Piston And Cylinder Bore, Checking

WARNING: This page is about a different car, the 2022 Audi Q8, 2021 Audi Q8, 2020 Audi Q8, and 2019 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
Internal Dial Gauge: VAS6078

Pistons, Checking

Fig 1: Checking Piston Bore

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 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 2: Checking Cylinder Bore (Dimensions)

Courtesy of AUDI OF AMERICA, LLC

-- 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 3: Checking Piston Ring Gap

Courtesy of AUDI OF AMERICA, LLC

-- 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 4: Checking Piston Ring Groove Clearance

Courtesy of AUDI OF AMERICA, LLC

-- 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