Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Test results for the Phantom II expanding type carburettors.

Identifier  ExFiles\Box 13\3\  03-page387
Date  3rd February 1932
  
To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair}
c. SS.{S. Smith} Nor.
c. E.{Mr Elliott - Chief Engineer} De.
c. FY.

X7080

Hs.{Lord Ernest Hives - Chair}3/ADL3.2.32.

PHANTOM II EXPANDING TYPE CARBURETTERS

Following on our preliminary report He/adl.5/MJ. 12.2.32, the following results have been obtained :-

The first tests carried out were made to prove the metering up of the point at which the air valve lifts. When carrying out these tests it was found that a considerable amount of petrol collected round the outside of the small choke. As soon as the air valve commenced to lift all this petrol went through into the engine. This fault was overcome by making a suitable arrangement to drain this petrol into holes through the small choke. By attention to the diffuser we arrived at a position where the metering from the throttle edge and the small choke was satisfactory.

E.{Mr Elliott - Chief Engineer} has supplied us with a modified design of the suction piston to Lec.2997, combining the piston and diaphragm in one unit. With this valve we obtain full lift at 2600 RPM. full throttle, the depression in the dashpot being .75" Hg.

By increasing the weight of the piston from 13 ozs. to 18 ozs. the maximum lift was then reached at 3000 R.P.M. and the depression in the dashpot of 1.05" Hg. with an induction pipe depression of 3" Hg. In this form the piston commences to lift at 550 R.P.M. full throttle. This type of piston is working very successfully and we have had no trouble with sticking.

A test was made by removing the air valve completely from the carburetter and under these conditions the power at 3000 R.P.M. was increased from 155 B.H.P. to 162, whilst the induction pipe depression was reduced from 3" to 2.25". Under these conditions we approach the power obtained with the single S.U. carburetter which has a depression of 2.25" at 3000 RPM.

The engine which we are at present using for tests on this carburetter, has a standard compression ratio. With the high compression, as proposed for the new continental car, the maximum HP, we should expect with this carburetter, if it can be made free enough, is 176 BHP. We believe we shall find that this present carburetter is on the small side for the Phantom engine because at 90 M.P.H. it is approximately 3500 R.P.M.
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