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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).
Analysis of cylinder head designs, air consumption, and detonation characteristics with various fuels.

Identifier  ExFiles\Box 133\1\  scan0007
Date  13th March 1936 guessed
  
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Section II.

A considerable amount of work has been done under these conditions. Tests have been carried out on three different cylinder heads, viz: the semi-hemispherical, hemispherical and penthouse, and comparative curves are shown in Fig. IV. The general conclusion arrived at was that there was very little to choose between the heads from the point of view of power.

Air consumptions and detonation (Fig.VI) were also investigated in the cases of the penthouse and hemispherical heads, and once again the differences found were almost within the range of experimental error. Volumetric efficiency peaked at about 88%, and with mixture set at weakest maintained for maximum power, there was no detonation on Shell No.1.

The only other test carried out was with one exhaust rocker removed, thus allowing one exhaust valve only to operate. Results were rather startling (Fig.VIII) as there was a power drop of nearly 23% at 5500 R.P.M.

Section III.

The work done in this section consists mainly of a detonation investigation, power curves (Fig.IX) being taken as a check rather than anything else. Detonation curves have been run on D.T.D.230 and a 50/50 mixture of Benzole and Shell No.1, but in neither of these cases was it possible to make the unit detonate, even with the ignition fully advanced. On Shell No.1, rather different conditions prevailed, detonation setting in at about 3500 R.P.M. As soon as the unit began to detonate, it was observed that the plug temperature rose, and detonation intensity increased to the point of pre-ignition, even when a copper electrode plug was used and ultimately, in one instance, culminated in slight piston seizure.
  
  


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