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).
Test report comparing single downdraught and horizontal carburetters with different inlet pipe configurations.
| Identifier | ExFiles\Box 93\2\ scan0053 | |
| Date | 8th July 1935 | |
| -4- Test No. 4. (Single Downdraught Carburetter). Fig. 6. Main bore of pipe below the inlet ports - ('dropped pipe'). Object To delay unvaporised fuel. Result Slow Running: Worse than previous test. Pick up: As test 3. Power: Same in each case. Distribution: As test 3. Reasons. It is interesting to note that whereas before, with a horizontal carburetter, an improvement resulted from the dropped pipe, we now find that with a downdraught carb. on the same pipe, the tick-over is actually worse; but in the case of the horizontal carb. the "wet stuff" was deposited on the floor of the pipe, and could be dealt with by the hot spot (by virtue of the fact that it was so delayed). With the downdraught, however, we have said that the unvaporised fuel enters into the main gas stream and is swept into the ports without being affected very much by the hot spot. All the "dropped pipe" is doing is to cause the wet stuff to be deposited on the curved inlet branches. Test No. 5. Comparison between horizontal and single downdraught carburetter on four port buffer-ended pipe (Leo.3637). Figs 9 & 10. Result. (1) Horizontal Carburetter. Slow Running: Very poor (centre cylinders rich). Pick up: Fair. Distribution: Centre cyls: very rich over the whole range. | ||