BT03.10-W-0002-01A | Piston and piston rings changed | |
ENGINES 924.9## ## as of 810731,
926.9## ## as of 811140
W03.20-1202-79
A Previous version piston and piston ring
1 Piston
2 Piston pin bushing
3 Compression ring (double trapezoidal ring)
4 Oil wiper ring (bevel-edged ring with garter spring)
5 Coil spring
B Modified version piston and piston ring
1 Piston
3 Compression ring (double trapezoidal ring)
4 Oil wiper ring (bevel-edged ring with garter spring)
5 Coil spring
6 Drain hole
The piston (1), compression ring rings (3) and oil control ring (4) have modified within the scope of technical advancement.
The following modifications have been made to the piston (1).
Use of different piston material with better alloy. This has eliminated the piston pin bushing (2) and reduce the weight of the piston (1) by 97 to 1193 g.
Optimized piston tolerance (1) in cylinder bore. This reduces the carbon deposits on the piston land (1) and cylinder bore land.
-----------------------------------------------------------------------------------------
The 2nd piston ring groove has been moved upward on the piston (1).
The height of the 3rd piston ring groove for the oil control ring (4) has been increased from 3 mm to 4 mm on the
piston (1).
In addition four drain holes (6) have been added around the circumference of the 3rd piston ring groove. This allows the engine oil to return more quickly from the 3rd piston ring groove reducing carbon deposits.
-----------------------------------------------------------------------------------------
The following obligations have been made to the compression ring (3) installed in the 1st piston ring groove on the piston (1).
The new piston compression ring (3) is a double trapezoidal ring chambered on the one side with sharp-edged bottom. The coating on the running surface of the new piston compression ring (3) has also been modified. This achieves a better oil wiping effect in the cylinder bore.
-----------------------------------------------------------------------------------------
The following modifications have been made to the oil control ring (4) installed in the 3rd piston ring groove on the piston (1).
On the oil control ring (4) the height has been changed from 3 mm to 4 mm.
The diameter of the holes in the piston oil control ring (4) for return of the engine oil has been increased from 1.0 mm to 1.2 mm; the number of holes is the same.
The diameter of the tubular spring (5) in the oil control ring (4) has been increased from 1.95 mm to 2.35 mm.
The coating on the running surface of the new oil control ring (4) has been modified from a chrome layer to a chrome-ceramic coating.
The initial piston ring tension been increased to achieve a better engine oil wiping effect