The amount of air entering the engine is determined by the throttle opening angle and the engine speed. The air flow passes through the air filter, the throttle body passage and enters the upper part of the intake manifold, from where it is distributed to the engine cylinders. When the coolant temperature is low, the idle speed control valve opens and air enters the top of the intake manifold through the bypass in addition to the air passing through the throttle. When the engine warms up, even if the throttle is fully closed, air enters the upper part of the intake manifold, therefore, the idle speed increases (1st stage idle speed control). The top of the intake manifold reduces airflow pulsations.
Pic. 2.194. 1MZ-FE engine intake and exhaust system: 1 - exhaust manifold; 2 - intake manifold; 3 - receiver; 4 - EGR valve; 5 - throttle branch pipe; 6 - main muffler; 7 - three-way catalytic converters
Throttle assembly
The use of ETCS-i without mechanical linkage provided excellent throttle control. The throttle control uses a DC motor with minimal power consumption. The ECM in standby mode controls the throttle motor current to control the throttle opening angle.
Pic. 2.195. Throttle assembly: 1 - throttle position sensor; 2 - throttle actuator motor
Receiver
The receiver consists of upper and lower sections and has an intake air control valve. This valve is activated by the ACIS system (Acoustic intake control) and is used to change the length of the suction pipe to improve engine performance over the entire speed range.
Pic. 2.196. Receiver: 1 - actuator (for ACIS); 2 - intake air control valve