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Light duty RCCI can deliver engine-out Tier 2 Bin 5 NOx; potential for 52% gross indicated efficiency

A study by Sage Kokjohn, Senior Engineer in Combustion Research at Cummins Inc., and Prof. Rolf Reitz of the University of Wisconsin found that reactivity controlled compression ignition (RCCI) (earlier post) in a light-duty engine can meet Tier 2 Bin 5 NOx levels without aftertreatment, while offering a 4% improvement in fuel consumption and 7.3% improvement in total fluid consumption (diesel + diesel exhaust fluid for SCR) over conventional diesel combustion.

RCCI is a promising low-temperature combustion strategy offering a pathway to high-efficiency clean combustion using in-cylinder blending of fuels with different auto-ignition characteristics. (Earlier post.)

Their paper is published in the International Journal of Engine Research. The pair assumed that the conventional diesel combustion mode used selective catalytic reduction (SCR) to meet NOx constraints.

Kokjohn and Reitz said that the fuel consumption improvement is due primarily to lower heat transfer losses.

Additionally, it was found that the efficiency of reactivity controlled compression ignition can be further improved by careful selection of operating conditions and the combustion chamber configuration. The modeling shows that over 52% gross indicated efficiency can be achieved in the light-duty engine while meeting NOx targets in-cylinder.

—Kokjohn and Reitz


  • Sage L Kokjohn and Rolf D. Reitz (2013) Reactivity Controlled Compression Ignition and Conventional Diesel Combustion: A Comparison of Methods to Meet Light-Duty NOxand Fuel Economy Targets. International Journal of Engine Research doi: 10.1177/1468087413476032



A downsized smaller unit (under 1000 cc), running at a optimum steady speed, could become one of the most fuel efficiency PHEV range extender? With appropriate inter-phase, could also become a valuable (very low cost) emergency generator.

Mass production in lower labor cost countries could make it affordable.


25 Kw would probably do it for a PHEV.
Enough to cruise on a motorway at the legal limit, and use a blended strategy for acceleration and mountains.
You might even use the GPS (and route planning) to determine if it needed to "pre-charge" the battery for long climbs.
People seem to be doing a lot with coasting now, which would work even better on the down-grades.

I suppose the question is would people tolerate a car where the ICE kicks in and out every 10-20 minutes as it charges the battery at its most efficient setting.

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