Manifold (automotive engineering)

A manifold is an optimized exhaust manifold. Through optimized and adapted to the vehicle Krümmerrohrlängen purpose, diameter and guides for each individual cylinder engine performance and torque characteristics can be improved. The manifold uses the principle of interference.

Operation

The exhaust emissions from a piston engine is not continuous. When the charge cycle is created when you open the exhaust valve a strong pressure gradient between the cylinder and the exhaust system. This pre-discharge valve creates a pressure wave in the exhaust system. The pressure wave propagates at the speed of sound in the exhaust system. As a result, it comes through gas congestion and reflections to a return of the pressure wave. Exceeds the reflected pressure wave at the wrong time again on the exhaust valve, the gas exchange is impeded. By size and shape of a Fächerkrümmers the emergence of interference is encouraged. These produce at the right time ( when the exhaust valve opens ) a negative pressure in the exhaust pipe. The exhaust gases can leave the cylinder without significant back pressure, the piston requires less force to eject the exhaust gas. There remain scarcely residual gases, therefore the filling with fresh gas is better. The saved power and better combustion ( less residual gases) cause an increase in performance.

Construction

The exhaust pipes of the cylinder with the maximum firing interval are grouped and culminate in a string (each 2 to 3, depending on engine type ). The largest firing interval is the four-cylinder 360 ° and the six-cylinder 240 °. As a result, the cylinders 1 and 4 and 2 and 3 are summarized in the four- cylinder in-line engine. The exhaust pipes of six-cylinder in-line engines are often grouped according to the scheme 1, 2 and 3 and 4, 5 and 6. These thicker tubes, also called down pipe can also be joined later. The inner diameter of said exhaust tube is larger than the sum of the inside diameter of the tubes combined. Even the type of merge is not the characteristic of the engine, for example, change the torque curve. In high-performance racing engines all exhaust pipes of a cylinder bank, will take individual tubes to group, headed in a collection hopper with a final diffuser. In the construction of an equal length of all Fächerkrümmers exhaust pipes is desired. As a result, optimized manifold will always have a very curved, sweeping shape. This construction is in series production vehicles but often a lack of space or because of manufacturing problems can not be realized.

Application

Unlike manifolds cast iron manifolds can not be machined inexpensive, so they are installed mainly in motor sports, and sports cars. Factory manifolds for example, came the Audi 90 ( 2.3 liter 20V 170 PS), the Opel Astra F GSI and the Kadett E and Calibra 16V 16V (2.0 liter 16V, 150 hp, C20XE ), the Escort RS2000 16V, the Ford Capri ( 1.6 GT 88HP, 150HP 2.6RS ) and the Peugeot 206 RC ( GTI 206 in some markets called 180 ) is used. Today, Mazda installed a 4-2-1 - ( subjects) in the manifold Skyactive petrol engines. Here the elbow prevented by its longer exhaust paths backflow of hot exhaust gas. This high compressions are made possible in the new engine concept. Otherwise there would be by the hot exhaust gases a danger of knocking combustion.