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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).
The influence of fuel mixture strength on engine cooling, featuring a graph specific to a Silver Ghost engine.

Identifier  ExFiles\Box 178\1\  img024
Date  15th February 1926 guessed
  
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(e) Influence of mixture strength.

Mixture strength has a marked effect on the quantity of heat imparted to the cooling water. An exceptional case is that of the Hispano where by running with the strongest mixture at which the power is maintained, the heat to the cooling water is 40% less than when the weakest mixture for maintained power is adopted. In every case that has come to our notice, however, a weak mixture tends to promote over-heating.

Graph V demonstrates the result of varying the mixture strength on a Silver Ghost engine. Compression ratio 3.9 - 1. We do not measure such large differences on the road, however.

[Graph]
Title: GRAPH V
Y-Axis Label: B.TH.U MINS TO WATER
X-Axis Label: PTS/HR
Data Labels on graph: WEAKEST POWER MAINTAINED, STRONGEST POWER MAINTAINED
[/Graph]

The main point is that on cars which are likely to suffer from over-heating, a weak mixture setting should be avoided.

(f) Influence of detonation.

See section on this item.

contd.
  
  


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