Will Split-Cycle Engine Compete With EV Powertrains?
One cylinder of Scuderi's split-cycle engine performs intake and compression, while the other handles power and exhaust. The engine completes all four strokes in one crankshaft revolution. (Figure courtesy of Scuderi Group.)
I think this is going to be a good technology to watch. With the government mandating higher fuel efficiencies and "good enough" battery technology still a few years away, this might be the technology that gets us there.
Proving this works in high output engines will be an important factor. It does have some interesting characteristics, for one, the hot side of the engine stays hot and the cool side does not heat up too much. This is in contrast to the Otto cycle characteristics.
I would be very curious as to just why the retardation of the spark helps so much in this design compared to the Otto cycle. And another obvious question to me is if the split cycle is amenable to creating a split Diesel cycle? Would there be any benefits in that?
Seems to me that any kind of technology that has the potential to advance the cause of fuel efficiency is to be taken seriously. Glad to hear that analyst groups and automotive OEMs have this on their radar screens even if it's some time out before we see the actual technology in production vehicles.
Isn't this essentially an internal supercharger? Seems a traditional supercharger would have less parasitic loss, no fricton from extra pistons and valve train, and would accomplish exactly the same thing....
Not likely: the Mechanically driven Supercharger not only introduce a power drag, but their compression efficiency is not that great (the Turbo driven supercharger is almost always more efficient). Either won't match the air compression and handling needs of the cylinder-piston over the whole range of RPM's and loads that the auto engine commonly faces.
The thing with a Turbo or Supercharger is that both have performance maps that do not match the performance map of the piston engine entirely. The Turbocharger produces way too much compressed air at high RPM's, and the mecahnically driven Supercharger does the opposite. Thus, the Turbo needs a waste gate to avoid overcharging the combustion chamber of the piston-cylinder engine, and presents some lag; the Supercharger has lower overall compression efficiency but does deliver pressure boost inmediately, and then runs off at higher RPM's. The idea is that the pressure boost needed by the cylinder-piston is not really well met by both devices; thus the concept shown could well be a better match for the cylinder charging needs, maybe better than the traditional Otto cycle. Please consider that the Otto cycle engine usually operates at very low effective compresion ratios, due to the throttle valve being open completely only when the accelerator pedal is pushed hard! This concept remainds me of the so called "Turbo-Compound" engines used in the 50's in the last piston driven airliners like the DC-7 Super and the latter Super Costellations... but were overly complex and unreliable, and were soon replaced by the jet turbine.
Amclaussen, good summary of Turbo vs. Supercharger. You said:
The idea is that the pressure boost needed by the cylinder-piston is not really well met by both devices; thus the concept shown could well be a better match for the cylinder charging needs, maybe better than the traditional Otto cycle.
However, the piston-driven compressor in the prototype is mechanically matched to the engine rpm, and it's volumetric output is thus rpm dependent, and has parasitic power draw, which is the same as a supercharger. The qualitative issue is whether it is a more eficient air pump across all rpm ranges than a external supercharger. Also, I tend to surmise that the gains are from what is essentially a two-stage forced induction, turbocharger and then internal compressor. Seems I have seen people trying this with external turbo pumping into external supercharger into engine with encouraging results.
That's exactly the point: The engine airflow needs need to be matched by the section feeding the air in. Let's remember so called "affinity Laws" that govern flow, pressure and power in dynamic machines. Very different from positive displacement or piston devices. (Flow proportional to speed, Pressure proportional to speed squared, Power proportional to speed elevated to the third power...)
