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).
Engine firing order, bonnet temperature, and Spectre carburetion.
| Identifier | ExFiles\Box 173\1\ img033 | |
| Date | 5th January 1934 guessed | |
| -2- (3) Order of Firing. The suggestion has been made by several people that, on a 3-cyl. pipe, the reversal of flow should take place after the outer cylinder has fired when the pipe is relatively full, and not when the inner cylinder has fired and the pipe is more or less empty, i.e., existing firing order - 142635. Better for 2 carbs - 153624. This requires a new camshaft but I think we ought to try it. Both the smaller carbs, and altered firing may make air silencing easier, thereby allowing a smaller balance hole in pipe. (4) Bonnet Temperature. It may be, that for Winter conditions, the louvred bonnet may just be the last straw. If it were not for these, the radiator shutters being nearly closed, the air round the intake should be reasonably warm. Could we see - (a) If warm intake air will improve matters. (b) How many louvres have to be blanked off to raise bonnet temp. appreciably. I am sure with the large Marston matrix that we are at present using we have a margin of cooling at top speed even without bonnet ventilation but we may require the latter for idling. With regard to SpectreCodename for Phantom III carburetion, if the induction port centres are as on the Bentley, I can see little chance of ever using a single carb, without a long uptake or downtake and a very hot spot. I'm sure it will be worth our while to reproduce exactly (by tilting the engine if necessary) the induction system that E.{Mr Elliott - Chief Engineer} has drawn for the SpectreCodename for Phantom III to make sure there is no snag. I had anticipated carbs. on one bank between 2 & 3 and 4 & 5 and on the other bank between 1 & 2 and 5 & 6 but E.{Mr Elliott - Chief Engineer} has not done this so we have no experience. I hope that in your campaign on Aero work you will not forget the car single cylinder unit, our first ewe lamb for serious investigation as opposed to development. R.H. | ||