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).
Piston compression ratios, over-oiling, and ignition systems for the EAC car.
| Identifier | WestWitteringFiles\L\Jan1924-March1924\ Scan119 | |
| Date | 1st February 1924 | |
| R.R. 493A (40 H) (EL 42 12-7-23). J.H., D.{John DeLooze - Company Secretary} EXPERIMENTAL REPORT. ORIGINAL Expl. No. 9040 4187 REF: Hs{Lord Ernest Hives - Chair}2/LG1 2. 24. To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair} c. to CJ. RG.{Mr Rowledge} c. to E.{Mr Elliott - Chief Engineer} DA.{Bernard Day - Chassis Design} c. to EY. PN.{Mr Northey} c. to Wor.{Arthur Wormald - General Works Manager} S E C R E T. PISTONS FOR EAC. We are running the original EAC. car with lower compression pistons. These give us a compression ratio of 4.3 instead of 4.6. Reducing the compression this amount has considerably reduced the tendency for detonations, and also made the engine smoother. The drop in performance cannot be appreciated under average conditions. On the car PN.{Mr Northey} 4.6 PK has taken, we have fitted the 4.6 compression ratio pistons. Probably with a light open car this ratio could be used but for the average cars 4.3 ratio would, in our opinion, appear to be the best. On the original engine we are troubled with over-oiling - the engine smokes badly after running light. We suggest that we endeavour to make the scraper ring more effective by using a wider ring bevelled similar to the scraper ring we used on the 20 HP. We have carried out tests and we cannot measure any difference in HP. when running on either one or both ignitions. With the present ungoverned magneto ignition, apart from the reduced tendency to detonate, we also find that we get better slow running if we switch off the magneto ignition and run on battery only, unless we do this we must definitely retard the ignition control. Experimentally, we are proposing to try a Scintilla contd:- | ||