Engine Features

4-Cylinder Engine Cutaway
1 – camshaft;
2 – hydraulic lifters;
3 – tensioner roller;
4 – piston;
5 – timing belt;
6 – intermediate shaft;
7 – crankshaft pulley;
8 – coolant pump;
9 – cylinder head cover;
10 – spark plug, fourth cylinder;
11 – ignition distributor;
12 – connecting rod;
13 – oil pump.

Originally designed for the Audi 80, this engine is also used in the Audi 100 and in Volkswagen models Golf, Jetta and Passat. Its most important design features: a 4-cylinder engine with overhead camshaft. The valves are actuated by hydraulic bucket tappets. The intermediate shaft drives the oil pump and the ignition distributor. The camshaft and intermediate shaft are driven by a toothed belt.

5-Cylinder Engine Cutaway
1 – piston;
2 – valve;
3 – hydraulic lifters;
4 – camshaft timing belt sprocket;
5 – camshaft;
6 – cylinder head;
7 – engine block;
8 – oil pan;
9 – crankshaft;
10 – oil pump inlet tube;
11 – oil pump;
12 – crankshaft timing belt sprocket;
13 – crankshaft pulley with vibration damper.

The main design features of the 4-cylinder engine also apply to the 5-cylinder engine, introduced for the first time in 1976 on the Audi 100. Two common features are sufficient to mention: this engine also uses a toothed belt to drive the camshaft and coolant pump, and it uses hydraulic bucket tappets to actuate the valves.

The crankshaft design of the 5-cylinder engine is particularly interesting: the crankpins are offset by 72° relative to each other, and each cylinder has two counterweights on the shaft. Furthermore, the specially designed flywheel imbalance and the damper at its front end serve to absorb torsional vibrations.

6-Cylinder Engine Cutaway
1 – intake manifold;
2 – ignition coil pack;
3 – toothed belt;
4 – poly-V belt;
5 – crankshaft pulley with damper;
6 – oil pump
7 – oil pump inlet tube;
8 – crankshaft;
9 – connecting rod;
10 – piston;
11 – hydraulic lifters;
12 – valve;
13 – camshaft;

Redesigned for the fourth generation Audi 100 in 1991, the 6-cylinder V-engine is a very compact unit, specifically designed for longitudinal installation. Two overhead camshafts, driven by toothed belts, operate the valves via hydraulic bucket tappets. The exhaust manifold is located in the space between the cylinder heads.

The 2.8-liter version is equipped with a variable-length intake manifold, which changes the effective length of the intake passages depending on engine speed. In this way, optimal engine torque is achieved across all speed ranges. The distributorless ignition system should also be mentioned; it is described in more detail in the Ignition System chapter.