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).
Analysis of engine performance, focusing on spark plug placement, compression ratios, and induction, comparing against a Mercedes engine.
| Identifier | ExFiles\Box 34\2\ Scan093 | |
| Date | 10th December 1917 | |
| Contd. -2- tried more advance. We have packed out the long reach "Bosch" plugs so that they come inside a pocket, this makes the engine fire irregularly. With our own engine, if we definitely put the plugs in a pocket, it does not make anything like the difference we get on this engine. The plug position on this engine is so definitely poor, worse than any previous Mercedes engines with plugs on the side, that one would suggest that the large diameter cylinder makes it worse. The fact that they crowd both the plugs together, goes to show that they have had difficulty with the plug position. The engine detonates more than our engines, this may be improved with the aluminium pistons. The compression ratio on this engine is 4.94 to 1. Compression by gauge at 1400 r.p.m. is 91 lbs (with mixture) Our own Eagle engine 5th to 7th series compression ratio is 4.95 to 1. Compression by gauge at 1600 r.p.m. is 110 lbs. (with mixture) It would appear that the low power on this Mercedes engine is due to it not filling up. The vacuum in the induction pipes, taken at 3 points is 4" of mercury. On our engine it is 1.8". We have the coppersmiths making us a set of induction pipes so that we can use two carburetters (R.R.C.H.) b bored out to 46 or 48 m/m.{Mr Moon / Mr Moore} The distribution is poor. Petrol consumption curves will be sent later. EH. | ||