In a turbo you need to match a very different performance map (that's because a dynamic compressor -or expander- uses -or produces- power to the cube of it's RPM, therefore the operation line is curved, where the line for a piston engine would be straight). The Turbocharger in a typical engine does not produce any real power surge at lower RPM's, it needs a relatively large exhaust flow to be eable to speed-up and start producing appreciable pressure into the inate manifold, and at high RPM's, the pressure and flow will be way too much over the piston engine needs, requiring a wastegate and controls to avoid overboosting the engine, overheating piton tops and valves or blowing the engine! By coupling the a compression cylinder to the same crankshaft, the matching of the flows and power appears to be easier to be established and kept over the RPM range of the engine... At least that's the main advantage I guess this design could have. Now, a piston compressor is always more efficient than a dynamic (centrifugal or axial, or screw compressor types). by placing the compression piston on the same crankshaft would be advantageous compared to having an external supercharger, not only for its intrinsic compression efficiency, but taking together the unavoidable transmission losses at the Supercharger belt and pulleys or gears. I hope I made it clear, sorry for the lenghty explanation, English isn't my native language.
The more I look to the idea, the more advantageous it seems.. unless I'm ignoring some catch! Someone ready to find it?
"Now, a piston compressor is always more efficient than a dynamic (centrifugal or axial, or screw compressor types)."
THAT is the part that I question. Any emperical data to qualify that? It seems almost all industrial air compressors have adopted screw type designs over the older piston type design, why would they do that if it were less efficient?
Your observation about the abundance of screw type compressors is correct, but efficiency is not the only aspect to consider. The actual popularity of the Screw type compressors that have almost replaced the older piston types is more related to other important aspects: smaller size, lower weight, relative freedom from vibration, relative freedom from pulsations, easy to be directly coupled to common speeds of electric motors without speed reducing gearboxes or belts and pulleys; additionally, the modern capabilities to manufacture the rotors with computerized machinning explains their cost becoming lower compared to the situation 15-20 years ago. As you say, most common AIR compressors are now screw types, being that for most common air pressure requirements, they can produce it in a single stage easily. For higher pressures, they are not that advantageous, and at very high pressures piston types are more adequate for the task. Compared to dynamic types, thermodynamic efficiency in piston types is higher due to the process of the compression cycle is more towards isothermic than the polytropic cycle more closely followed in dynamic types; in screw compressors cooling-sealing oil is sprayed into the casing to aid sealing and actually remove a good part of the gas heating during compression, but that requires oil injection (and posterior removal). In dry type screw compressors, there are some "Slip" looses accounting for a lower overall efficiency.
As I'm not close to office at this moment, I can't give you specific values for the sizes similar to the requirements of the supercharger in an Automotive IC engine, but I plan to write them soon.
Ivan: Here's Scuderi's answer to the question that you and many other readers posed: "Firing after top dead center (when the piston is on the way down) puts more energy on the piston's downward stroke which results in more power on the crankshaft. In a conventional engine, the spark occurs when the piston is on the way up (and almost at the top), which creates more negative work because the piston is initially fighting against the force before moving down."
Retarding timing reduces negative work, but it also reduces peak pressures (which negatively affects burn efficiency) and combustion time (which negatively affects burn efficiency). When ignition happens at or after top dead center, the flame front has to chase a retreating piston and the flame front move more slowly because of the falling combustion chamber pressure & temperature.
Their unconventional ignition timing implies to me that they are running into detonation issues; probably due to too much boost, poor scavenging, excessive heat, and a poorly shaped combustion chamber. They might make up some of the loss in burn efficiency by using multiple spark plugs, but it strikes me as a kludge.
This seems only possible in a stationary industrial application. The ignition atdc pretty much rules out rapid speed changes and taking advantage of flow dynamics in the power cylinder. I sense a money grab based on hype.
I have been dealing with engine efficiency for over ten years with the product of the
Sonic Spark Plug. In todays market, we have a complexity of products that claim increases of fuel mileage. The market customers are squeezed with increase of the cost fuel, and the cost of new vehicles with their complexity of design costs.
