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).
Tests of induction pipe and carburettor configurations to improve fuel distribution and power output.
| Identifier | ExFiles\Box 181\M13\M13.2\ img132 | |
| Date | 17th November 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to B. Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}1/M.17.11.31. X5771. X5080. DISTRIBUTION AND POWER OUTPUT. J.l. You will recollect that we managed to obtain good power with a 1 7/8 throttle dia. horizontal S.U. but we could not get the distribution satisfactory with the pipes as shewn on Rm.{William Robotham - Chief Engineer}51. We therefore built up a pipe as shewn in the attached photographs, in which the carburetter was as close as possible to the induction pipe directly between cyls. 3 and 4. This pipe gave considerably the best distribution we have so far had with a horizontal low depn. carburetter, in fact, the results were excellent down to 1000 R.P.M. where the distribution became unstable. (Shewn on the curve) The big fall in M.E.P. at 500 R.P.M. is of course partially due to the late closing of the inlet valve with this camshaft. We did not expect this pipe to be any good because with a fan shaped spray from the jet as on the S.U., we thought cyls. 3 and 4 were bound to be rich. However, as every bend has been bad for distribution and 3 & 4 cyls. have always been weak, the above pipe seemed logical, especially as two small carburettors worked well on 'T' pipes placed right close to the induction pipe on the 40/50. In parallel with these tests we have been trying single large carburettors on the 40/50 and again to get them under the bonnet have been using various bends with which the distribution has been unstable and bad. Our conclusions therefore are that once the mixture has be been thrown on the side of the pipe by rounding a bend, it is most difficult to distribute it even with a super hot spot. We have used a blow lamp on some of the bends on the 40/50 without success. The three 'T' pipes we have been using, two vertical with Claudels and one horizontal with the S.U. have shewn the most promise of any. We are therefore proposing to try such a pipe with our standard 40/50 carburetter, as we think we may possibly get better distribution than with the weir. We have had the Claudel on the weir pipe and on the whole the results are not as good as when we use the straight forward vertical 'T' pipe. Generally speaking, on a carb. like the S.U. where we can try all sizes made to exactly the same scheme, we find that | ||