Invaluable press with no mention of costs.
(SULEV, Tier 2 Bin 2) without compromising customer appeal- sounds like a GM partnership, e.g. we really can restore our manhood buying a Hummer

Yes, Ricardo worked with QinetiQ and PSA Peugeot Citroën on the Efficient-C project in the UK (a parallel hybrid-electric diesel demonstrator), along with other ongoing hybrid work...

This could prove to be very significant for light-duty diesel engines in the U.S. if true. A diesel engine that meets SULEV emission levels should be eligible for PZEV credit in California since diesels inherently have virtually zero evaporative emissions.

This could prove to be very significant for light-duty diesel engines in the U.S. if true. A diesel engine that meets SULEV emission levels should be eligible for PZEV credit in California since diesels inherently have virtually zero evaporative emissions.

King Pao Chicken

Uh, that's pretty racist. Is that necessary, Sid?

Yeah, that was uncalled for. An apology would look good.

The needed engine cycle is the multifuel capable HCCI in my view. Because it is a synthetic fuel, HCCI can likely burn syncrude directly and cleanly and be capable of being equipped with self-cleaning particulate filter and catalytic converter. We will come to rely on syncrude and mixed alcohols in the U.S. as manufactured from gasification processes, even if the carbon source is the biomass fraction of household trash. Thus, we are going in the wrong direction with R&D trying to doctor up the diesel compression ignition cycle. Compression ignition yes, but do it HCCI and really achieve something. Like so much R&D these days, this announced work is not innovative enough; it’s same-old same-old.

Sid,

To minimize engine emissions and maximize fuel efficiency, a low-temperature combustion process without EGR is required. High fuel efficiency requires high thermal and mechanical efficiencies. High thermal efficiency without high combustion temperature requires an expansion ratio much greater than the compression ratio. High mechanical efficiency requires high power density such that mechanical losses per unit power output is reduced. For meeting all of there requirements, an overexpanded two-stoke engine has been created. Existing four-stroke engine has absolutely no possibility to meet all these requirements because expansion ratio is equal to or less than the compression ratio instead of much greater.

Don, the recent trend in diesel engines is towards *lower* compression ratios. It may seem counter-intuitive, but very high compression ratios result in high thermal losses in the combustion chamber and add greatly to the stresses imposed on the engine block, etc. It seems like there is an "optimum" compression ratio somewhere in the 14:1 - 16:1 range if you want best efficiency in the real world. Higher than this results in diminishing returns from the theoretical-cycle-efficiency point of view, but exponentially higher heat losses and stresses on the engine's mechanical components.

Lowering the compression ratio from the historical diesel "standard" in the 20:1 range does the following:

- Increases ignition delay, which facilitates not-quite-HCCI operation. (True HCCI operation gives extremely high noise level and stress on the engine to be useful anywhere outside the laboratory, but plenty of the newer diesels are taking advantage of the concept, albeit not taking it to the extreme.)
- Reduces peak cylinder pressure. This facilitates increasing turbo boost pressure to keep peak cylinder pressure the same. *That* allows better power output from the engine to satisfy consumer demands, and allows more dilution of the charge at part-load for emission reasons (reduces peak combustion temperature).
- Tends to give smoother operation on engines with not too many cylinders. On a 4-banger, the variation in crankshaft speed through each revolution at idle is significant.

It's worth noting that modern diesel engines don't really operate on the official "diesel" cycle (constant pressure combustion over a certain duration of crank rotation), just as gasoline engines have never really operated on the official "Otto" cycle (constant volume, i.e. instantaneous, combustion). For the same compression ratio, the theoretical Otto cycle is more efficient. The faster you can burn the fuel closer to top-dead-center on the power stroke, the more efficient it will be ... the tough part is making the engine not blow itself to smithereens when you do that.