The innovative combined cycle, stepped piston, heavy fuel solution for Aviation, OEM's, Drones, Generators, Compressors, Marine, Land Vehicles, Military and other space / weight single fuel restricted designated use applications.

Extended Mission Duration

It is necessary to emphasize the importance of the very high volumetric efficiency of the traditional piston controlled ports employed by the standard two cycle engine. Until now no existing type of inlet valve could produce the essential requirements of presenting the maximum inlet area to the air in the minimum time. The new design outlined below, significantly increases both the utility and the efficiency of the of the two cycle engine, which may now be more efficiently scavenged. The port layout adopted concentrates the scavenge flow at the wall of the cylinder opposite the exhaust port. This compares with more evenly dispersed scavenge flows common in conventional engines. Scavenge flow within the cylinder provides, in effect, a form of stratified charging and explains improvements in fuel economy obtained with such a simple layout. This enables combined cycle engines to compete with four-cycle engines in terms of fuel economy, especially under cruise conditions.



 We use the following tools: 3D Catia modeling; Solidworks; ProE; thermal and mechanical finite element analysis; computational fluid dynamics and fatigue post processing software. 


We have developed proprietary valve-train software, and have a vast experience with advanced materials and coatings.


We have a number of proprietary elements within our manufacturing and casting technologies. 

Combined Cycle Spark Ignited

The Higgs Diesel is not really a diesel in the traditional sense, it is a spark ignited “Combined Cycle Technology” engine, burning JET A, diesel and gaseous fuels such as hydrogen. It is in fact, a true multi fuel engine.

‘Combined Cycle Technology’ (CCT). This refers to the combined forced scavenge of the engine via the pump attached to the bottom of the piston and pre-charging of the cylinder. Removing the need for a separate supercharger or mechanical pump, this all takes place in a single action, hence “combined cycle”.

As we are a spark ignited engine and not a diesel, the compression is considerably lower, in the range of 6.5~7.5:1 (this being trapped compression ratio not full compression as measured on a four stroke engine). Unlike a ‘normal’ two stroke engine, we do not premix or use any oil with the fuel for lubrication. The lubrication is separate and is identical to most four cycle engine types. The pumping piston, attached to the bottom of the working piston only draws in air for combustion, this air is transferred to the working piston and fuel is directly injected into the cylinder avoiding any short circuit of fuel out the exhaust, which is a common trait of many two stroke engines and allows for a very clean burn engine.

As we are not a “diesel” engine, as in the form of a traditional Compression Ignition type (C.I), this allows us to design components that are considerably smaller and substantially lighter than a “traditional” diesel engine. The reduced weight of these components, combined with a reduction of part count as we have no valves, cams or supercharger etc, allows for a small and lightweight footprint than would otherwise not be viable with any other solution.


The crankcase, freed from any gas exchange functions, is well lubricated; the working processes being sealed above the piston. Isolation of the crankcase also permits a full pressure lubrication system to be used, as in four-cycle engines.

Inherent piston cooling characteristics of the combined cycle piston design offer a major durability advantage over conventional two-cycle engines, allowing much leaner fuel delivery than can be sustained with traditional crankcase scavenging, where usually piston overheating and consequent seizure are common.

This technology operates without complex mechanical components such as cams, valves mechanisms and the other various precision components necessary to operate them.

The absence of these mechanical components eliminates a large number of moving parts, thereby considerably reducing the costs and maintenance requirements, whilst significantly increasing reliability and retaining the simplicity of the two cycle engine.

With this novel cycle engine technology, combined with the enormous benefits together with their appealing simplicity, a new generation of light weight high performance power plants can be achieved. Which until now would have been almost impossible.

The use of combined cycle pistons, for charge transfer and combustion, allows the key advantages of two and four-cycle engines to be combined, with the elimination of disadvantages inherent in each of these engine types.

Using a combined cycle piston in we are able to completely separate the scavenging from the crankcase.

Isolation of the fresh charge from the crankcase is made possible by the provision of normal four-cycle engine compression and oil control rings on the larger diameter part of the piston.

Stepped Piston.

Gearbox & Accessory Drive

The engine is designed from the outset to run with a reduction gearbox. Generally speaking the design of such a unit for aviation is complex due to the highly stressed loading and the necessity to remove vibration from the crank, coupled with undesirable instantaneous torque fluctuations, these units tend to be massive, complex and require high maintenance. 

The E1000-J/G and E300-J/G with their low torque fluctuations inherent with a two stroke, allow for a different approach to gear sizing, materials and integration.

The gearbox low axial load is achieved by using a double pinion, which is supported independently by it’s own bearings and attached to the crank via a spline (no bending transmitted to the pinion). This method allows the torque loading to be shared between the two idler gears with a corresponding increase in service life. The gear-case is an integral part of the crank case with a gear cover containing both rolling elements for load and thrust.

Comparitive Data Tables

*Estimated and includes instal kit.

Fuel Type & Consumption

This platform of engines has been designed from the ground up to be a true multifuel unit.

Designed to run on industry standard Jet fuel (Diesel (EN 590), Jet A, Jet A-1, JP-5, DEF STAN 91-86, JP-8, DEF STAN 91-91, JP-8+100, Chinese Jet Fuel No 3)

Will also run and perform on all gasolines where necessary, 80,87,91,95 including 100LL along with all bio derivitives.

Hydrogen gas.

BSFC, 0.398 lb/hp-h (231g/kW-h) Pratt & Whitney PT-6 Turboprop by comparison is 0.507 lb/hp-h (308 g/kW-h) (on approach and idle 0.825 lb/hp-h (502 g/kW-h))

Performance continued

Performance predictions of the naturally aspirated AX-100 CONDOR V12 engine were conducted to examine power output at altitudes ranging from sea level to 60,000 feet. This study reflects the WOT (wide open throttle) performance at the altitudes considered. A propeller power absorption curve is shown for reference. The propeller absorbs 1000 hp @ 5300 rpm at sea level. As altitude is increased, fuel injection rate is reduced to maintain a best power air/fuel ratio of 12.0 to 13.5 at all rpms.

The power predictions reflect that of an un-tuned engine as inlet and exhaust system ducting have not been defined at this time. Maximum rated power at sea level is 1259 bhp @ 5300 rpm with corresponding bmep of 94 psi (6.5 bar).

Approximately 930 bhp @ 5150 rpm is available at 8k feet, the maximum altitude requirement for the NA engine.


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