Piston And Cylinder Bore, Checking

Special tools and workshop equipment required 

• Outside Micrometer - 75-100mm :VAS 6071 
  Fig 1: Outside Micrometer - 75-100mm

  Courtesy of AUDI OF AMERICA, LLC
• Internal Dial Gauge :VAS 6078  , not illustrated

-- Measure approximately 10 mm from the lower edge at a 90° angle to the piston pin axis using Outside Micrometer - 75-100mm :VAS 6071  .

• 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.

-- Using the Cylinder Dial Bore Gauge :VAS 6078  , 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.

-- 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

-- 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