The previous blog explained the dyno set-up at Chrysler. This blog deals with actual testing.
Water-feed problems
The municipal-water feed to the dyno also proved to be far from ideal. Sometimes the water supply lost pressure, and this meant that the engine would suddenly lose its load, and run away (ie rev dangerously high). I would have to leap up and close the throttle before the engine had a chance to put a leg out of bed (ie break a conrod). We then fitted a pressure sensor to the water supply, and coupled this to the engine’s ignition, so that a pressure failure would stop the engine. We used this system all the time I was there, in spite of the trouble it caused. When the engine stopped suddenly the heat dammed-up inside the engine would cause the no-longer-flowing water to turn to steam, with the result that the engine would dance on its mountings like a mechanical monster as the steam tried to migrate back to the water tank. (Years later I read that a sudden loss of load at full throttle could break a conrod, because the inertia loads oppose the load due to the combustion pressure. This means that if the combustion loads are removed, the conrod gets over-stressed).
Quality-control testing
Most of the testing was for quality control purposes. A randomly-chosen recently-assembled engine would be brought to me on a trolley, and I would install it on the dyno bed and couple it to the dyno. I would then run it for 9,5 hours at various speeds and loads to run the engine in. This would be followed by a full-throttle run for half-an-hour at speeds from 1 600 r/min to 4 000 r/min (in the case of a Valiant) in 400 r/min steps to get a set of power and torque curves. During the test the dipstick hole and the crankcase breathing openings would be sealed, and an airflow meter would be attached to the oil filler opening on the tappet cover. This would measure the blowby (gas getting past the rings into the sump) in cubic feet per minute. At first the blowby would be quite severe but as the rings bedded in the blowby would decrease so that in most cases it would stabilize for the last hour, to signify that the engine is run-in.
The engine was coupled to a standard full-length car exhaust system that snaked across the concrete floor towards an opening in the wall. During the full-throttle runs the exhaust manifold would get red hot, but the rest of the exhaust would be cooler. However, sometimes a test engine would arrive with retarded ignition timing, and then the whole length of the exhaust pipe would change colour to red, because combustion would still be in progress when the exhaust valves opened.
The engines would have to be tested as received, but afterwards I had to strip them and give demerits for any fault I came across. By far the most demerits were given to dirt spots on the bearing shells, but wrong ignition timing and low torque readings were also high on the list. Finally, I had to assemble the engine, mark the block with a paint spot, and send it back to the assembly line. The lucky person who bought that car would have a perfectly run-in engine, assembled by me. If I was working at AMG my nameplate would be riveted to the cylinder block.
To be continued