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Concept Engines: Theory and Resulting Design Targets 30% Increase in ICE Efficiency

With this post, we’re formalizing a new category in GCC: Concept Engines.

Even in the most optimistic scenarios about transitions to a hydrogen economy, combustion engines will be with us for decades to come. (The applications, however, will begin to differentiate—downsized engines in plug-in or conventional hybrids, for example, running on synthetic or biofuels.)

Given the current pressures of ongoing rises in fuel prices and the need to reduce criteria pollutants and CO2 emissions, creating cleaner, more efficient engines is a key area for the industry. Accordingly, the major vendors and research labs are spending large sums on money on exactly that.

It’s not the easiest task. With 100 years+ of history, combustion engines are one of the most—if not the most—studied and refined class of machines around. The industry is making significant breakthroughs now due to the increased microprocessor control that can now be applied to engine and combustion management, to new materials, to better fuels and to a better understanding of the chemistry of combustion itself.

But inventing a successful major variant of the combustion engine (as Wankel did last century), or inventing a major modification to an existing engine type is rare, to put it kindly.

Nonetheless, engineers and scientists keep at it. (And that’s a good thing.) In this Concept Engines category, we’ll provide exposure to some of the out-of-the-box thinking and directions we encounter.

Now, to the specifics of the first.

The inventor, Frank Tinker, has a doctorate in Physics and an interest in mathematical and computer modelling of physical systems, computer programming, and prototype design/implementation.


He derived his design for improving efficiency through a major modification to piston design based on his theory for predicting the experimental efficiency of internal combustion engines.

According to Dr. Tinker, the method he devised identifies a flaw in existing ICE implementations that prohibits them from achieving the efficiencies predicted by the universally accepted fuel-air cycle model. (The chart to the right plots his model applied to Otto-cycle engines.)

The hypothesis on which the paper hinges approaches, but does not quite reach, thermodynamic heresy in questioning an assumption relied on by physicists, chemists, and engineers for 200 years. My only source of solace in light of the enormous target on my back for asking such a question is the remarkable correlation between the theory and the experimental data. A factor that is too compelling to be ignored.

—Frank Tinker

According to Dr. Tinker, his theory (which he describes mathematically in the paper referenced in Resources below) successfully models internal combustion engine (ICE) efficiencies as reported in the scientific literature, including an as-yet-unresolved, 1959 discovery of a 17:1 compression ratio efficiency peak reported by Caris and Nelson  (C.F. Caris and E.E. Nelson, “A New Look at High Compression Engines”, SAE Technical Paper #590015).

Based on what he sees as a flaw in existing ICE implementations, Tinker proposes the Engine Cycle Interdependence Frustration Method (ECIFM) that in his conclusion could lead to increases on the order of 30% to the thermodynamic efficiency of ICEs.

The theory explored in the paper identifies the heat energy that must be introduced to the engine in order to produce the work required to compress the gas in a subsequent cycle as exceeding the work energy returned when the gas decompresses (power stroke).

Therefore, in order to “frustrate” this inefficiency and, consequently, recover the traditional efficiency prediction, one must counter the pressure force as a function of piston position.

This can be done by coupling a conservative force (spring, gravitational, magnetostatic, electrostatic, etc.) through a properly designed cam to the piston in such a way that the pressure force is exactly countered.

This reduces the heat required to compress the gas to zero (since the compression is now being performed by the properly applied conservative force) and the traditional assumption of zero net effect on engine efficiency achieved.

Tinker is running a set of experiments to test his theory. Initial results show a 71% reduction in the mean energy required to operate his test device.

The actual purpose of the experiment was to show that one could design and implement such a counterforce mechanism. It was not optimized, but served the intended purpose. It also showed that the technology has application in compressors and heat pumps, also subjects of the patent application. I want to repeat the experiment a few more times before publishing the results to confirm what has been seen so far. I do not expect substantially different results, but I want to certain.

Tinker has submitted his paper on engine efficiency to the Journal of Applied Physics. The DOE and several corporations are in the process of reviewing his findings.

The next step would be further, repeatable experimental verification of his approach.



Rob McMillin

The "Journal of Applied Physics" link is busted.


Fixed. Sorry about that! Thanks.


It is important to note that this discovery is in its infancy. The purpose of submitting the details of the derivation to a scientific journal is to begin the important process of peer review. As other scientists review my proposed modification to heat engine analysis the full weight of their training and experience will test the validity of the hypothesis. I am hopeful that the work will pass such a test, but your readers should bear in mind that at this point my proposal is more theoretical than practical.