To increase fuel mileage, the industry has gone to turbo chargers that work. However, there is a down side to this path. The air charge is 78% Nitrogen. Turbo Chargers, the lean burn techniques, Hydrogen inputs increase the combustion energy with the splitting of the Nitrogen Molecule that releases 236,000 of calories per mole. Then, there is the increase of Nitrogen Oxides, NOX, with its environmental effects. And, the Hydrogen Inputs coupled with Nitrogen Oxides will form Nitric Acid. The biological effects of the NOX components are not fully recognized other than biological with asthmatics. However, the effects on the Photosynthesis System should be studied.
The Sonic Spark Plug is the simplest. and least expensive product that improves engine efficiency by the shattering of fuel droplets, and homogenizing the air/fuel mixture. With a tightening of market price, the addition of Turbo Chargers added expense, and the costs of expensive systems to increase mileage, and power may eventually be out priced in the market.
This sounds a lot like our two stroke engine, except for being more complicated and having six valves. Clearly it allows much more variation in timing of all the several parameters like when to start the air intake portion and when to inject the fuel. Depending on the timing requirements, the same functions could possibly be delivered by a standard two-stroke engine, even better if it had direct fuel injection. Such an engine might possibly also fare better in emissions testing, although efficiency and low emissions seldom peak at the same time. But as the split stroke is compared to a two stroke, it is clear that they are similar.
A two-Stroke is VERY different... and it's Specific Fuel Consumption (efficiency) is lower than in a 4-Stroke. By optimizing the charging cylinder to perform a charging task only, and then making the power cylinder optimum for producing the downstroke better, can suspect this concept couls have advantages. But is is definitely NOT a two-stroke. (the better eficiency Two-strokers are those that burn diesel and have an integral blower to sweep the burnt gasses out of the combustion chamber, but the ubiquitous gasoline two-strokers are notably less efficient and produce a lot more contaminant gasses in their operation. Please analize in detail the article's drawing, then the alleged advantages can be visualized. Anyway, the idea of using a crankshaft driven compressor in order to handle the air, and a power cylinder to drive the same crankshaft, with both relative sizes optimized to match the volumetric needs of the engine, always working at the same exac RPM, looks like an elegant solution to me. It needs to be built and througly tested before anyone can claim it a success. But the idea looks like a good one. Other elegant engineering ideas were not as sucessful as desired, like the variable compresion engine from Volvo (If I remember correctly), that was so difficult to run in practice or expensive to produce so that today none are seen in the streets.
Hello to all. Scuderiengine.com answers many of your questions. THIS innovative engine technology will definitely shange the engine world (ICE) forever. Lets NOT be "Car-Centric" here. There are ICE Internal Combustion Engines in many other applications and not only the automobile. Lawnmowers, tractors, big generators, boat engines (large + small) basicly ANY ICE with piston technology. As a former Rubber+ Plastics engineer and a youthful "Motor-head",,,, I knew this project was a winner within 30 minutes of a complete inspection of their technologies and developments...
Go to the web-site. This concept "ATDC" is not only central but its been their focus for many years; at Team Scudei. I immediately invested upon being offered the opportunity to get on board with this "Gamechanger" ..
In my opinion....look at the progress and then the depth and gameplan that Scuderi employs. They are asked...they answer beyond expectations and then they engineer beyond expectations. Right now...at 65 mpg proven via simulation,,,there is talk in the 80 mpg range and a longer view of 100 mpg. Will they breach these barriers? I do not know; but they have repeatedly pushed foward beyond their expectations many times before.
Right now....I await the announcement of our 1st leassee of the technology and I am preparing for the push to "Go Public " as Sal Scuderi has stated may times in the past; as the GOAL of Scuderi Motors. The time has come for a real world demonstration. The significant strides foward can no-longer be kept in the closet. It's time to show the public and get ready for the stampede !!!!
