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).
Page detailing the causes of smoking exhaust and a summary of findings on controlling engine oil consumption.
| Identifier | WestWitteringFiles\O\2April1926-June1926\ Scan108 | |
| Date | 1st May 1926 guessed | |
| contd :- -5- been found to actually increase the consumption due to the increased suction past the baffles as the piston moves towards the top of its stroke. SMOKING EXHAUST MAY BE CAUSED BY OIL LEAKAGE DOWN VALVE STEMS. The oil holes in the end of the inlet rockers are now plugged as it was found that if the inlet valve stem was slightly on the 'free' side in the guide, oil would be sucked down the stem into the induction pipe when running with small throttle openings. This produced smoking exhaust and fouled plugs. We also experience similar trouble with smoking exhaust with slack exhaust guides. The oil runs down the guides at low speeds or when the engine stops. SUMMARY :- From consideration of the above results we find that :- (1) The rate of aggregate oil discharge through the bearings is one of the chief factors controlling oil consumption. By reducing the flow we can reduce the consumption. (2) 'L' section rings are excellent oil scrapers when new and when worn are as good as plain rings. (3) Oil flow can be reduced by (a) Smaller bearing clear-ances (b) Lower oil pressure. (4) Reduced bearing clearance is better than a very low oil pressure. (5) A Phantom engine has run satisfactorily on the test bench with an oil flow of .7 pts/min. at 1000 r.p.m. increasing to 3 pts/min. at 2500 r.p.m. This engine was fitted with piston contd :- | ||