Natural aspirated engine Vs turbo engine

In today’s article we will talk about a very popular engine, the first type of internal combustion engine ever produced, the one that started it all.

We will talk about the naturally aspirated engine. You may think that the naturally aspirated internal combustion engine does not offer you very good performance and that it is a very simple one but you are wrong, because there are naturally aspirated 2.0 litre engines that develop over 200 hp.

Also the reliability of naturally aspirated engines is very high and very well known. But first of all we have to start with the beginning, namely a short isotric to see when an internal combustion engine first appeared.

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Internal combustion engine

The internal combustion engine is the “device” that converts the chemical energy of a fuel into mechanical energy through controlled combustion.

More precisely, the heat released in the combustion chamber is transformed by means of pressure into cyclic, rectilinear motion, after which into uniform rotational motion, obtained at the crankshaft. The fuel (gasoline, diesel or liquefied petroleum gas) mixed with air is called fuel.

Combustion can be initiated either by putting the fuel in direct contact with a heat source (an electric spark plug) or even just by simple compression (in the case of diesel engines) where the mixture ignites thanks to compression.

When the fuel burns in the combustion chamber, the temperature reaches somewhere above 2000 degrees. After combustion, very hot gases result which are eliminated in the exhaust gallery (then in the catalyst, in the drums and finally in the atmosphere).

How we classify engines

Now that we have specified some essential and basic things, we can move on to more serious and much more interesting things. Nowadays, if you look on the street, our cars are equipped with internal combustion engines that can be classified according to many criteria. We can catalog them either by the fuel used, or by the number of pistons, or by their positioning or by the way the air enters the combustion chamber.

We are interested in how cars can be classified according to the way the air is allowed in the combustion chamber. They are naturally aspirated engines (which we will talk about mostly today), turbo, with compressor or those that have “double induction” that is, they also have turbo and compressor.

Which is the best? Well, here we can’t really answer concretely because it varies according to needs. Even the biggest producers can’t answer this question “which is better?” because a century after the appearance of the first internal combustion engines, big developers have not decided yet, naturally aspirated engines and turbo engines are manufactured, so we can not answer this question at the moment, but each engine has its advantages and disadvantages.

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Engine aspirated vs turbo engine

We will start with a small comparison between the naturally aspirated engine and a turbo engine to better see the differences. For starters we need to know that the naturally aspirated engine is much more reliable than the turbo one.

The naturally aspirated engine will always be more reliable than a turbo one because first and foremost there are fewer moving parts (we no longer have a turbine or compressor, we no longer have so many solenoid valves and sensors, we no longer have an intercooler and other parts that could give way in time).

Also, the components of a naturally aspirated engine are subjected to much lower voltages than those of a turbo engine (in a turbo engine, the temperature and pressures inside the engine are much higher than in an aspirated one).

Unfortunately, in the last 10 years, due to pollution and commercial reasons, no longer as long-lived engines have been manufactured as they used to be, i.e. the most reliable engines are aspirated V8s or aspirated diesels that simply seem immortal.

I mean, have you ever seen the latest generation turbo engines that exceed 1 million kilometers, or at least reach 1 million kilometers? Not much, there are many new generation engines that from 100,000 kilometers start to have quite big and expensive problems and at a maximum of 250,000 kilometers start to fail or simply need to be changed altogether

Engines are no longer manufactured as in the past, engines from Chevrolet, Mercedes-Benz, Ford or those of the VAG group that were immortal. In the case of a diesel engine, without turbo it is very “stinky” and they do not develop a big amount horsepower or too much torque (develops a reasonable torque but not impressive), but in the case of this type of engine even with turbo they are very reliable (if properly maintained and operated).

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However, you should know that a naturally aspirated diesel engine, even if it is not as powerful, is by far the most reliable engine ever built. Such an engine can easily exceed 1 million kilometers.

For example, I talked to several mechanics and engineers and they told me that they have seen aspirated diesel cars that had done 1.5 million kilometers , they sounded and worked flawlessly.

