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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).
Feasibility and limitations of increasing the Phantom II's compression ratio.

Identifier  ExFiles\Box 92\2\  scan0128
Date  11th June 1931
  
To R.{Sir Henry Royce} from Hs.{Lord Ernest Hives - Chair}
c. SG.{Arthur F. Sidgreaves - MD}
c. WOF. E.{Mr Elliott - Chief Engineer}
c. Da.{Bernard Day - Chassis Design} EV.{Ivan Evernden - coachwork}

87771.

Hs{Lord Ernest Hives - Chair}2/AD11.6.31.

8777°

PHANTOM II. 6 : 1 COMPRESSION RATIO.

In a recent memo you asked for P.2. to be fitted up with 6 : 1 compression ratio. We have no cylinder head which will give us this ratio.
We have modified the present one so that we can obtain 5 : 1 instead of the standard 4.6, but to make it suitable for 6 : 1 we think the design should be gone into.

We are certain that we shall never be able to use a 6 : 1 compression ratio on a car which we could sell to a customer. It would only be useful purely as a car to run on the track with special fuel.
In our opinion a compression ratio of about 5 1/2 : 1 is about as high as we can go on the P.2.

If you wish us to carry on with 6 : 1 ratio we should like a scheme showing how it should be arranged.

Hs.{Lord Ernest Hives - Chair}
  
  


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