Carburettor performance issues, including luffing, poor acceleration, and increased petrol consumption.
| Identifier | ExFiles\Box 11\4\ 04-page032 | |
| Date | 5th May 1932 guessed | |
| to have any information that you may be able to give us. For our own part we have been making some very interesting tests, and the results may be of benefit to you. We have come to the conclusion that the luffing up or misfiring is definitely due to weakness and shortage of petrol. To prove this we have tried out the following. We have soldered a thin piece of wire on to the top of the air valve, or petrol controlled valve, and carefully watched its operation on the road whilst picking up from slow speeds. We find that running along at 20 m.p.h. the valve does not lift at all. When the accelerator is depressed and the throttle opened for maximum acceleration, there is no movement until the car has reached the speed of 35 m.p.h., and even then the movement is so sluggish that one can hardly see it move. It then apparently falls slightly, then starts to rise very gradually, as the speed of the car increases. Again when running at approx 15 m.p.h. and the throttle is fully open, there is no rise of the air valve until an approx speed of 30 m.p.h. is reached, when the air valve then starts to rise slightly more, but its action is very very sluggish. We can definitely, and have, overcome the luffing up period by getting hold of the air valve and lifting it up quickly approx. 1/8". We have then better acceleration with no flat spot. We are of the opinion that if the air valve could be made to rise more rapidly, our difficulties would be overcome, rather than incorporate the wells of petrol that you are trying. There is also another feature which attention may be paid to; we have during the last two days been running at maximum speeds, and our petrol consumption has dropped down from 10.4 to 8.6 m.p.h., which means that we are definitely worse off than ever we were, - with our standard carburetter on 23-EX, as our speeds are no greater than with that car. It would point to the fact that the taper of the needle is too acute. The mixture evidently wants weakening off for the maximum lift of the valve. I have a needle here which I believe will give me this result, but at the moment I am not certain of the size of the needle already in the carburetter. We will let you know later if we obtain any data. G.W.H. -4- | ||
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).