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).
Power gains by modifying the cylinder block passage for the 20/25 Horizontal Carburetter.
| Identifier | ExFiles\Box 102\1\ scan0187 | |
| Date | 25th June 1934 | |
| Hs{Lord Ernest Hives - Chair}/CTS.{C. Trot Salt - Carburation}15/KW.25.6.34. 20/25 Horizontal Carburetter. Further power gain by modifying the shape of the hole through the cylinder block. Tests have shown that there is a considerable increase in depressions caused by the passage through the cylinder block, i.e., the depression in the induction pipe is considerably higher than that in the carburetter on the suction side of the throttle. Different sizes and shapes of hole through the cylinder block have been tried, with the following results. To begin with, the power gain with the new horizontal carb. over the present standard carb. (on a standard cyl. block) is 12 B.H.P. (15% gain), while the depression in the induction pipe is lowered relatively 35%. Increasing the diameter of the passage through the block at the point of minimum area, to within the minimum limit of section between the hole and the cylinder walls, 30% increase in area results; with a further gain in power of 5 to 6 B.H.P. An experimental cylinder block has been tried, Lec.3795, which has this passage increased by 60% in area by using an elliptical hole. The power gain at the peak is the same as with the 30% increased round hole, but beyond this point the power falls away quicker. An explanation for this is as follows. The sides of the 60% oval hole are narrower than the dia. of the 30% round hole, and sufficient friction is set up to prevent further power gain. This is further borne out by the fact that the power falls off quicker above the peak, with the oval hole, as the gas velocity increases. HS{Lord Ernest Hives - Chair}/C.T.Salt. | ||