From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Experimental test results on engine performance with altered exhaust, throttle, and mixture settings.
| Identifier | WestWitteringFiles\P\2July1926-September1926\ Scan050 | |
| Date | 13th August 1926 guessed | |
| contd :- -3- We put forward some experimental test results in support of the above theory. One exhaust manifold was removed to give a clear view through the exhaust ports. The engine was motored over at 1000 r.p.m. and the throttle adjusted so that explosions readily occurred in the remaining manifold and down pipe - no silencer was used. While this was happening it could be observed that the cylinders having the open exhaust ports i.e., no manifold, passed the charge through without firing. If however the mixture was strengthened by lifting the low speed jet needle, the explosions in the manifold would stop and the cylinders with the open exhaust ports would fire regularly. This was found to follow through at other speeds. Another way of demonstrating the above was to run the engine under its own power on a small throttle opening and then speed up without altering the throttle by means of the auxiliary engine. A speed could be reached when the cylinder would not fire regularly but could be made to do so by richening the mixture. It was also found during this experiment that the wider the thro-ttle opening the higher the motoring speed necessary. This experiment bears out the suggested explanation and shews that when the motoring speed becomes much higher than the normal engine speed for that particular throttle opening, the mixture passing through the carburetter has to be stronger before it will fire. We have tried increasing the spark plug gap up to .125" in the endeavour to fire the normal mixture but without success. contd :- | ||