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Scuderi to Show Air-Hybrid Diesel Engine Design at Hanover Show

The split-cylinder design of the Scuderi engine.

The Scuderi Group will unveil the design of a prototype diesel application of its air-hybrid engine at the International Automobile Association’s Commercial Vehicle Show (IAA) in Hanover, Germany, 21-28 September.

The split-cycle engine divides the conventional four-stroke engine cycle across two paired cylinders—one compression cylinder and one power cylinder. Intake air is compressed in the compression cylinder and transferred via a gas passage to the power cylinder for combustion. The Scuderi air-hybrid implementation leverages the split-cycle technology by recapturing and storing energy in the form of compressed air. (Earlier post.)

By adding a small air storage tank with some simple controls costing only a few hundred dollars, the Scuderi engine can recapture energy normally lost during the braking of a vehicle. In addition, unlike electric hybrids, the Scuderi Air-Hybrid promises to be able to recapture energy from the exhaust of the engine, making it possible to utilize a Scuderi Air-Hybrid design in stationary applications such as electric generators—an application where electric hybrids are considered impractical. The concept is applicable to either Otto or diesel engines.

The innovations in the design of the Scuderi engine reduces the cost of diesel systems by eliminating or dramatically reducing three of the most expensive and complex parts of a diesel system—turbocharging, injectors and exhaust treatment. Because of the inherent design advantages of the Scuderi Air-Hybrid diesel engine, we estimate that this engine can lower the cost of diesel engines by as much as 40-50%. We strongly believe that the Scuderi Air-Hybrid engine is the diesel engine design of the future.

—Sal Scuderi, president of The Scuderi Group

The unique method of firing after top dead center and a very fast moving power piston eliminate or drastically reduce the two biggest emission problems for diesel engines: NOx and PM, according to Scuderi. As a result, the company claims, expensive exhaust aftertreatment systems can be scaled down dramatically.

Other potential cost savings come from the elimination of the turbocharger and the halving of the number of fuel injectors. In addition, because of the high turbulence created by the air transferring into the power cylinder from the transfer passage, the Scuderi Diesel Engine will be able to use low pressure, low cost injectors instead of expensive high-pressure injectors, according to the company.

Scuderi expects its engine to:

  • Improve fuel efficiency in today’s gas and diesel engines by almost one third;

  • Emit 80 percent less toxic emissions than today’s gas and diesel engines;

  • Enhance the performance of hybrid engines;

  • Provide significantly more power than a conventional engine; and

  • Be easy to manufacture because it utilizes the same components found in today’s engines.

Scuderi expects to have the first diesel and gasoline prototypes of its air-hybrid engines completed by late 2007.




In essence this has the advantage of both two-cycle and four-cycle engines since a power stroke is delivered every time the power piston starts down.

I'm looking forward to the production of an experimental engine.

Bill Young

This engine would be very interesting to adapt for aviation. The weight savings combined with the compression replacing a turbocharger for high altitude flight are a good fit. I look forward to its fuel consumption numbers.

Sid Hoffman

Using a cylinder for compression would mean it only compresses at a fixed rate, i.e. 1 bar. Turbochargers can increase their compression rate so as to achieve a fixed manifold pressure. For example, a turbonormalized aircraft engine may be flat rated at 235hp from 0 to 20,000 feet by having the ability to run 35 inMg total manifold pressure at all altitudes in that range. That would mean at sea level the turbo only contributes 5 inMg but at 20,000 feet it would be added some 20 inMg to arrive at 35 inMg manifold pressure. That variable boost characteristic is what makes turbos ideal in aviation.


A variable valving scheme could be employed to control the pressure developed in the compression cylinder.


Since when did pressure start being measured in inches of magnesium?

It's worth noting here that, even according to Scuderi's own explanations, the benefits are over-sold; an engine CAN achieve greater expansion than compression ratios, OR can apply more air to the power piston than its own displacement would allow, but not both at once.  Further, it still can't move more air than its compression cylinder displaces.  A turbocharger is still the smallest and lightest way to get more power out of a given displacement engine; the more-complete-expansion cycle would complement that by recovering otherwise-wasted expansion energy without turbocompounding.


Maybe they're using the exhaust to heat the compressed air, increasing the pressure in the reservoir (rather than using the heat in the exhaust to turn a turbine) to give the same effect as "doing both at once".

I'm not an engineer, so don't slam me...


There's no heat exchanger in their diagrams on the site.

On the other hand, it's an obvious improvement.  Unfortunately, the recent patents on internal-combustion Ericcson cycle engines may have made it problematic.

Bill Young

Turbocharged piston aircraft frequently use a waste gate to limit the manifold pressure. A similar arrangement could be used with the compression cylinder on this engine.

The peak pressure available would be greater than ambient atmospheric pressure because of the compression ratio.

Manifold pressure is normally expressed in inches of mercury (absolute). Normal sea level would be 30inches MAP.

Because the pressure boost would be integral to the engine, it should be less expensive and more reliable than an external turbocharger.

tom deplume

They are presenting a design not a real working engine. The basic idea is the same as the 19th century Brayton 2-stroke of the Selden patent. That engine only ran once and for only a few minutes.

Roger Pham

I agree with Tom. Heat will be the problem that will hold back this design, unless they have found a way to withstand the intense heat of combustion with every power stroke without an intake stroke with cool air to cool off the piston and cylinder. Ceramic piston and cylinder (that does not require lubrication)?


Do aircrafts brake?


Do aircrafts brake?

Roger Pham

"Do Aircrafts Brake?"

That's a very profound question! The last time I checked, non-helicopter aircraft do not stop in midair, meaning that Scuderi engine will not be an advantage for recuperative braking.

Actually, other posters have suggested the use of Scuderi engine in aircraft, and the equivalent of the Scuderi engine in aircraft is the gas turbine engine. Gas turbines have a separate compressor section from a combustor and a turbine aka expander, like the Scuderi engine. The difference is that the turbine blades are constantly exposed to 2300 degrees F of heat, and therefore are made from "unobtainium" as is referred to in the aviation world, being very expensive and hard to fabricate. Aluminum melt at ~1200 degrees F, and most piston engines are made of mostly aluminum, including the piston, cylinder and head. Unless Scuderi have found a way to solve the heat problem, their effort will be like "much ado about nothing."

John Schreiber

This puppy will be too heavy for aviation in my opinion, and I don't see efficiency increases above 15% over todays engines.

Roger Pham

Yup, I can't see how they can claim much higher efficiency than today's diesel engine, neither.

dan voak

"Unless Scuderi have found a way to solve the heat problem, their effort will be like "much ado about nothing."

actualy to combat this, perhaps scuderi could combine the split cylce with the crower six-stroke cycle, injecting a smallamount of water into the expansion cylinder. like in the crower this would not only cool the cylinder, but also produce an extra power stroke. any thoughts?

dan voak

ofcoarse, unless the water is recuperated from the exaust, it would be a tottal loss. perhaps by useing a set of specialised valves, and a secondary refrigurated exaust chamber separate from the main exuast, the water could be recirculated back into the engine again


My Name is Tom Crowden. I am looking to further my Knowledge in the Automotive and related engineering sector in the UK. I am focusing on Hybrid engineers and technologies. I would very much like to speak to anyone who could shed some light on this issues from a Degree point of view.

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