How engines have evolved.
"The main developments in the history of the automotive engine."
The array of available automotive engines continues to grow, we shall look at the main types of engines looking at how they have evolved over time.
Petrol engines are the most popular fuel type followed closely by Diesel engines. Then we have the more unusual power sources including Propane, Gas (LPG and hydrogen), Fuel cell and electric cars as well as hybrids, where 2 or more fuel types coexist.
As manufacturers drive to meet ever more stringent fuel economy figures they add technological advances to the engine increasing efficiency.
Development of automotive engines
These work by compressing the intake charge in a cylinder and then using a spark to ignite this, forcing the piston down the cylinder and this turns the crank. Suck, Squish Bang Blow are the 4 phases of a petrol engine. Fuel is sucked in along with oxygen containing air, this mixture is compressed and then ignited when ready to reverse the direction of the piston.
The piston based engine is one of the oldest technologies around and has served us well. Developments include the addition of forced induction *(turbo charging and supercharging), direct injection of fuel into the cylinders and various combustion chamber angles.
Generally speaking the more cylinders you have the smoother the engine will be. V and W configuration engines work quite well but many purists prefer an inline engine.
The downside of inline engines is that they are longer than a V or W configuration. We have seen some interesting 5 cylinder designs, but 4 dominates the worldwide car market with anything from 2 to 24 cylinders or more being offered.
Diesel engines work by compressing the fuel to the point it ignites so there is no spark.Other than this they work in a very similar way to petrol engines. Fuel can be warmed up before injecting to maximize the burn and speed of the flame front.
The boxer engines are very low and flat, the cylinders are mounted horizontally and the pistons do not have to work against gravity. You could argue that this only applies in one direction and gravity helps on the down stroke and this is a mute point anyway.
Boxer engines are useful as they provide a very low center of gravity and allow a lower mounting of the engine in a car. They make a lovely sound as well due to the way the air and exhaust flows around the engine bay.
Direct injection on petrols avoid the problem of premature ignition as fuel is only available at the last possible moment. Increases in fuel pressure and injectors have allowed this development, and it permits a car maker to run greater boost and higher compression ratios releasing more power and better economy.
Diesels have benefited greatly from direct injection and turbocharging transforming them from noisy slow units into the refined torque monsters we see today. We are pleased to see some of these developments making it's way into petrol engines.
Mazda have pioneered the rotary engine in the form of the Wankel and Renesis units. The lemon shaped piston rotates around the centre of the combustion chamber so the intake, compression, bang and exhaust phases of the engine cycle happen in different areas as the piston rotates.
This allows an engine to rev to very high levels as it rotates in one direction and we see very high power figures extracted from relatively small capacity engines. These engines tend to be quite fuel heavy and are rather torque shy at the lower end, but considering the really wide power band this should not be a limitation.
Hydrogen works well in rotary engines as the hot exhaust port area is the last the fuel charge comes into contact with during the rotation phase.
All electric cars are making an appearance, the main problem with these is battery lifespan, storing enough energy and recharging times. As battery technologies improve, this will make electric cars an appealing proposition.
Most popular manufacturers are introducing part electric drive systems and kinetic energy recovery systems that kick in under braking. This reduces the use of the combustion engine and allows a car to achieve very low emissions levels and high economy figures.
Fuel types such as LPG are gaining popularity, and most engines can be converted to run on these. In the case of a diesel LPG is injected along with Diesel. Petrol engines can be converted easily though and may run almost exclusively on LPG except for most converted cars needing petrol for the warm up phase.
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