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).
Investigation into poor slow running (idling) on the 30 HP model.
| Identifier | ExFiles\Box 101\3\ scan0058 | |
| Date | 6th May 1937 | |
| To Hs.{Lord Ernest Hives - Chair} Rm{William Robotham - Chief Engineer}/Swdl.{Len H. Swindell}11/JH.6.5.37. 30 H.P. Slow Running. The following report is the result of a visit to Cricklewood to observe and investigate the complaints received of poor idling on the 30 H.P. Irrespective of whether the owner complains or not, the slow running is poor. Five or six cars were observed regarding this trouble and the following are the conclusions arrived at. (1) Definite improvement in the steadiness of idling with tappet clearances (inlet and exhaust) set at .008. Further improvement is obtained by further increasing the tappet clearance up to .015" but at .010 or above the tappets become noisy. Tappet noise at .008 is no worse than at normal .004 setting. (2) Sparking plug gaps when increased from .020 to .025 gives appreciable improvement. The improvement from .025 to .030 is not so marked and at the latter setting trouble is experienced on misfires picking up. The new standardised procelain spark plugs K.L.G. F.L.B.30.X. are better than the old standard mica plugs K.L.G.831 in the respect of less misfiring when idling. (3) Low speed jet size in the Stromberg carburetter makes no difference to the idling but we are going to carry out investigation here with regard to increasing the velocity in the low speed jet passage. (4) By retarding the ignition setting from 13° B.T.D.C. to T.D.C. in conjunction the tappets set at .008 and F.L.B.30.X plugs at .025, reasonably even idling can be obtained but still not as good as desired. As we see, there are two issues regarding the improvement that should be made to idling are as follows. (a) 30 H.P. cars already in service and in production where improvements should be made at the minimum expence. We have recommended Cricklewood to set tappets at .008, set spark plug gaps at .025 and fit new porcelain plugs when available. | ||