and reliability of results
While dyno graphing software can monitor and compensate for variations in temperature, barometric pressure, intake air and exhaust gas temperatures, etc., it cannot reliably compensate for inaccurate feedback from the roller itself. When a roller lacks precision or is prone to vibration, spikes in torque and speed will appear at random in the test results. When this random data contaminates test results, accurate tuning becomes problematic. For example, air and fuel flow adjustments are fine-tuned based on data generated by repeated dyno passes. But how can these adjustments be made accurately when the dyno results are inconsistent?
By installing a roller with a precision of 0.00001 inches and paring it with vibration-free bearings and pillow blocks on concrete footings, we eliminate these false torque and speed spikes so that our test data that can be consistently replicated from pass-to-pass and our technicians can fine-tune engines with accuracy.
dyno testing and validity of results
Our dyno roller has a diameter of 24.5,” a mass of 2,500 lbs, and generates 2,278 ft—lbs. of inertia. Having a large, high-inertia dyno that can reach 8,000 RPM ensures our test results are not only reliable but also accurate.
Accurate tuning relies on the dyno’s ability to simulate the traction that vehicles experience in the real asphalt world. Small, low-inertia dynos aren’t able to adequately simulate road-load conditions or deceleration (coast-down) because the rollers don’t provide enough traction, and they decelerate too fast.
Horsepower calculations are also skewed on these smaller setups because of wheel slippage and tire deformation. The tire deformation occurs when operators attempt to compensate for tire slippage by applying excessive strap force. While the extra pressure reduces the slippage, the flexing of the tire negates the validity of any reduction in slippage – and can cause sidewall damage to your tires.