Having a long history of watching these various technologies I am very skeptical until they actually build one and run it on a dyno or an instrumented vehicle. They need to build it and test it, otherwise it is just another idea that is good on paper but will never materialize. The world is full of failed attemps. like the ECOmotor. So far no one has been able to violate the laws of thermodynamics
Currently the most efficient practical engines are the direct injected European Diesels at over 30% actual dyno efficiency. We cannot use these in the US becaus of the high combustion pressures and temperatures (the key to efficiency) causes too much NOx
I have written letters E Mails to my congressman, president, EPA etc and received absolutly no response to the idea that perhaps the US should reconsider our emission requirements for NOx and other emissions in light of new knowledge and better understanding of global warming and effects of these various regulations.
The politicians are not interested in dealing with the rulings of an entrenched bureaucracy and perhaps making them revaluate their regulations
FYI Based on the fleet milage obtained in Europe and in the US, if the US adopted the european emission regulations, the US fleet average mileage could be in the order of 50% better. In other words we would use a lot less foreign oil if we changed our automotive emission requirements. thus reducing drastically the CO2 emissions among other things
We all need to push to make sure our government revalutes things in the light of new information.
I suspect that we will be using fossil fuels a lot longer than many people suspect or desire. Reducing emissions is a laudable goal but the world is going to use up all the fossil fuel we can no matter what the green climate folks would like to see happen.
I would really like to see the EV replace ICE powered ones but the target to beat is still the ICE and the availability of fossile fuels is still good enough. How good and for how long is difficult to say but we keep finding more and figuring out how to get it in a relatively cost effective manner. Oil, coal, natural gas, methane hydrates, we are going to use them all.
I've followed and studied alternative engines for many years. Many are pure scams, such as the MYT engine and quasiturbine. The split-cycle concept has some merit, but in the end has only a tiny advantage over conventional technology, and some large disadvantages. For example, conv. engines benefit from doing all 4 cycles in one cylinder, because the avg. temperature is lowered. The split-cycle will have a very hot power cylinder. The "one power cycle per revolution" is no advantage, if you view the mechanism as two pistons (which it actually is). In the end, it is just running a rather conventional 4-stroke process with a different mechanism. A better use of research dollars is to figure out how to clean-up turbodiesels (with proven superior efficiency), or incrementally improve conventional engines (reduce friction, direct injection, eliminate throttling losses, downsizing, hybrids). These approaches can give as much or actually more efficiency improvements. And...I need to mention that lower weight and better aerodynamics are probably the best path to better efficiency, as the Edison2 car has proven in actual results in the Automotive X-Prize competition (>100mpg, good real-world performance).
EV's are not a panacea anytime soon either, although someday maybe. I would like to see a renewable-based liquid fuel (biofuel or solar-synthesized fuel) take the place of gasoline. This could allow the most benefit with the least change to current infastructure and user convenience profiles.
Sometimes you need to go totally outside of the box to get any advancement at all. It is totally possible that this engine is hype and will never work its way into a common mainstream vehicle like an F150, but it just might. Due to limited range, EV's are not always the best choice, so redesigning the existing liquid fuel engines might the best bet to meet new government regulations.
IF I AM NOT MISTAKEN ,THIS HAS BEEN IN PRODUCTION BY A MOTORCYCLE COMPANY( STEYR,DAIMLER,PUCH )FOR MANY YEARS.IT IS A 2 STROKE VERSION.WHCH EXECPT FOR IT BEING A BALANCE NIGHTMARE , WAS QUITE SUCCESSFUL
"However, split-cycle efficiency was never very good until Scuderi changed a key part of the combustion process."
"But if you fire after top dead center, the efficiency exceeds that of a conventional engine."
With all the backyard mechanics working of engines over the years, and with the racing industry squeezing every drop of out of engines while looking for an edge, I'll be shocked if a simple change in timing leads to something as big as they are claiming.
And I agree that balancing the airflow is a concern.
Yes, Mazda's new Skyactiv G engine is a practical example of what I was talking about - they are optimizing existing technology without resorting to strange new engine mechanisms: reducing chamber temp by better scavenging of exhaust gasses, multi-point direct injection, increasing compression ratio. They claim a 15% efficiency boost - which seems quite credible (unlike Scuderi's claims of "20%-30% and ultimately up to 50%", which are ridiculous IMO).
