Pistons
Pistons are cast from aluminum alloy. Depending on the vehicle model, the piston crowns may be flat (on «323i») or convex with a height of 2.1 mm (on «320i»).
Pistons brand: Mahle or Karl Schmidt (KS).
The engine type is marked on the piston crown (2.0 or 2.3), compression ratio (9.2 or 9.5), piston diameter class, piston mass group («+» or «-»). The arrow on the bottom of the piston shows how to correctly orient the piston when it is installed in the cylinder.
Piston diameter, mm:
- normal: 79.98±0.009;
- intermediate size: 80.06±0.009;
- 1st repair size (increased by 0.25): 80,23±0,009;
- 2nd repair size (increased by 0.50): 80,48±0,009.
Gap between piston and cylinder, mm: 0.035—0.040.
Difference in mass of pistons in assembly, g, not more than: 10.
Piston pin hole diameter, mm: 22+0.0040
Displacement of the axis of the hole for the piston pin in the piston bosses (For «320»), mm: 0.7.
Piston pins
The piston pin is made of steel, polished. The pin rotates freely in the upper head of the connecting rod and in the piston bosses. From axial displacement, it is held by retaining rings.
Piston pin outer diameter, mm: 22-0.0040
Gap between piston pin and piston, mm:
- for Mahle brand pistons: 0.001-0.005;
- for KS brand pistons: 0.002-0.006.
Piston rings
Three grooves are machined on the outer surface of the piston for the installation of rings. Rings are set with the label TOP («Top») to the bottom of the cylinder. The top compression ring is made of nodular cast iron with a chrome outer surface. Oil scraper ring with spacer spring.
Piston ring specifications
* The numerator is for Mahle pistons, the denominator is for KS pistons.
Connecting rods
Connecting rod - steel, forged, with replaceable trimetallic liners.
The distance between the axes of the holes of the connecting rod heads, mm: 130±0.1.
Hole diameter, mm:
- bottom end of connecting rod: 48+0.01+0
- connecting rod head: 24+0.021+0
Diameter of the bushing of the upper head of the connecting rod, mm:
- external: 24.060-24.100;
- inner: 22+0.010+0.005
Misalignment of the holes of the connecting rod heads when measured at a distance of 150 mm from the rod of the connecting rod, mm, not more than: 0.04.
Maximum allowable buckling of connecting rod: 0°30'.
Weight difference between connecting rods, g, no more: +4.
Connecting rod bearing shells
Conrod bearing shells are thin-walled, trimetallic grades Glyco or KS.
Characteristics of connecting rod bearing shells
Crankshaft
The crankshaft is cast steel. The shaft is semi-supported, with 12 counterweights and trimetallic main bearings. Engines can be fitted with a crankshaft with a red or blue index.
Characteristics of the crankshaft
* The numerator indicates the values for the crankshaft with a red index, the denominator - with a blue one.
Permissible unbalance of the crankshaft, gf cm, no more than: 25.
Axial clearance of the crankshaft, mm: 0.080-0.163.
Permissible runout of the middle main neck when supported on the extreme main necks, mm, no more than: 0.15.
Inserts of radical bearings of a cranked shaft
The main bearing shells are trimetallic, with radial holes for the passage of oil.
Characteristics of the main bearing shells
* The numerator indicates the values for the crankshaft with a red index, the denominator - with a blue one.
Flywheel
The flywheel is mounted on the crankshaft on the flange and fastened with eight bolts, and due to the presence of a centering pin, the flywheel can only be installed in one position.
The flywheel is dynamically balanced, the allowable imbalance should be no more than 15 gf cm.
Flywheel runout when measured at a point at a diameter of 90 mm for vehicles with a manual transmission and at a diameter of 93 mm for vehicles with an automatic transmission, mm, no more than: 0.02.
Flywheel runout when measured at a point on a diameter of 233 mm, mm: 0.1.
The maximum thickness of the metal layer removed when grinding the flywheel surface under the clutch disc, mm: 0.4 + 0.1.
Flywheel surface thickness for clutch driven disk, mm, not less: 13.5.
Vibration damper
Pulley diameter, mm: 146.
Unbalance at crankshaft speed of 1000 rpm, gf cm, not more than: 8.
Radial runout when measured at a point on a diameter of 200 mm (For «320») and on a diameter of 235 mm (For «323i»), mm, not more than: 0.2.
Axial runout when measured at a point on a diameter of 200 mm (For «320») and on a diameter of 235 mm (For «323i»), mm, not more than: 0.3.