Engine Performance Measurement

Assignment

Nowadays, there is fierce competition from the rolling test benches, with which its no problem to determine the performance on the clutch. If however, an engine is in the development stage and/or its performance map is renewed, or if the engine has been overhauled, then, engine test benches are unrivaled. They are also more suitable for longer series of measurements because in these cases the tyre wear is enormous on a rolling test bench.

Function

Admittedly, the test bench shown above cannot be operated as it stands, because, e.g., the exhaust gas, the cooling system and the electrical system are incomplete. If however, the system was complete, and a suitable noise protection would exist, one could test, not only effectively, but also exchange the test objects relatively quickly. What is, in fact, an engine-performance test bench? In principle, one could attach a large brake-drum to a functioning engine. The brake linings would then have to be operated by the hand brake. Apart from that, the rear anchor plate may by no means, be static, but pivot-mounted and connected with a one meter long bar. If the end of this bar is then bolted to a spring balance hanging from the ceiling, one can, with this primitive apparatus, indeed measure performance, more accurately actually, torque at various RPMs. Oh yes, one also needs a rev-counter. If one now operates the accelerator pedal slowly up to full load, and pulls at the same time the parking brake in such a way that a certain RPM is maintained, one can read, from the spring balance, the generated torque, and using the suitable formula, work out the performance.

This arrangement is also called the 'Prony brake', from which basically, all other test benches originate. Of course, the above described test bench, because of the heat developing in the brake drum, will not last very long. For this reason, the old test bench in the figure above, has a water brake. This allows, the same as the hand brake, a continuous deceleration of the flywheel. This is reached with the display in the handwheel. The engine, not visible in figure 2, is mounted on the right. It runs on the test bench as it would run in reality. If one considers the hand-wheel (or the hand brake) to be a clutch, one can also stall the engine by giving too little gas when letting it in too quickly. The load on the engine is then too high and it stalls.

In the old test benches one finds no electronics. Even the rev-counter is connected through a fan-belt with the drive. In the new test benches, this is completly different. It generally has a hydraulic or electric brake and can be connected up to a computer. With it one can have data calculated, compared and, e.g., also saved. In this respect, it is once again similar to the modern rolling test benches. 09/09

Subjects