Low-pressure EGR explained simply

What is internal EGR?
How does it differ from external or external exhaust gas recirculation?
And what are the differences between high-pressure EGR and low-pressure EGR?
Everyone will understand with this video!

00:00 Exhaust gas recirculation (EGR)
01:06 Structure and function of low-pressure EGR
01:36 Advantages of low-pressure EGR

In the case of exhaust gas recirculation, a certain amount of exhaust gas is mixed with the intake air. This means that less oxygen reaches the cylinder, leading to a lower combustion temperature. As a result, the amount of nitrogen oxides in the exhaust gas can be reduced by up to 50%. In petrol engines, this can also reduce carbon dioxide emissions and fuel consumption.

There are various positions for exhaust gas removal:

INTERNAL EGR
• Valve overlapping means that some exhaust gas remains in the combustion chamber or is sucked back into the cylinder from the outlet duct.
• The timing of the intake and exhaust valves is changed by means of adjustable cams.

EXTERNAL EGR
• Exhaust gas is removed outside the cylinder head on the exhaust gas side and is fed back via lines or ducts to the fresh air side through an external valve.
• This provides the opportunity for additional exhaust gas cooling by an optional cooler with / without bypass flap.

There are two types of external EGR:

HIGH-PRESSURE EGR
The exhaust gas is
• removed immediately after the cylinders, upstream of the turbocharger turbine and
• fed back to the fresh air side after the throttle valve.

LOW-PRESSURE EGR
The exhaust gas is
• removed downstream of the turbocharger turbine or only after the exhaust treatment systems and
• fed back upstream of the turbocharger compressor.

An exhaust gas flap provides the necessary exhaust gas back pressure if the pressure difference is not sufficient for the required EGR mass flow rates. The exhaust gas is also cooled by a special low-pressure EGR cooler.