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).
Road tests of a twin carburetter, detailing fuel metering adjustments and performance on hill climbs.
| Identifier | Morton\M19\ img144 | |
| Date | 2nd April 1931 | |
| (2) Hs{Lord Ernest Hives - Chair}/LoV.{Mr Lovesey}2/AT.2.4.31.cont. With regard to the metering we found on the road that it shewed a rich characteristic just above the change over position at full throttle and reached a normal mixture again about 35 MPH. From this speed to 60 MPH. the metering appeared reasonably uniform. The over-rich tendency at low speed, full throttle (12 MPH.) was chiefly manifest by "building up". We overcame this trouble by modifications to the diffusers in placing the second row of emulsion holes .45 higher. This resulted in reducing the mixture strength at the low speeds without appreciably affecting the metering at high speeds. The metering now appears much more uniform over the speed range. A trouble we have encountered is partial cutting out or starvation on sharp right hand turns at full throttle and also flooding and over richness on left hand turns. The partial starvation we think may be accounted for by the low gravity head from the std. autovac, which we are temporarily employing, to enable us to carry out the carburetter tests. The fuel head, with the car level, is only 10 ins. and due to the position of the autovac situated away from the carburetter on the left hand side an inclination of 28° to the left would reduce the head to zero. This would be equivalent to a side acceleration of approx. .57 g.{Mr Griffiths - Chief Accountant / Mr Gnapp} We are at present going into this question and can eliminate the temporary loss of fuel head by fitting up a temporary feed tank inorder to see that the float chamber is functioning properly under reasonable turning conditions. This will be reported upon as soon as we have some information. With regard to performance we have made some check tests on 28-EX on some of our local test hills. Full throttle climb of one hill from 10 M.P.H. start, and where the max. speed does not exceed 40 MPH. shows a reduction from 67 secs. to 60.4 secs. on the time of climb. A similar test on Ticknall hill where the max. speed reached exceeds 60 MPH. the time of climb is reduced from 63.5 secs. to 59 secs. SUMMARY. From early tests the twin carburetter appears quite promising. Improvement in performance is appreciable most at speeds of 35 - 40 M.P.H. On the road there is not much to appreciate at max. speeds. The operation immediately after a cold start seems better than our std. carb. | ||