INN Engine: What is it? How does it work? Advantages, parts…

INNengine It is an engine designed and developed by Spaniards, which is called to go one step further in the capacities obtained to date with combustion engines.

It is a combination of technologies, which give it the and advantages of the two stroke engines, four times and even make it comparable to electric motors in some factors. Hence, it is showing a greater potential than what we are used to in terms of performance, efficiency y emissions.

What is the INN Engine?

In this opposed piston engine of the Granada company INNengine SL. Therefore, its operation is very similar to that usual in two-stroke engines, but without the typical inconvenience of excess emissions. This is because it does not need to mix oil with fuel to lubricate itself. What led to the almost disappearance of two-stroke engines with the tightening of regulations.

Furthermore, the INNEngine is an engine without crankshaft because it transforms the longitudinal movement of the pistons in circular by means of cam plates and a few followers. As you will see in the section on Advantages, this allows it to be much simpler and with a compact cylindrical shape.

This engine complete the cycle in one time or, what is the same, in just 180º of rotation of the motor. Hence, there is some controversy as to whether to call it two times or directly one. Moreover, according to its creators, if a larger model were built, the cycle could be completed in 60º of rotation of the motor or even in only 45º. It would be a matter of having cam discs with more elevations and valleys, which would achieve few revolutions and enormous torque.

How Does It Work?

To understand how this engine works, you have to know what each of the technologies that make it up:

opposing pistons

Instead of having a single piston for each combustion chamber, the INN Engine has one for each side of the camera. So that two pistons are displaced with a single detonation made out of fuel. In total, the current version is made up of four combustion chambers arranged horizontally and two pistons in each, for a total of eight pistons.

It is a design that it has been used in heavy military machinery for many decades. However, despite its great efficiency and low emissions, it has not been used in the automotive sector due to its larger size, having two crankshafts, two pistons per cylinder with their corresponding connecting rods and other components in duplicate.

However, in the INNEngine the problems of space and costs are reduced for its clever design. Instead of having the cylinders in line, as they usually are in opposed piston engines, this engine has them placed horizontally and forming a square. Hence, it can have a much more compact cylindrical shape.

Cam plates or sine plates

Having this cylindrical shape, the passage of the linear movement of the pistons to the circular one it cannot be done by the typical crankshaft. For this reason, it has two cam plates at the ends, which are nothing more than discs with elevations and valleys that the pistons will use to force them to rotate. In the following video you can see how it works in a clear and simple way:

As you can see, the pistons they push the plate by some followers when the slope that passes through it already tends to go down. In addition, each plate has two elevations placed diametrically opposite each other. So diametrically opposite pistons in the block will push them at the same time.

As it is an opposed piston engine, on the other side of the engine the same process is carried out on the other cam plate. Therefore, whenever there is a push, It is applied by four pistons at the same time. Two on one side and two on the other. What, as you will see in the Advantages section, gives it a perfect balance. In addition, with this system the pressure against the plates that makes the engine turn is divided between four points and friction that would cause wear is minimized.

Those in charge of you the pistons go back into the cylinders are other smaller cam plates. Discs with opposite elevations and valleys, which are part of the same piece as the other cam plates.

Variable compression ratio and timing

The INN Engine has variable distribution to regulate when air is allowed to enter the combustion chambers and for how long it is kept open. Thus, it can adapt to the needs inherent to each speed and load regime.

Su compression ratio is also variable, to achieve maximum efficiency both at high and low loads. That is, when a lot of air and fuel mixture is put into the combustion chambers and when little is put into it.

To understand this, you have to know that the optimal compression ratio is high when you put a little mixture into the combustion chamber and low when you put a lot. In the following video you can see what this technology consists of, even if it is in a conventional four-stroke engine:

Apart from this, its distribution generally works as follows: always open the exhaust before the intake for spontaneous escape to occur. Exhaust closes before intake, unlike in traditional engines, to avoid losses through the exhaust port and to take advantage of the inertia of the gas stream.

intake and exhaust ports

As it is an opposed piston engine, the intake and exhaust are not carried out through valves, the camshafts that open them and other synchronizations. It works like a two-stroke engine in the sense that it is the pistons that cover and uncover the ports where the air-fuel mixture enters (intake) and the gases leave (exhaust).

Where it doesn't work like a two-stroke engine is regarding lubrication, which does not require mixing with the fuel with the consequent increase in emissions. In this section runs like a four stroke engine, so the pistons have lubrication and compression rings.

As described by those responsible for INNEngine SL, the compression rings exceed the intake and exhaust ports, but the oil rings never do. In addition, the piston heads do not rub against the cylinder walls, but the bodies do, which are the ones that are specially lubricated.

Advantages of the INN Engine

Compact and light, how much does it weigh?

