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Introduction to Engine Tuning: Not all dynos are created equal

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Not all dynos are created equal

02.07

00:00 - When it comes to chassis dynos we can also break these down further into load bearing dynos and inertia dynos.
00:08 The difference is important so it pays to understand what these terms mean.
00:13 As we've previously discussed accurately tuning an EFI system requires us to be able to operate the engine in steady state where the engine RPM is controlled by the dyno as we open the throttle, as well as performing ramp runs where the dyno allows the engine to accelerate under full throttle conditions.
00:34 In order to run in steady state though the dyno needs to be able to provide a varying load so that it can maintain a consistent engine speed as we open and close the throttle and hence the engine torque changes.
00:50 This is the sort of dyno we refer to as a load bearing dyno.
00:54 The dyno will include what's known as a power absorber that can generate a variable load to control the roller speed.
01:03 An inertia dyno on the other hand is a much simpler design in that it just consists of a roller of a large known mass and diameter.
01:12 These dynos work on the principle that if we know the mass and diameter of the roller, as well as how quickly it is being accelerated, we can calculate how much power was required to achieve the measured acceleration.
01:27 Since the inertia dyno has no power absorber and it doesn't require a sophisticated control system to alter the load being applied to the roller they are usually much cheaper than a load bearing dyno.
01:40 If you are only interested in testing under wide open throttle ramp runs then an inertia dyno can be remarkably effective.
01:47 However they're not really any use for tuning in steady state.