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).
Engine tests comparing different riser pipe and choke sizes for power output and efficiency.
| Identifier | ExFiles\Box 5\4\ 04-page236 | |
| Date | 23th May 1930 | |
| -2- tests it was an advantage to keep the riser pipes as short as possible both with regard to power output and quick engine response to throttle opening. The hot spot was formed by a patch round the elbow of the riser and distributing pipe. The exhaust gas was supplied through a port in the cylinder head - leading from the centre exhaust port - and taken away through a pipe open to atmosphere. The large and small bore pipes were compared with the results given on V.867 and it is seen that the small bore - 1.250 dia - gave the better results over the whole range. A similar result was found on the Phantom which is rather surprising - particularly at high speeds - because in this case the diameter of the pipe is actually smaller than the valve port - the valve ports being 1.350 dia. With three cylinder pipes it appears we can with advantage employ rather high velocities which, due to no overlapping of induction periods, helps to charge the cylinders. (A drawing of the induction pipe is appended.) Various size chokes were tested and it was found we could go down to 26 M.M. before the power started to suffer. Actually the 26 M.M. was found better at the lower speeds which again appeared to point to slight charging effect. The mixture was kept the same in each case. Distribution was excellent and the hot spot appeared very effective. Just the patch on the bend was hot while the remainder of the induction pipe was quite cold at full throttle. Another noticeable improvement on the test bed was absence from loading up when running for lengthy periods | ||