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).
8-cylinder engine experiment report discussing induction, detonation, exhaust systems, and valve gear.
| Identifier | ExFiles\Box 123\5\ scan0320 | |
| Date | 23th February 1939 | |
| -2- It is hardly possible to comment on these results without knowing how much the characteristics of an 8-cylinder engine are involved. These engines have different valve lift curves. Experiments have been carried out to endeavour to reduce the induction pipe depression, but up to the present have only resulted in impairing the distribution which offsets any power gain due to the lower depression. DETONATIONS. Including the good features of the B.60, namely sodium filled exhaust valves, increased transfer throat in cylinder head, but not the flush top pistons, the engine is very good in respect of its non-detonating characteristics. Running on Redline fuel (No.3, 70 octane) it is only necessary to drop 1-2 lbs. per sq.in. MP by retarding to be clear of detonations up to 1000 R.P.M. above which speed the engine gives full power without any detonations. In view of the above we have not plotted a non detonating curve, but include the ignition advance curve for this condition on Rm.{William Robotham - Chief Engineer}583, the advance ranging from 5° before TDC at 500 R.P.M. to 34° before TDC at 4000 R.P.M. EXHAUST SYSTEMS. An interesting experiment has been tried comparing the power loss to open exhaust with (a) a single system, and (b) a duplex system. These systems, identical, were as the BII system, but minus the front expansion box, the downtake pipe continuing from the manifold to the intermediate silencer. Taking the open exhaust maximum power of 172 BHP at 4000 R.P.M. this falls to 160 BHP with the duplex system at the same speed, and 140 BHP with the single system. Further tests are necessary to show what gain we get from a duplex system that has the same effective back press as a single which it replaces. VALVE GEAR. The camshaft used was EB.4021 which includes a longer duration inlet giving a resultant valve lift of .450 on the inlets and in conjunction Ph.II double valve springs were used in the inlet valves. Continued. | ||