The problem is that you have to accept low compression ratio at low load when the turbo doesn't do much. Ideally you want the CR to be higher at low load , but that might not apply for the Scuderi engine where the highly turbulent combustion can allows ignition of very lean mixture.

Anyway I am still waiting a demonstration in real of all the promises they keep claiming with, so far, little facts to support it.

I dont get how the big piston which is power/exhaust is supposed to be acting like Im assuming a two-stroke if there is an exhaust valve at the top of the cylinder. Shouldnt it be a port at the bottom?? so when the piston passes, exhaust gasses exhaust, on the up stroke, the inlet opens for a split-second, allowing high-pressure air in, and is now ready for another combustion??

This is sort of two stage forced induction, the turbo is the first and the air piston is the second. Combine that with "MAHLE Powertrain’s Turbulent Jet Ignition (TJI) spark-initiated pre-chamber combustion system" and who knows?

"operating in a 2004 Chevrolet Cavalier" January 2011

It sounds like they have a working engine that they can compare with the stock engine in the same car.

Toyota, which I presume to be far more reputable than Scuderi, has already promised a new engine for 2014 which is around 45% peak thermal efficiency. The current generation Atkinson cycle 1.8L Prius engine returns 38% peak thermal efficiency.

If Toyota hits their number, then Scuderi has to be 50% or higher to even stand a prayer of being successful in the marketplace.

I think ideally we should aim for around 70% peak thermal efficiency -- which would probably involve multiple stages -- because once the design is mass-produced the fuel saving benefits transfer quickly around the world and without the need of hybrid technology.

Ralph

@Ralph,
"I think ideally we should aim for around 70% peak thermal efficiency ..."

How do you go about achieving that? 70% efficiency is real close to Carnot's efficiency...meaning not even friction loss nor gas leakage nor cooling loss nor exhaust heat loss is allowed! Carnot efficiency means that only compression heat loss is allowed during the isothermal compression phase of the Carnot cycle! The most efficient combine-cycle large-scale power plant can only manage 60% thermal efficiency!

Meanwhile, major auto mfg's have promised to crank out mass-produced FCV's (Fuel Cell Vehicles) that can achieve ~70% efficiency by 2015! They will be squeaky clean without any air pollution issue, nor noise issue, nor any more oil stain in the garage or parking lot. They will require much less maintenance.
Best of all, they will be able to run on renewable H2 if and when H2 will be produced from solar and wind energy.

The Scuderi engine and the Toyota engine have one thing in common; they do not (yet) exist as commercial products. At best, we could say that both companies have showed “proof of concept”. Between this state and a commercial product, we have a period, which we tend to call the “development phase”. For a conventional engine, this is a period of 3-5 years. It is difficult to shorten too much (<3 years), since endurance testing per definition takes time, cannot be accelerated at will and must be conducted at the end of the development period. For new concepts, it is likely that the development phase is at the longer end of the mentioned period (5 years), or even longer, depending on the difficult encountered with a new revolutionary concept.

According to Toyota they have achieved a 42.4% thermal efficiency with concept 1 and 43.7% with concept 2. A “good” automotive diesel engine today achieves an efficiency of ~43%, so Toyota’s concept engines would be on pair with that level. However, diesel engines are available at the dealers today (not in the USA, of course…) in contrast to concepts engines in the laboratories. Scuderi shows BSFC of ~232 g/kWh at 1400 rpm and ~250 g/kWh 4000 rpm. Presumably, BSFC could be marginally lower at the most favorable engine speed, presumably close to 2000 rpm. A BSFC level of 230 g/kWh is equal to ~36.6% efficiency. It appears to me that Scuderi has not tested a “full-size” multicylinder engine with a turbocharger but a “single cylinder” (albeit that you have two cylinders of each kind in this case) and a “simulated” turbocharger, i.e. charge pressure and back pressure are simulated with other means. The pressure difference corresponds to a turbocharger efficiency of 40%. This is common practice for prototype engines but it does not, of course, give the exact efficiency of a multi cylinder engine. The turbocharger efficiency might be somewhat conservative, so we could say that they have demonstrated an efficiency of 37%. It might also be that the Scuderi engine has additional advantages at low load (e.g. the “air hybrid”). Still, the results are not that impressive. During a period of more than a decade from the introduction in Japan, Toyota has increased the efficiency from 37% to 38%. The latter is about the highest figure we have seen for a commercial gasoline engine. We should also be realistic about what features from their Concept 1 and Concept 2 engines that could be realized in a commercial product. We will certainly not have a 45% efficient Toyota engine in 2014! Not even in our dreams (recall that it took about 10 years to improve from 37 to 38%)… It is more realistic to foresee something in the range of ~40% on a 5-year timeframe. It will be interesting to see if Scuderi can compete on that level for their first commercial product on a similar timeframe.

"So far a proof-of-concept, one-liter prototype has been built and tested."

http://www.greencar.com/articles/scuderi-air-hybrid-engine-could-offer-big-mpg-gains.php

So far, they have spent more than $50 million on developing the engine, which could explain why there may be many patents, but few working engines.

They have car makers interested under NDA and are waiting for more of the patents to be issued. Honda sent people to look at the engine and they stayed a while to look in more detail.

@Roger: "How do you go about achieving that? 70% efficiency is real close to Carnot's efficiency..."

First of all, I said that 70% should be the aim. Second, you presuppose I'm talking about gasoline as the only possible fuel. The Carnot efficency can either be raised by increasing the fuel combustion temperature or reducing the ambient temperature. The key to hitting 70% without resorting to exotic fuel cells is to either burn hotter fuels or reduce the ambient temperature.

Ralph

While the 2015 date for affordable and reliable fuel cells may slip a bit, they are the most promising. M100 can run them without high pressure tanks, Daimler proved that over more than a decade with NECAR. Once they operate PEMs above 212F, the balance of system goes down and efficiency goes up. Reduce the platinum content and bring the cost down even more.