Patent GB-1480409-A (GB)
Title: Method and apparatus for testing ic engines by running under load
IPC: F02D28/00
Filed: 1974-12-17
Abstract: 1480409 Test running I C engines SCANS ASSOCIATES Inc 17 Dec 1974 [7 Jan 1974] 54468/74 Heading F1B [Also in Division G1] A method of testing, by running under load, assembled I.C. engines to reveal malfunctions therein by an analysis of the exhaust gas emissions, the method including the steps of providing a support apparatus in which the engine can be run, placing the engine in the support, providing means to load the engine based on its cubic displacement which provides a torque load on the engine which is as close as possible to that which it would experience if the engine were installed in and used to drive a motor vehicle of a suitable weight class, connecting the engine to the loading means, starting the engine and withdrawing an exhaust gas sample, operating the engine in more than one test mode at which malfunctions of the engine are likely to occur and measuring the value of CO and HC in the exhaust gas sample at each mode of operation, comparing the measured value of the CO and HC at each mode of operation with permissible values and indicating which, if any, test values exceed the permissible values so as to indicate an engine malfunction. Three modes of operation, which are described as "Key Modes" are used:- KEY MODE 1 simulates "high cruise," the main carburetter and ignition systems being in full operation e.g. 1700 to 2600 r.p.m. with a load on the engine of 35 to 60% of the maximum engine torque; KEY MODE 2 simulates "low cruise" and is the transition between idle speed and full operation of the main carburetter e.g. 1250 to 1700 r.p.m. and an imposed load of 3.5 to 12% of the maximum engine torque; KEY MODE 3 is idling speed. A conveyer is provided, which serves a number of test stands and which has a repair loop. An engine which fails testing is transferred to the repair loop and subsequently re-tested. Load is imposed on the engine by using a water-filled power absorption unit which applies a load which varies as the cube of the speed and by using such a unit, engines of different capacities can be tested by running them at a speed which causes the absorption unit to apply the appropriate load. Fig. 23 shows a unit 91 connected to a water supply through valve V which opens when at a temperature controlled by bulb 104. Probe 69 in the exhaust pipe is connected to pump 72 which supplies exhaust gas samples to analyzer 159. Generator 143 provides a voltage output proportional to engine speed, the actual speed being shown on meter 145. The output voltage is also compared with high and low limits for the engine and KEY MODE concerned and inaccuracy is corrected by a throttle drive motor through throttle drive controller 157. The apparatus also includes means for pre-setting the acceptable high limit for CO and HC for each KEY MODE and if the amount of either constituent exceeds the limit, a reject light e.g. 169 is illuminated. An automatic time and sequence control circuit 142 causes the engine to be started and to be run for one minute to warm up at high cruise r.p.m. i.e. KEY MODE 3. Control circuit 142 then energizes pump 72 for 15 seconds, the gas analysis is performed and the appropriate signal illuminated. Circuit 142 then readjusts the engine speed and also energizes relays which alters the CO and HC limits to those which apply to KEY MODE 2, gas analysis is made and the results indicated. Circuit 142 then resets the apparatus to the test for KEY MODE 3. At the end of the test the results of all the testing stages are shown by the indicator lights.