Air Induction Unit 5

​Air Induction and Throttle Control

By Brian OLeary

"An engine wants to run"...

Something a master tech told me early on in my career.

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​Air Induction

Air Induction

A Combustion Ingredient

Engine power is limited by an engine's volumetric efficiency. Volumetric efficiency is a measure of an engines ability to draw air into it's cylinders during intake strokes.

Fill in the Blank

_ refers to how air enters the engine, or how the engine breathes.

Multiple Choice

Uses atmospheric pressure, which measures 14.7 psi at sea level, to push air into the combustion chambers

• Turbocharger

• Supercharger

• Natural Aspiration

• Boost Pressure

​The induction of air, on its own or without assistance. NA is made up of the intake manifold, throttle valve, intake air tube, and air filter/filter housing

​Natural Aspiration

Throttle Speed Control

​Throttle it down!!

The throttle body or throttle valve limits the amount of air entering the engine. Throttle valves are controlled by a cable or a wire. The throttle cable is connected between the gas pedal and the throttle valve. Throttle-by-wire is electronically controlled, using a APP sensor(s) and an electronic throttle motor.

A butterfly valve that controls the air flow and engine power output. When closed, throttle valve restricts airflow allowing for lower engine speeds. Opposite applies.

​Throttle Body

Feeds and electric signal to the ECM that corresponds to accelerator pedal position. The APP sensor is a 3 wire sensor and the pedal consists of two sensors.

APP Sensor

Throttle Control

The purpose of the intake manifold is to route outside air into the combustion chamber.

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​Naturally Aspirated

Turbocharged or supercharged engines use an air pump or blower to increase the pressure of the intake air.

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​Forced Air Induction

Where a turbocharger or supercharger is used to increase the density of the air entering the engine.

​Forced Air Induction

Fill in the Blank

The increased intake manifold pressure that helps improve volumetric efficiency and increase power output while reducing exhaust emissions

Multiple Choice

An air pump that uses turbines to direct engine exhaust gases to increase air pressure going into the cylinders.

• Turbocharger

• Supercharger

This illustration shows how exhaust flow is used to turn a turbine which compresses incoming air and pushes it into the intake manifold.

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Forced Air Induction

Turbochargers help burn and use wasted heat energy flowing and expanding in the exhaust manifold. By harnessing exhaust energy, a turbo an improve engine efficiency (fuel economy and emission levels).

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Turbocharger

Fill in the Blank

The short delay before the turbocharger develops sufficient boost (pressure above atmospheric pressure) to meet engine demands.

Turbocharger Operation

Exhaust gases leaving the engine spin the turbine wheel ?(exhaust side) of the turbocharger. The turbine wheel is connected to the compressor wheel (intake side). The compressor wheel takes atmospheric pressure and compresses it, sending compressed air into the intake manifold.

Turbocharger Part I.D.

Multiple Choice

All of these are names of turbocharger parts except:

• Turbine Housing

• Shaft

• Compressor Wheel

• Pulley

Uses a set of blades mounted inside the turbine housing to control exhaust gas flow over the turbine wheel or fan. The blades are controlled by an actuator to be angled, controlling the speed of the turbine wheel.

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​Variable Vane Turbocharger

Multiple Select

Where are turbochargers normally located?

• Side of the Engine

• Under the Engine

• Top of the Engine

• Front of the Engine

Turbocharger Locations

Theoretically, turbochargers should be located as close to the exhaust manifold as possible. This allows maximum amount of exhaust heat to enter and expand inside the turbine housing. When the hot gases blow onto the spinning turbine wheel, they are still burning and expanding to help rotate the turbine.

Exhaust manifold mounted turbocharger. Found on most modern gas engine, the turbocharger is part of our mounted to the exhaust manifold.

Engine V mounted turbocharger. Turbocharger is used as support between the cylinder heads. Exhaust pipes (up pipes)

Turbocharger Lubrication and Cooling

The turbocharger is lubricated from the engines lubrication system. A turbocharger can operate at speeds up to 100,000 RPM. You must lubricate rotating parts at that speed or high heat failure will occur.

Oil passages are located in the in the turbo housing and bearings. An oil supply line runs from the engine to the turbocharger. An oil return line returns oil to the oil pan.

The turbocharger is also cooled using the engines cooling system. Coolant lines are routed to and from the turbocharger.

Fill in the Blank

A butterfly or poppet-type valve operated by a mechanical diaphragm assembly that allows exhaust to bypass the turbine wheel.

​Waste Gate Operation

A waste gate is a valve that allows boost pressure to be wasted.

Without a waste gate, a turbocharger could produce too much pressure in the combustion chamber and this could lead to detonation and severe engine damage.

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The maximum allowable intake manifold pressure the turbocharger system should build under a full engine load

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An air pressure release valve that limits maximum boost pressure as the engine throttle valves are closed rapidly for deceleration.

​Turbocharger Intercooler

A turbocharger intercooler is an air-to-air or air-to-water heat exchanger that cools the air entering the engine. It is a radiator-like device mounted at the pressure outlet of the turbocharger. When you compress air, its temperature increases. Hot air contains less oxygen by volume. Air with a low amount of oxygen will produce less power. A cooler charge of air is denser and can be mixed with more fuel to increase combustion pressure and engine power.

​Engine Controlled Boost

As with other engine systems, the vehicle’s main computer (ECM or PCM) often controls the turbocharger. The ECM operates the waste gate and adjusts the ignition timing as needed. Several sensor signals are sent to the ECM that affect turbocharger operation. These commonly include inputs from the manifold absolute pressure (MAP) sensor, intake air temperature (IAT) sensor, knock sensor (KS), throttle position sensor (TPS), crankshaft and camshaft position sensors, and other system-sharing sensors.

Open Ended

Explain how a turbocharger works.