This in mind, I am impressed by your efforts to keep your readership informed of the work being done in maximizing the efficiency with which society implements its transportation needs. It is important work, and you do it well.



Since you're here, Mr. Tinker, perhaps you'd be so good as to explain part of the above quoted (italicized) paragraphs which I find unclear?  I'll quote them again:

The theory explored in the paper identifies the heat energy that must be introduced to the engine in order to produce the work required to compress the gas in a subsequent cycle as exceeding the work energy returned when the gas decompresses (power stroke).

Therefore, in order to “frustrate” this inefficiency and, consequently, recover the traditional efficiency prediction, one must counter the pressure force as a function of piston position.

This can be done by coupling a conservative force (spring, gravitational, magnetostatic, electrostatic, etc.) through a properly designed cam to the piston in such a way that the pressure force is exactly countered.

This reduces the heat required to compress the gas to zero (since the compression is now being performed by the properly applied conservative force) and the traditional assumption of zero net effect on engine efficiency achieved.

It is my impression that the storage of energy from the power stroke of one cylinder to the compression stroke of the next is also a conservative force, as is the storage of energy in the flywheel of a single-cylinder engine (minus bearing and piston/cylinder friction losses in both cases).

The language above does not make it obvious just what is new and different here.  Would you care to elucidate?


You bring up two separate issues here. The first is the action of decompression of one cylinder on compressing the gas in another. This particular action does not result in the cancellation of the two since there exists only one point in that process where the forces balance. The pressure in the cylinder is proportional to the piston position to some power. The decompressing cylinder's piston position is, necessarily, different from the compressing cylinder's piston position except at the midpoint of each. Therefore they cannot have the same pressure except at that point.

Your second point deals with the inertial action of the flywheel in compressing the gas. The kinetic energy of the flywheel is provided only by the operation of the engine and, therefore, possesses the efficiency of the engine itself. Therefore, any work done by the flywheel is done with the efficiency of the engine. This includes the work done in compressing the gas.

It is particularly important to note that the Caris and Nelson data shown in the plots of the paper were obtained using a standard General Motors V8 engine. Therefore, that data includes the effects of opposed pistons and the actions of the flywheel. As you can see, the theory that I've developed nearly exactly matches that data indicating that the existence of multiple pistons and a flywheel do not effect the applicability of the theory.

What is new in the theory is my contention that the heat required to compress the gas is greater than the work that is obtained when the gas is decompressed. This results in a reduction of the engine efficiency.

It may be easier to visualize this if you consider a pile driver. An inefficient engine lifts an enormous mass, which is then released to do work by driving a stake into the ground. The amount of energy required to lift the mass is greater than the energy delivered to the stake since an inefficient engine is to do the lifting. This is equivalent to using an inefficient engine to compress a gas the then using the compressed gas to do some work--the exact action of a heat engine.



To amplify on the previous post, one should also note that the Kerley and Thurston data shown in the plot is from a single cylinder engine and it, too, is properly predicted by the theory. This indicates that the multiple-cylinder engine performs substantially equivalent to a set of independent single-cylinder engines. Therefore, the opposition of cylinders in the Caris experiment does not eliminate the single-cylinder behavior of the Kerley experiment.

It may also be of interest that the submitted patent that anticipates the use of *properly coupled* multiple cylinders to increase engine efficiency.



After rereading those posts it is evident that there are some extra words here and there. Feel free to ignore them as you see fit! :)



To avoid you having to wade through the paper, the plot above shows Caris and Nelson's data as round data points and the Kerley/Thurston data points are shown as squares.



I very carefully read all of your material posted here. I don't have the vaguest idea what you are writing about.

Related to real world experiance, I have promoted a two-cycle, two cylinder, opposed diesel engine that simply drives a generator at a constant speed to recharge a Lithium-ion battery pack. On the back, the generator would be a part of the crankshaft. On the front an impeller would be attached to the same crankshaft to scavage the cylinder that has just delivered it's power stroke. The inertia of the electric generator rotor and impeller would propel the compressing opposite piston the very short distance until it's cylinder fired and started delivering it's power stroke.

The whole system would be recharged from the grid and the generator only used when that was not possible.

With existing technology that would be after about 200 miles.

The engine would be designed to use B100 BioDiesel.

Simple is better.


You might note the following reference:

which essentially mirrors your proposal.

The theory I've proposed is general in nature which means that it applies to your configuration as well. Therefore, the generator you propose would also gain efficiency using the technology that results from my theory...provided the theory is verified, of course.