They also saw turbo-diesel cars of slightly older generation (1995-2003) that made weekly trips abroad and had 2.2 million kilometers and only then began to show signs of little wear on the camshaft, so think about what 2.2 means. 2 millions of kilometers and the engine only needs oil and filters, what more do you want..?

There are also famous, naturally aspirated diesel engines that have reached 2.5 million kilometers and still work quite well and do not require major repairs.

If we say that it is worth choosing a turbo diesel, especially due to the fact that the reliability is not much lower (here we are talking about the slightly newer generation engines, because the ones just released now are questionable because they have been a bit disappointing lately ).

Naturally aspirated diesel engines are still found but only the old generation, all new diesel engines are equipped with turbo. If in the case of a diesel engine you can choose only one turbo, then you should know that in the case of gasoline you can choose between naturally aspirated and turbo (yes, naturally aspirated engines are still manufactured).

Even if most car manufacturers no longer sell naturally aspirated engines, but only supercharged (turbo or turbocharged) there are also “mass” manufacturers that produce compact and sub-compact cars that also give you the option to choose a naturally aspirated engine.

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First of all, the advantage of a naturally aspirated engine is the lower maintenance cost, because it has fewer moving parts, but also due to the fact that the turbine is missing, in the long run you will spend less money on maintenance.

A naturally aspirated engine will never consume oil like a turbo will but there are also naturally aspirated engines that consume a lot of oil, but not all, in those cases there were some design errors (as in the case of the 1.6 engine. ).

You also don’t have to be as careful with an aspirated engine as you are with a turbo (you don’t have to wait for the turbine to heat up or cool down). Long-term reliability is on the side of the naturally aspirated engine and not on the turbo side.

For the aspirated engine you only have to change the oil and filters, sometimes you also need to change the spark plugs and for the rest petrol and many kilometers, while for the turbo engine you have to be careful how you operate the turbine because it can fail at the worst moment possible. and repairing it is not cheap at all.

What would be the advantages of a turbo engine? Well, we have more power, which has on average 25-40% more power than an engine of the same cylinder capacity but without turbo.

How so? Well, if you want to have a 300 hp engine, you have two options, or you buy a naturally aspirated V8 or a 2.0 turbo. Also a turbo engine will produce in certain conditions and better consumption.

Because you have a smaller capacity, but more power, you can usually drive in the city without forcing the engine, so you will have a decent consumption. And on the long road, the turbine gives you much more power from low revs, so you won’t have to turn the engine so hard to overtake.

Overall, if a turbo engine is not forced, it will consume less than a naturally aspirated one.

As disadvantages we have like this, a turbo engine will always have a more expensive maintenance and a lower long-term reliability. The naturally aspirated engine will have a lower power than the turbo, higher taxes in relation to the power and a higher consumption for the same capacity (here in some cases it is debatable depending on the driver and the mode of operation).

We better choose a naturally aspirated engine for much lower maintenance costs, but also for the fact that you can get behind the wheel, start the engine, wait 30 seconds and you can leave without waiting for the engine to warm up.

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For example, in a turbo engine, if you accelerate with the engine cold or suddenly stop the car with the engine hot, then you will drastically reduce the life of the turbine.

Our opinion is that you better opt for a smaller engine (less than 2000 cc), for lower taxes, for the resistance in the infernal agglomeration of our cities and because it is not as demanding as a turbo one.

If we drive mainly outside the city then it is better to opt for a turbo engine, it will consume less and the extra power will help us if we have to overcome a shot in just a few seconds.

It all depends on the driver’s preferences, how far it goes, where it goes and how If you are someone who is not in a hurry, scared by service visits and who cares about the last penny, then opt for an aspirated engine.

If you are a driver who steps on it, then probably you will opt for a turbo engine.

If we were to make a list of the most reliable engines, it would look something like this: In the first place would be the famous 1.9 D engine from Vw, a naturally aspirated diesel engine, which simply seems to be immortal since it was exploited in very harsh conditions and still resists brilliantly.

Most of today’s engines have at least 700,000-800,000 kilometers, rarely we find some that have 500,000 kilometers, and even though it has so many kilometers it can still be considered “ young “

Although it has only 65-68 hp, they do their job very well on almost any car on which they were mounted and also make amazing small consumption.

