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New Toroidal Internal Combustion Engine Promises 20:1 Power-to-Weight Ratio

The Massive Yet Tiny (MYT) engine

A California inventor is developing a new compact and highly efficient engine—the Massive Yet Tiny (MYT) engine—that promises high power output with a very high power to weight ratio (20:1). The inventor, Raphial Morgado, recently won first prize in the 2005 Emhart-NASA Tech Briefs Design Contest for his work on the engine.

The engine moves pistons on different rotors relative to each other to form combustion chambers of variable volume in a toroidal cylinder. The pistons move in stepwise fashion, with the pistons on one rotor travelling a predetermined distance while the pistons on the other rotor remain substantially stationary.

Fuel is drawn into a chamber as one of the pistons defining the chamber moves away from the other, and then compressed as the second piston moves toward the first.

The cycles of the MYT engine. Click to enlarge.

Combustion of the fuel drives the first piston away from the second, and the spent gases are then expelled from the chamber by the second piston moving again toward the first. An output shaft is connected to the rotors in such manner that the shaft rotates continuously while the rotors and pistons move in their stepwise fashion.

The engine fires 16 times on one revolution of the crankshaft, 32 times on two. By comparison, a standard V8 fires four times per crankshaft revolution—one-quarter the number of the MYT. Angel Labs, the company developing the engine, calculates the equivalent displacement of the MYT as 848 cubic inches (13.9 liters), with a 3-inch bore and a 3.75-inch stroke. The company further calculates that the 14" x 14", 150-pound prototype could produce power in excess of 3,000 hp.

[The 3,000 hp rating] is conservatively estimated from 850 CID. A conventional engine can produce 4 hp per CID (when turbo charged). Four times 850 [the equivalent displacement] is more than 3,000. Our data of air motoring (800 lb.ft. of torque from 150 psi of compressed air) extrapolates to more than 4,000 lb.ft. of torque when fuel is ignited, exceeding our conservative estimate.

—Jin K. Kim, Managing Member, Angel Labs

The design is also modular. Additional MYT units can be connected by removing the rear cover of the engine and connecting another ME chamber assembly. With a dual-assembly configuration, the engine becomes a “64-cylinder” engine with 1,695 cubic inches displacement (27.8 liters), raising the power-to-weight ratio up to a projected 40:1.

The engine uses only about 20% of the number of parts normally found in a reciprocating internal combustion engine, and only 12 of the MYT parts are moving parts, reducing friction and parasitic losses.

Unlike a reciprocating combustion engine, the MYT engine permits a piston dwell at the equivalent of Top Dead Center (TDC)—the starting point for combustion. The current prototype is set for a piston dwell of approximately 12 degrees of the crankshaft rotation. By adding in that delay under combustion before permitting the power stroke, the MYT burns a greater percentage of the fuel and air mixture in the combustion chamber, resulting in a more complete combustion.

All we know is that 12-degrees dwell at the TDC, which no other engine can do, will burn all the fuels completely. Therefore, we expect very clean emissions.

—Jin K. Kim

Other features of the engine include:

  • The ability to support a compression ratio as high as 70:1.

  • No valves. The MYT uses open ports with no restriction. Airflow action is one way.

  • The entire engine acts as a heat sink and a radiator. It is both air and oil cooled.

  • There is no thrust loading on piston skirts.

  • Pistons do not touch the cylinder walls, only the rings do.

  • Pistons travel only the same direction. No reciprocation, only stop and go.

  • There are no cylinder heads, no cam shaft, no valves (the ME is equivalent to the bottom end of a reciprocating engine).

  • Intake compression and power stroke and exhaust stroke events are happening all at the same time, so there are no load strokes.

The MYT engine is not the first implementation of rotating pistons in a toroidal cylinder—the 1968 Tschudi engine is very similar in concept. (A newer derivative is by Hoose, 2005.) The key to the MYT engine is its timing mechanism.

The stop and go actions can be generated in many different ways, but you can not have active locking mechanism, because it will break under repeated stress. It took Raphial, who usually can invent in a couple of hours per invention, more than two years to come up with this invention (he threw away about 10 different ways of implementation.)

—Jin Kim, in the Angel Labs forum

Angel Labs is targeting a number of application: autombiles and trucks, pumps and compressors, aviation (helicopter, fixed wing and UAV), and military. Their goal is to license the technology non-exclusively to everyone. According to Jin Kim, Angel Labs is currently in discussions with Lockheed Margin, Boeing, Ford and several smaller potential licensees.

(A hat-tip to Bob C!)




If this is really practical, the applications for light aircraft should be huge.

