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What is a Carter?

Meaning of Carter

An intrinsic component of an internal combustion engine, the crankcase is a perforated metal frame that houses various parts, most notably the crankshaft. Its primary universal function is to protect the crankshaft and connecting rods from debris.

In simple two-stroke engines, the crankcase serves several functions and is used as a pressurization chamber for the fuel-air mixture. In more complex four-stroke designs, the pistons seal it off from this mixture, instead working primarily to store and circulate the oil. In a four-stroke engine, it sits below the cylinder block, and in both types it comprises the largest physical cavity in the engine.

The crankcase is a perforated metal frame that houses various parts, most notably the crankshaft.

Most modern crankcases are made from aluminium, providing a lightweight yet strong design capable of withstanding the pressures exerted during normal engine use.

In normally aspirated four-stroke engines, that is, engines that do not feature a turbocharger, a small level of pressure in the casing is desirable to keep out dust and other potentially damaging particles, while keeping the oil properly located.

All engines, as part of their normal operation, allow a small amount of unburned fuel and exhaust gases to escape into the crankcase. This collective material is known as blowing.

Clean oil is crucial for a crankcase.

A positive crankcase ventilation valve, or PCV valve, is usually employed as part of an overall pressure control system, to regulate the amount of exhaust expelled from the crankcase. Passing through the PCV valve, the expelled exhaust is returned through the system, back to a part known as the intake manifold, where it is reused in the combustion process.

This design was adopted in part out of legislative impetus, because earlier designs were not enclosed and allowed exhaust to escape directly from the engine, causing significant environmental damage.

PCV systems are not used on two-stroke engines, since all of the exhaust is burned in the normal flow of air and fuel.

Proper care of the crankcase and its internal components is essential to the proper functioning of an engine. Maintaining an adequate amount of clean oil is crucial, and can be measured by using a simple tool known as a dipstick, a simple length of metal that visibly shows the oil level.

While checking it regularly will show how much oil is present, unburnt fuel that builds up in the crankcase can negatively affect the lubrication quality of the oil, so regular oil changes are vital.

Also, an engine with an improper break-in or one with dry, cracked piston seals can allow too much gas to escape from the pistons into the crankcase, creating dangerously high pressure levels that can cause engine damage and failure.

Early symptoms of seal failure include oil leaking from the PCV valve or past the dipstick.

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