In the next place would be another aspirated diesel, namely the 2.0 D engine manufactured by Mercedes-Benz, which develops only 55 hp. Engine mounted on Mercedes W123 also called “Cobra”. The Mercedes engines of the time were designed to be able to reach 1 million kilometers easily without too much intervention, whether they were on gasoline or diesel, they were very well designed and very reliable in the long run.

But this naturally aspirated 2-liter engine, which develops only 55 hp, has remained in automotive history as the most reliable engine ever designed, although with very poor performance it withstands any conditions.

It is always said about this engine that it did not know much, except one and good, to work until there is nothing left of the rest of the car, which is very true because the body gives way (due to rust) but the engine still works perfectly.

Other reliable engines would be: the 2.0 SDI engine from Vw that develops 68 hp and was mounted on newer cars (golf 5 and caddy). It is called SDI because it does not have a turbine, it is naturally aspirated, the power being between 68 or 75 hp, but the performance was not the main goal but to consume little and to be reliable.

The 2.0 petrol engine from Honda (k20) that develops 221 hp. Honda has made a lot of reliable engines, But what is special about Honda is the fact that it knows how to make naturally aspirated engines very powerful and very reliable.

We will talk about this shortly. The case of the engine shown, for example, has 4 pistons and a capacity of 2 liters, but it can produce somewhere from 160 hp to 221 hp in the best performance.

This engine was installed on the Civic Type-R, after which it was improved for the Honda S2000 where it produced approximately 240 hp. BMW’s engines are also very reliable, for example the 2.5 petrol engine has stood out for its reliability.

This M50B25 engine, which develops 192 hp, has been mounted on several models in the BMW range and copes brilliantly with heavier bodies such as the 5 Series or 7 Series.

In fact, almost all petrol engines from BMW are reliable, they are very successful 6-cylinder engines.

The naturally aspirated 4.2 V8 engine with 40 valves from Audi has become known not only for its power but also for its long-term reliability. It equips cars such as the Audi A8 or A6 and it has also been mounted on the S8, S6 and S4.

The reliability of this engine is very extraordinary, i.e. it is a flawless engine. Returning to Honda and the 3.2-liter engine (C32A) that develops 235 hp and equips Japanese limousines is a true legend, unfortunately it is no longer sold in Europe, only in America.

This engine has shown a very good long-term reliability considering that it was mounted on cars with fairly large and heavy bodies (it was mostly mounted on limousines).

This was our little top with the most reliable naturally aspirated engines, both on gasoline and diesel. Now let’s move on to more interesting things.

Even if they are not equipped with a turbine or a supercharger, they are suction motors that develop quite a lot of power. For example, Honda engines that are equipped with a VTEC system.

Although this variable distribution system will seem quite complicated, if it works and is maintained properly, it will work wonders and give you a unique driving sensation. For starters we need to know that a classic (i.e. fixed) timing system is designed to ensure stable engine operation at low revs, lower fuel consumption and decent power.

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It is the middle way, to have a low consumption, a stable operation and a decent power. Camshafts have a “geometry” (ie when and how long to open each valve), and this geometry is fixed in the case of this distribution system (classic distribution), which achieves a compromise between stability and low consumption at low-medium speeds. and power at high speeds.

Explaining this process is quite tricky , so I will try to explain as simply as I can.

The lift height of the valves greatly influences the “volumetric efficiency” of the engine.

The volumetric efficiency represents the ratio between the volume of air entering the engine and the available geometric volume, the engine displacement. The higher the volumetric efficiency, the higher the power developed by the engine, because it receives enough air for combustion.

For naturally aspirated engines, the higher the speed, the lower this efficiency. Due to the inertia of the air and the flow section (given the height of the valves) at high speeds it cannot suck in enough air, so the engine will run “suffocated or choked”.

But this problem can be solved with the help of a camshaft with a special geometry for high speeds that will increase the lifting height of the intake valve. Basically this is what the VTEC system comes from and this acronym for VTEC from “Variable Valve Timing and Lift Electric Control” designed by Honda.

