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).
Performance comparison between a 20 HP RR and a Lorraine car, analysing M.E.P., acceleration, and engine characteristics.
| Identifier | ExFiles\Box 22\4\ Scan067 | |
| Date | 11th September 1926 guessed | |
| contd : - -3- CAR. WEIGHT CWTS. GEAR RATIO. ENGINE CAPACITY. 20 HP. RR. 31 4.20 3160 Lorraine. 33 3.60 3447 The M.E.P. of the high compression 20 HP. is about 8% better than standard. From the above figures, if the MEP. of the Lorraine was the same as that of the 20 HP. one would expect its acceleration to be only 85% of that of the RR. due to its high gear ratio, the weights and capacities more or less cancelling out. However, our tests shew that the acceleration of the two cars are equal. Therefore, we anticipate that our bench test will shew that the Lorraine with its noisy exhaust has an MEP. of about 110 lbs/sq.in. at the lower speeds or 10-15% better than the high compression 20 HP. with the standard exhaust system. It appears that with similar exhaust systems the Lorraine has an advantage of about 10% in MEP. due to double carburettors, quick lift camshaft and, from the feeling of the car on the overrun, pistons with the minimum friction. The valve gear is also noisy, indicating somewhat abrupt cam contours, strong valve springs and large clearances. However, we consider it will be well worth while analysing the performance of this engine on the test bench to determine the relative importance of these factors. He/W. A.{Mr Adams} Robotham. | ||