Technical characteristics of the valve timing mechanism (Audi 80 B2)

Table of contents: Camshaft ↓ Valve timing* ↓ Toothed belt ↓

The engine uses a valve timing mechanism with an overhead camshaft, the drive of which is carried out by a toothed belt from a toothed pulley of the crankshaft. The belt tension is adjusted mechanically by turning the water pump housing. The toothed pulleys of the crankshaft and camshaft are mounted on segment keys.

Camshaft

The camshaft is three-bearing. The rear end of the shaft is drilled for the ignition distributor drive, and there are bosses between the cams of the 2nd and 3rd cylinders. The camshaft is marked with the letter FZ.

Camshaft journal diameter, mm:

front: 31.45;
average: 39.45;
back: 40,45.

Axial displacement of the camshaft, no more than, mm: 0.15.

Maximum radial runout of the middle journal of the shaft, no more than, mm: 0.01.

Valve timing*

Start of opening of the intake valve before TDC of the intake stroke with advance: 7°.
Intake valve closing after BDC of compression stroke with delay: 42°.
Start of opening of the exhaust valve before BDC of the working stroke with advance: 51°.
Closing of the exhaust valve after TDC of the intake stroke with a delay of 4°.

*With a calculated zero clearance between the camshaft cams and levers and with a valve lift of 1 mm.

When the valve timing is set correctly, the mark on the crankshaft pulley should be aligned with the pointer on the cylinder block, and the mark on the camshaft toothed pulley should be aligned with the installation plate on the cylinder head.