#How to measure the engine power of a car?

05 / June 2023
How to measure the engine power of a car?

Seletron Performance

How to measure the power of a car?


There are cases in which one would like to be able to measure the power of a car engine. This need arises not only in the field of tuning but also for checking and controlling the state of the engine or even just for simple curiosity and education. Today we want to answer the question "How to measure car power simply?" by examining the main ways of measuring power and torque and how they work.



Brake test bench


This is the most accurate method but also the most complex to conduct. This test is performed by removing the engine from the vehicle and fastening it on a specific test stand. The test stand has all the auxiliary accessories that serve to cool the engine, and the power and torque values are measured by means of load cells that detect the torque at any speed of rotation. This is a complex but very accurate device in that it can run the engine for an indefinite time at any fixed rotational speed by reading its current output. This system is used for tuning engines and ECU software and is also the best tool for tweaking major engine tuning.


2WD and 4WD inertia dynamometer


These are the most common test benches, and they can be more or less expensive depending on build quality, but they are a convenient and fairly accurate means of measuring (by deduction) engine torque and power. As we said, they are convenient to use, as the car is placed on the rollers of the dyno, and the belts that ensure that the car does not move dangerously during the test are secured. The dyno gets its name "inertial" from the fact that it works through the acceleration of heavy rollers (inertials) that are caused to accelerate by the vehicle's driving wheels (2 or even 4). The greater the engine power, the faster the rollers (the inertial masses) gain speed over time. An RPM sensor detects the speed of rotation of the rollers while a software program deduces the torque delivered by the engine. This is referred to as deduction because the torque (and therefore power) value is deduced using a mathematical calculation on the acceleration capacity of the mass. It is not a matter of direct detection of the torque as is done on the more accurate braked benches, but the accuracy of the measurement is high, at least with the higher-quality inertial benches.


Smartphone applications for measuring power


These are simple apps that can be installed on standard smartphones and deduce torque (and thus engine power) from the vehicle's acceleration capability. In order to work, these systems require the input of the vehicle's total mass figure. These systems are not among the most accurate, but they also allow for other chronometric measurements such as 0-50 km/h acceleration, 0-100 km/h, 0-150 km/h, recovery times, and speed measurements. They are nevertheless very useful for checking performance differences before and after a modification.


DynoRoad Power Measurement


This other performance measurement system consists of an electronic device that can be easily attached to one of the car's wheel nuts (it should be attached to a non-drive wheel in cars without all-wheel drive as skidding can distort the measurement) and a smartphone app. This system also provides an indirect, deductive measurement as it calculates torque and power based on the engine's ability to accelerate the car's known mass. The system has a 90% accuracy rate (the manufacturer's stated figure) and is still very useful for measuring values with an acceptable tolerance. It is even more useful for measuring the difference in power and torque before and after tuning, for example, after the installation of a chip tuning additional unit.


Watch how the Magic Motorsport DynoRoad works

* Subtitle in english available, activate it in the video settings, on the bottom right button


Technical note on measuring engine power and torque


As mentioned at the beginning of this article, braking test benches are virtually the only ones that directly measure torque values at low RPMs of heavily turbocharged engines with strong turbo-lag, something that other measurement systems cannot do as accurately. This is because on braking benches, it is possible to determine the RPM of the static engine (e.g., 1500 RPM) and wait as long as it takes to overcome turbo/lag and have the maximum torque in Nm available at that given RPM.


If you are an electronic tuning enthusiast or simply love technology and the automotive industry, we recommend you also read our other articles that talk about fuel injection systems, supercharging systems, exhaust system back pressure, operation of all-wheel drives, and the tuning of gasoline and diesel cars in general. There is also no shortage of articles that talk about electric cars!


If you are looking for ways to tune your car with non-invasive chip tuning modules that are removable when needed and able to increase power, torque, and performance while also optimizing fuel consumption, search here for your exact car model.




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