Rolls-Royce Archives
         « Prev  Box Series  Next »        

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).
Engine head performance detailing compression ratio tests and ignition characteristics.

Identifier  ExFiles\Box 17\6\  Scan007
Date  10th December 1926 guessed
  
contd :-
-3-

the simplest ways of increasing the MEP - as previously demon-
strated on the 20 HP. and Phantom - the blue sports 10-EX, but
we have been limited in this direction by the increased tendency
to detonate.

The new head, after the bench test, was fitted to
car 14-EX and gave a compression ratio of 4.66 to 1 as the pistons
on this engine had .128 head clearance. From road performance it
seemed particularly good but detonation was reported to be a little
more evident than on the std. 4.2 to 1 ratio engine. The engine
was also 'livelier' than the standard product. We must not
adhere too rigidly to this first impression re. detonation because
the ignition relay which was fitted gave the range required by a
standard engine which, as we shew later, is earlier than required
for this type of head.

IGNITION CHARACTERISTICS.
--------------------------
This head - LeC.2230 - displays similar character-
istics to the previous one tested in respect to the difference in
the advance required between synchronised and single ignition.
The spark advance necessary to give maximum torque can be consid-
erably reduced by using synchronised ignition - see appended curves
on sheet 4. It will be noted the power output shewn on these
curves is a little higher with the synchronised than with the
single ignition, but this is small and only amounts to 1%.

A point of importance shewn by these curves is the
comparative lateness of ignition which can be employed when
synchronised without appreciably reducing the B.M.E.P. In the
example given at 1000 r.p.m., we could reduce the spark contd :-
  
  


Copyright Sustain 2025, All Rights Reserved.    whatever is rightly done, however humble, is noble
An unhandled error has occurred. Reload 🗙