Lotus TURBO ESPRIT Service Manual page 383

SECT/ON LD Page
I 7
Distributor Differential Valves One distributor differential valve for each engine
cylinder
i s
incorporated i n the fuel distributor to maintain a constant pressure drop
across the metering slits regardless of their opening. This
i s necessary i n order to
ensure that the fuel flow to the injecton i s dependant only on the length of metering
slit exposed, and also i s not affected by any variation i n primary pressure.
The valves are mounted i n
4
cavities inside the fuel distributor. Each cavity i s divided
into upper and lower chambers by a steel diaphragm. A l l the lower chambers are
interconnected by a ring main and are supplied with fuel at primary pressure from the
pumps. The upper chamben are isolated from each other and each
i s
connected individually
to one of the metering slits. Each diaphragm i s spring loaded downwards away from a
seat valve leading to one of the fuel iniecton
.
Fuel Intake a t
Primary Pressure
Upper Chamber
To Fuel Injector
Control Valve
Metering Slit
Helical Spring
Steel Diaphragm
Lower Chamber
LOW
FUEL
D
ELIVERY
HIGH
FUEL
DELIVERY
flat
As
the metering slit
i s
opened, and the upper chamber pressure tends to increase, the
diaphragm is pushed downwards increasing the flat seat valve opening to the injector
line such that the upper chamber pressure remains a t
0.1
bar below that o f the lower
chamber, This pressure differential
i s
set by the helical spring. Hence, during
operation, the diaphragm is held i n equilibrium by the force of the primary fuel pressure
on the underside, and by the upper chamber press&e plus the spring- pressu.re on the
topride