TWIN
VENTURI
CARBURETTORS (TWIN CHOKE) PROGRESSION TYPE
On this type two venturis are incorporated in the same casting. One throttle plate
opens before the other
(observe while operating the throttle linkage). At low speeds and
for idle mixture adjustment this type can be considered similar to the single choke type,
all adjustments being carried out on the barrel which opens first.
The
Pierburg 2E3 shown in figure 4 has a diaphragm operated second barrel and
the idle adjustment is by the throttle stop screw and idle mixture screw shown.
On
theG.M. Varajet carburettor shown in Figure9 the secondary barrel is of variable
venturi design. This has no bearing on the idle setting which is of the by-pass type.
Idle
speed is adjusted on the throttle by-pass screw.
GM
VARAJET
IGNITION VACUUM
ADVANCE
PIPE
Figure
9
LE
BYPASS
/
IDLE SPEEDSCREW
IDLE
MIXTURE
(CO) SCREW
TWIN VENTURI CARBURETTOR SIMULTANEOUS TYPE
On this type the two venturis are incorporated in the same casting and both throttle
platesoperate at the same time. There is usually no need to balance
theair flowsthrough
the two barrels. they are
often linked by a single throttle spindle. Balancing of the two
m~xture screws is obtained by setting to the same number of turns open.
10.
PETROL INJECTION SYSTEMS
Modern fuel injection systems can be either of the continuous type (e.g. Bosch K
&
KE-Jetronic),
or
intermittent type (e.g. Bosch L, LE, LE2-Jetronic, Motronic, Lucas LH
etc) Adjustment screws are provided for idle
mixture(C0). In some versions idlespeed is
not mechanically adjustable. The manufacturer's instructions should be carefully
followed for particular models. The illustrations below show examples of types of
adjustments.
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