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E - THEORY/OPERATION Article Text
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Short Description: Land Cruiser, MR2, Pickup, Previa,. Supra, Tercel, 4Runner. INTRODUCTION .... input usage on a specific model, see appropriate wiring diagram in L - ...
Content Inside: E - THEORY/OPERATION Article Text 1991 Toyota MR2 For Electronics & Computers El Camino Real Santa Clara CA 95051 Copyright © 1997 Mitchell International Wednesday, November 25, 1998 03:00AM ARTICLE BEGINNING 1991 ENGINE PERFORMANCE Toyota Theory & Operation Camry, Celica, Corolla, Cressida, Land Cruiser, MR2, Pickup, Previa, Supra, Tercel, 4Runner INTRODUCTION This article covers basic description and operation of engine performance-related systems and components. Read this article before diagnosing vehicles or systems with which you are not completely familiar. AIR INDUCTION SYSTEM INTAKE AIR CONTROL SYSTEM SUPRA (7M-GE) ECU uses inputs from engine RPM and throttle position sensor to change amount of airflow into manifold runner. This is done to increase power in low speed range. ECU opens an air control valve through a vacuum switching valve. VARIABLE INDUCTION SYSTEM CELICA TURBO & MR2 TURBO Each cylinder runner in the intake manifold is divided into 2 parts. An intake air control valve is installed in one passage on each cylinder runner. The opening and closing of this valve gives the best airflow possible, preventing low-speed performance loss and improved fuel economy. The intake control valves are vacuum actuated. The vacuum signal is controlled by the ECU through a vacuum switching valve. TURBOCHARGERS CELICA TURBO, MR2 TURBO & SUPRA TURBO All systems are equipped with an air-cooled intercooler and use a wastegate system to control maximum boost pressure. On Celica and MR2, maximum boost pressure is controlled by a dual control wastegate actuator. One pressure signal is direct from downstream of the impeller wheel and one pressure signal is ECU controlled, through a vacuum switching valve, from upstream of the impeller wheel. On Supra, wastegate valve is actuated by pressure signal from intake manifold. Celica and MR2 use a vane-type airflow meter and turbocharging pressure sensor to signal the ECU. On Supra, there is not a separate pressure sensor for the ECU. The Karman-Vortex mass airflow meter senses boost pressure for the ECU.
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