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).
Engine design modifications, including compression ratio, plug cooling, and ignition advance.
Identifier | ExFiles\Box 33\3\ Scan272 | |
Date | 10th April 1929 guessed | |
contd :- -2- With the proposed reduction in the India 4. compression ratio however there is a distinct opportunity of considerably improving the water cooling of the plug. We propose to add .125" approx. to the height of the head to reduce the ratio from 5.5 to 5.1 and to put this all into the water space under the plug to ensure the complete penetration of the water into the large area shewn in plan - fig. 3. Lec. 2689. We also propose to withdraw the plug boss about .200" from the combustion space for reasons given elsewhere, and this allows of two water ways passing up, one on each side of the plug boss close to the surface of the cyl. head, which passages can be inspected, and if necessary drilled out, inserting the drill through the water-ports provided for making connection with the cyl. block - see again fig.3. (3) USE OF COOLER PLUGS. An important point that should not be overlooked is that the RR. cyl. head is arranged for turbulence is reported to possess peculiar properties in protecting the ignition plugs from oil when the latter is present in excessive quantities in the cyl. This, if true, appears to be a definite advance, and should enable us to use cooler running ignition plugs which will stand higher comp. ratios without setting up preignition, but at the same time will be hot enough for general running purposes. All engines can be said to be sensitive to sparking plug design, and it is not unusual to call for different plugs when the comp. pressure is raised, to which there can be seen no objection if there is equal immunity from fouling of the insulators. (4) COMPARISON WITH PHANTOM. We had 5 to 1 comp: ratio running on the big car engine for some time on 14-EX very successfully, and there was no complaint of preignition. Logically we can see no reason for not obtaining a similar result with 5.1 to 1 ratio on the 'Twenty' given equal facilities for cooling the plug. (5) IGNITION ADVANCE. We should like to know what particular curve of ignition advance is being used with the turbulent head. Less advance may produce more satisfactory results with turbulence present. It is assumed that we are using the same degree of clearance between piston and cyl. head at top of stroke as on the big car engine. contd :- | ||