BENDIX RSA FUEL INJECTION SYSTEM

PRINCIPLE

Continuous flow system as pressure type carburetors

To meter fuel in direct ratio to the volume of air being consumed by the engine at a given time by sensing the impact pressure

When air velocity increases, pressure @ impact tubes is relatively constant depending on the inlet duct, the pressure at the venturi throat decreases.

It uses the measurement of air volume to generate a force which regulates the fuel flow to engine by channeling the impact and suction pressures to opposites sides of diaphragm

Includes a boost pump. Engine driven fuel pump receives the

fuel from the system at a relatively constant pressure to fuel injector servo unit

Its heart is the SERVO PRESSURE REGULATOR

Two opposing forces (fuel & air differentials) are equal & the regulator servo valve is held at a position that allows discharge of just entered metered fuel to maintain pressure balance.

If the throttle is opened to increase power, airflow increases resulting in pressure differential across the air diaphragm.

Requires fuel flow to balance the power level requested.

SLIDING IDLE VALVE&MANUAL MIXTURE CONTROL

Begins to uncover the enrichment jet at a preset throttle position.

Parallel flow path increases the F/A mixture strength to provide for “fuel cooling” of the engine in the high power range

Effectively reduce the size of the metering jet.

To shut off fuel flow to the engine at engine shutdown

CONSTANT HEAD IDLE SPRING

Augments the force of the air diaphragm in the idle range when the air pr.differential is not sufficient to open the servo valve.

As airflow increases above idle, air diaphragm will start to move right in response to increasing air pr.

Transition to servo regulator controlled fuel

CONSTANT EFFORT SPRING

Supplements the transition from idle to servo regulator controlled fuel flow.

Assists the air diaphragm in moving smoothly from the low airflow idle range to higher power range of operation.

Fuel section of the servo regulator is separated from the air section by a centre body seal assembly.

AUTOMATIC MIXTURE CONTROL

AMC adjusts the F/A ratio to compensate for the decreases air density at higher altitudes.

Two rotating valve assemblies are spring loaded together, back to back with an O-ring seal between them.

Inlet strainer underneath the fuel inlet fitting.

No approved method of cleaning the screen for reuse

W/o AMC, necessary to continually lean the mixture manually to maintain the desired 0.08 F/A ratio.

FLOW DIVIDERS Consists of a valve, sleeve, diaphragm and

spring. Valve is spring loaded to closed position in

the sleeve. Effectively closes the path of fuel from the

fuel injector servo to nozzles. Functions: (1) ensures equal distribution of

metered fuel to nozzle at and just above idle;(2) provide isolation of each nozzle from all the others for clean engine shutdown

FUEL NOZZLES

Nozzles are air bleed type. Fuel is discharged inside the nozzle

body chamber which is vented to atmospheric air.

Mounted in the intake valve port of cylinder head.

Exit is exposed to MAP, results in air being drawn in thru the air bleed and mixed with fuel in fuel-air chamber to provide for fuel atomization.

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