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).
Dynamometer testing procedures, valve timing, and fuel consumption for engine performance evaluation.
| Identifier | ExFiles\Box 75\2\ scan0250 | |
| Date | 8th August 1921 guessed | |
| Oy2 - G 8821 Sheet #8. You would not expect the distribution to be much good from a consideration of the complicated shape of the pipe with its many bends and the consequent violent whirlings which must be set up in the pipe (see photos March Journal, page 282). I wish to suggest therefore that if on the chassis dynamometer test the resistance were set so that the car would take full throttle at say 2000 revs. and a power and fuel consumption curve taken for all speeds between that and 300 revs. controlling the speed by the throttle and not by the load, one would get a close approximation to road conditions. I was forgetting, however, that your chassis dynamometers have a dry brake. On ours we have a fluid brake, the characteristic of which will vary with the square of the speed, like wind resistance, while the transmission losses and belt losses on 2 wheels will perhaps approximate to the road losses of four wheels on a good level road. It will be interesting in any case to get some fuel consumption and power data, and some notes on distribution under these conditions on the dynamometer, and we intend to do it on several test chassis as they come through. (6) Valve Timing: This will also tend to show whether, as we have suspected, some of the slow running difficulty may be due to our extreme high speed valve timing, which is, from what we can learn, later on the inlet closing and earlier on the exhaust opening than almost anyone else's except racing cars. I have recently written the Works Committee at Derby about the two standards of valve timing, Test & D.O. Perhaps you can give us some advice about this. At present it appears to be a solemn secret that only the elect are permitted to know. It certainly seems to us that quite apart from axle ratios, our engines do not hang on to the last gasp like some of the other cars, and how much of this is due to inlet pipes and how much to valve timing we cannot tell. Maximum speed matters little in this country. What does count is a quick "get-away" from cold, ability to keep clean and undiluted on fuel far worse at the "heavy end" than your specially prepared low grade mixture, acceleration, and ability to hang-on on a hill. (6) Consumption of R-R: You considered last winter that our distribution must be good because of our excellent gasoline mileage. I suggest that our excellent mileage is due principally | ||