Piston And Cylinder Bore, Checking

Pistons, Checking

Fig 1: Checking Piston Bore

Courtesy of AUDI OF AMERICA, LLC

-- Measure approximately 15 mm from the lower edge at a 90° angle to the piston pin axis using a 75 to 100 mm external micrometer.

Piston Diameter in mm
Specified size	82.42 ¹⁾
¹⁾ Measurement without coating (thickness = 0.02 mm). The coating wears off.

Cylinder Bore, Checking

Fig 2: Checking Cylinder Bore (Dimensions)

Courtesy of AUDI OF AMERICA, LLC

Special tools and workshop equipment required

The cylinder bore must not be measured when the cylinder block is mounted on the engine and transmission holder because the measurements may be incorrect.

CAUTION:

Risk of damaging the cylinder bore surface through incorrect handling.

- Never handle the cylinder bore with service equipment (drilling, honing, grinding).

-- Using the Cylinder Dial Bore Gauge: VAS6078 , measure in a diagonal sequence at three positions transversely -A- and longitudinally -B-.

Cylinder Bore Diameter in mm
Specified size	82.51 ¹⁾
¹⁾ measure 50 mm inside the cylinder bore.

Piston Ring Gap, Checking

Fig 3: Checking Piston Ring Gap

Courtesy of AUDI OF AMERICA, LLC

-- Push the piston ring squarely from above down to approximately 15 mm from the edge of the cylinder. To push in use a piston without rings.

Piston Ring	New mm	Wear Limit mm
1. Compression ring	0.30 to 0.40	0.80
2. Compression ring	0.40 to 0.50	0.80
Two-piece oil scraping ring	0.20 to 0.40	0.80
Three-piece oil scraping ring	cannot be measured

Piston Ring Groove Clearance, Checking

Fig 4: Checking Piston Ring Groove Clearance

Courtesy of AUDI OF AMERICA, LLC

-- Clean the piston ring groove before checking.

Piston Ring in Connection with the Two-Piece Oil Scraping Ring	New mm	Wear Limit mm
1. Compression ring	0.06 to 0.09	0.20
2. Compression ring	0.03 to 0.06	0.15
Oil scraping rings	cannot be measured