Pistons And Cylinder Bore, Checking

WARNING: This page is about a different car, the 2018 Audi S6, 2017 Audi S6, and 2016 Audi S6. However, it is still accessible from the selected car via links, so may be relevant.

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.

Maximum deviation from nominal dimension: 0.03 mm.

Matching Pistons Are Allocated To The Different Manufacturing Stages Of The Cylinder Block.

Piston Diameter in mm
Engine Codes	CEUC/CEUD/CTGE	CRDB/CUWB/CUWC
Specified size	84.470 ¹⁾	84.490 ¹⁾
Repair stage	84.580 ¹⁾	84.590 ¹⁾
¹⁾ Measurement with coating (thickness = 0.018 mm). The coating wears off.

Courtesy of AUDI OF AMERICA, LLC

-- Using the :VAS6078 measure in a diagonal sequence at three positions transversely -A- and longitudinally -B-.

Maximum deviation from nominal dimension: 0.08 mm.

Cylinder Bore Diameter In mm
Nominal Dimension	84.510 ± 0.005 ¹⁾
Repair Stage	84.610 ± 0.005 ¹⁾
¹⁾ Measure 50 mm inside the cylinder bore.

Courtesy of AUDI OF AMERICA, LLC

-- Push the piston ring squarely from above down to approximately 15 mm from the bottom end of the cylinder.

-- Use A Piston Without A Piston Ring For Sliding In.

Piston Ring	New mm	Wear limit mm
1st Compression ring	0.20 to 0.35	0.80
2nd Compression ring	0.20 to 0.40	0.80
Oil scraping ring	0.20 to 0.40	0.80

Courtesy of AUDI OF AMERICA, LLC

-- Clean The Piston Ring Groove Before Checking.

Piston Ring	New mm	Wear limit mm
1st Compression ring	0.035 to 0.085	0.200
2nd Compression ring	0.005 to 0.045	0.150
Oil scraping ring	0.020 to 0.055	0.200