Mazda Speed 6. Manual - part 4

01 ENGINE

18

Air Ducts and Charge Air Cooler

Air cleaner to turbo inlet (low pressure/low temperature)

Turbo outlet to charge air cooler (high pressure/high 
temperature)
Charge air cooler to throttle body/intake manifold (high 
pressure/low temperature)

Air bypass valve to turbo inlet

01 ENGINE

19

Turbo

Turbochargers consist of a housing, a blade assembly, inlet ducts for low pressure 
air and outlet ducts for high pressure air, an intercooler, oil inlet and return, coolant 
inlet and return, and boost control circuits.  

The turbine blade is on the exhaust side of the turbocharger and  the compressor 
blade is on the intake side of the turbocharger.  The turbine blade is spun by exhaust 
pressure.The compressor blade spins and pressurizes the intake air.

The hot/high pressure air coming out of the turbo is sent to the intercooler to cool it 
and make it denser.

The shaft between the turbocharger’s blades rides on bearing surfaces and a thin 
fi lm of oil.  The turbo’s center upper housing has an oil feed line that connects to the 
engines lubrication system to provide pressurized oil.  On the bottom of the turbo 
housing is an oil drain line to return oil back to the engines crankcase.

Compressed 
air to charge 
air cooler/
intercooler

Exhaust pressure 
to spin turbine from 
exhaust manifold

Air from air 
cleaner

Out to 
exhaust

01 ENGINE

20

Turbocharger Inlet and Outlet Pressures and Temperatures

Waste Gate 
Solenoid

Exhaust to spin the 
turbine

High pressure hot air 
to intercooler

Low pressure 
air from air 
cleaner 

Exhaust bypassing 
turbine when the 
waste gate opens

Compressor 
blade

Turbine 
blade

01 ENGINE

21

Waste Gate
The waste gate is a valve that allows exhaust pressure to bypass the turbocharger 
turbine and dump directly into the exhaust.  The waste gate valve actuator controls 
the waste gate.  When the waste gate opens, the turbine spins slower.

Waste Gate Actuator
The waste gate actuator consists of a control rod connected to the waste gate valve 
and a spring and diaphragm that hold the waste gate valve closed. The actuator 
pops open to allow the exhaust to bypass the turbocharger turbine and dump directly 
into the exhaust. 

Waste gate 
valve open

Spring
and 
diaphragm

Waste Gate 
Actuator Rod