RalphyBoy & JesseL,
Yeah...your comments are pointing out some of the areas where I believe Scuderi's hype extends beyond credibility. Any company that claims that one of their TOP PRIORITIES is to "go public" before they have 100% operational prototypes should be viewed with great caution. They have been around a long time, burned though mountains of venture capital, and yet the data on their website says "The data in the above tables is simulated". They should complete a proof-of-concept prototype and then use the actual data to sell the product, no hype needed!
The other thing you can see on the Scuderi website (but seems strangely absent from this article, although the tank in the CAD image shows it) is that they accumulate "extra" compressed air from the first piston stage into a tank, during cruising or during deceleration (regenerative braking). Then, during acceleration they plan to use this stored energy for a "boost". I find this idea interesting, because it theoretically could allow hybrid-like advantages without any extra batteries or electric motor. However, I think that in practice this is a dubious claim, as the PSI and volume required for significant energy storage is HUGE, the inefficiency of storing energy as compressed air, and there are many other practical problems, such as the varying pressure in the tank. Also, if this concept could be made workable - I'd rather see it done in a diesel instead of a newfangled split-cycle engine. Diesels already have "jake brakes" - why not try to recover the braking energy?
I don't see how this design reduces negative work. You have the dead zone of the transfer port from one cylinder to the other absorbing your compressed air and then you don't ignite the power cylinder until after the expansion stroke has started. How is this anything more than a complicated Miller Cycle engine?
Like a two-stroke, this engine requires the incoming charge to displace the exhaust in the power cylinder. This can obviously be made to work, but it's hard to tune across a very wide dynamic range. If the incoming charge doesn't adequately displace the exhaust you run a higher risk of preignition due to the higher temperature and remaining partially burned hydrocarbons, and you're reducing the output potential of the engine. If too much incoming charge is used to thoroghly scavenge the exhaust, you're wasting energy by pumping fresh air out the exhaust.
The usual two-stroke tricks for optimizing scavenging, such as shaping the piston to minimize the mixing of fresh air with exhaust, also comes at the price of reducing combestion chamber swirl (and burn efficiency).
I just don't seen anything here that isn't done better with a Miller-Cyle or even an arrangement more like a blown two-stroke diesel.
Josborne & JesseL, I concur completely, this is an (interesting) variation of a miller cycle engine, perhaps even closer to an Adkinson cycle engine, the difference being that instead of an external supercharger, there are TWO sources of pressure induction...a turbocharger AND what is essentially a direct-drive internal supercharger. Could this be a good design...perhaps, but until there are working engines IN REAL CARS, ON REAL ROADS, the issue of drivability, efficiency, and NVH are unknown. What makes me most suspect is the designers claims that this is a game-changing new design. Show me the beef....
In 1990 I 'designed' a concept car. Ideas were shared with friends, mostly Electrical Engineers. At the time I had a Mazda RX-7 GSL-SE. It was best car I ever owned. (Stolen in 1995!). Concept car was to be like a Ford Escort 2/4/5 door car - small and light. (Maybe even a VW Beatle). Rear wheel drive by a 30 kw motor (40 hp). Top speed could be about 75 mph. Lithium-Ion was just starting then, but it seemed that a 20 kwh battery would do. Onboard would be a generator set of about 25 kw & optimized for maximum effiency at a specific constant speed. Car would have regenerative braking and a 120/240 volt charger.
Problem today is the 'Safety Standards' have added so much weight. It is no fun driving one today.
I'm skeptical on this concept. How is efficiency improved when an extra non-power producing cylinder with its parasitic friction is part of the package?
In high-rpm and high-performance engines, ignition before TDC is necessary because of the time it takes to establish combustion. Therefore a slow turning engine would likely be less efficient with a lot of advance ignition timing because early combustion will produce pressure against the rising pistion. Ignition after TDC as a means to improve efficiency/performance is a necessity in the split-cycle engine, but is illusory in a high speed engine.