Okay, I'm still not clear on this.  Perhaps we need to use a different example with some of the complicating factors removed.

Suppose that we eliminate the crank, flywheel and everything else in this hypothetical engine.  We reduce the bottom of the engine to a piston mounted on a perfect spring sliding in the cylinder.

This satisfies the requirements of your model:  the combination of the spring and the mass of the piston form a perfectly conservative system, where every erg of energy used to compress the air charge comes from energy stored during the previous power stroke.  (Energy would have to be removed otherwise the amplitude of the motion would increase without bound.)  In theory, you could extract work on the power stroke by applying a force exactly equal to the excess pressure of the power stroke over the pressure applied on the compression stroke, then allow the spring to return the piston for the compression stroke.

This is almost exactly what free-piston engines have been doing for a century, but they don't appear have any great efficiency advantage over conventional engines.  Where's the big improvement coming from?


Actually, it doesn't quite meet the requirement of my model. It lacks the component where the spring force exactly counters the pressure force.

Your model is almost complete. Couple the spring to the piston via a cam so that the sum of the pressure force and the spring force on the piston at every point along the stroke of the piston exactly cancel. Now it takes no work to push the piston into the cylinder. In the same way, no work is done by the piston if it is pulled back out of the cylinder (assume no fuel burning). So, the sum of the work required to compress the gas and the work done in decompressing the gas (still no fuel burning) is zero. This is the assumption of traditional theory and therefore the efficiency of that theory (fuel-air model) will apply.



The only difference you've made is that no energy is exchanged with the kinetic energy of the piston.  This has nothing whatsoever to do with the thermodynamic properties of the gas in the cylinder.


If you'll re-read the paper, you'll note that the process efficiency, i.e., the efficiency of converting heat to work according to the thermodynamic properties of the gas are unchanged by the analysis. None of the configurational changes proposed will alter the thermodynamic properties of the gas nor was that ever stated.

The difference between my theory and the traditional theory is in the accounting of how much heat is necessarily added to the system in order to traverse the PV diagram. In the traditional view only the heat added during the cycle is pertinent. In my theory, heat added in previous cycles is required in order to compress the gas in the cycle of interest. This is because the engine itself is all that is available to do the compression. This additional heat introduced to the engine in previous cycles in order to do the work of compressing the gas serves to reduce the efficiency of the engine. It does not effect the thermodynamic process.



Ah, that clarifies it (the purpose of the exercise) much.


I would like to thank you, Engineer-Poet, for your insistence on a clear explanation. I frequently rely too heavily on mathematical proof and often am so familiar with the problem that I have no empathy for the confusion of others. You have shown me one of the key components of the theory that I take for granted but others find vague. Thank you again.



"Couple the spring to the piston via a cam so that the sum of the pressure force and the spring force on the piston at every point along the stroke of the piston exactly cancel."

In a hypothetical engine what would drive the cam? Is this an external power supply?


"Couple the spring to the piston via a cam so that the sum of the pressure force and the spring force on the piston at every point along the stroke of the piston exactly cancel."

In a hypothetical engine what would drive the cam? Is this an external power supply?


The cam serves to match the work done by the spring to the work done on the gas. Since the spring force as a function of piston position does not generally match the force resulting from the compression of the gas, a cam can be used to cause a spring displacement different from the piston displacement such that the pressure and spring forces match.

This is also true when using any other conservative force to counter the compression force. Magnetostatic forces can actually provide a force profile that matches the compression force over a fairly wide range of piston motion without the use of a cam. This is one of the specific embodiments of the patent.

There is no external power supply.


James Warren

I have invented a 100 mpg engine (seriously).

An engine in which power actually increases over the current architecture, displacement remaining constant. we think that this engine could be the bridge between otto-cycle and whatever follows it.

The engineering firm we contracted with to perform an independent engineering analysis states that particulate emissions are down by a minimum of 40%-(power remaining constant/displacement down 50%). All of this accomplished with 26 moving parts in a four cylinder configuration. The architecture has infinite scaleability and is considerably easier to construct than the current poppet valve design.

It employs an inwardly-opposed design with a clever variation on the old sleeve valve idea. You may view the engine running on our site by contacting me for the passwords.

What is amazing is the difficulty of getting any traction for the design. One would think that armed with the patent, and independent verification of the architecture's high-performance and 'green-appeal', the doors to the corridors of power would magically swing swing open. Alas, that does not seem to be the case. The money guys want to see what's in it for them, and the manufacturers can't be bothered with something they didn't invent.

