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).
The performance of 14 M.M. plugs, a semi-expanding carburettor, pistons, and a turbulent cylinder head.
| Identifier | ExFiles\Box 1\8\ B001_X100 Engine Chassis-page225 | |
| Date | 14th November 1932 | |
| -2- HS{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer}S/MA.14.11.32. Cont'd.{John DeLooze - Company Secretary} 14 M.M. Plugs. Generally speaking, these are behaving as well as the 18 M.M. plugs. The cooling seems satisfactory up to 6.25 C/R.{Sir Henry Royce} R.R. Semi-Expanding Carburetter. We have not done a great deal of work on this carburetter as yet. Rm.{William Robotham - Chief Engineer}PT.31 shows the results we obtained before we sent the car to France. However the metering etc., was not good enough to give an impressive performance on the road. We have now got a better needle. We were surprised that we could not equal the single S.U. M.P. from 1500 to 3000 R.P.M., but on referring back to the curves on the 40/50 (Rm.{William Robotham - Chief Engineer}P 53) we note that the same results were obtained. We are therefore carrying out tests to see how we can reduce the depression on the R.R. semi-expanding carburetter. Below 1000 R.P.M. the semi-expander shows up well. Pistons. We suspected that we were losing power with the original piston to E.100035 owing to excessive stiffness in the skirt. We therefore gave us a more flexible piston to E.100525 which is more nearly comparable with the existing 20/25 with a resultant gain of some 4% in maximum power. These pistons have now done a considerable amount of running without trouble. (Rm.{William Robotham - Chief Engineer}PT.29) Turbulent Head. Curve Rm.{William Robotham - Chief Engineer}PT.33, shows a comparison between turbulent and non turbulent heads on Peregrine. This is the first time we have been able to compare the two types of head with the same induction system and valving. The compression ratios were adjusted exactly. The results show that, at the same compression ratio, the turbulent head has a very slight advantage from 1000 to 4000 R.P.M., and after that is down in power. Since our previous road results have shown that the turbulent head enables us to run between 1/4 & 1/2 C/R higher than with the normal head, we anticipate that we ought to gain about 7% at low speeds and lose nothing at high speeds under road conditions. However, further tests will show more exactly the advantage of the respective heads. | ||