Air-cooled vs water-cooled engines

Nearly all modern production cars have water cooled engines nowadays, however, there was a time when air cooled cars held their own. Cars like the VW Beetle, Porsche 911 and the Fiat 500, all used air cooled engines. There were some advantages to an air-cooled system but ultimately the efficiency and reliability of water-cooled systems won out.

A water-cooled engine has coolant pumped around it’s cooling channels by a water pump to keep the engine cool. An air-cooled engine uses cooling fins and serious oil cooling to accomplish the same thing, keeping the engine ‘at temperature’.

How does an engine stay cool?

An engine creates a lot of heat when it’s running. Constant combustion, high revs, moving parts, high loads and stress – all need to be kept at bay. If they aren’t, the engine will warp and become inoperable.

This is where your cooling system comes in. A water/coolant cooled engine has a radiator and fan to cool the coolant, a waterpump to force the coolant through the engine block and cylinder head via machined coolant passages. This means that the heat created is carried away by the coolant. Providing a cool running engine.

A liquid cooled engine requires a lot of gaskets, which can fail and leak, to stop coolant mixing with oil, combustion or air. It also incurs the weight of the coolant and the accessories to move the coolant.

Despite this, a water cooled engine is more reliable. It can sit in traffic and under large load, all while keeping the engine at 90° there or thereabouts.

So how did air-cooling work?

Air-cooling was more radical. Instead of using coolant to carry heat away it used air and oil.

By flowing air around the cylinder head and block, past fins to help heat dissipation, it kept the engine cool. At normal speeds this worked a treat. A very large oil cooler helped keep internal engine block temperatures down. Heat easily escaping from around the top of the engine into the air that was blown or sucked by.

The chief issue is that this all works very well when the car is moving and air is flowing. The engine and oil stay nice and cool when that’s happening.

But what about when the car is sitting in traffic on a hot day? Well, your car could easily overheat. Overheating leads to a host of expensive issues that makes liquid-cooling very attractive.

Because of this, air-cooling lost out. It couldn’t provide the same properties, consistency and range of operation that water cooling could. Not to mention transmission cooling and oil cooling being equally available to a liquid cooled engine.

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