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Scuderi Split-Cycle Engine Obtaining Better Combustion Consistency Under Low Load When One Crossover Passage Is Shut Off

When operating under low load conditions, the pressure—and ultimately the efficiency—of the Scuderi Engine prototype increases, and becomes more repeatable from cycle to cycle, when one of the two crossover passages is shut off (thereby effectively doubling the pressure in the single open crossover passage), testing by Southwest Research Institute (SwRI) has shown.

The Scuderi Engine is a split-cycle engine that divides the four strokes of the Otto cycle over a paired combination of one compression cylinder and one power cylinder. Intake air is compressed in the compression cylinder and transferred to the power cylinder for combustion. The Scuderi Engine prototype (earlier post) has two crossover (Xovr) passages that connect the two cylinders, which separate the four strokes of the pistons.

Each crossover passage has a crossover compression (XovrC) valve on its upstream end and a crossover expansion (XovrE) valve on its downstream end, which control flow through the crossover passage. In one, cylinder intake and compression occur while combustion and exhaust take place in the other. Fuel is injected in the downstream end of the crossover passages just as the XovrE valve opens. Compressed air then travels at sonic velocity from the XovrE passage to the combustion cylinder, where combustion occurs.

One of the things that was always critical to us was whether or not we would be able to maintain our pressure [at low load]...one of the keys to the Scuderi engine is to maintain high pressure in the crossover passage. We have had several schemes to do that at low loads, low pressure...because we knew that as we went down in load and speed we would be losing pressure in the crossover passages.

—Stephen Scuderi, vice president and patent attorney for Scuderi Group

One concern the Scuderi Group had about the scheme of shutting down one crossover passage at low load was a potential degradation of the mixing of air and fuel, Scuderi said. In fact, he noted, the testing showed that mixing improved with one passage, resulting in a more consistent combustion process.

In tests of the prototype running at near idle load and speed (i.e., less than 2 bar load and 700 rpm) to loads of up to 4 bar and speeds of up to 1600 rpm, shutting down one of the two crossover passages yields a coefficient of variance (COV) as low as 1.4%, according to tests conducted by SwRI.

Typically, a conventional auto engine running on the Otto Cycle will produce COV rates ranging from 2.5 to 4.0%. COV is a measure of the variability between each combustion cycle. Lower COV figures correlate with higher efficiency and more complete combustion. Moreover, the very low COV in the Scuderi Engine indicates that the combustion mix (oxygen and fuel) is even more complete and robust than in a conventional engine.

This makes us very confident that, when fully mapped and analyzed, the efficiency of the engine will be even higher than previously predicted, which so far has been the pattern in the measured data we have acquired to date.

—Stephen Scuderi


Henry Gibson

After years of computer simulations and no prototypes it is a big surprize that such a discovery can be made. Computers simulations are perfect examples of how machines and global warming works.

Computer controlled valve can be built and installed and operated for all engines.

Or perhaps we can see that the Scuderi engine is just a piston version of a jet engine and just go with the Capstone turbines.

If you want a combination of turbine and piston you can go with the Electro-turbine-supercharger of the new OPOC or you could go in the other direction with the Pescara free piston turbine combinations that could burn crude oil without refining like the super large piston ship engines. ..HG..

bill coughlin


It appears you take the time to post a reply without any understanding of this technology. Perhaps, if you "read" the article, you would see that this press release discusses the "tests of the prototype running at near idle load and speed".

Please don't waste anyone's time replying to this post.

Henry Gibson

I was commenting that the many years of computer similations of Scuderi did not reveal the whole truth, and that a prototype should have been built and tested years ago. Scuderi has been long known for relying on simulations rather than tests to keep the investors excited. Please read my prior comment carefully to try and get the irony about computer simulations that was built into it. You can also read my prior posts about Scuderi to find out, fully, that I knew that they were testing now a prototype at long last.

Except for the interesting concept of an air-hybrid version of their engine, the efficiency increases proposed are achieved by plug in hybrids which can use far less gasoline, and turbines are simpler and sufficiently efficient for the low efficiency of traveling at high speeds on motorways.

Wasting energy by traveling at 80 instead of 55, even for long trips, is an issue that will eventually have to be looked at in this world of required energy efficient appliances and water efficient toilets.

If you cannot describe to me, without looking it up, how a Pescara engine worked, please restrain your comments about my understanding of engines. You may also consider what you know about the Still engine used in several ships and stationary engines as well as a locomotive first. ..HG..

bill coughlin

Your disparaging comments towards "Scuderi" appear to have skewed your objectiveness. Sounds like you have been following this years and this has become "personal" for you.
You lack an understanding the new "Scuderi Cycle", the thermodynamics properties that are present in this new technology and the efficiencies gained when the engine is run in the air-hybrid mode.
When you develop a full understanding of these concepts, perhaps you may well be able to provide more insightful comments, instead of bashing.