This system uses cams with different profiles, a cam with a lower profile intended for normal use at low and medium speeds and a second cam with a more aggressive profile for high speeds (over 4000 rpm). You may have heard of the phrase “enter the VTEC”, well yes, that’s where it comes from, after 4000 rpm the aggressive cam starts up and the engine develops much more power than usual.

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The VTEC system consists in the introduction of an additional cam (both for intake and exhaust) with a special profile for high speeds. The cam with an aggressive profile is put into operation at the control of the injection computer depending on the operating point of the engine.

The operation on the entire speed range is as follows: when the engine is running at low and medium speeds, the valves are operated by low profile cams through the rocker arms. The cam with an aggressive profile also acts on the rockers, only moving in a vacuum (independent of the rest of the system, waiting for it to start working and do its job).

When the engine reaches high speeds, the injection computer controls an electro-hydraulic valve that supplies oil under pressure inside the rockers in which there is a semi-bolt.

Under the action of the oil, it moves inside the rocker arm and pushes the fixing bolt that moves inside the rocker arm to the right. This procedure joins three rockers that will be operated by the cam with aggressive profile and thus the geometry of the distribution is modified.

When the return is made, the injection computer commands the oil to drain and the return piston will push the semi-bolt into the rocker arm and the large bolt. It seems complicated when it is explained in this way, but if you see with your own eyes how everything works then it would not seem so complicated.

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Although it is a bit more complicated than a simple naturally aspirated engine, this system has many advantages and if it is properly maintained (oil changed on time and always quality oil) then there will be no problems.

Also this variable distribution system extends the maximum engine speed up to 8000-9000 rpm. Due to the use of the high profile cam, the intake valves rise more and allow the engine to better suck air at high speeds so it will not be limited to 6500-7000 rpm.

The extension of the engine speed range allowed to obtain higher maximum powers, the Honda aspirated VTEC engines having a liter power of over 100 hp / litre. The first engine of this type (equipped with VTEC variable distribution) equipped the Honda Integra RSI in 1989.

This engine had a maximum power of 160 hp at 7600 rpm, from a cylinder capacity of only 1.6 liters. Another reference car is the 1998 Honda S2000, which with a 2.0-liter VTEC engine produced 250 hp at 8300 rpm, but also had a top speed of around 9000 rpm.

A naturally aspirated engine that is equipped with variable distribution of this type will take out for example from 2 litres somewhere at 220-250 hp, while if we look at a Vw engine, 2 L (let’s take as an example the 2 L TFSI engine which equips the GTI Golfs) which, thanks to the turbine, produces just over 200 hp

The advantages of a naturally aspirated engine are reliability and consumption,they have the disadvantage that it is limited to higher power increases, always keeping in mind that not all naturally aspirated engines are lazy or need very large cylinder capacity to develop some power.

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BMW has a similar system, called VANOS, which can be found on the intake side or can be on both sides and then is called Double-Vanos.

Next we will talk about the new SkyActive engine. You may have recently heard that Mazda has launched a revolutionary engine, which is very similar to the VTEC but is much more special and more powerful.

Mazda started this project in 2008 and proposed to improve as much as possible all engine components that have a great impact on performance and consumption. Speaking from a physical and chemical point of view, in a normal internal combustion engine, approximately 70-80% of the energy resulting from combustion is available, the rest are losses that are no longer used.

Here Mazda engineers had a bright idea, namely to combine a diesel engine (which consumes little, has more torque but is stinky without a turbo) and a gasoline engine (which has power but has no torque and consumption is higher). They have increased the compression ratio so as to improve the combustion process.

Skyactive-G is the Mazda program that optimizes the gasoline engine. The compression ratio is the one that improves the thermal efficiency of the engine. Normal gasoline engines have a compression ratio of 10: 1 to 12: 1. If the compression ratio is increased from 10: 1 to 15: 1, the thermal efficiency of the engine will be higher by about 10%.

Depending on the technology used for the injection system and the distribution system, current gasoline engines reach values of compression ratio around 10.0: 1 or 11.0: 1. Ferrari 458 Italia has a gasoline engine with a compression ratio of 12.5: 1, but uses only premium fuel with an octane number of 98 or 100.

