toyota training course t874 engine control systems II ch04

Toyota Engine Control Systems I Course 852 23Engine Control Systems Section 4 Air induction systems measure and control the air entering the cylinders.. • The throttle valve regulates th

Toyota Engine Control Systems I Course 852 23

Engine Control Systems

Section 4

Air induction systems measure and control the air entering the cylinders They include:

• The air flow sensor (commonly called the mass air flow sensor) measures air after it has been filtered by the air cleaner

• The throttle valve regulates the volume of air entering the induction system (based on driver demand)

• The air intake chamber and intake manifold are tuned for efficient engine operation

There are many variations on the basic air induction system, such as:

• Electronic Throttle Control System-intelligent (ETCS-i) allows the ECM to adjust throttle opening according to driver demand and vehicle conditions

• Acoustic Control Induction System (ACIS) allows the ECM to vary the effective intake runner length for better engine performance

• Variable Valve Timing-intelligent (VVT-i) allows the ECM to adjust when the valves open for optimum engine performance at varying speeds

Air Induction

Systems

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Fuel systems deliver the correct volume of fuel to the cylinders to satisfy

a variety of engine operating conditions

Fuel system components include:

• A fuel pump pressurizes fuel for use by the fuel injectors

• A fuel pressure regulator, located in the fuel tank or after the injectors, regulates fuel pressure

• The fuel injectors, when on, allow fuel to flow into the intake manifold

The ECM calculates:

• How much fuel to be injected

• When to inject fuel These calculations are based on a variety of factors, primarily intake air volume and temperature The ECM also calculates fuel injection duration and timing based on engine RPM, crankshaft position, and engine load Other system components that modify fuel injection operation are detailed

in the Fuel Systems section

Fuel Systems

Fuel Systems Engine Control Systems

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The ECM is programmed to monitor engine operating conditions and determine the optimum time to ignite the air/fuel mixture

• Based on a signal from the ECM, the igniter starts and stops current through the ignition coil(s) by providing and taking away a path to ground

• When coil current is turned OFF, high voltage is generated in the coil

• High voltage applied to the spark plug creates the spark needed for ignition

Ignition Systems

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The ECM manages systems and components to meet state and federal regulations Systems may include:

• The evaporative system (EVAP) prevents hydrocarbons (HC) from entering the atmosphere

• Variable Valve Timing with intelligence (VVT-i) improves engine performance while lowering engine emissions, primarily oxides of nitrogen (NOx)

• The fuel control program adjusts the air/fuel ratio so the catalytic converter runs at peak efficiency This lowers HC, carbon monoxide (CO), and NOx emissions

• The exhaust gas recirculation system (EGR) feeds a small amount

of exhaust gas back into the air induction system to reduce combustion chamber temperature, lowering NOx EGR has been phased out as other control systems accomplish the same function

Exhaust/Emission Control

Systems

Exhaust and Emission Control Systems Engine Control Systems

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