I remain astounded by the capacity of people to act against their own best interest.

Thanks for giving me a forum to vent. And contact me for the passwords if you want to see it, it's pretty cool if I do say so myself.

Jim warren

John Slusser

Well James Warren, how do I go about getting the password? Your link goes directly to the username/password log-in. Do you have an e-mail address? Dr. Tinker is on vacation at the moment, however, I would like very much to take a look at your site.

John Slusser
CardioPneumatics Research, Ltd.


The theory has three premises that I find confusing. Please discuss:

1. Compression and decompression under "ldeal" conditions similar to an engine cylinder have mistakenly been considered 100% efficient for centuries.

What is this premise based on, and how is the energy lost?

2. Energy from a previous cycle is needed to perform the work of compression in the current cycle. That energy is provided by the (inefficient) engine.

Yes. Compression cannot proceed "on it's own" - even the proposed cam/spring must have previously stored the energy in order to releases it as a force during the first compression. The idea that the flywheel "stores" neeeded compression energy or that a "conservative" cam/spring stores the energy appears to be equivalent.

The energy initially placed into the cam/spring, and the "replenishment" of that energy after it is expended in assisting with compression comes from the same inefficient source that the flywheel draws from - the engine. How can one be more efficient than the other? In fact, flywheel energy storage is likely to be more efficient than spring storage, is it not? Perhaps a flywheel should be considered as the conservative force storage device? But then what is new?

3. Wouldn't the "conservative force" have to be "one way" to contribute useful work to the compression action? In other words, if a "force" could be crafted that "pushed" on the bottom of the piston with exactly the force necessary to shove the piston up to full compression, wouldn't that force have to "stop pushing" at that point, or risk "absorbing" just as much energy on the down stroke as it provided to assist with compression?

If it "pushes" all the way "up" and "down" it adds no net force - how does this help anything? It would "disappear" as a term in all the equations as the (possibly incorrect) "perfect" compression/decompression term disappears.

If it "pushes" "one way" it's doing work and it will suck that work out of the inefficient engine. What progress has been made in either scenario?

Thanks for the discussion.


1. The premise upon which traditional heat engine analysis hypothesizes 100% efficiency in compression/decompression is mathematical in nature. The analysis assumes that the pressure is a repeatable function of position during each compression stroke. This identifies the compression as a generalized conservative force. The integral around any closed path of a generalized conservative force is identically zero indicating, in this analysis, that the work of compression is exactly matched by the work of decompression. Voila, 100% efficiency in having the decompression perform the work of compression.

The energy lost, according to my analysis, comes from the view that the output work comprises the energy resulting from the ignition of the fuel added to the pre-ignition energy of the compressed gas. This total work is achieved at some efficiency that, according to the second law of thermodynamics, is required to be less than unity. This being the case, it is the stipulation of traditional theory that the work performed in compressing the gas in the subsequent stroke be done at 100% efficiency while all other work is carried out at some different, less than unity, efficiency. Therefore, traditional theory would have you believe that work from some entity can be applied to two different tasks simultaneously but at different base thermodynamic efficiencies. The possibility that this is true seems remote and my hypothesis simply requires that all work done by the engine be done at the same thermodynamic efficiency. The result, therefore, must be that more energy is required to compress the gas than will be returned upon gas decompression by the very definition of efficiency.

2. Consider a large wheel driven by an electric motor. Now assume that a large mass is attached to some point on the circumference of the wheel thereby unbalancing it. When the mass is ascending, the inefficient electric motor uses more electrical energy than the mass gains in potential energy in the gravitational field. When the mass descends assume that the electric motor becomes a generator with the 100% efficiency. The “generator”, then, will energize batteries to a value equal to the potential energy lost by the mass. There will exist, then, an energy deficit equal to the difference between the energy required when the motor is an inefficient motor and the energy generated when it is an efficient generator. Now attach a similar mass opposite the original one such that the two are balanced through the center of the wheel. In this configuration, the motor no longer has to lift the mass inefficiently nor generate electricity as it falls. The kinetic energy of the wheel is immaterial. It is the addition of the counterweight that reduces the energy required to turn the wheel at any speed.

3. As explored above, one does not require that the counterweight “jump off” the wheel at the bottom. In fact, it this were the case one would need, at some time, to lift the counter weight back up to the top of the wheel to make the journey again. If done with the electric motor, this would take more energy than that gained by the altitude change of the weight, ad infinitum. No, it is the balanced motion of the two weights that sum to zero energy change over the entire rotation of the wheel. Once arranged, the configuration would not need to change. This is also true of the spring/cam configuration. Once it is properly synchronized with the compression it need not be removed during operation.

