Pistons
Pistons are cast from aluminum alloy. Depending on the engine model, the piston crowns may be flat or convex.
Pistons make: Mahle, Karl Schmidt (KS) or Nueral Alcan.
Piston diameter
Piston diameters are measured at a distance «A» from a skirt.
Gap between piston and cylinder, mm: 0.045.
Piston marking
On the bottom of the pistons, the mark of the piston group by mass is stamped: «+» or «—».
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.
Displacement of the axis of the hole for the piston pin in the piston bosses, mm: 1.0.
Piston pin outer diameter, mm:
- with white label: 22-0-0.003;
- with black mark: 22-0.003-0.006.
Piston pin hole diameter, mm: 22+0.0040.
Gap between piston pin and piston, nm:
- for Mahle and Nueral-Akan pistons: 0.001-0.005;
- for KS brand pistons: 0.002-0.006.
Clearance between the piston pin and the bushing of the upper head of the connecting rod, mm:
- for fingers with a white mark: 0.005-0.013
- for fingers with a black mark: 0.008-0.016.
Piston rings
Piston ring specifications
* The numerator is for Mahle and Nueral-Akan pistons, the denominator is for KS pistons.
Spare parts are supplied with piston rings with the following repair dimensions: +0.10; +0.25; +0.50.
Connecting rods
I-section connecting rod - steel, forged, with replaceable trimetallic liners. A cap of the lower head of a connecting rod of direct section. The characteristics of the connecting rods of engines of all models are the same.
Connecting rod length, mm: 135±0.1.
Hole diameter, mm:
- the lower head of the connecting rod: 52 + 0.15;
- the upper head of the connecting rod: 24 + 0.21.
Diameter of the bushing of the upper head of the connecting rod, mm:
- outer: 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.
The maximum allowable buckling of the connecting rod: 0°30.
Weight difference between connecting rods, g, not more than: 4.
Gap between liners and connecting rod journals, mm: 0.023-0.078.
Connecting rod bearing shells
Nominal thickness of liners, mm: 1.983-1.993.
Repair dimensions 1st: 2.108-2.118; 2nd: 2.233-2.243; 3rd: 2.358-2.368.
Crankshaft
Crankshaft - steel, forged, five-bearing (the middle main bearing is wider than the other main bearings). The design of the crankshafts of engine models «315», «316», «318», «318i» And «320», «320i» different.
Main bearing housing diameter, mm:
- for crankshaft with red index: 60+0.0100;
- for crankshaft with blue index: 60+0.010+0.019.
Characteristics of crankshafts
* The numerator indicates the values for the crankshaft with a red index, and the denominator - with blue.
Permissible unbalance of a dynamically balanced crankshaft without a flywheel, gf cm, not more than: 50.
Axial clearance of the crankshaft, mm: 0.085-0.174.
Permissible runout of the middle main neck when supported on the extreme main necks, mm, not more than: 0.1.
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.
Before pressing the toothed rim of the flywheel, it is necessary to heat it up to a temperature of 200-230°C, then install it, directing the ends of the teeth from the engagement side to the engine, and press it in until it stops. It is recommended to check the temperature of the rim with a thermochromic pencil.
The flywheel is statically balanced, the allowable imbalance should be no more than 15 g cm.
Flywheel runout, mm, no more:
- when measured at a point on a diameter of 92 mm: 0.03;
- when measured at a point on a diameter of 100 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 disc, mm, not less than: 14.5; 13.5 (For «320i»).