Although a much used word in the world of R/C model cars, there are a few people who do not know what one is, or how they work. This article aims to better inform such people in a non-technical manner and only introduces the basic facts about dynamometers. A more in-depth article may be published in the future.
The dynamometers shown in this article are ones actually used on large scale model car engines, but the same principles apply to the testing of engines of all sizes.
A dyno is a piece of machinery that is used to measure, amongst other things, the torque and power output of an engine. The testing is done with the engine removed from the car and connected directly to the dyno. This gives accurate results, as there are no losses to consider due transmission and tyre friction, etc. Engine testing with the engine in the car is usually done on a rolling road.
There are a two basic different types of dyno, Steady State and Inertia. There are many variations of both in existence, but they all operate on the same basic principles.
Examples of both types of dyno are shown below. Both are used on large scale model car engines and use a computer to record the information from the dyno, although the actual computer is not shown on the top example.
Pictured right is an example of a steady state dyno. This dyno is the actual one used to produce the dyno test results featured on this site and was built by Ian Oddie of Oddified Motors for his engine tuning and pipe testing. A bigger version of the photograph is available by clicking here.
The steady state type dyno works by running the engine against an alternator, the output of which is used to calculate the torque produced by the engine at certain rpm levels. The steady state description refers to the fact that the output of the engine is measured at a steady rpm level. Other examples of steady state dynos use oil or water, which is forced through a pump, as a means of measuring the output of the engine.
The design of this particular dyno is compact enough to allow Ian Oddie to take it with him around the UK and abroad to test engines and pipes on the spot.
Pictured right is an example of an inertia dyno and is the one used by FirstOne Tuning for developing and testing their large scale tuned pipes. A bigger version of the photograph is available by clicking here.
The inertia type dynamometer uses the test engine to accelerate a flywheel from a standing start up through the engines maximum workable rpm range. The inertia description refers to the flywheels natural tendency to want to stay in a non-moving state, i.e. in order to make it move, you have to use the power of the engine to make it turn, otherwise it is quite happy to stay where it is.
The dyno used by FirstOne Tuning is complete with a stand to put both the engine and computer at a convenient working height.
Engines are rated by various terms such as torque and horsepower. The various figures quoted for any given engine cannot be compared with all other engines. Although one horsepower is one horsepower, it is the other variables that make direct comparisons all but impossible.
There are numerous different dynamometers in use, which vary widely in their results. The conditions which they are conducted in also has a great effect on the results, as well as the fuel used and the exhaust pipe.
The only directly comparable results will come from the same dyno under the same test conditions.
Many thanks to both Massimo Torelli of FirstOne Tuning and Ian Oddie of Oddified Motors for supplying the original photographs.
Please check our Glossary for explanations of any unfamiliar terms.