By using cam plates and followers, crankshafts, connecting rods and other components needed to turn them are eliminated. In this way, the engine is much smaller and lighter than a four-stroke. This also contributes to the fact that the pairs of pistons are placed in a square and horizontal position, giving the block a very compact cylindrical shape.

The next version of this engine will weigh just 35kg even though it will retain the 500cc displacement. Which is an extremely low weight compared to current engines.

Simple

Being an opposed piston engine, does not have valves, camshafts and timing elements necessary for them. This is due to the fact that the intake and exhaust are carried out through their corresponding ports, which are covered or uncovered by the pistons themselves (just like in a conventional two-stroke engine).

low emissions

As we have mentioned before, it works like a two-stroke engine in terms of the use of ports, but its lubrication is like that of one of four times (less emissions). That is, it has lubrication segments equal to those of the latter type of engine. In addition, the fact that it is with opposed pistons, allows a very good combustion thanks to the effects Swirl y Tumble. That is, the mixture moves in the form of a whirlpool inside the cylinder. Therefore, it is very good choice for range extender for electric cars.

As you can see in the following image, the motor INNengine could also be used in the future with Liquefied petroleum gas (LPG) or LPG in English. A fuel that would further reduce its level of emissions.

High performance, how much power does it have?

According to its designers, the INNEngine can give Twice the thrust of a two-stroke and four times that of a four-stroke. At the beginning of 2020 they were already achieving 155 Nm with a 500 cc engine from 800 rpm. To which it contributes greatly that for each revolution of the engine two complete cycles have already been completed.

INNEngine SL is not yet at the appropriate stage of development to give definitive figures for power, consumption or emissions. However, they did anticipate that with the 0.5-liter displacement they could achieve a performance similar to that of a 2.0-liter engine.

very good balance

Due to its operation and configuration, their masses are always balanced. So it has no vibrations and its noise is minimal. Which will allow a very high comfort for the user, whether it is used as the main engine or as a generator of a Range Extender system (Range Extender). The regularity of its thrust is similar to that of a V8 engine.

Efficient

According to its creators, INNEngine will be able to achieve very high levels of efficiency, precisely by the combination of technologies that brings together. Especially due to the architecture of opposed pistons, the variable compression and distribution ratio and its low weight.

In addition, as the compression and expansion phases take place in half the time, it has the advantage that the gases have less time to heat the cylinder walls and to lose airtightness through the compression segments. So that uses energy very well.

INN Engine Parts

The INNEngine engine has a very particular architecture, although uses proprietary parts from two-stroke and four-stroke engines. Below we present its main parts so that you better understand how it works:

• horizontal cylindrical block which houses the combustion chambers arranged in a square
• pistons with compression and lubrication rings as in a four-stroke engine.
• followers: they are the training wheels that are supported against the cam plates to transform the linear movement into a circular one
• cam plates: discs with mountains and valleys that receive the movement of the pistons to rotate
• indirect injection. Although in the future they want it to work by direct injection.
• refrigeration system: refrigeration surrounds the entire block. It enters at the bottom and exits at the top. Those responsible for the INNEngine engine maintain that they achieve a temperature jump of between 1 and 2 degrees between the input and output. Since more heat tends to be generated near the exhaust than the intake, the flow rates are not the same at both ends of the engine.
• lubrication system: The lubrication system is very separate from the cooling system. The block is a cylinder, so there is no cylinder head or head gasket, so there cannot be communication between oil and antifreeze by the engine.
• turbo: Although they currently work with a very low compression level: 1,15 or 1,2 bar.

Applications that INNEngine will have

Although theoretically it could be used for almost any function, the INNEngine is being targeted mainly towards two applications: on the one hand, a 500 cc version is being developed that will work as generator to extend the autonomy of electric or hybrid cars. On the other a smaller version of 125 cc for model airplanes or karts.

According to its creators, its use as a generator of a Range Extender system is the one in which the company INNEngine SL is becoming more involved. For which it would not have to work at levels as demanding as in an engine that moves the car. Currently they are being asked for 40 hp at 2.500 rpm.

Today, within the Technology Readiness Levels scale (TRLS) or Technological Maturity Levels, are between level 4 and 5. That is to say, they are about to move on to tests outside the laboratory.

The future of the INNEngine engine

According to Juan Garrido Requena, the main person responsible for the design of the engine, they are also working on the application of the external combustion to complement your INNEngine engine (internal combustion). Although it would work with any propellant type.

An external combustion engine is the one that converts the heat energy, obtained in a combustion external to it, into mechanical energy. For example, a steam engine. In this way, the heat of the INN Engine could be used to generate more energy, instead of simply dissipating it as has been traditionally done.

As Garrido described it in an interview on Juan Francisco Calero's YouTube channel: with this they would achieve "that each engine has its own small combined cycle thermal power plant". Therefore, the use of energy would be much greater than that obtained to date.