Pistons And Cylinder Bore, Checking

WARNING: This page is about a different car, the 2015 Audi Q7, 2014 Audi Q7, and 2013 Audi Q7. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Checking Piston Deviation

Courtesy of AUDI OF AMERICA, LLC

-- Measure approximately 10 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 the specified dimension: 0.05 mm.

Matching pistons are allocated to the different dimensions of the cylinder block.

Piston Diameter mm
Specified dimension	82.924 and 82.936 ¹⁾
Repair stage	82.964 to 82.976 ¹⁾
¹⁾ Measurement without coating (thickness = 0.02 mm). The coating wears off partially.

Fig 2: Checking Cylinder Bores

Courtesy of AUDI OF AMERICA, LLC

-- Using the Cylinder Dial Bore GaugeVAS6078 measure in a diagonal sequence at three positions transversely -A- and longitudinally -B-.

Maximum deviation from the specified dimension: 0.08 mm.

Cylinder Bore Diameter in mm
Specified dimension	83.006 and 83.014 ¹⁾
Repair stage	83.046 to 83.054 ¹⁾
¹⁾ measure 50 mm inside the cylinder bore.

Fig 3: Checking Piston Ring Gap

Courtesy of AUDI OF AMERICA, LLC

-- Push the piston ring squarely from above down to approximately 50 mm from the bottom end of the cylinder.

-- To do this use a piston without piston rings.

Piston Ring	New mm	Wear Limit mm
1st Compression ring	0.25 to 0.40	0.60
2nd Compression ring	0.70 to 0.90	1.20
Oil Scraping Ring	0.25 to 0.50	0.70

Fig 4: Checking Piston Ring Groove Clearance

Courtesy of AUDI OF AMERICA, LLC

-- Clean the piston ring groove before checking.

Piston Ring	New mm	Wear Limit mm
1st Compression ring	0.09 to 0.130	0.160
2nd Compression ring	0.05 to 0.09	0.11
Oil Scraping Ring	0.03 to 0.07	0.10