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 4 and 5 detailing modifications to induction pipes and carburettors and their performance results.
| Identifier | ExFiles\Box 124\3\ scan0259 | |
| Date | 4th December 1934 | |
| -3- Test No. 4. Induction pipes and carbs. as Test No. 3, but with carbs. placed 5.0" further away from pipe by extensions, water heated along their entire length. Result. Definite improvement, but slow running not as good as 20/25 standard, being uneven below 300 r.p.m. At this point we have to consider why the improvement results from Test No. 4, and we have to decide whether it is due to the extra heat, or the increased distance of the carbs. from the inlet ports. From tests carried out so far we find that increased heat on the induction pipe has very little effect, but increased distance between the carburetters and the inlet ports makes an appreciable difference. This factor may therefore account for the slow running on the standard 20/25 engine, where we have a long induction passage to the main pipe. The "length" of induction passages serving to damp out pulsation effect due to overlap before it can affect the suction on the throttle edge. The main induction pipe on the 20/25 is lower than the inlet ports; the possibility therefore of wet vapour entering the cylinders is very small. Test No. 5. Induction pipe EX.16451, similar to 20/25 design inasmuch as an attempt is made to prevent wet mixture dropping straight into the inlet ports. The same degree of water heat is applied as standard Bentley. Carburetter positions as Test No. 1. Result. Only very slight improvement over Test No. 3 but not quite as good as Test No. 4. | ||