Pistons

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Pistons

The operational safety and durability of a repaired engine depends primarily on the used pistons and the mechanic's quality of work. When repairing the engine, all the necessary conditions must be created to ensure the high quality of the KS Kolbenschmidt pistons can become fully effective.

For this reason, installation of KS Kolbenschmidt pistons during engine repair work already starts with preparation or reconditioning of the engine to be repaired.

All original KS Kolbenschmidt pistons are supplied ready to install together with the relevant piston rings, piston pins and pin retainers.

Piston designs

Kolbenschmidt is an OE supplier and supplies parts to all well-known engine manufacturers – all over the world. For every engine type the most suitable alloy is selected from the KS Kolbenschmidt alloy range, and the most effective piston design is employed.

Motorservice always supplies pistons complete with piston rings, piston pins and the associated piston pin circlips.

Diesel piston with cooling channel, bolt bush and ring carrier

Articulated piston with forged upper steel section and aluminium skirt

Gasoline engine piston in weight-optimised LiteKS® design with ring carrier

Pistons in different forms

Cast-in ring carriers of cast iron increase the durability of the first ring groove of diesel pistons many times over. Kolbenschmidt is a leader in the development of Alfin ring-carrier bonding.

Hard-anodised ring grooves prevent wear and micro welding in pistons for petrol engines

Laser-hardened grooves ensure optimum wear resistance and maximum durability for steel pistons

KS Kolbenschmidt pistons feature special LofriKS®, NanofriKS® or graphite coatings on the piston skirt. These reduce friction inside the engine and ensure good emergency running properties. LofriKS® coatings are also employed for acoustic reasons. Their use minimises piston slap noises. NanofriKS® is a further development of the tried and tested LofriKS® coating, and additionally contains nanoparticles of titanium oxide, to increase the coating’s wear resistance and durability.

Iron-coated piston skirts (Ferrocoat®) guarantee reliable operation when used in aluminium silicon cylinder surfaces (Alusil®).

Specially shaped piston pin bores (Hi-SpeKS®) raise the dynamic load capacity of the piston pin bed, thereby increasing the piston’s durability.

Technical names and names on the piston

1 Ø bowl
2 Piston crown
3 Combustion chamber (bowl)
4 Piston crown edge
5 Piston top land
6 Compression ring groove
7 Ring land
8 Groove base
9 Recessed ring land
10 Groove sides
11 Oil scraper ring groove
12 Oil return bore
13 Piston pin boss
14 Retention for groove distance
15 Groove for retainer ring
16 Piston boss distance
17 Piston boss distance
18 Stepped edge
19 Piston diameter 90 °C against the piston pin bore
20 Piston pin bore
21 Bowl depth
22 Skirt
23 Ring zone
24 Piston compression height
25 Piston length
26 Oil cooler duct
27 Ring carrier
28 Bolt bush
29 Ø measuring window
30 Crown camber

Gap Dimension and Top Dead Centre

Gap dimension

The gap dimension (B) is the protrusion or recess of the piston in the top dead centre in relation to the sealing face of the cylinder block. The thickness of the cylinder head gasket and a possible recess in the cylinder head are taken into account for measuring. This dimension is also known as “lead dimension”.

Piston protrusion or piston recess dimension in top dead centre for different engine versions

Below the dimension C, the protrusion (marked by + ) or the recess (marked by - ) of the piston in the top dead centre is to be understood in relation to the cylinder block sealing face. The seal thickness or geometrical shapes of the cylinder head are not taken into account.

For engines with wet cylinder liner, the protrusion or recess of the piston is also measured in relation to the cylinder block face. A protrusion of the cylinder liner or an existing land edge is not taken into account.

For air-cooled cylinders, dimension C refers to the distance between piston crown and the seat of the cylinder head on the air cooled cylinder. 

For setting the piston protrusion, pistons with reduced compression height are
also available in addition to the standard pistons.

For pistons the crown for setting the piston protrusion must not be turned off.