In the engine, compression serves the same role as the off-balanced weight while the counterforce serves the purpose of the counterweight. In both cases, the sum of the energies remains constant over the entire motion of the system.


David BUtcher

Thanks for the detailed reply.

To simplify things:

In a single cylinder engine, once it is rotating, compression is accomplished solely though the release of kinetic energy stored in the flywheel.

If compression and expansion of combustion gasses were 100% efficient, and there was no friction, once started rotating, the engine would continue rotating indefinitely with no addedd energy (exactly as the electric motor plus two-mass example you provided above). Indeed, if the electric motor in the example given above were 100% efficient as a motor AND a generator, and there was no friction, it would not matter whether there was one weight or two, or any other number. The motor would not spin at a constant velocity if it were in a gravity field, but it would spin indefinitely regardless of the distribution of weight.

We know the experiments described above would result in the both the engine and the electric motor slowing and stopping, due to friction losses.

You seem to be suggesting that the addition of a mechanism to the combustion engine or a change in the distribution of weight on the electric motor rotor would change the "spin down" behavior of the two devices.

To isolate this further, it is the differences in efficiencies for the electric motor between "powering" and "generating" that result in the loss of energy in the system (as heat) when the electric motor is rotating an unbalanced mass vs. a balanced mass. It is a flow of energy into and out of the motor from the rotating mass that introduces this inefficiency, even if the flow of energy into and out of the rotating mass is 100% efficient. (I hope I have understood your example correctly)

However, in the combustion engine, theoretically, the energy is flowing between two 100% efficient processes - the flywheel and "compression." That is different than the electric motor example.

In both examples, the flywheel (or rotating mass in the electric motor example) whether balanced or not will be equally efficient at storing and releasing energy, so it can be ignored for comparison purposes.

Now, have I reached understanding? Is the claim that compression and decompression is not 100% efficient at the root of this concept, as that would model the behavior of the electric motor - "x" energy goes into the "upstroke" (equivalent to the electric motor as a power source) and "y" energy is returned through the downstroke (equivalent to the efficiency of the electric motor as a generator) - and there is a difference between the two, and THAT is the loss you are proposing to counter?

And that would require disproving that compression and decompression are 100% efficient?

And the maginitude of that loss (the difference in efficiency between compressing and decompressing) can be as much as 30% of the engine's power output?

Thanks for helping me understand this, I am really curious.



The energy in the flywheel was obtained by the operation of the engine. Therefore, any work it does is done using fuel at a rate dictated by the efficiency of the engine. It is equivalent to any energy storage medium. The fuel is burned and inefficiently transformed into the rotational kinetic energy of the flywheel. That rotational energy is used at 100% efficiency to compress the gas in the cylinder in the next cycle. So the net efficiency of compressing the gas is the efficiency of the engine multiplied by the unit efficiency of transferring the kinetic energy of the flywheel to the compression of the gas. Therefore, the net efficiency of compressing the gas is the efficiency of the engine—which by the second law of thermodynamics is less than unity.

There is no need to factor friction into the argument. The energy of the flywheel is always obtained at the efficiency of the engine whether it is spun up and allowed to run freely or not. Any work it does is done at the efficiency of the engine this includes work against friction, but it is not germane to the analysis.

This is also true of the electric-motor-driven unbalanced wheel. Lifting the weight is done at the efficiency of the engine. Converting this potential energy into electrical energy stored in a battery leaves the unbalanced mass motionless at the bottom of its path of motion and the energy in the battery. Even if the motor is an ideal generator, its less-than-unity efficiency in lifting the weight for the next rotation will take more electrical energy than will be recovered when the weight descends.

Contrary to your assumption, this all means that I do not suggest that the effect has anything to do with the “spin down” behavior of these devices. That is dependent only on the nonconservative forces in the system which I have ignored in my analysis.

Further, your statement about the flywheel being “100% efficient” is inaccurate. As I stated above, the flywheel obtains its kinetic energy from the consumption of fuel at less than unit efficiency. Therefore, before that energy is ever applied to any task it is already inefficiently obtained.

The compression work is done by the flywheel at the efficiency of the engine. The decompression work is added to the work provided by the burning of the fuel and the sum total of this work, by definition, is done at the efficiency of the engine. Part of it is applied to performing compression for the next cycle of the engine and part is applied to some other task.


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