Roger Pham

Pretty soon, most cars will be HEV's, and the ICE will only run when it's most efficient to do so. This will make this discovery moot. No need to run ICE at low power setting, low efficiency level anymore.

I move that the nation should have plan to retrofit many many existing cars into HEV's, in the wake of the Gulf oil spill disaster.

bill coughlin

You mean to tell me that if your ICE in your HEV could be was 50% more efficient you would not use Scuderi technology.
...your comment.. "This will make this discovery moot"....
You need to do some research on this before you discount it so quickly.


I think Henry understands this "technology" quite well, even amidst the BS that comes from Scuderi.

So now, just like daytime TV they create a problem where none existed and say they solved it and, in fact, the "very low COV in the Scuderi Engine indicates that the combustion mix is even more complete and robust than in a conventional engine."

I will be relieved when all the other auto makers are forced to quit unloading those high COV engine on us.

And then
"This makes us very confident that, when fully mapped and analyzed, the efficiency of the engine will be even higher than previously predicted, which so far has been the pattern in the measured data we have acquired to date."

I guess they mean after another decade of simulation and fund raising.

Roger Pham

Current HEV's using Atkinson-cycle ICE has already demonstrated higher peak efficiency and even higher part-load efficiency than the Otto-cycle ICE that are in conventional non-hybrid vehicles. Scuderi-cycle engine claims 10-15% higher efficiency than Otto-cycle engine in conventional cars, but cannot be more efficient than the Atkinson-cycle engine, the latter is simpler and does not have the losses of moving compressed air through a series of valves and pipes instead of combusting the compressed air directly.

Watch out for HEV's using HCCI combustion in conjunction with high expansion Atkinson cycle, and HEV's with turbocharging Atkinson-cycle engine with electrical turbocompounding for larger vehicles in order to wring out the last BTU's from every drop of fuel.

And after 2015, watch out for FCV's with tank-to-wheel thermal efficiency above 60% that will solve the oil spill and oil pollution problem once for all the coming milleniums.


I don't think the Scuderi concept is really promising for gasoline engines, it is more interesting for diesel because its highly turbulent combustion and injection after TDC reduces NOx and soot, at least if we beleive their claim which they haven't really proved yet...

But any concept of ICE will have hard time to make it through, turbo charged high pressure diesel are already very efficient and powerful. Future will tell but they will have to show really strong benefits to convince cars manufacturers. I think new ICE concept could be successful in emerging countries where marketing has not yet established standards so the market is more open, and hybrid are probably too expensive for India or china.


After having read your often bold statements, pro and con the Scuderi principle, I am curios where you get the information for such assessments. For example, at the home page of Scuderi, I find mostly information adapted to investors, not engineers. There are many patents and patent applications but mostly such information tend to be somewhat misleading and do not fully reveal how the idea will be applied. I have been in the business since mid-1980´s and I think that I could grasp that, at least theoretically, this combustion cycle could have a potential for high efficiency (as many other modifications to the otto and diesel cycles do...). However, when you try to make a practical application, you sometimes have to make compromises that reduce this potential. To be able to better assess the potential of the Scuderi engine in practical applications, I would like to study some technical/scientific publication where the current development status and the routes chosen are clearly stated. Since I have not seen any information of this kind, I come back to my initial question: Where do you find the information to make your assessments?

I can fully understand that Scuderi want to keep some aspects confidential and therefore, they choose to reveal just as much (or little) information as they want, i.e. just enough to keep current investors happy and to attract new investors but not enough for anyone else to get any insight.


ESStor is following Scuderi's foot steps?


The thing I still can't get past is how the Scuderi engine's combustion piston/cylinder will survive constant exposure to high temperatures. Inconel engines anyone?


You mean, "if they ever build a production prototype, will the combustion piston/cylinder will survive constant exposure to high temperatures".

The computer simulation does just fine, I am sure.


Most of the Scuderi comments on this web site have been anti-Scuderi from the same group of naysayers however the Scuderi Group continues to keep the interest of 15 of the top 20 OEM'S. Why so? Do you think the top OEM's executives and engineers would pay them the time of day if there was no real substance in this technology? After licensing agreements are sign and the company goes public will you still have reason to continue to bash the Scuderi Group? Your future credibility is at stake.


Scuderi has no intention of building a full engine, they just want to licence their patents, that means that if an engine or car manufacturer isn't convinced in the first place, this engine will stay as it is : vaporware.


The claim that "Scuderi Group continues to keep the interest of 15 of the top 20 OEM'S." is suspect, to say the least.

What history and science say about Scuderi is clear and damning.
And it is open for all to see, just use common sense.