But once the compression is increased, the torque losses will also increase (ie you will get power but not torque, not a good thing because torque is very necessary). Also the detonations will intensify and for this reason the compression ratio is limited.

Detonation is the process by which the fuel (air-gasoline mixture) ignites and burns very quickly and very aggressively. This phenomenon occurs largely due to very high temperature and pressure.

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To combat the risk of detonation, the temperature in the cylinder at the end of the compression stroke must be reduced. Waste gases left over from combustion cannot be completely discharged every time and have an extremely high impact on the temperature in the cylinders.

Let’s take a more concrete example, if we have a gasoline engine, with a compression ratio of 10: 1, if the exhaust gas temperature is 750 ° C and the intake air temperature is 25 ° C, if 10% of the gases burns remain in the cylinder, after evacuation, the temperature of the air-fuel mixture in the cylinder will increase by 70 ° C before compression and by 160 ° C at the end of the compression stroke.

In more technical terms and to understand exactly what I am trying to explain. At this rate the percentage of residual flue gas in the cylinder can be reduced from 8% to 4% the temperature at the end of the compression stroke (PMI) has the same value as if we increase the compression ratio from 11: 1 to 14: 1. This is exactly the process on which the development of the Skyactive-G engine is based, reducing the percentage of waste gases to allow operation without detonations.

For this, they also designed a gallery and a special exhaust system, which collects the exhaust gases from 2 cylinders each and then joins them. That’s about the principle of the Skyactive-G engine.

But at the beginning before I started talking about the Skyactive-G project, I said that Mazda thought of combining a petrol engine with a diesel one, but I didn’t say anything about it, because this is the Skyactive-X project. This project is the most innovative and in my opinion it is something unique and represents the future of internal combustion engines.

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According to the major Japanese carmaker, the Skyactive-X engine is the first commercial gasoline engine with a spark-controlled compression ignition system, being the first production engine of its kind in the world. This technology produces more power, less emissions and uses less fuel than a normal engine to deliver much higher performance without having to compromise.

The acronym SPCCI comes from Ignition by spark controlled control. SPCCI practically combines the fuel efficiency of a diesel engine and the behavior and power of a gasoline engine. The engine switches between conventional spark ignition and a compression ignition mode where the mixture will be poorer and thanks to compression will burn even more efficiently.

As advantages we can say that this gasoline engine is very powerful, has a fairly high maximum speed but at the same time consumes the same as a diesel engine. Specifically, this engine can change its compression (variable compression).

This engine has 2 rows of compression connecting rods, from the compression of a normal gasoline engine to a slightly higher compression than a diesel engine, this is the secret of this engine. In this combination the engine is very efficient and combines the advantages of the other 2 classic engines. These engines are mainly naturally aspirated, but as it was too much for the Japanese to stop here, they thought of supercharging this engine. So they will appear soon, if supercharged engines such as Skyactive-X have not already appeared.

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Many drivers have asked if they should drive differently so as not to damage the engine. The answer to this question is that no, the car can be driven anyway because mainly the engine will run on compression ignition mode and when you need all the power then it switches to spark ignition and will provide maximum power.

My opinion is that this will be the future of engines, but I have a little reluctance on long-term reliability because this engine is a bit complex, although it does not have a turbo it is still a bit complicated inside and there are many things that can start to go wrong if they are not properly maintained. But still the invention is a very good one and as long as everything works correctly the engine has only advantages compared to a normal one.

To conclude we will discuss a little about a famous engine, which has gone down in history, namely about the Wankel engine or as it is also called “rotary engine”. Here are many questions I will try to answer briefly but comprehensively. The first and most asked is the following: How can an engine run without cylinders and produce a lot of power? As in the case of the Skyactive- X and G engine, the Wankel engine was and is a discovery or an innovation that marked the automotive history.

If we were still talking about history, it would be good to start with the beginning and find out where all this madness started. This engine was invented by Dr. Felix Wankel and dates back to before 1900 but was never put into production. It seems that the first to create and patent such an engine was Felix Millet, in 1888, who made a 5-cylinder rotary engine that spun a bicycle wheel.

