In the five-valve cylinder head of the engine with a displacement of 1.8 liters, the sprocket (4) exhaust camshaft transmits its speed to a double-row chain (2) on a chain wheel (4) inlet distributor. A hydraulic chain tensioner is used to eliminate noise from the chains (3).
Underside view of a five-valve cylinder head: the photo shows the large flow cross-section that exhaust valves can create when they open (1) and intake (2) valves.
Four cylinder engine
Our four-cylinder engine began in 1972, when Audi laid the foundation for its current position on the market with the introduction of the new Audi 80. Not only the body and chassis, but also the new engine impressed the professionals. Its most important design features: a four-cylinder engine with an overhead camshaft, valves are driven by poppet pushers. The oil pump and distributor are driven by an intermediate shaft. The camshaft and intermediate shaft are driven by a toothed belt.
Little remains of the old engine, but the main features of the crank mechanism remain the same. Especially for use in the Audi A4, fundamental changes have been made to the cylinder head: the engine with a displacement of 1.6 liters has received a so-called head with a cross flow of gases to improve gas exchange. Fresh gases enter from the left side of the engine, and exhaust gases are released from the right side. In addition, the new 1.6-liter engine received very long intake pipes for maximum traction (maximum torque) in the lower rpm range.
A similar goal was pursued in the design of five-valve heads. Here, due to the larger flow cross section, which allows five valves to be obtained, gas exchange is also improved over a wide range of engine speeds.
The 1.8 T turbo creates powerful torque at the lowest revs. Power is generated that is normally only expected for much higher displacement classes.
All in all, the four-cylinder engines make for a relaxing ride, and the power palette is extremely convincing across the entire rev range. At the same time, fuel consumption remains at a pleasantly low level due to the small displacement.
Six-cylinder engine
The new six-cylinder engine, developed in 1991 to represent the latest generation of the Audi 100, is a very compact powerplant and seems to be designed for the typical Audi mounting along the front axle. Two overhead camshafts driven by toothed belts actuate the valves via poppet followers. The intake manifold is located in the space between the cylinder heads. The 2.8L version is equipped with a switchable intake manifold that changes the active length of the intake ports depending on the engine speed range. In this way, optimum engine torque is achieved in all speed ranges.
For the Audi A4, the six-cylinder engine was fitted with a new oil circulation system and a new, three-section crankcase. The oil circulation system is designed in such a way that the oil pressure is regulated after the oil filter and oil cooler.
Due to this, exactly the pressure that the control valve creates in the lubrication points is created.
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