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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).
Single cylinder Bentley unit, comparing the performance and detonation characteristics of a revised 'Ramp' cylinder head against the standard version.

Identifier  ExFiles\Box 133\2\  scan0077
Date  11th October 1934
  
SINGLE CYLINDER BENTLEY UNIT.

Period covered by this report - 22nd July to 11th Oct.1934.

This engine has completed a further 62 hours, 30 mins. running time since the last report was issued. The work carried out during this period consists mainly of an investigation into the characteristics of "No.2 Ramp" cylinder head (Lec.3871). Some volumetric efficiency figures for the standard Bentley head (E.B.1517) and No.1 Ramp (LeC.3739) have been taken and the unit has also been calibrated for motoring losses.

SUMMARY.

Comparison of "No.2 Ramp" Cylinder Head with Standard Bentley.

The revised "Ramp" head, as shown on Le.C.3871, gives a marked improvement in power throughout the speed range; amounting to 7% at 1000 R.P.M., gradually diminishing to 5.4% at 2500 R.P.M. and increasing again to 7% at 4000 R.P.M. With regard to detonation the No.2 Ramp head is actually better than the standard Bentley below 1600 R.P.M., but above that speed is slightly worse. Detonation ceases at 2350 R.P.M. compared with 2150 R.P.M. for the standard. At 1000 R.P.M. the detonation is 38% less than standard. The above figures represent the capabilities of the No.2 Ramp running with the best all-round valve timing. Greater power can be obtained (and incidentally, worse detonation) by a valve timing having more overlap than the 12° (approx.) of the standard Bentley timing, but this cannot be tolerated on the score of good slow running.

It will be seen from the above that No.2 Ramp head is quite suitable for fitting to the car engines so far as power output and freedom from detonation are concerned. It is thought that the slightly worse detonation between 1600 and 2350 R.P.M. would be hardly noticeable.

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(Contd)
  
  


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