Piston And Cylinder Bore, Checking

WARNING: This page is about a different car, the 2023 Audi Q8. However, it is still accessible from the selected car via links, so may be relevant.

Special tools and workshop equipment required

Outside Micrometer - 75-100mm:VAS6071

Fig 1: Outside Micrometer - 75-100mm
Courtesy of AUDI
Internal Dial Gauge:VAS6078 , not illustrated

Pistons, Checking

Fig 2: Checking Piston Bore

Courtesy of AUDI

-- Measure approximately 10 mm from the lower edge at a 90° angle to the piston pin axis using Outside Micrometer - 75-100mm:VAS6071 .

Maximum variance from the specified size: 0.017 mm.

Piston Diameter in mm
	2.9L	3.0L
Specified size	84.47 ¹⁾	84.45 ¹⁾
¹⁾ Measurement with coating (thickness = 0.018 mm). The coating wears off.

Cylinder Bore, Measuring

Fig 3: Checking Cylinder Bore (Dimensions)

Courtesy of AUDI

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

Maximum variance from the specified size: 0.08 mm.

Cylinder Bore Diameter in mm
Specified size	84.510 ± 0.005 ¹⁾
¹⁾ measure 50 mm inside the cylinder bore.

Piston Ring Gap, Measuring

Fig 4: Checking Piston Ring Gap

Courtesy of AUDI

-- At a right angle to the cylinder wall, push the piston ring from above down into the lower cylinder opening until it is approximately 15 mm from the edge of the cylinder.

-- Use a piston without a piston ring for pushing it in.

2.9L Engine

Piston Ring	New mm	Wear Limit mm
1. Compression ring	0.20 to 0.35	0.45
2. Compression ring	0.50 to 0.70	0.80
3-part oil scraping ring	cannot be measured

3.0L Engine

Piston Ring	New mm	Wear Limit mm
1. Compression ring	0.15 to 0.25	0.35
2. Compression ring	0.30 to 0.45	0.55
3-part oil scraping ring	cannot be measured

Piston Ring Height Clearance, Measuring

Fig 5: Checking Piston Ring Groove Clearance

Courtesy of AUDI

-- Clean the piston ring groove before checking.

2.9L Engine

Piston Ring	New mm	Wear Limit mm
1. Compression ring	0.03 to 0.07	0.15
2. Compression ring	0.015 to 0.060	0.15
3-part oil scraping ring	cannot be measured

3.0L Engine

Piston Ring	New mm	Wear Limit mm
1. Compression ring	0.03 to 0.08	0.15
2. Compression ring	0.02 to 0.07	0.15
3 - Part oil scraping ring	cannot be measured