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).
Deductions from tests on the Phantom engine, focusing on valve lift, efficiency, and size.
| Identifier | ExFiles\Box 31\2\ Scan103 | |
| Date | 24th August 1933 | |
| -5- Hs{Lord Ernest Hives - Chair}/Std.11/MA.24. 8.33. Deduction from Tests :- Phantom:- Valve Lift:- As already mentioned, the first comparisons of heads at various valve lifts Curves 1, 2, & 3. indicated that the amount of valve lift did not affect the comparison, provided it was same for each head, and subsequently all tests were carried out at full lift. Further examination of the valve lift/air flow curve attached Curve 5 indicated that the valve lift may be increased up to its practical mechanical limit with resulting increase in volumetric efficiency the present lift of 0.480" seems definitely much too low from a volumetric efficiency point of view. Full scale tests on various experimental engines have indicated an optimum lift of 1/3 the valve dia, or .66 for the 2" valve. This shews up the disadvantage of the large single inlet valve. Efficiency of portions of the valve itself. From the curves on curve 4, it can be seen that a considerable portion of the valve is masked, and so rendered very inefficient, by the end of the combustion chamber (which can only be slightly trepanned)- the air flow through the inner half of valve opening being 50% greater than through other half, for same pressure difference, across them. Effect of regrinding lips on valves. These appear to have no effect on the air flow through the port. (See diagram 3). Effect of Valve Size. From comparison of curves on Curve 6 it is seen that the valve size can be usefully increased to give increased air flow and volumetric efficiency - although an increase of 0.1" on dia. of valve on standard drawing only gives an increase of 5.8% in air flow through port. On curve 6, curves for three sizes of inlet valve are shewn - power curves for these valves are also attached. | ||