A: The dynamometer (dyno or dyne for short) is a measurement tool used to indicate the output torque of an engine. There are two ways of accomplishing this, Inertia, or Brakes.

A: In Physics terms, Torque is a twisting force acting upon an axis. To think of this visually, imagine tightening a bolt with a 12-inch long spanner; the torque is the known force (say 30Lb) acting on a lever of a known length (12” or 1Ft.), resulting in a twisting force being applied to the bolt at a rate of 30Lb-Ft, pronounced either ‘pound-feet’ or ‘foot-pounds’.

A: We all want to know the power output of our cars, but something you may not know is that Horsepower is only a calculated number. That’s right, Horsepower can’t be measured! It is only an imaginary representation used to quantify HOW QUICKLY a machine produces torque. The dyno computer completes a calculation for HP with every data input of Torque that it measures using the formula HP = TQ x RPM / 5252. In this equation, ‘5252’ is simply the constant used when the torque is being measured in Pound-Feet. If you were calculating with a different set of units, commonly Newton-meter, then this number changes. Also of note is that HP = TQ when engine speed is equal to this constant, so on a dyno graph measured in Horsepower and Lb-Ft, the two lines will always cross at 5252 rpm.

A: The INERTIA dyno is the cheapest and easiest type to build. It measures torque based on the rate of acceleration of a known mass, usually a heavy drum-roller or flywheel that is spun by the drive-wheels of the car. When the car is accelerated, a computer measures the rpm of the roller at any given time, and from this determines the change in RPM, and how long that change takes to occur. With additional equations, the torque required to cause that acceleration is calculated and output. Unfortunately, in order to accurately tune an ECU, it is essential to be able to hold the engine stable at one speed to isolate out any accel/decel ancilliary changes to fueling or timing, which the inertia dyno cannot do.

A: Simply put, a BRAKE dyno applies load to the engine via any one of a variety of actual brake systems. The first brake dynos used large drums and shoes, very similar to the brakes on a lorry in order to restrict the speed of the dyno. These systems were ultimately limited by the amount of heat that built up in the materials. Most brake dynos today use water, oil, or electro-magnetic principles to apply a load, as well as carry away the heat generated. Our dyno has an ‘eddy-current’ absorber that functions similarly to the alternator that charges your battery. Brake dynos allow the operator to hold an engine at any speed or load within its operating range, allowing cell-by-cell calibration of an ECU, and is the only proper way to fully tune a modern fuel-injected engine.

A: There are many inherent risks that become apparent as we consider attempting to tune a car on the road; namely that we’re jeopardising our safety and members of the public, the vehicle, and points on our license. On top of that, we find that it is next to impossible to maintain a steady load or RPM for any useful length of time. Even if you have capability to data log, you’re still left with weeding out any transient data points (times where engine speed or load are changing) to try to extract data points that could effectively be used for altering the tune. Not to mention the speeds required in order to load a turbocharged car at full boost put you well into the realm of license forfeiture, and nobody wants that. This is not to say that there is no merit to VERIFYING a tune by road testing a vehicle, or to adjust acceleration parameters within a tune, but as a primary means of tuning a vehicle, your hands are tied, just about as much as with an Inertia Dyno, yet without the comfort of a controlled environment.


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