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).
Test report on 114° camshafts, comparing power curves and valve timing.
| Identifier | ExFiles\Box 181\M13\M13.2\ img085 | |
| Date | 26th August 1931 | |
| To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} c. to Sg.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager} c. to B. Da.{Bernard Day - Chassis Design} c. to By.{R.W. Bailey - Chief Engineer} 87090. P.11 114° CAMSHAFTS. Lec.2918. We have now completed a series of tests on a camshaft for forms Lec.2918. Curve Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} P.17 shews power curves with the 114° angle between the cams. These curves were taken with the best test bed carburetter we have for power. It will be observed that there is very little difference in the power output whether the inlet valve is opened 3° or 10° before T.D.C. Curve Rm.{William Robotham - Chief Engineer}P.17 gives a comparison of the 120° and 114° shafts (curves 1 and 2). It will be observed that the inlet valve timing is almost the same in both cases but the exhaust valve timing has been altered 10° later with a consequent gain of 10 H.P. at high speeds and 5 lbs. M.E.P. at low speeds. This suggests that it might be worth trying the exhaust a further 4° later 112° shaft as we have previously found that we did not lose power with an exhaust opening 48° B.B.C. (Hs.{Lord Ernest Hives - Chair}379 to E). On the other hand the 114° two inlet cam forms we are about to try will give a position half way to this. The slow running with this camshaft as tested is very fair with the twin carburetters, we cannot judge the amount of roar until we get this camshaft in the car. We will make a more accurate determination of these two features now that we have got power curves. It will be observed that these tests were run with an inlet valve having a 2" throat instead of the standard 1.9" throat. We utilised this head as it is the best we have for power and in consequence emphasise any small differences in timing or camshafts. We are repeating the tests, now that we have established the best timing, on the standard head, and at the same time making an analysis of the effect of different valve sizes and twin carburetter balance pipes. As an approx. figure the maximum B.H.P. difference between the 1.9 and 2" valve heads with the Claudel Carburetter is the same as the difference between 4.6 and 5-1 C/R.{Sir Henry Royce} Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} | ||