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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).
Supercharger test, detailing performance, issues encountered, and proposed changes.

Identifier  ExFiles\Box 33\4\  Scan119
Date  30th August 1928 guessed
  
contd :- -2-

SUPERCHARGER.

A test has been made with 10/1 gears in the supercharger drive, the S/C. being throttled to limit the boost to 8 lbs/sq.in. At 2200 r.p.m. the power obtained was 1060 B.HP. giving an actual BMEP. of 171 lbs/sq.in.

Plug trouble in the form of pre-ignition prevented any further readings being taken at higher speeds, and caused a backfire resulting in the destruction of the blower (see separate report).

For the boost pressure obtained, we should expect a greater increase in BMEP., the low figure being due to :-

(a) The higher mixture pipe temperature resulting from running the blower partially throttled.

(b) The higher mixture temperature which would naturally accompany the increased pressure, taking adiabatic compression.

(c) The increased power to drive the S/C.

At the time of the test the throttle was just over two-thirds open (angular movement). It is proposed to try an intermediate gear ratio of 8.12/1 in the S/C. to enable full throttle to be used - our objective being a B.HP. of 1500 at 2750 r.p.m. This gives a BMEP. of 193 lbs/sq.in. - a figure which we have slightly exceeded during tests on the S/C. F.Xl. engine.

Hs{Lord Ernest Hives - Chair}/V.Halliwell.
  
  


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