What a rolling road measures
A chassis dyno, often called a rolling road, puts the car under a controlled load so the operator can record power and torque through the rev range. A before-and-after run can show where the delivery has changed, as well as what happened to the peak figure. Ask whether a chart shows measured wheel output or an estimated engine figure before comparing the numbers.
What happens during mobile fitting
We identify the ECU and fit a pre-developed calibration matched to the vehicle. The important details include the exact engine, ECU software and any hardware changes. Two cars with the same badge can need different files. We check the vehicle before fitting and check it again afterwards.
How to read a quoted gain
Ask which engine, fuel and setup produced the figure. A result from another car is a reference for that setup. A before-and-after measurement from your own car is the way to quantify the change on yours. If you mainly want the car to respond better in normal driving, describe where it feels sluggish so the conversation starts with something more useful than a peak number.
Further reading APR’s example of measured calibration results