The NEVIS (New Exhaust Valve & Intake System) engine is an innovative Internal Combustion Engine (ICE) that within a single patented engine design is estimated to nearly double the fuel efficiency attained by conventional ICE technologies.  Additionally, its modular cylinder construction (e.g. 2, 4, 6 or 8 cylinder engines from a one-cylinder block) offers opportunities to enhance manufacturing efficiency while allowing a single facility to produce a wide range of engine sizes for varying power needs suited for diverse applications (automotive, aeronautic and marine).   Its versatile design means it can be configured to be fuelled not only by gasoline but also by diesel, hydrogen and bio-fuels.

The history of the NEVIS Engine begins with Cesare Bortone (45) and his interest in improving an engine performance. A self-taught engineer, Cesare Bortone was encouraged to register his first patent in 1992[1] by Prof. Domenico Laforgia, originator of the common rail system for diesel engines and inventor of the Multijet system now used by FIAT.  The first patent dealt with an annular valve system within the engine’s cylinder to achieve variable valve actuation.  This invention inspired the variable valve actuation system present in the NEVIS engine and set in motion the 1st phase of the NEVIS project.

This first stage of the NEVIS project was carried out in cooperation with the University of Perugia with over €400,000 in grant funding made available through the Italian Ministry of Agriculture. The Ministry was interested in advancing engine technology for agricultural applications and accepted the scope of the NEVIS project as ultimately helpful in this regard.   With the grant funding in place, Cesare Bortone was given the responsibility to lead the research project which extended over a 4-year period between 1992 and 1996.  The project led to further research on the technology at the heart of the patent and to the fabrication of a demonstration prototype which illustrated how the technology would function. 

Following this phase and while continuing to work in fields unrelated to engine development, Cesare Bortone began to bring together his thoughts for an improved internal combustion engine.  His approach was to consider what was learned in the first stages of the NEVIS project as well as all past advances in ICE development with the objective to combine multiple improvements within a single engine design.  The result of these efforts was the design of the NEVIS engine first registered with the European patent office in 2000. 

In 2001, Cesare Bortone began the second phase of the NEVIS project based on the new engine patent entitled New Exhaust Valve & Intake System (i.e. NEVIS).   This second phase focused on the development of a functional prototype based on the NEVIS engine design and was funded, in part, by an Italian government grant  from MUIR (Ministry of Education, University and Research).  Grant funding of approximately € 2.1 million was approved in 2002 and work began on this 2nd phase of the NEVIS project in 2003 with Cesare Bortone heading the project.  This phase was concluded in early 2006 with the successful testing of the two cylinder 1.000 cc 250hp/187kw NEVIS prototype in early 2006.

Cesare Bortone is a self-taught engineer who has focused on the issue of improving engine performance for over 20 years. He received his first patent for a valve timing innovation in 1994 and has dedicated over ten years on the NEVIS engine design receiving a European patent in 2002 and a US patent in 2006. 




The thermodynamic cycle or rather the manner in which the internal combustion process takes place within most of today’s conventional ICEs dates back over 100 years: most automobiles either use the four-stroke[2] spark ignition Otto cycle, conceptualized by the German engineer Nikolaus Otto in 1876, or the four-stroke compression ignition Diesel cycle invented by Rudolf Diesel and patented in 1892.  The most efficient cycle for internal combustion is known as the Carnot cycle as studied by Nicolas Léonard Sadi Carnot in the 1820s. However, the problem with the Carnot cycle is that there is no engine available to make the theory of the cycle work.

Cesare Bortone’s outside-the-box approach was to conceive a new cycle for maximum efficiency, which we have termed the “Bortone Cycle,” and design an engine that could make this new cycle work.  The NEVIS engine, constructed using conventional methods and materials,  singularly addresses a variety of strategies for enhancing efficiency:

  • Engine weight and size are reduced with its doughnut-shaped piston but power is increased for the same cylinder displacement, in part, due to an innovative use of the energy of the engine’s exhaust vacuum and to the fact that the engine has 6 times the number of power strokes per revolution than a traditional four-stroke engine
  • Optimum combustion occurs at all power levels with the engine’s variable combustion ratio and variable valve timing/duration

While industry players have been seeking ways to improve the ICE for decades by making incremental improvements on the Otto and Diesel cycle engines, the time has come where the slow progress of improving the basic design invented over 100 years ago is no longer sufficient to address these issues.  In fact, the industry as a whole is actively seeking to make progress on next generation technology such as hybrid ICE vehicles and fuel cell vehicles.  The appearance of the first commercial hybrid automobiles (e.g. Toyota Prius and Ford Escape) along with significant investments being made in fuel cell technology is confirmation that incremental change is no longer sufficient. 




