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).
Supercharger tests for the 'K' engine, detailing issues with cylinder gaskets and boost temperatures.
| Identifier | ExFiles\Box 1\8\ B001_X100 Engine Chassis-page219 | |
| Date | 23th February 1932 | |
| -2- SUPERCHARGED 'K' ENGINE. We have carried out one or two tests on the unit fitted with a No.10 Powerplus supercharger (1850 cc.) The worst trouble we have so far encountered is with the cylinder gaskets. Originally, it will be remembered, when we ran with the C & A gaskets, we found that after a few moments running full throttle, these burnt out. We have since tried solid metal gaskets. With the solid metal gasket water leaks occur all round the cylinder head, when running supercharged, and become very bad at the higher speeds of 4500-5000 r.p.m. It would appear that the cylinder head studs are stretching, and in consequence the joint is suffering. We also find that the solid aluminium washer will not stand up to 14 lbs. of boost under this condition, for more than about 5 mins. We are sending you under separate cover two samples of gaskets which have failed. The other point which we are concerned about, is the boost temperature. We find that our induction pipe temperature at 5000 r.p.m. takes up a fixed value of about 60°C above atmosphere. This at first seems ridiculously high, but on referring to the curves taken by Hs{Lord Ernest Hives - Chair}/Aln - 9.7.31 - it will be observed that at 5000 r.p.m. 17" of boost, the adiabatic efficiency of the Powerplus blower is only about 40%, and calculations show that this means we are doing as well as can be expected with this machine. However, it is clear that this efficiency compares very unfavourably with that obtained with our centrifugal blowers (i.e. on Kestrel IV we get 10 lbs. of boost for 20°C temperature rise) and with other efficiencies alleged to have been obtained with direct displacement blowers by the Americans, and the matter is therefore being investigated. The attached curve Rn.{Mr Robinson}Pr.27 shows the recent M.E.P.s we have obtained when supercharging, the boost temperature rise, and the H.P. attained. We were using a shorter duration camshaft than previously which gave us a considerably better low speed M.E.P. and with the same top power. We previously experienced a certain amount of exhaust valve burning under these boosts, but have found that by cutting out some of the toe of the camshaft by running with increased tappet clearance, this trouble is greatly reduced. Apart from the gasket, and the exhaust valve trouble which we believe we now know how to cure, we have had no mechanical trouble of any sort so far. Hs{Lord Ernest Hives - Chair}/Hs.{Lord Ernest Hives - Chair} | ||