Piston And Cylinder Bore, Checking

Special tools and workshop equipment required 

• Outside Micrometer - 75-100mm: VAS6071 
  Fig 1: Outside Micrometer - 75-100mm

  Courtesy of AUDI OF AMERICA, LLC
• Internal Dial Gauge: VAS6078  , not illustrated

Pistons, Checking 

-- 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 

-- 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 

-- 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 

-- 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