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    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
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    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
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      <title>A LOW-POLLUTION ENGINE SOLUTION</title>
      <link>https://trid.trb.org/View/686511</link>
      <description><![CDATA[The condition known as after-run is an annoying and now rare condition in which an engine keeps turning over for a few seconds after the ignition is turned off.  Today the fundamental fuel burning process that causes after-run is firing the interest of the automotive industry.  Known as homogeneous-charge compression-ignition combustion, or HCCI, the process could provide the basis for a new class of low-emission, high-mileage power plants.  An HCCI power plant combines the premixed fuel-air charge of a spark-ignition gasoline engine and the pressure-heated auto-ignition of the compression-ignition diesel engine to produce a low-temperature, even burning combustion process that yields good fuel efficiency as well as low emissions of nitrogen oxides and soot in the exhaust.  While it is too early to tell whether HCCI will prove to be successful, most engineers agree that it is worth exploring while waiting for something cleaner to come along.]]></description>
      <pubDate>Wed, 27 Jun 2001 00:00:00 GMT</pubDate>
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      <title>EFFECT OF GASOLINE OCTANE QUALITY AND HYDROCARBON COMPOSITION ON AFTERRUN</title>
      <link>https://trid.trb.org/View/148163</link>
      <description><![CDATA[A survey of recent-model cars was made to evaluate their tendency to afterrun (continued running of the engine after the ignition is turned off) and to see what devices were used to control afterrun.  The effects of idle operating conditions on afterrun were studied with two of the cars. Thirteen of the cars were used to evaluate the effects of gasoline octane quality and hydrocarbon composition on afterrun.  The results of the studies give a good overall picture of how afterrun is affected by idle settings, octane quality, and fuel composition.]]></description>
      <pubDate>Sun, 22 Apr 1984 00:00:00 GMT</pubDate>
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      <title>WHAT CAUSES ENGINE AFTERRUN?</title>
      <link>https://trid.trb.org/View/161447</link>
      <description><![CDATA[A study conducted by Chevron Research Co.  into the problem of afterrun (also known as run-on or dieseling) has determined that idle speeds 200 rpm above standard settings contribute to afterrun.  Retarded ignition timing and lean mixtures were also factors which increased afterrun. Research octane number (RON) and motor octane number (MON) affected the incidence and severity of afterrun.  Afterrun is generally due to autoignition of the air/fuel mixture at high combustion chamber temperatures and pressures.  It can occur because of high idle speeds when the engine is not warmed-up.]]></description>
      <pubDate>Wed, 15 Apr 1981 00:00:00 GMT</pubDate>
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      <title>ENGINE AFTER-RUN</title>
      <link>https://trid.trb.org/View/115559</link>
      <description><![CDATA[THE PROBLEM OF ENGINE AFTER-RUN (DIESELING) HAS COME UNDER CLOSE SCRUTINY IN A VEHICLE TEST PROGRAM AT GM. RESULTS: (1) INCREASED ENGINE IDLE SPEED, LEAN IDLE MIXTURES, AND RETARDED BASIC SPARK TIMING INCREASE POSSIBILITIES OF AFTER- RUN. FOR EACH OF THESE VARIABLES, AFTER-RUN INCREASES AS THROTTLE OPENING INCREASES. UNFORTUNATELY, PREVENTING AFTER- RUN BY ADJUSTING ENGINE-OPERATING VARIABLES CONFLICTS WITH CURRENT EMISSION-CONTROL SYSTEMS REQUIRING HIGH IDLE SPEEDS, LEAN MIXTURES, AND RETARDED SPARK TIMING. (2) OF ALL THE FUEL VARIABLES STUDIED, RESEARCH-OCTANE NUMBER HAD THE GREATEST EFFECT ON AFTER-RUN; DECREASING THE RESEARCH-OCTANE NUMBER OF THE FUEL INCREASES AFTER-RUN FREQUENCY AT CONSTANT ENGINE-OPERATING CONDITIONS. THE RESEARCH-OCTANE LEVEL REQUIRED TO PREVENT AFTER-RUN INCREASES AS THE ENGINE-IDLE SPEED INCREASES. MOTOR-OCTANE NUMBER, FUEL SENSITIVITY, AND HYDROCARBON COMPOSITION DID NOT AFFECT AFTER-RUN FREQUENCY. (3) IN A SURVEY OF DIFFERENT MAKES AND MODELS OF 1971 CARS, AFTER-RUN OCCURRED WITH 4 OF THE I0 CARS WHEN THEY WERE ADJUSTED TO MANUFACTURER'S IDLE SPECIFICATIONS. SIX OF THE 20 VEHICLES WERE FACTORY-EQUIPPED WITH "ANTI-DIESELING" SOLENOIDS, AND TWO OF THESE EXPERIENCED AFTER-RUN, BUT AT A LOWER FREQUENCY THAN WHEN TESTED WITHOUT THE SOLENOID. (4) AFTER-RUN EXHAUST WAS OBNOXIOUS AND CAUSED SOME EYE IRRITATION. CONCENTRATIONS OF HYDROCARBONS, NITRIC OXIDE, AND TOTAL ALDEHYDES WERE 2500, 5, AND 125 TIMES GREATER, RESPECTIVELY, IN AFTER-RUN EXHAUST THAN IN NORMAL IDLE EXHAUST. AFTER-RUN EXHAUST CONTAINED 1000 TIMES HIGHER ACROLEIN CONCENTRATION THAN THAT WHICH HAS CAUSED NOTICEABLE EYE IRRITATION IN OTHER EXPERIMENTS. /SAE/]]></description>
      <pubDate>Tue, 09 May 1972 00:00:00 GMT</pubDate>
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