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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).
Increasing power output by lowering induction pipe depression, comparing different carburetter configurations.

Identifier  ExFiles\Box 22\4\  Scan115
Date  1st April 1927 guessed
  
contd :-

-3-

INCREASED POWER WITH LOWER INDUCTION PIPE
DEPRESSION.

Referring to the first set of results taken which
are given on Print No.1. we have the power output with the std.
cyl. head for the different induction pipe depressions given
with the different carburetters.

The full line curves are the power and corresponding
induction pipe depression given with the std. RR. carburetter.
A note on the induction pipe depression shewn here is necessary.
Previous tests on the standard engine fitted with
exhaust pipes and hot spot, the maximum induction pipe depression
was 2.7 in.Hg. while in this case with open exhaust and no hot
spot the depression was 3.5 in.Hg. This can be explained by the
charge in the former case at a certain depression gaining heat
from the 'hot spot' and consequently increasing in pressure
thereby giving a lower depression than when running without a
hot spot. The lower depression in the former case does not
however mean any greater volumetric efficiency than with the
higher depression.

The other two curves shew the power improvement with
one and two Zenith carburetters respectively.

The reason for the curve with the single Zenith
falling below the curve with the standard RR. at 1300 r.p.m. is
due to the mixture becoming excessively rich. At speeds above
1750 r.p.m. the mixture was correct for maximum power. These
carbs. were proportioned for feeding three cyls. which would
account for the better metering when the two were employed.

contd :-
  
  


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