Nearly more than half of the world, especially Eco Enthusiasts have a firm belief in the zero-carbon fantasy, and they believe that zero emission means total environment friendliness. That is the main reason electric cars are a hype nowadays. And the ever-increasing performance figures, like a 2 second 0-60mph time are making people like them more and more .So does that mean is it the end of Petrol and diesel power. Certainly not. The Internal Combustion Engine still has maybe half a century to live, because EVs are still plagued by a lot of problems such as range, price and charging station density etc. And that is why a lot of Automobile manufacturers worldwide are spending a lot of dollars to make Internal Combustion Engines workable in a possible electric era. So how are they going to do it. To know that you will have to read this article till the end (might change your view about cars):

Opposing piston design:

The opposing piston design is a revolutionary design, in which no energy is wasted to the cylinder head. Instead, the energy wasted to the cylinder head in other layouts is used in moving another piston at the top, resulting in thermal efficiencies approaching that of 50%. The major contender in this technology is ACHATES POWER, that is developing such engines for US Army Next Generation Combat Vehicles.

Kinetic Energy Recovery System:

When brakes are applied to wheels that are already spinning then a lot of energy is lost due to friction. This energy can be recovered in Hybrid Vehicles by motor acting as a generator unit when the gas pedal is lifted off. This also enhances breaking distance of the car. The energy is then stored in Flywheels or Batteries, and can later be used to drive the car. Thus, this system results in a very improved mpg.

Homogeneous Charge Compression Ignition (HCCI):

Spark ignition (HCSI )engines have a problem of low efficiency as they have compression ratios .Meanwhile Compression ignition (SCCI)engines have the problem of Nitrous pollutants and soot formation .This happens because diesel engines may start combustion before proper Air Fuel mixture forms .So to solve these problems ,HCCI engines have a port injection instead of direct injection .As in the spark ignition engines a proper Air Fuel mixture forms ,so does in HCCI because fuel is added too early ,and then the fuel is compression ignited .The problem is that there is nothing to control the timing of the engine and the engines have a very narrow operation range .These engines have good efficiency but still a problem of NOx (Nitrogen oxides) emissions exists.

Premixed Charge Compression Ignition (PCCI):

Now to solve the problems of HCCI engines, a combination of port injection and direct injection is used in PCCI engines. The fuel now is added in two stages. These engines have better efficiency than HCCI but still a problem of NOx emissions exist. The operation range for PCCI is also noticeably short. Though the timing problem is a bit resolved in these engines.

Reactivity Controlled Compression Ignition (RCCI):

Now to solve the problems of PCCI engines, a combination of a reactive fuel and diesel is now used in RCCI engines. The fuel now is still added in two stages. The reactive fuel is added by port injection and then diesel is added by direct injection. These engines have better efficiency than PCCI but still a problem of NOx emissions exist. The operation range for RCCI is long enough. But the use of two fuels at one time is not much possible.

Spark controlled Compression ignition (SCCI):

Thermal efficiency can also be increased by increasing the Compression Ratio .This leads to proper combustion of all the fuel that is present in the air fuel mixture thus generating more power out of lesser fuel .Mazda has pioneered such a technology in one of its engines nicknamed “Sky-Activ X” in which the compression ratio is so high that the air fuel mixture is heated to a level where it is just about to compression ignite, and at that level a small spark sets of a chain reaction of combustion of all the fuel molecules. Thus, increasing thermal efficiency and fuel efficiency too as now lesser fuel will be giving more power.

This engine in theory is an HCCI engine but here the timing of the ignition is controlled by a spark to cut the timing problem of HCCI engines

Mild Hybrid:

Even when the engine employs variable displacement ,and has very high compression ratio along with forced induction which essentially gives a very good efficiency .Engine is going to waste fuel during Idling .This is because the car is not running and still engine is revving in the range of 800-1500 rpm .Therefor a lot of fuel is being wasted during idling operation ,as no power is going to the wheels .This wastage of energy has been reduced by addition of a more powerful 48 volt starter motor and a separate 48 volt battery pack by some manufacturers at the rear of the car .So when the driver lifts foot of the gas pedal for a few seconds ,a computer unit senses this input and switches of the engine .But when the gas pedal is pressed again ,computer unit again senses it ,and then the 48 volt motor starts the engine rapidly again .This may theoretically seem to make the drive train turbulent but the now bigger motor makes the engine operation very smooth still.