Harvey D.

Could it be used for a much lighter weight genset for PHEVs?

John Allison

What is power to weight ratio of other ICEs? 20:1 is a nice ratio but i would like something in which to compare.


I note that this engine has only been run with compressed air, not on a combustion cycle.  This means that the following are not characterized yet:

  • Mechanical loading of the various mechanisms (including the stop/start system).
  • Stress on the cooling system.
  • Thermal efficiency.
This thing sounds a lot like the next Wankel, and could have problems of its own.  Let's wait and see before gushing over it.  That said, 40 HP/lb puts it into territory where it competes with gas turbines!


Er, even 20 HP/lb does.

The state of the art in auto engines is about 100 HP/liter for high performance models (about 1.6 HP per cubic inch).  I can't tell you what the typical power/weight is for cars, but for opposed-piston light aircraft engines it is about 0.5 HP per pound.


Sounds like a bunch of hot air to me. These "im going to revolutionize the internal combusition engine" ideas come out of nowhere every 5 minutes. They haven't even run the engine with fuel yet. Just compressed air so don't hold your breath.


Looks much like the Sarich Orbital engine:

This is what happened to it:


Trying to get electronics TSO'd for aircraft use is enough of a headache. I could just imagine what he will have to go through to get a brand new powerplant certified for aviation use.


"...that promises high power output with a very high power to weight ratio (20:1)."
Sorry but as long as power and weight are not expressed in the same units, such a sentence is pure nonsense. I would certainly never trust an inventor who is not even able to use proper terms to describe his "discovery".


I'm supposed to know a little bit about mechanics. This thing is greek to me.

I don't know greek.


Given that it is an American inventor I would hazard a guess that they are saying 20hp to 1lb, but that is only specualtion since it isn't explicitly defined.

I believe the LS1 from GM weighs ~400-450lbs and developed 400hp in Z06 form that would give 1hp per lb but that is with emissions equipment (catalytic converters & mufflers), emissions requirements and driven accessories. Until they have this engine running in an EPA lab to ascertain compliance with automotive emissions standards the power it produces can't be compared.

For example: A drag car from Puerto Rico, known as Sakura, was running mid 7 second 1/4 mile times using a 2.6L 4 cylinder turbocharged engine developing somewhere around 1000hp (the motor used with turbocharger weighed around 350lbs) but don't expect that engine to meet emissions standards for noise or air.


If this thing can really pull this kind of power to weight ratio, maybe I can finally get a flying car in my lifetime. It looks like this prototype runs on diesel as well - I wonder what the thermodynamic efficiency of this motor will end up being.


Well, if you read the article, you would see that the claim was 150Lbs and 3000hp.

20hp : 1Lbs

Modern high output street legal engines Are between 1:1 HP:Lbs and 1.5. (Some bike engines offer 2:1 but not for very long :)

Someone earlier mentioned HP/Liter, but that is a measurment not useful for anything but marketing.
It bears no relivance to HP:Weight, nor reliability, nor thermal efficiency or emissions. It is a moron's litmus test.

This engine is potentially exciting, but I agree with previous posts, I want to see it run on a fuel, and I have doubts about 150Lbs worth of material handeling the stresses from 3000hp, or even half of that.

tom deplume

Consider this. 3000hp is over 7,500,000 btus/hr. If this engine is a very good 50% efficient a very small surface area would need to dissipate this much heat every hour. The surface temp may need to be over 1000F. Skepticism is very much in order.

Barry R. Guthrie

I agree Tom,

With this much heat thermal cooling is a big problem.
I'm not sure how they are going to achieve good combustion in only 90 degrees CA. This is too short even with hydrogen. The exhaust heat losses will be very high and reduce the thermal efficney. I'm not sure how they are also achieving a high compression ratio with this configuration.

The engine has high surface area for the outer housing this will disapate much of the heat and lower the thermal efficiency. The cooling the center rotor will be a big problem.

You also have a strange split line running down the center of the combustion chamber that separates the two different rotor groups of four. This split line will be prone to combustion gas penetration, especially at very high compression ratios.

How does this keep the combustion rotation in the desired direction? It looks like it would just produce center pressure that would go both forward and backward.

I think that they use some elaborate gearing system, but this will add friction and be prone to wear. This will add to the reduction of the brake thermal efficiency.

You might somehow get high power density, but you won't be able to maintain it for very long due to the thermal loading and you certainly won't get very good fuel efficiency from high surface heat and exhaust losses. This would be something that the military might try, but I can't see what it will do to help reduce our oil and fuel consumption.

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