Uncooled Engines


The Foundation is arranging to design, build and test up to six pre-production long-life commercial (300 to 450 kW [400 to 600 hp]) prototypes, running at constant speed and load. Output shaft efficiencies will be around twice today’s at about 50% and weighing around seven times less than today’s industrial engines. The Litus engines are for ALL applications and for all currently used fuels, including hydrogen.

The cost of long-life uncooled prototypes of any size is large, whatever is built. Small prototypes would cost nearly as much as the large-power ones, but could only be sold for a fraction of the estimated $60,000 the larger engines we are working on could fetch.

Litus is establishing a consulting Alliance with research institutions and early-enabling companies. Commercial partners’ only obligation will be to provide monthly consulting, for preferential access to the technology in their industry.

A business and design office has been established in London. Interest in fuel efficiency and CO2 reduction is strong in Europe and key technical expertise is also based there. The ceramics department of a major government research laboratory, will be helping with studies, and is due to make the prototypes’ ceramic components.




Because there is no cooling other than the constant incoming air, the engines will run at temperatures and pressures about one-and-a-half times those of today’s engines. Key components will be of impact resistant ceramic materials, able to withstand much higher temperatures than today’s metals. High temperatures mean there can no longer be a traditional oil system as the oil would boil away. The only practical way to separate piston and cylinder is by a gas bearing, a well-established technology. A central load transfer rod works the piston to the crank shaft.EngineFig 1.

Figure 1 shows schematically one of many possible uncooled engines. Inside a cylinder assembly with closed ends / heads, a hollow piston/rod assembly reciprocates, separating two toroidal (doughnut shaped) combustion chambers operating in two-stroke mode, all in a thermally / acoustically insulating casing. Air is supplied via charge volume(s), which could house crankshaft or generator, both in dashed outline. The piston assembly has a circumferential projection or flange – the piston part – on a hollow rod, all shaped like a rolling pin with a central hollow and fat handles. Air goes from the charge volume through the hollow to the combustion chambers via a series of clearances at ports. Exhaust exits via common ports in the cylinder to a surrounding exhaust processing volume. A central load transfer rod works the piston to the crank shaft.quarter engineFig 2.

Figure 2 shows schematically a piston (dark shading) reciprocating a cylinder (light shading), with an output shaft supported by rollers, connecting the piston to a crankshaft. Piston and cylinder are shown differentiated for sake of clarity, but both are of the same ceramic material.

With doubled two-stroke combustion chamber, the layout of Figure 1 is equivalent to today’s four-stroke four cylinder engines. Nearly all engines will have only one cylinder. Toroidal volumes need multiple fuel delivery devices, but this is cheaper than more pistons / cylinders.Figure 3

Fig 3.

With no oil, cooling system, plumbing or need to circulate air around a metal block, engines in insulating casings perhaps including a generator could be “snap-in” units. Figure 3 shows a casing, with a grille for air in. The recess in which the casing fits has connections for exhaust out, fuel in, electronic controls and drive shaft or electric power out. Because they are so light, engines could be changed in minutes by one or two people. Figure 4 outlines what such an engine might look like.

UntitledFig 4.






      1. Extreme Efficiency:  Uncooled engines run much hotter, so a far greater portion of fuel energy is used to push the piston, with nearly all remaining energy in the super-hot exhaust gas. Most engines now have real output shaft efficiencies of 15% to 30%. Smaller engines are less efficient than larger engines. Uncooled units show about 47% to 53% efficiencies in all size ranges, for all fuels, before any energy is recovered from the hot exhaust.

      2. Reduced COEmissions:  They are in proportion to fuel usage, so uncooled engines would produce about half the CO2 emissions of cooled engines. Higher temperatures reduce other emissions, with exception of NOx. Litus has found ways of limiting NOx formation at high temperatures.

      3.  No Traditional Cooling and Oil Systems: Gas bearings separate piston and cylinder, so there is no traditional oil lubrication. Coolant and oil no longer need to be disposed of / recycled. The cost, weight and bulk of cooling and oil systems is eliminated.

      4. Lower Life-Cycle Costs:  They are cut due to halved fuel use, no engine oil changes and reduced maintenance / breakdowns. At $4.25/gallon, a US Class 8 truck driving 200,000 miles annually at 7 mpg will save over $60,000 per year just in fuel and oil changes. Today’s truck engines cost around $30,000, so buying a $60,000 uncooled unit pays back in six months; more quickly in Europe, Asia.