Scuderi's concept is not new as earliest concepts of supercharging included an extra cylinder. Even Scuderi admits the addition of the turbocharger made the difference, and I think that's the real efficiency enhancer. I sense smoke and mirrors here, and see academics on a grant-hunting expedition.
I'll be glad to revise my opinion when we are past the paper studies and see some actual dynamometer comparisons between conventional, turbocharged, and Scuderi engines.
1. Forget comparing combustionable pressures to the lower precompression pressures of a supercharger. It is not a two stroke - it is a split cycle four stroke. There are some distinct advantages wrt to cylinder sealing in a noncorrosive, non-explosion, lower temperature environment.
2. I do not see any extra piston friction - it could be lower. Two complete cycles occur in 720 degrees - current engines [to my knowledge cannot do this]. In 'computer talk', I would describe the engine as a four cycle engine with 2 cycles of pipeline.
3. It would appear to me that allowing the cylinder to be designed for a more focused task - power or compression - would eliminate compromises that are required in todays engines.
4. I see advantages to firing the power cylinder just after TDC *IF* the mixture can be ignited quick enough. I noticed 2 spark plugs and no mention of the fuel injection system.
5. Todays engines "are not my father's engines" - they are more complex. It is not clear that significant additional complexity would be required - beyond the 'magic retention tank'. I am a bit skeptical - but I do not have enough info to comment.
6. The text "When tested on several European economy-class vehicles (including an Audi A1 and a Citroen C1), the engine boosted fuel efficiency from an average of 53.5mpg to 65.4mpg, Scuderi said. It also lowered CO2 emissions from 104g/km to 85g/km." leads me to believe that it was tested in an actual vehicle. The fact that it appeared right after SWR simulations makes me wonder.
7. The *idea* of separating the cycles sounds very appealling temperature, different bore/stroke combos BUT the proof is in the pudding.
'The text "When tested on several European economy-class vehicles (including an Audi A1 and a Citroen C1), the engine boosted fuel efficiency from an average of 53.5mpg to 65.4mpg, Scuderi said. It also lowered CO2 emissions from 104g/km to 85g/km." leads me to believe that it was tested in an actual vehicle. The fact that it appeared right after SWR simulations makes me wonder.'
Unfortunately, the Scuderi engine was never tested in an actual vehicle. The 'test results' for the European economy-class vehicles were only computer simulations. SWRI has built a 'proof of concept' prototype engine for Scuderi about two years ago, and that prototype has been running. This prototype has never been tested with a turbocharger or with the 'air-storage' tank, however. Scuderi has not built a 'full-size' prototype of their engine for testing in an actual car. The fact that Scuderi has not done this, especially after raising over $85 million, has prevented me from taking them very seriously, despite the fact that the Scuderi engine design may have merit.
My curiosity got the best of me. Before making any wild accusations or sipping any Koolaide, I snipped a few facts. Except for #5, they came from Scuderi web pages.
1. Based in West Springfield, Mass., USA, with offices in Frankfurt, Germany, the Scuderi Group is a research and development company focused on proliferating its technology through R&D and licensing. 2. Oct. 18, 2005 ...the company was recently awarded a $2 million engine development grant by the U.S. House of Representatives. The Scuderi technology is patented worldwide with four patents issued and three pending in the U.S. and three pending in over 45 countries. 3. Posted on 29 March 2006 Fulfilling a family dream and passing another milestone in internal combustion engine efficiency, the Scuderi Group will unveil on April 20 a working model of the first proof-of-concept prototype for its Scuderi Split-Cycle Engine. 4. 3 November 2008 With a proof-of-concept prototype on schedule to be built this year, the Scuderi Engine will undergo rigorous testing before being unveiled to the industry in April 2009 at the SAE World Congress in Detroit. 5. https://www.greentechmedia.com/articles/read/here-comes-the-air-hybrid-engine Michael Kanellos: August 20, 2010 Carmelo Scuderi finalized the Scuderi engine design in 2001. Scuderi completed a four-cylinder prototype last year and in about a month will come out with comprehensive test data on how it performs. A few months after that, the company hopes to show data pertaining to how well the engine did in a retrofitted Chevy Cavalier. 6. Sept. 7, 2011 The company’s global patent portfolio contains more than 476 patent applications filed and 154 issued in 50 countries. 7. Posted on 7 September 2011 Anyone who follows the world of alternative propulsion systems or new engines, can tell you that at the end of the day, many claims are made but very few are backed up by real data. So at Scuderi Group, it's a constant priority to dedicate ourselves to measuring and testing the Scuderi split-cycle technology as accurately and genuinely as possible.
