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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).
Comparing power output from a single jet and expanding carburettor to a fixed choke diffuser type.

Identifier  ExFiles\Box 31\4\  Scan101
Date  28th October 1931
  
To R.{Sir Henry Royce} From Hs{Lord Ernest Hives - Chair}/Ra.
c. to SG.{Arthur F. Sidgreaves - MD} Wor.{Arthur Wormald - General Works Manager}
c. to CA. E.{Mr Elliott - Chief Engineer}
c. to Hy.{Tom Haldenby - Plant Engineer}

81487

Hs{Lord Ernest Hives - Chair}/Ra.3/KT.28.10.31.

POWER OUTPUT. SINGLE JET & EXPANDING CARB. COMPARED WITH FIXED CHOKE DIFFUSER TYPE.

Y1487
X1452

We obtained a power of 34 B.H.P. with a Claudel carb., free area past choke 1.45 sq.in., on a japan unit with a 112º shaft, high lift valves and a c/r of 5.13 When we tried to reproduce this with an S.U. we were 10 HP. down, as shewn on Curve (1). The distribution with the S.U. appeared to be quite good at the top speeds with pipe "B", but in view of the large discrepancy in power output between the two carbs. we decided to try another pipe on the S.U. "A". This pipe gave an increase of 8 B.H.P. and almost equalled the Claudel though it was poor for distribution at low speeds.

The inference we draw from these results is that we can get as good power from a single jet as a diffuser, though the former is more susceptible to distribution troubles. Incidentally we took the induction pipe depn. opposite No.4 & No.6 cyls. in these tests and you will note that the results show quite a wide variation in depression between the two points.

Hs{Lord Ernest Hives - Chair}/Ra.
  
  


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