Lotus Esprit Series - Temperature Compensator

FUEL SYSTEM
Page L13
The jet/needle relotionship is set during production and SHOULD NOT be altered.
When the throttle
is opened, air flow under the air volve increases ond a temporary
rise in mixing chamber depression
is transferred vio drillings in the air volve to the
depression chamber which
is seoled from the main body by a diaphragm. Pressure
difference between the depression chamber and the under
diaphragm chomber covses
the air valve to lift. Thus
ony increase in engine speed or lood will enlarge the
effective choke area until maximum air valve lift, since the oir volve lift is
proportional to the rate of air flowing beneath it. Therefore, air velocity and
pressure drop across the
iet orifice remain approximately constant at all engine speeds.
As the air valve rises, it withdrows the tapered metering needle held in its base from
the
iet orificie, so that fuel flow is increased proportionate to the greater oir flow.
The metering needle is
a varioble and machined to very close limits. It provides a
mixture ratio for
011 speeds and loods in line with engine requirements that are
determined by exhaustive tests on bench and rood during ori
g
inal manufacture. To
maintain correct results, it
is essential that only the recommended needle is vsed.
Temperature Compensator
-
Testing has shown the need for a temperature compensator, operating over a wide
range of air valve lift, to cater for
minor mixture strength variations caused through
heat transfer to the carburetter castings.
An air flow channel
is employed which permits some of the air passing through the
d
carburetters to by - pass the bridge section. With the introduction of this air into the
mixing chamber, the air valve, in order to maintain depression on its downstream
side, rides in a lower position, thus giving a
smoller fuel flow annulus. To adjust the
quantity of air by
- passed, a bimetallic blade is used to regulate the movement of a
tapered plug
.
Two screws attach the temperature compensator assembly to the carburetter and two
seal are provided to ensure that no
leakoge can occur at the joint with the main body.
THIS ASSEMBLY
IS PRE - SET AND MUST NOT BE RE - ADJUSTED IN SERVICE. If it
is suspected of malfunction and the tapered plug moves freely when tested corefully
by hand with the engine both cold
and hot, the compensator assembly shot~ld be
chan
g
ed for another of the correct specification.
4%:
ESPRIT
Issue 04/78