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The functioning of the EGR valve.

Model: (Various brands) Various
Part: EGR valve

Video tutorial

Let's see how an EGR valve works: it reduces NOx by mixing inert and oxygen-free exhaust gases back into the intake, lowering the combustion temperature. In fact, NOx is formed at high temperatures.

In modern diesel engines, two EGR valves are used: a high-pressure valve and a low-pressure valve, to further optimize the reduction of NOx and improve efficiency. The high-pressure EGR is located before the turbine of the turbocharger and reintroduces the gases into the intake manifold.

It is mainly active at low engine speeds or when the turbo is not yet under pressure, making it ideal for urban driving. The low-pressure EGR takes exhaust gases after the DPF and reintroduces them before the turbocharger.

It comes into play at medium to high engine speeds, such as on the highway, and reduces NOx under high load conditions.


Posted on 4 January 2026 by ScegliAuto


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