Direct drive technology/Motor aided engine:

Koenigsegg first pioneered this technology a s a new type of hybrid, in one of their models called “Regera” ,in which there was no gearbox, and just a single torque converter /hydraulic coupling. The engine is directly connected to the wheels, which means that at speed below 30mph the engine will stall .Instead there is an electric motor that starts the engine ,and takes the drive train all the way to 1000 Revolutions per minute ,or 30mph .From then the engine takes over ,and accelerates the car further . This as such doesn't seem that good for the environment, but this means that first losses to the transmission are reduced and secondly in the future this gives manufacturers an opportunity to combine this technology with mild hybrid systems totally cutting emissions in the idle to 1000 rpm area of the engine. Such a technology also exists in many Honda cars, nicknamed “I-MMD”.

Cam less valves /Free Valve Technology:

This is a truly next generation technology, in which the valves are controlled by hydraulic or electric actuators and not by a camshaft thus allowing variable valve lift, valve timing, valve duration and displacement thus electronically controlling the intake in a far more advanced way than traditional VVTs and VTECs. The free valve technology liberates the valve timing from mechanical components. This results in Use of intake runner inertia at all RPMs,100% scavenging of residuals at all speeds and loads, increasing volumetric efficiency, Reducing or cutting knock even with high compression ratios. Besides that, individually controllable valves may allow fuel saving technologies like selective disabling of single cylinders. The ECU (Engine Control Unit) leaves all valves for only one cylinder open and keeps its fuel injector switched on, and this one cylinder only just runs on idle, as in a single cylinder engine. This also results in an enhanced engine brake mechanism. The ECU the exhaust valves closed for longer and the engine will supply more brake power.

Variable compression ratio Engines:

The pioneer in this design is Infiniti and Nissan which have designed the VC-Turbo engine. A VC-Turbo engine uses a multi-link system in place of a traditional connecting rod to rotate the crankshaft, and an actuator motor changes the multi-link system endpoint to vary the pistons’ reach to transform the compression ratio and  continuously varies piston top dead center (TDC) /bottom dead center (BDC) positions, allowing free control of the compression ratio.

HIGH EFFICIENCY HYBRID CYCLE (HEHC):

Liquid Piston's HEHC is a patented thermodynamic cycle that combines the advantages of Diesel, Otto and Atkinson thermodynamic cycles, resulting in up to 30% improved efficiency. Liquid Piston's rotary engines are the first disruption to engine technology in over a century. These engines are not Wankel engines; they are uniquely configured to adopt the company’s patented thermodynamic cycle and its associated efficiency and low-noise benefits. Liquid Piston's X Engine improves virtually all parameters – efficiency, weight, size, vibration, and noise. This results in an impressively high power to weight ratio. And the engine size is also considerably smaller. A similar cycle engine is pioneered by libralato .

Pre-Chamber Ignition:

This technology was mostly pioneered by formula 1. In which a separate chamber ignites the fuel at the top of cylinder head. Active Pre-chambers have a spark plug and fuel injector, and ignite after a lean air-fuel mixture is brought into the cylinder. When the spark plug ignites, the chamber spreads the flame over a wide area throughout the cylinder, making for an ultra-quick combustion cycle. This leads to complete combustion of all the fuel available and thus better fuel efficiency. Maserati MC20 is the first road car to feature this.

Tumble flow improvement:

Toyota has pioneered this engine technology with their dynamic force .In this engine very simple adjustments like increasing the angle between intake and exhaust valves from 31-41 degrees ,decreasing the bore from 90 to 87.5 ,redesigning intake valve area and employing variable electric systems to minimize heat loss have been employed .The tumble flow of intake air has been improved which ensures better mixing of air and fuel ,the piston has to now move a shorter distance which ensures faster combustion and the variable electric systems can switch off or lower their performance when not needed which regulates energy usage by onboard systems .All this means an efficiency of 40% or more

Plasma Ignition:

Another concept of improvement for ICE (Internal Combustion Engine) engines is the enhancement of ignition systems. A laser ignition system was first conceived which heated certain parts of the cylinder to trigger combustion, but it proved not to be suitable enough for high operating temperatures of IC (Integrated Circuit) engines. Another concept is plasma ignition, which promises to combust all the available fuel in the cylinder at relatively lower temperatures, thus promising extremely high efficiency and low heat loss to engine loss .