The NEVIS engine design is believed to be sufficiently advanced to compete against hybrid powertrains within the automotive sector as these have largely been conceived in order to compensate for the ICEs poor performance across a range of partial power demands.  This weakness of conventional ICEs is not present in the NEVIS engine and together with NEVIS’s other efficiency enhancements, performance is expected to exceed that of hybrids.  This, together with the added costs of hybrids (projected to remain between 9 to 29% more expensive than a conventional port injection spark ignition ICE in 2010 [3]), provides comfort that the NEVIS engine represents an advance in efficiency capable of maintaining a long-term advantage.  It is anticipated that the cost of a NEVIS-powered vehicle would approximate conventional ICE powertrains and could actually turn out to cost less, given its more simple and modular construction using traditional materials. Fuel cells represent another next generation technology that is very efficient in transforming energy into power.  However, one must also examine the entire “Well-to-Wheel” process, that is from the source of the energy (e.g. an oil well) to the delivery of this energy to the vehicle and finally from the vehicle to the motion of the wheels.   On this basis, according to an analysis by Toyota, its Hybrid Prius automobile has a Well-to-Wheel efficiency of 29% compared to 22% for a Fuel Cell vehicle powered by hydrogen made from natural gas. Furthermore, the retail cost of fuel cell vehicles is projected to remain between 50 to 105% more expensive than a conventional port injection spark ignition ICE in 2010. 





Engine specifications compared



BMW R6 Engine







1,000 cc

3.000 cc

Power density Kw/L






80mm internal

1.78 mm external

85 mm




88 mm



250/187 » @ 2.000 rpm

258/190 @ 6.650 rpm

Average piston velocity


7.5 meters/second

19.5 meters/second

Engine Block



composite magnesium-aluminium





Power/Weight ratio (Kw/kg)




Compression ratio


7:1  to  38:1



The horsepower data above marked as estimated is derived from research carried out by the University of Catania based on the specifications of the NEVIS prototype and an assumption of 2.000 rpms.  However, as can be inferred from the table above, the NEVIS engine could run at nearly 3 times this level of rpms, yielding still more power – approximately 500HP, yet maintain an average piston speed (key to the life of an engine) similar to that of the BMW engine.  Given that the specifications of the prototype were purposely conservative, other enhancements in terms of performance, size and weight are anticipated. 

The two-cylinder prototype was put through a bench test with engine ignition for the first time in Lecce, Italy in early 2006 as part of the review process by MUIR (Ministry of Education, University and Research) for the government grants that funded the development of the prototype. This first test confirmed the correct functioning of the Bortone Cycle and the basic mechanical operation of the NEVIS engine.  Preliminary testing without ignition also confirmed nearly 50% less friction/pumping resistance for an engine with a comparable displacement.  

A further enhancement that is being considered which would have a major impact on emissions is adapting the NEVIS for HCCI -- Homogeneous Charge Compression Ignition.  HCCI relies upon a very lean (high proportion of air to fuel) and well-mixed (Homogeneous) air-fuel mixture (Charge) that is compressed (Compression) until it autoignites (Ignition). The resulting spontaneous burn produces a flameless energy release in a large zone almost simultaneously -- very different than the spark/gasoline burn or the compression/diesel burn.  The NEVIS engine adapted for HCCI would not only increase efficiency further but would also do away with NOx without the PM (particulate matter) emissions of a diesel.  




[1] US Patent number 5,803,042 – Italian patent protection filed in 1992

[2] intake, compression, power/combustion and exhaust

[3] TANK-TO-WHEELS Report - European Commission Joint Research Centre, December 2003