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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).
Graph plotting Inlet and Exhaust Valve B.M.E.P against Engine R.P.M, showing the effect of varying tappet clearances.

Identifier  ExFiles\Box 13\2\  02-page095
Date  12th June 1931 guessed
  
SHEET 1
EFFECT OF VARYING TAPPET CLEARANCE
P.V. UNIT
VALVE LIFT SCH. 1065
4.9 COMP RATIO
OPEN EXHAUST
CAMS E.32381

INLET VALVE B.M.E.P
(Axis values: 85, 90, 95, 100, 105, 110, 115)

ENGINE R.P.M
(Axis values: 750, 1000, 1500, 2000, 2500, 3000)

EX VALVE M.E.P
(Axis values: 85, 90, 95, 100, 105, 110)

Plot line labels (Tappet Clearances):
.040
.030
.020
.006
.007 CLCE

Timing Diagrams:
At 1000 RPM: .020 CLCE; IN .256; EX .257; Values: 58, 18, 18, 57
At 1500 RPM: .050 CLCE; IN .295; EX .293; Values: 53, 12, 12, 51
At ~1750 RPM: .020 CLCE; IN .284; EX .280; Values: 72, 32
At 2000 RPM: .040 CLCE; IN .339; EX .336; Values: 50, 9, 9, 48.5
At 2500 RPM: .050 CLCE; IN .234; EX .231; Values: 47, 6, 7, 45.5

Other Data:
B.H.P values: 163, 161.8, 158.5, 156, 153.5
I.H.P values: 155, 165
  
  


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