      5. Simplicity, Superior Reliability, Reduced Maintenance, Silence & No Heat Signature:  There are no cooling or piston oil systems to fail, with only contact between piston and cylinder at start / shut down. Uncooled engines have one to three base moving parts, excluding small fuel system parts, instead of over thirty as in today’s engines. Thermal and acoustic insulation will mask virtually all sound and heat.

      6. Better Power-to-Weight Ratios:  For equal power, uncooled engines will be between two and ten times smaller and lighter than today’s.

        1. Equal or Lower Production Costs:While ceramic pistons and cylinders today are up to three times more costly than metal ones, most Litus units need only one of each, with far fewer other parts, and have no piston oil or cooling systems. Production costs of large engines could be lower than today’s.

        2. Improved Compounding:  If systems such as turbines are added (‘compounding’) to extract work from the energy-rich exhaust gas – thereby cooling it down – can boost efficiencies up to around 70%.

        3. Increased Applications:  Uncooled piston engines will replace expensive turbines in many uses (e.g. auxiliary power units), due to far lower costs, much better efficiencies and equal or lower weight.

        4. Snap-in Cartridges:  There is little or no plumbing and no need to circulate air around an engine block. Small, light engines in casings can be swapped in minutes, or exchanged for varying uses. Vehicles, marine craft and equipment no longer need to be towed for repair, a real game changer.







Around 1890, Daimler, Benz, Diesel and others commercialised the internal combustion (IC) engine, keeping metal pistons, cylinders, crankshafts and production methods of the 1750’s-onward steam era.  By the 1930’s nearly all of today’s piston engine secondary technologies were developed, as was the 1950’s conversion of the 19th century steam turbine into an IC turbine, for jet engines and power generation.

There have been other combustion engines, including Wankel and Stirling units. Today, only piston and turbine engines are in serious production, as they are the most efficient, cost-effective and / or have the best power density. The Litus engines are for all applications and for any current fuel.

The table below shows today’s real world output-shaft efficiencies for new and run-in engines, in comparison with those of the Litus uncooled engines. They differ from manufacturers’ figures, given at optimum speed / load operation, often at the piston crown and not the output shaft.

Whole graph

In the 90s, a few ceramic parts were unsuccessfully used in metal engines of unchanged design, e.g. as crowns / linings for metal pistons and cylinders.

Litus has resolved all past problems, designing around: 1) no cooling, so no engine block; 2) ceramics’ unique material characteristics; 3) using ceramics only structurally and providing insulation in the non-ceramic casing.

In future, a few producers covered by patents will make ceramic parts / engines to tight tolerances in clean rooms and high volume for many clients, as Intel now makes part-ceramic chips or “engines” for about 60% of desk / laptop computers.

A  quantum leap, a 21st century re-invention of the piston engine is overdue.background




The more efficient the IC engines of hybrid and plug-in hybrid vehicles, the better the fuel economy. All-electric vehicles are expected to eventually grow only up to 10% of the global vehicle market (as second cars or city transport), due to higher cost, and the power / range required for most applications.

In commercial use, only IC engines have the needed power density and range either alone or as part of hybrid-electric drives. These are already being used in trucks, ships, aircraft, trains, mining / farm / industrial equipment.

“Wells-to-wheels” efficiencies and emissions of hydrogen produced from fossil fuels – the only bulk source now available – are only a little better than that of other fuels. Greater energy use (rarely from renewables) and emissions caused by production and freezing or compression is offset by fuel cells’ better efficiency, nearly double that of today’s engines. Hydrogen can be produced away from cities and resulting emissions more effectively cleaned up in bulk.

A hydrogen-fueled IC engine – long established by BMW and others – running uncooled with a generator would have equivalent efficiencies and be smaller, lighter and cost between a tenth and twentieth of a fuel cell.

Fuel cell stacks are replaced about every 15,000 hours; the IC engine would have a life of 75,000 to 150,000 hours.

Using hydrogen in long-life uncooled engines of doubled efficiency and  at a fractional cost would be much cheaper and simpler than using it in fuel cells and lead to wide adoption of “zero-emissions” systems.