The above items contain adequate information for me to make a personal judgement.
A. Scuderi has invested heavily in Marketing, Legal [patent factory], and Research. There is no clear indication that they have invested in Development [or development has been an unadvertised failure]. On Mar 29, 2006, they were scheduled to unveil a working model on April 20 - meaning that it was already working or ???. Then on Nov 3, 2008, they announce a proof of concept prototype to be complete by year end.
B. Scuderi's statement [#7] wrt 'measuring and testing' is contradictory to their demonstrated actions of 'simulate and advertise'.
All of us who have been involved in new ventures have misstepped and missed dates, but the 'whole history' seems a bit odd to me.
Does it look like a duck?? Walk like a duck?? Is it a duck??
Wow...I think the history of failed Scuderi claims you outline is very telling. Some of the other "breakthrough engines" I've followed over the years (and sometimes debunked) have similar many-year cycles of making bold claims then slipping dates and then coming back with new waves of promises as if the prior claims never happened.
For some reason, people get really hung-up on unique engine mechanisms. Many get obsessed with rotary engines. Rarely does this have any significant bearing on efficiency potential. It is the THERMODYNAMIC GAS PROCESSES that matter, and the engine mechanism is only the means to accomplish that. Even the most successful of the alternative engines, the wankel, actually has no efficiency advantage (in fact, disadvantages) and the only advantage is a little better compactness and fewer moving parts. Sorry Lonny Doyle, but your engine concept also falls into this category - less parts, creative mechanism, but no efficiency or power advantages whatsoever.
The Scuderi engine's gasses cycle through a rather conventional 4-stroke cycle. A big disadvantage is that the power cylinder sees very high avg. temperature: combustion/power-stroke/exhaust, then repeat. A conventional 4-stroke has intake(cool)/ compression(fairly cool)/combustion/power/exhaust all in the same cylinder - hence much lower temperature average. Once the avg. temperature gets too high, lubrication breaks down and engine reliability will suffer. Also, detonation sets in if the combustion chamber walls get too hot. Secondary things like oil "coking" which creates deposits on the cylinder walls also happen.
The only interesting / unique feature of the Scuderi I have seen is the "air hybrid" concept, the core concept which I believe has merit, but appears impractical (or at least undeveloped) in the current state.
I agree with most of your comments. However, the "Once the avg. temperature gets too high, lubrication breaks down and engine reliability will suffer" seems a bit unfair. Saab managed to make more than a few 2 cycle engines [similar heat issues] with lifetimes warranties over 40/50 years ago. I would think that the temp problems are about the same and that modern synthetic lubricants could handle the bottom end.
OK...I'll concede that of all my criticisms of the split-cycle concept, the temperature comments are the ones I'm least certain about. Although I still contend overheating will be a challenge based on my knowledge - it may indeed be engineerable. For example, the wankel engine has compression / combustion / exhaust always in the same location of the engine (except for the rotor). I know that this was a big development challenge for Mazda (I once owned a racing rotary), but they worked it out with special coatings on the walls, carbon seals, and (check it out) a huge radiator vs. engine size. Efficiency was (and is still) not good, unfortunately.
The main question for the split-cycle concept is "what does it bring to the table that a miller or atkinson cycle engine doesn't?". I contend - almost nothing, and it has some disadvantages to boot.