If licensing agreements are signed and the company goes public I will greatly respect their tenacity and guile.

But if they actually sell something substantial and significant money goes anywhere but their own pockets (like to investors) I will be astounded and will publicly admit I was unfair.


After the Scuderi Group goes public, significant returns/money would already be in the pockets of many small investors. These are investors who had the insight to be part of a this advanced technology and were not afraid to back it up with there hard earned dollars. It's not just about the Scuderi's personally but more like the Scuderi family which also includes all investors.


Hello guys.

Interesting in wider the subject ?

I doubt if you find there more valued engineering substance


Roger Pham

The tourengine is comparable to the OPOC in design.

OPOC has higher power density because both cylinders fire in 2-stroke cycle, whereas in the tourengine, only one cylinder fires at all. OPOC is very simple, having no valve train. OPOC has no heat loss to the cylinder head, since there is no cylinder head. OPOC is turbocharged wherein exhaust energy can further be captured. Electric motor/generator can be used to boost the turbocharger and also capture excess energy from the turbine and turn into electrical energy (electrical turbocompounding).

What is the advantage of the tourengine? A cooler intake cylinder in the tourengine can increase volumetric efficiency, but the force feeding (turbocharging) in the OPOC can do just that. No heat loss from the compressing cylinder? but then, there will be no cooling charge to help cool the expansion/combustion cylinder to keep the oil from burning. Higher expansion of the tourengine's power cylinder increase harnessing of exhaust gas' energy? That's the turbocharger/turbocompounder is for in the OPOC engine.

What is the advantage of the tourengine, again?


Compared to nowadays IC engines, wouldn't the tourengine reduce compression work and beef combustion work ?
How about utilizing hot cylinder ceramic insulator ?
Would the OPOC engine take it too ?
In regard to higher expansion cylinder, No need for Miller/Atikson features, turbocompounder is the answer ?

Roger Pham

No, Atkinson-cycle engines in HEV's are already doing that.
Heat loss in OPOC engine is already low, but it can use ceramic insulator too.
Turbocompounding captures residual pressure in the exhaust gas and turns it into work, just like the over-expansion cycle of Atkinson's.

OPOC engine has 1/2 the number of pistons for doing the same work as in a conventional or split-cycle engine, without any movable valve nor valve train. This tremendous cost and weight saving permits the use of turbocharging and electric boost/turbocompounding without increase in overall engine cost.


The OPOC layout is not new, in 2 or 4 cycle.
The Scuderi, OPOC, tourengine and many others offer advantages but, unless there is some breakthrough, it is unlikely these technologies have been "overlooked".

Much work has been done to toward replacing the combustor of a turbine with a diesel engine, using exotic lubes, but even after this work, problems with the "hot cylinder" remain.

For most of us, not on the cutting edge of the specific technolgy, ignorance as to why something does not work should not mean it will, nor might work.

It is like grade school kids (or teachers) believing in socialism.


Well, isn't it logic and fact that utilizing a single cylinder for intake and compression as well as for combustion and exhaust strokes drastically limits low heat rejection benefits (i.e Ceramic)?

Compared to common IC's, this engine (Tours) weigh less (compression side is lighter) and of course can also take turbocharging and electric boost/turbo compounding.

In regard to quote " OPOC engine has 1/2 the number of pistons for doing the same work as in a conventional or split-cycle engine " much can be said, it is not as "clean" as one may perceive but lets leave it for now.


Logic is not assuming some weird engine will compete with today's ICE when we don't have the facts.

Should all ideas, however weird and unlikely be investigated?


Should we assume they will work because some promoter says they will?


Roger Pham

"Well, isn't it logic and fact that utilizing a single cylinder for intake and compression as well as for combustion and exhaust strokes drastically limits low heat rejection benefits (i.e Ceramic)?"

OPOC by itself, without any ceramic coating,already has low-heat rejection benefit. The piston crown can be coated with ceramic, as well the circumferential part of the combustion area can also be coated to get further low-heat rejection benefit. The cool intake air goes right past the piston crown into the cylinder while the exhaust gas, which is already hot,goes sideward out of the cylinder without much contact with the piston crown. There is no cylinder head in the OPOC for heat loss to occur. The cylinder wall must be cooled or your lubricant will burn up, in any engines.

"In regard to quote " OPOC engine has 1/2 the number of pistons for doing the same work as in a conventional or split-cycle engine " much can be said, it is not as "clean" as one may perceive but lets leave it for now."

OPOC design may lose a minuscule amount of oil out of the exhaust, but the overall amount may be less than that of a older 4-stroker losing oil from the valve stems and through the piston rings. There are twice as much pistons and rings in a 4-stroker as in the 2-stroke OPOC design, and a lot of valves whereas the OPOC has none!

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