![]() On one new engine, adjustment of the idle mixture reduced CO concentrations from 44,500 ppm to 600 ppm. Unfortunately, most LPG engines have simple fuel delivery systems which can easily be adjusted too rich, allowing extra fuel into the engine and the subsequent high production of carbon monoxide. A difference in CO production from an engine operating on LPG and one operating on gasoline usually results from more complete combustion of the LPG because it is already a vapor. Industry sources report a properly tuned LPG engine will produce from 200 to 20,000 ppm, depending on load. Is carbon monoxide a problem with LPG engines? Yes, and the same precautions against running a gasoline engine in an enclosed space should be observed with an LPG engine. Diesels usually pollute the air with particulates and nitrogen oxides, not CO. When diesel fuel is burned incompletely or when overloaded and over-fueled (rich mixture), diesel engines will produce high concentrations of CO. Diesel (compression ignition) engines run with an excess of air and often produce less than 1200 ppm CO. Is carbon monoxide a problem with diesel engines? Usually not, although any engine, including diesel, produces CO when combustion is incomplete. CO concentrations as low as 15 ppm have been measured from a gasoline engine with fuel injection and a catalytic convertor. What do catalytic converters do? The three-way catalytic converter reduces the amounts of nitrogen dioxide, hydrocarbons (unburned fuel), and carbon monoxide. Improvements in fuel delivery systems, such as fuel injection coupled with oxygen sensors in the exhaust stream, greatly improve the control of the air/fuel mixture, improve fuel economy, and reduce carbon monoxide production. Tuning by “sound” and “performance” more likely will produce an excessively rich setting, with higher CO concentrations. Combustion analysis equipment showing the air/fuel ratio and/or carbon monoxide production assists in correctly tuning an engine. Excessively lean mixtures can cause engine problems, although fuel economy is improved with a lean mixture. To ensure all cylinders obtain sufficient fuel to produce maximum power, the mixture must be rich. Why would a gasoline engine be set rich? The distribution of a liquid fuel, such as gasoline delivered through a carburetor, is not uniform. Other causes of high CO production include a cold engine, misfiring, incorrect engine timing, defective or worn parts, exhaust system leaks, and defective catalytic converters. A gasoline engine producing 10,000 ppm CO at the ideal air-fuel ratio will produce over 60,000 ppm when the fuel is increased. Two major causes are a rich fuel mixture (more fuel than is needed), or restricted air supply (dirty or plugged air filter). Anything that leads to incomplete combustion increases CO production. Why does the concentration of CO produced vary? Carbon monoxide is produced during incomplete combustion. Recent regulations affect small engines such as those used on lawn mowers, chain saws, weed eaters, electric generators, water pumps, and boats, although the regulations for small engines will continue to allow considerably higher CO concentrations than the tighter regulations for on-road motor vehicles. Engines used indoors were not originally regulated. In 1968 the EPA regulated CO emissions from on-road motor vehicles. Carbon monoxide is a cumulative poison which can rise to harmful levels in the body in minutes.ĭoes the concentration of carbon monoxide produced by engines vary? Yes, CO emitted from the tailpipe of engines burning gasoline, diesel, or LPG (propane) varies from over 100,000 parts per million (ppm) to less than 15 ppm. High concentrations of CO interfere with thought processes complicating the diagnosis. The effects of carbon monoxide at low concentrations mimic common influenza and often are not recognized. ![]() Carbon monoxide (CO) is colorless, odorless, tasteless, and non-irritating. Several of these combustion products are linked to health problems.ĭuring incomplete combustion, carbon monoxide, a deadly toxin, is produced. ![]() During complete combustion, the typical combustion products from engines are carbon dioxide, nitrous oxides, particulates, water vapor, and numerous other contaminants. The use of internal combustion engines operating on gasoline, LPG, diesel fuel, or natural gas inside buildings presents a serious risk of carbon monoxide poisoning. ![]()
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