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Engines BMW VI - M-17 BMW 801 D Rolls-Royce Merlin Rolls-Royce Merlin 25 AM-35

ROOLS-ROYCE MERLIN

Engine Maintenance Manual

Derby, England, 1946

ENGINE DATA
TYPE OF ENGINE Supercharged, geared, pressure-liquid cooled, V-engine,
fitted with two-stage, two speed centrifugal supercharger
with intercooler.
NUMBER OF CICLINDERS 12
CILINDER ARRAGEMENT Two banks of six cylinderseach, with an included angle of 60
BORE AND STROKE 5.4 ins. X 6.0 ins
SWEPT VOLUME 1,648 cu. ins.
COMPRESSION RATIO 6.0 to 1.
SUPERCHARGER
Type Two-stage, two-speed
Gear Ratios Merlin 66, 67, 85, 100,
104, 130, & 131
5.79 to 1 & 7.06 to 1
Merlin 61, 67, 72, 73, 76, 77,
73, 76, 113 & 114
6.39 to 1 & 8.03 to 1
PROPELLER REDUCTION GEAR
Type Single spur
Ratio Merlin 61, 67, 72, 73, 76, 77
85, 100, 104, 113, 114 & 130
.420 to 1
Merlin 66, 70, & 71
Merlin 131
.477 to 1
.422 to 1
DIRECTION OF ROTATION
Propeller shaft Right-hand (Merlin 131 only).
Crankshaft Left-hand.
CYLINDER NUMBERING 1A, 2A, 3A, 4A, 5A, 6A.
1B, 2B, 3B, 4B, 5B. 6B.
WEIGHT OF ENGINE, NETT DRY Merlin 61
Merlin 66, 67, 70, 71, 72, 73, 76 & 77
Merlin 85
Merlin 100, 104, 130 & 131
Merlin 113
Merlin 114
1,640 lbs. 21 Tolerance
1,645 lbs. 21 Tolerance
1,665 lbs. 21 Tolerance
1,720 lbs. 21 Tolerance
1,650 lbs. 21 Tolerance
1,654 lbs. 21 Tolerance
PERFORMANCE
International Power Rating.
Low Gear
M.S.
High Gear
F.S.
Merlin 61, 72 & 73
Merlin 66, 67 & 85
Merlin 70, 71, 76 & 77
Merlin 100, 104, 130 & 131
Merlin 113 & 114
1,400 b.h.p. 12,000 ft
1,400 b.h.p. 9,250 ft
1,375 b.h.p. 13,500 ft
1,410 b.h.p. 10,000 ft
1,380 b.h.p. 15,750 ft
1,250 b.h.p. 24,000 ft
1,310 b.h.p. 19,000 ft
1,255 b.h.p. 25,250 ft
1,315 b.h.p. 21,500 ft
1,200 b.h.p. 29,750 ft

These powers are obtained at 12 lb. per sq. in boost pressure and 2,850 r.p.m.

Engine Data continued
IGNITION
Firing order 1A, 6B, 4A, 3B, 2A, 5B.
6A, 1B, 3A, 4B, 5A, 2B.
Magnetos Two.
Type B.T.H. C6SE-12 S, 12S 1 or 12 S 2, or ROTAX NSE 12-4 or 6.
Contact breaker gap 0.012 in. 0.001 in.
Sparking plug gap 0.018 in. - 0.021 in.
TIMING
Fully advanced Port 45 before T.D.C.
Stbd. 38 before T.D.C.
OIL
Consumption at max. cruising 6 to 20 pints per hour.
Minimum main oil pressure in flight min 30 normal 40 lb. per sq. at 2,200 r.p.m. & 60C/90C.
CARBURATION
Carburettor Merlin 61, 72 & 73
Merlin 66, 67, 70, 71, 76, 77 & 85
Merlin Merlin 100, 104, 113,
114, 130 & 131
S.U. Anti-G. Float Type.
R.R. Bendix SD 44 I.D.E.
S.U. Single-point, fuel
injection pump.
Fuel 100 octane
Max. fuel demand Merlin 61
Merlin 72 & 73
Merlin 66, 67, 70, 71, 76, 77 & 85
Merlin Merlin 100, 104, 113, 114, 130 & 131
135 galls. per hour.
154 galls. per hour.
153 galls. per hour.
205 galls. per hour.
Pump pressure to carburettor Merlin 61,72 & 73
Merlin 66, 67, 70, 71, 76, 77 & 85
9 lb. per sq. in. 1 lb.
14 lb. per sq. in. 1 lb.
Fuel pressure to injector pump Merlin 104, 113,114, 130 & 131 7 lb. per sq. in. 3 lb. per sq. in.
- booster pump pressure
VALVES
Type Tulip type poppet valves, exhaust valve sodium cooled.
VALVE TIMING
With 0.014 in cam clearance
Early type camshaft (Pre-mod. 987) Inlet opens
Inlet closes
Exhst.opens
Exhst. closes
31 deg. before T.D.C.
52 deg. after B.D.C.
72 deg. before B.D.C.
12 deg. after T.D.C.
Parabolic type camshaft (POst-mod 987) Inlet opens
Inlet closes
Exhst.opens
Exhst. closes
38 deg. before T.D.C.
72 deg. after B.D.C.
78 deg. before B.D.C.
32 deg. after T.D.C.
Running cam clearance (both types of camshaft) Set 0.009 in. Allow to fall to 0.006 in. before resetting (inlet).
Set 0.015 in. Allow to fall to 0.012 in. before resetting (exhst.).
ENGINE COOLANT
Type Pressure liquid (70% water - 30% ethylene glycol to Spec. DTD 344A).
System Merlin 61, 66,70, 71 & 100
Merlin 67, 72, 73, 76, 77
104, 113, 114, 130 & 131
Normal flow
Reverse flow
.
INTERCOOLER COOLANT
Type Pressure liquid (70% water - 30% ethylene glycol to Spec. DTD 344A).
STARTING SYSTEM Hand or electric turning gear.
PROPELLER Rotol or De-Havilland constant speed type.

This foolowing accessories may be fitted to engines not employing an accessory gearbox.

Accessory Speed Ratio
(relative to crankshaft)
Direction of Rotation
(looking on driving
spindle of accessory)
Constant-speed governor unit 0.828 Clockwise
Vacuum pump 0.828 Clockwise
*Electric generator 1.953 Anty-clockwise
**Electric generator 2.100 Anty-clockwise
***Electric generator 2.110 Clockwise
Starter motor -
Epacyclic type 91.560 Clockwise
Spar reduction type 86.500 Clockwise
Air compressor (camshaft) 6.500 Clockwise
Hydraulic pump (camshaft) 1.000 Clockwise
R.P.M. indicator drive (camshaft) 0.250 Clockwise
Hydraulic pump (crankcase) -
Vertical drive 0.810 Clockwise
****Cabin supercharger 0.913 Anty-clockwise
When the Rotel universal gearbox is fitted, the direction of rotation for the accessories will depend upon the particular aircraft reguirements. The gear ratios, however, relative to crankshaft, will be as follows: -
Electric generator 1.826 The accessories listed below will, in all cases,
be mounted on the engine itself, and run at
the speeds quoted under "Accessories": -
Constant-speed governor unit, Starter motor
and Engine-speed indicator drive
Hydraulic pump
Low-pressure air compressor 0.913
Vacuum pump
High-pressure air compressor 0.456

* Merlin 61, 66, 67, 70, 71, 72, 73, 76, 77, 85, 100, 104, 113 & 114.

** Merlin 130.

*** Merlin 131.

**** Merlin 61, 71, 73, 77, 104 & 114.

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