Cylinder liners with replaceable fire ring

In combustion engines operating under heavy loads, manufacturers use cylinder liners with a fire ring.

This ring is located at the top of the sleeve and is sealed directly by the cylinder head gasket. The pressing force of the head fixes and fixes the ring in the correct position. The innovative solution is that the internal diameter of the fire ring is slightly smaller (approximately 0.5 mm) than the cylinder liner bore. The piston cooperating with this type of sleeve has a reduced crown diameter - the area of the piston above the sealing ring contacting the fire ring.

Hazards: carbon deposits in the piston crown

The combustion process is always accompanied by high temperatures, which favor the decomposition of hydrocarbons, which leads to the formation of carbon deposits in the form of carbon deposits. A small amount of carbon deposit is not harmful, but efforts should be made to limit its amount whenever possible and to remove it from the combustion chamber in the event of excessive carbon formation. Large amounts of carbon deposits contribute to shortening the operating time of the sleeve as a result of intensive abrasive wear of the sleeve, and may lead to the piston rings sticking and loss of tightness of the piston-cylinder system. The use of a fire ring and a piston with a reduced crown diameter allows carbon deposits to be "scraped" and removed along with the exhaust gases, which reduces the intensity of wear of the piston-cylinder system.

The formation of an increased amount of carbon deposits is facilitated by operating the engine in unfavorable or difficult operating conditions, such as:

• using the car for short distances and parking the vehicle in traffic jams,
• low quality fuel • insufficient cooling,
• failure to comply with service intervals,
• long periods of engine idling.

Repair technology

1. Destructive method of disassembly
   The destructive method of dismantling the fire ring is a very common solution in the following cases: when installing a new piston-cylinder assembly equipped with a new fire ring, there is a limited amount of time to carry out the repair, or the fire ring is damaged and cannot be reused. To loosen the fire ring, you can use a chisel (chisel) between the fire ring and the sleeve. Once the fire ring is dismantled, the remaining parts can be disassembled in the usual way.
2. Non-destructive disassembly method
   If the cylinder liner and fire ring are to be reused, disassembly requires much more effort. First, rotate the crankshaft to bring the piston to bottom dead center. Then place the used piston ring with a diameter matching the cylinder liner diameter below the fire ring. To prevent the piston ring from slipping out from under the fire ring, after sliding them together, remove the play in the piston ring lock. A metal wedge or feeler gauge can be used for this purpose. If the cylinder liner is not to be dismantled, it should be secured against sliding out of the block using a pressure device. By turning the crankshaft, the piston moves towards top dead center, exerts pressure around the entire circumference of the fire ring and squeezes it out of the liner, thus becoming a tool for its disassembly.

More information about the Mahle brand range is available at Autos branches throughout the country. Please contact your branch.