PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
(b) The operating range of the engine can be increased, and
driveability improved, if the throttle linkage is arranged to phase in the
carburetor venturis gradually as the accelerator pedal is depressed.
There are two basic arrangements for the throttle linkage, depending on the
purpose for having multipleventuri carburetion. The linkage arrangements
are discussed in the next two subparagraphs.
(3) Fixed Throttle Linkage (figure 29). Fixed throttle linkage is
used mostly on twoventuri or twobarrel carburetors on engines containing
six or more cylinders. This linkage arrangement is usually installed on an
intake manifold so arranged that each venturi is feeding a selected half of
the cylinders. The separation of the carburetor venturis within the intake
manifold is usually to keep consecutively operating cylinders separated.
Whenever two cylinders go through power strokes consecutively, the second of
the two cylinders tends to have its fuel supply cut off. The fixed throttle
linkage arrangement is a solid throttle shaft that operates both throttle
valves simultaneously. There is an idle mixture screw on each side of the
carburetor. The accelerator pump discharge nozzle usually contains two
FIGURE 29. TWOBARREL CARBURETOR WITH FIXED LINKAGE.