Hybrid Turbo:

This technology was also mostly pioneered by formula 1. The f1 power unit consists of two energy recovery systems. MGU-H or Magnetic Generation Unit-Heat, which is attached to a turbocharger and recovers energy from the exhaust gases and MGU-K or Magnetic Generation Unit-Kinetic, which is attached to the engine and recovers energy from braking. This results in recovery of a lot of energy that would have been otherwise wasted.

Entry Ignition:

As Homogeneous Charge Compression Ignition (HCCI) and Premixed Charge Compression Ignition (PCCI) have the problem of relatively low range of operation with knocking at high RPM , Ignition timing and production of various pollutants. Reactivity Controlled Compression Ignition (RCCI) has the problem of running at two fuels at the same time, which is not quite possible in real life. To Solve these problems another theoretical design was started, which is called entry ignition. In this design all the cylinders have different bore and stroke sizes and this engine is essentially a two-stroke engine. Let us consider a four-cylinder layout of this engine. The first cylinder will be a high bore cylinder ,which will only serve to compress the air .The compression ratio of this cylinder is very low .The air then goes into a second cylinder which also serves to only compress the air but at a higher compression ratio .Now before going into a third cylinder ,the air is port injected with fuel .This is done so to let a proper air fuel mixture form .Then the third cylinder has a slider valve in place of a traditional valve .This slider valve opens to let the air enter a very hot third cylinder .This cylinder is kept hot by the exhaust valve closing early so that some exhaust gas ,which is now very hot ,to stay trapped inside .Due to this very hot temperature ,the air fuel mixture ignites upon entry .After this power stroke ,the exhaust gases then travel to a fourth cylinder ,where they are allowed to expand once more to get better efficiency . Now it is a two stroke engine ,because the 2nd and 3rd Cylinders are synchronized ,with the power stroke of 3rd cylinder resulting in the intake stroke of the second .Now the two stage compression ,two stage expansion and the lean air fuel mixture result in a very high efficiency and remove all the problems with HCCI,PCCI and RCCI .But this is still a theoretical concept and there are many things yet to sort out like balancing the engine as all cylinders are not of the same sizes, and the problem of keeping the 3rd cylinder intact even after taking too much heat.

This engine has a theoretical efficiency of 63% as compared to 49% of Otto cycle. The real-world numbers will certainly be lesser.

Hydrogen Internal Combustion Engine:

Toyota is currently researching an Internal Combustion Engine that will run on hydrogen rather than fossil fuels .Hydrogen will combust in the cylinders instead of petrol or diesel .Reason behind this innovation is that hydrogen fuel cell vehicles are quite complexed to build, and the demand for such vehicles is even lesser than that of EVs (Electric Vehicle) because in the end Hydrogen Fuel Cell Vehicles are in the end a complexed version of EVs that uses a hydrogen cylinder and Fuel Cells in place of batteries .That is why Toyota now wants to test Hydrogen as a fuel for petrol powered cars .This way Toyota will probably create a new type of zero emissions vehicle, which may not be as efficient as an EV (Electric Vehicle), but would be even greener than them .There are even more benefits as it won't be plagued by the problems which EVs have, because Hydrogen can be filled into cars with slight modification of current petrol filling technology as Hydrogen will be filled in liquid form .This won’t mean a total change of infrastructure .Large amounts of resources won't have to be wasted in developing charging station networks .And a further benefit would be that due to similarities with existing engine technology ,existing cars could be modified to use hydrogen fuel .This concept is way greener, because EV concept can render all petrol-powered vehicles a burden on environment as existing vehicles can't be that easily modified to make them battery electric .This concept wont also be plagued by range issues .