Why does a hot start work better than a cold start?


Also, does this apply to all engines? Are there some that can be started better when they are cold?

In: 2

Depends how hot and how cold. Generally engines are designed to run best with a certain range of temperatures that they would normally see when operating in normal conditions. Metals expand and contract with heat, oils and fuels and batteries operate differently at different temperatures.

For very cold starts batteries put out less power, oil is significantly thicker, compression in the engine is quite low.

Hot starts are much less of a problem because the engine is supposed to run while it’s hot, and nowhere in the world does the weather get hotter than an engine at operating temp. In extreme hot temps batteries can become damaged and fueling can be imprecise, but still less of a problem than extreme cold starts

The fuel vapor in an ICE will condense on the cold cylinder walls of the engine, leaving the mixture too lean to burn properly (which is why a choke enriches the mixture to compensate). This isn’t an issue when warm. If the fuel injection/carburetor is set up properly, it shouldn’t be that hard to start under either condition unless they are extreme.