I really like what Mazda is trying to do with their Activ engines - they are exploring limits of optimization from several angles: gasoline engines with high 14:1 compression ratios, and diesel engines with low 14:1 compression ratios.
A very good point has been brought up, which is that pesky old reality issue. All computer simulations are based on a model, and deliver performance and behavior based on that model, WHICH MAY HAVE MISSING TERMS! Losses due to the added friction of the second cylinder have not been mentioned, nor have the pressure drop and thermal losses that occur as the charge air passes from one cylinder to another. These losses are not something to be ignored. Next comes the question about timing. The reality is that combustion is not instantly complete, it takes a while for the flame to spread, unless detonation occurs, and this is why almost every engine fires a bit before top center. So it would be very educational for the inventors to explain how they have worked around that part of combustion dynamics. Perhaps, in the model, combustion is "instant" . IT is true that if combustion could be instant, that firing at TDC would be the best option.
So the reality is that there is a lot of highly enthusiastic speech, but no actual physical engine to show that the computer model is valid. Society will best be served if there is a real model to verify that all of the assumptions that went into the computer model actually were correct. There have been a few "next great thing" products introduced before, so investors should be wary.
Would anybody be willing to explain how firing after top center is ever effective? and how it can improve efficiency? I really want to hear that explanation. Really.
I have an offer standing to build a full scale working model for real world testing for the Scuderi Engine. I have all machines and testing equipment necessary for building and testing their engine.
I hope they take me up on my offer.
I too am building a Split cycle engine (Doyle Rotary Engine) although it is not as well funded. It was shown at the SAE World congress last April for the first time. It was very well received. Energy Now flew here to Texas to do a story about it and while we were there a Ford Powertrain engineer had us delay our trip back from Michigan so he could take us to their research facility in Dearborn. They went over the engine design for several hours.
I too fire after TDC. I fire after TDC of the compression stroke but 30 degrees before TDC of the Power Stroke. This gives the engine time for complete combustion before the combustion is introduced to the power cylinder.
The DRE runs un-throttled. The power output is controlled by a direct injected stratified charge in the single combustion chamber.
I have built a simplified working prototype and I am working on a full scale prototype. When it is finished I will post the BSFC numbers on the DRE website. We are hoping to have the numbers before the next SAE World Congress.
I wish the best for the Scuderis, Tour, OPOC and all of the other people trying to build a better engine.
It’s a tough road. If you take a look my engine feel free to give your negative thoughts. If I can't answer them now they will not work in the real world. Physics has very tough rules that have to be followed.
Although I have a bias opinion, because of the DRE, I do not believe cooling the power cylinder is going to be a problem.
We build race engines that have no water jackets between each cylinder to allow for very large cylinder bores. These engines are used in sprint cars that run nearly wide open throttle for the entire race and produce more than 700 hp. The average amount of heat that is developed in each cylinder to produce this much HP has to be far higher than that of a power cylinder on a split cycle engine even when you consider the cool intake air bringing the average temperature down. Yet we can do this lap after lap with no cooling issues.
Today’s direct injection engines also introduce oil under the pistons to assist with cooling.
Also if the engine is in fact more efficient it will have less heat to deal with.
When running superchargers the compressor discharge temperature can exceed 200 degrees F. Since this is higher than the normal operating temperature of an engine it has a negative cooling effect. Yet they too can be run for long periods of time without adverse effects.
This is basically a supercharged two-stroke, with stage one being a turbo-supercharger, and the 2nd, a piston pump.
I have a pair of engines which could be regarded as split cycle, albeit with just a single stage supercharger. They are Foden FD6's, which have a Rootes blower and a 2-stroke diesel engine. The Rootes blower is more compact that a piston pump, and far simpler. This arangement could easilly have a turbo-supercharger added to compete with the current split cycle engines that are being developed, but more compact, and far fewer parts, moving and otherwise.
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