His invention was put on a car in 1900 by Darracq. But this engine was more for airplanes.

Because it has no pistons, the Wankel engine is also called a piston-free rotary engine. Starting with the 60’s, the strong development of the engine created by Wankel began, but even so, only Mazda managed to successfully modify the initial design and integrate it into the brand identity, being the only brand that put the engine on cars. series.

How does this “pistonless” engine work? Well, this engine is an internal combustion engine that uses the same principles to convert pressure into rotational motion as piston engines. But without vibrations and mechanical stress at high rotations. The development of this engine has an interesting story.

Dr. Wankel began to create the engine as follows: an outer gear was fixed to a white sheet. This was followed by the integration of another larger gear with teeth on the inside, with a ratio of two wheels of 2: 3.

The next step was to attach an arm with a pencil to the outside of the large wheel. When the small wheel rotated, the pencil drew an oval with irregular sides on the sheet (inside the engine block). This is how the Wankel engine was invented, which equipped the Rx-8 model. Although it is different, this engine also does all 4 strokes as one with a normal piston, only the times are made by the central rotor.

Both the classic engine and the Wankel engine work according to the same principles, the differences being in the transformation of the movement into mechanical force. In the Wankel engine the combustion chamber is rotating, the pressure is applied to one side of the rotor. The rotor is triangular and the inside of the oval block is divided into 3 parts, ie 3 operating chambers. That is, each engine time takes place in another part of the block, only one will be repeated, while in the classic engine all times take place in the same place, in the cylinder.

What would be the advantages of a Wankel engine? Well, first and foremost, the size is smaller and implicitly the weight. This is very important in creating a light car with a powerful engine.

The weight distribution will also be much better and the dynamics of the car improved. Another interesting detail is the range of the engine torque which is constant regardless of speed.

A rotary engine with 2 rotors produces a torque similar to that of a classic V6 engine, and one with 3 rotors produces the torque of a V8 engine.

But this engine also has its disadvantages, for example the first would be high fuel consumption. Because an engine cycle lasts 50% longer than a classic engine, and in operation the engine lets more carbon dioxide to escape, i.e. completely unburned gas, which makes it less environmentally friendly.

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Although it has a capacity of only 1,300 cc, or as some say 2,600 cc, here is a very long story because many people contradict themselves in measuring the cylinder capacity of the engine. Comparative tests show that a Mazda RX8 consumes more than a heavier car, with a V8 engine, with a cylinder capacity of more than 4 times, obtaining similar performances.

But I don’t know what to say about this test, because there are also videos on the internet where the owners and enthusiasts of these engines say that at normal running the engine can easily produce consumption of less than 10%, sometimes it can approach the value of 8.5 %, a respectable consumption for what it offers.

Another disadvantage would be that oil gets into the combustion chamber, especially if the car is driven sportily, then it will “eat” oil.

We need to know that Mazda also invented the Renesis rotary engine. This is a 654 cc x 2 engine that produces 250 hp at 8,500 rpm and 216 Nm of torque at 5,500 rpm. The engine won the “Engine of the Year” award in 2003. The latest evolution of the rotary engine is in development and made its first appearance on the Mazda Taiki concept.

It promises a larger capacity of 1600 cc, i.e. 800 x 2, so a much higher power of over 300 hp. And even if the pollution problem is solved, Mazda will continue to face those related to oil and gasoline consumption, which will remain, due to the initial design.

But here we just want to point out that there are naturally aspirated engines that develop impressive power and are not boring to drive, ie how to get bored when the red line is at 9000 rpm.

In conclusion, the naturally aspirated engine is not only for “the old ones”, it just depends on which naturally aspirated engine you choose, because if you choose the 1.2 petrol engine, naturally aspirated from Dacia then yes, you will get bored and pray for overtaking, but still this engine is good for the city and the daily commute because it is quite reliable and consumes little.

But if you want the reliability of a naturally aspirated engine but you also want power, then you can opt for a VTEC, Skyactive-G or X engine or even a Wankel engine, why not?

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