Exhaust manifold

The exhaust manifold is a component of the exhaust system of internal combustion engines. Bolted directly to the engine, the manifold directs the exhaust gases in the exhaust. Takes its name from his elbow usually curved design as they have to divert from the mostly horizontal engine openings into the lower lying exhaust line, the exhaust gases. As the material alloyed cast iron is often used, which meets the high temperatures of the exhaust gases ( about 900 ° C). Alternatively, steel manifold are used. Both ferrite (for example, 1.4509 ) and austenitic steels (such as 1.4301, 1.4828, 1.4845 ) can be used. Built manifold may be more expensive than cast manifolds. However, they have emission benefits (see below) and the additional cost can be usually compensated by reducing the precious metal content in the catalyst.

The statutory limitation of pollutant emissions suggested the mid-1980s to the development of thin -built manifolds, because as the thermal mass and thus the response of the catalyst was improved after a cold start. Alternatively, so-called LSI manifold (LSI air gap insulated) are installed, here is a Krümmergehäuse around the actual elbow with a few millimeters distance built; This ensures the insulation of the air gap of low heat loss of the exhaust gas on its way to the catalyst and thereby achieve a quick heating or the operating temperature of the catalyst after the engine cold start. Because of the limited space in the engine compartment individual components of modern manifolds are thick from one to two millimeters in the internal high, manufactured since 2002 from 0.8 millimeters thick and pipes.

The biggest challenge in the development of manifolds is the consideration of thermal expansion and the associated stress distribution in the manifold. These stresses are so large that they destroy the Elbow after a finite number of heating- cooling cycles in general. Nevertheless, today the manifold are developed, which, accordingly, several hundred thousand kilometers above there are several thousand such cycles. That was not always so. Therefore, it was the first generation of assembled headers regularly cracks, leading to expensive repairs.

In addition, the manifold is an important element in two-stroke engines. He, together with the exhaust bulb that build up in the exhaust system pressure oscillations that result in a certain speed range to a recharging effect. In four-stroke engines also rely on pressure fluctuations that cause a power increase with skillful design of the entire exhaust system.