Tests on air silencers for 25 HP & Phantom II cars to investigate and resolve excessive oil consumption.
| Identifier | ExFiles\Box 102\1\ scan0118 | |
| Date | 30th March 1933 | |
| X5080 Hs. {Lord Ernest Hives - Chair} Rem. W. 30.3.33. AIR SILENCERS ON 25 HP. & P.II. CARS. Y7080 Further to our report of 16.3.33. re excessive oil consumption since fitting the new air silencers, we have now run a series of tests with various fitments to try and overcome this. As stated in our previous report the oil consumption on 18.G.IV. with the new air silencer and crankcase breather pipe fitted was 320 m.p.g., and with the breather pipe blocked up 640 m.p.g., and so our first test was to revert to the old type of breather pipe which is connected with the air intake pipe approx. 3" higher up. In this position we obtained 680 m.p.g. We then ran two tests on a production chassis No. GWX.80. (a) with a standard air silencer fitted (this incidently had a gauge filter fitted of 50 gauge material), and (b) with our new air silencer fitted and a gauze filter of 16 gauge material, and obtained - (a) 2100 m.p.g. and (b) 1870 m.p.g. We consider that the finer mesh gauze is more or less responsible for the difference in these consumption figures, and would point out that the longer the car is run, the more the filter becomes choked up, thus rendering it a good oil stopper, but a very inefficient crankcase breather. We then turned our attention to the P.II. job and ran our tests on 27-EX. We did not take any consumption figures with the new type of breather fitted, because after only 20 miles or so the carb. intake was simply swamped in oil, and so we blocked up the breather altogether and obtained a consumption of 900 m.p.g. Considerably more oil was thrown out of the P.II. crankcase breather hole than the 25 HP. crankcase, even when not coupled up to the air intake, in fact the oil was literally pumped out at high speeds, so we fitted a form of baffle Lec.3420 (drawing attached) and ran another consumption test. This was not too good, only giving us a consumption of 400 m.p.g. We next removed the .500" baffle pipe and replaced it with a .250" pipe. This improved matters considerably as we obtained a consumption of 700 m.p.g. and the breathing did not appear to be affected in any way. A run with the original air silencer fitted gave us a figure of 680 m.p.g. We had now reached a point where we were getting the same oil consumption with our new air silencer fitted as with the old one, and the D.O. | ||
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).