Intake System
Each cylinder has an intake manifold which comes from a plenum chamber. The injectors are on the lower aluminum intake manifold close to the intake valves. This is so that the fuel mixes as well as possible with the turbulent air. The position of the injectors is optimized to minimize wetting the cylinder walls and therefore emissions. There are ducts in the lower intake manifold for the crankcase gases so that they can reach the combustion chamber.
For B5xx4Sx
The air enters via the air intake on the front member. The air is routed via a cold air hose in the air cleaner (ACL) housing. Here there is also a snow valve. This valve opens if the air cleaner (ACL) housing and air intake are blocked by snow. This lets the air flow through and also uses cooling flanges to cool the engine control module (ECM). The air then flows through a funnel with a net which reduces air turbulence before the air reaches the mass air flow (MAF) sensor.
The mass air flow (MAF) sensor controls the mass air flow to the engine. The air then flows to the electrical throttle body (TB) and into the intake manifold. The manifold absolute pressure (MAP) sensor gauges the pressure in the intake manifold. The evaporative emission system (EVAP) valve recirculates the fuel/air mixtures for further combustion. The evaporative emission system (EVAP) valve is by the throttle body (TB). There is a direct terminal from the air cleaner (ACL) to the intake manifold which by-passes the mass air flow (MAF) sensor. There is a brake vacuum ejector in the middle of the hose. The brake vacuum ejector uses the pressure differences in the air cleaner (ACL) housing and plenum chamber to create a flow in the hose to create a vacuum in the brake booster.
For B5xx4Tx
The air enters via the air intake on the front member. There is a rail in the air intake pipe which divides the pipe to minimize drops in pressure. The air then flows on to the air cleaner (ACL) housing. Here there is also a snow valve. This valve opens if the air cleaner (ACL) housing and air intake are blocked by snow. This lets the air flow through and also uses cooling flanges to cool the engine control module (ECM).
The air then flows through a funnel to the mass air flow (MAF) sensor. The mass air flow (MAF) sensor controls the mass air flow to the engine. The air then flows through a fresh air hose over the engine. The air then passes the turbocharger (TC) and charge air cooler before reaching the electronic throttle body (TB) and being released into the intake manifold. The evaporative emission system (EVAP) valve recirculates the fuel/air mixtures for further combustion. The evaporative emission system (EVAP) valve is by the throttle body (TB).