Drive alternatives
Combustion engines are characterized by the fact that they convert chemically bound energy into kinetic energy. To do this, they require combustible and oxygen, although they do not carry the latter with them (as in a
rocket), but take it from the ambient air.
The liquid fuel also represents a uniquely compact accumulation of energy, which gives the combustion engine a unique selling point in this respect. The electric drive has no chance in the long term against this
accumulation of energy in the smallest space and with the lowest weight.
Basically, a distinction is made between petrol and diesel engines. Petrol engines rely on a particularly precise ratio of fuel to air, which should be optimized so that energy is used as best as possible and pollutant
emissions are minimized. Only the desire for a certain level of capability breaks this principle.
This is the case, for example, when overgreasing is necessary when spontaneous acceleration is required. Cold starts can also be demanding such a thing, with the guidance of the intake air and the addition of fuel
playing a special role.
The compression ratio between the largest and smallest possible combustion chamber in a gasoline engine also deserves special attention. Depending on the shape of the smallest possible combustion chamber, it
must not exceed a certain value, otherwise uncontrollable self-ignition can occur.
This value is irrelevant to the diesel engine as long as a certain total pressure is not exceeded, which would place an unacceptable load on its crankshaft drive. There is also no mixture ratio that must be strictly adhered to,
because it only takes air into the combustion chamber and compresses it to a high degree. The fuel is only injected under high pressure at the most favorable time for the mechanical process.
Self-ignition is typical for diesel engines because the compression alone generates a higher temperature than in a gasoline engine. The spark on the spark plug(s) is responsible for igniting the mixture. The flame then
spreads from there, which is referred to as a flame front through the entire combustion chamber.
The fuel injected into the diesel engine ignites along the entire jet, where it has already become gaseous, because it can only burn in this state. And it needs oxygen to do this, which is of course only available in sufficient
quantities at the edges of the jet. In the gasoline engine, fuel and air are already premixed.
In order to prevent combustion from being too intense, the jet in a diesel engine is always aimed at a surface where it then continues to burn up in layers. In the past, this was a chamber in front of the combustion chamber,
but today it is a very open space in the piston. The different processes make corresponding demands on the fuels; petrol boils at 30°C to 200°C, diesel at 200°C to 400°C.
Diesel is significantly heavier than petrol and therefore contains 13 percent more energy, which makes a major contribution to the diesel engine's said to be economy. But that's not the only reason it's so popular with taxi
companies, it's also because of its relatively lower sensitivity to cold starts.
This is where the electric drive comes into play again, which of course is not at all sensitive in this regard. In addition, all the energy available in the battery can be converted into movement, while with both combustion
engines a third of the energy cannot be converted into cooling or exhaust gases.
But that's not all. The fact that an electric car is significantly heavier also means that nothing is lost from the beginning to the end of the journey, whereas with a combustion engine all the available fuel virtually disappears
into thin air. In principle, all the fuel used in the car's life is irretrievably lost, while the battery can be dismantled into its components at the end.
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