Understanding Catalytic converters

What some people are stating about catalytic converters and their ability to control some of the harmful elements stemming from automotive emissions can not be completely discounted. There is a correlation between the temperature of the converter and the efficiency at which it operates from a pollution reduction perspective.
We are still quite confident that when one takes into consideration the amount of fossil fuel wasted – by individuals in the drive-through lineup, and what we believe to be significant quantities of additional harmful emissions coming out of these individuals tailpipes, we are doing a great service to our planet and ourselves by parking and walking in rather than fostering the drive-through industry.
There will be those who disagree, the industry is “pushing Back” and there are others who for what ever reason don’t seem to embrace the facts. Remember – 60% of a 129 billion dollar fast food industry is done at the drive-thru window.

Controlling Pollution and Improving Performance

The third stage of conversion is a control system that monitors the exhaust stream, and uses this information to control the fuel injection system. There is an oxygen sensor mounted upstream of the catalytic converter, meaning it is closer to the engine than the converter. This sensor tells the engine computer how much oxygen is in the exhaust. The engine computer can increase or decrease the amount of oxygen in the exhaust by adjusting the air-to-fuel ratio. This control scheme allows the engine computer to make sure that the engine is running at close to the stoichiometric point, and also to make sure that there is enough oxygen in the exhaust to allow the oxidization catalyst to burn the unburned hydrocarbons and CO.

The catalytic converter does a great job at reducing the pollution, but it can still be improved substantially. One of its biggest shortcomings is that it only works at a fairly high temperature. When you start your car cold, the catalytic converter does almost nothing to reduce the pollution in your exhaust.

One simple solution to this problem is to move the catalytic converter closer to the engine. This means that hotter exhaust gases reach the converter and it heats up faster, but this may also reduce the life of the converter by exposing it to extremely high temperatures. Most carmakers position the converter under the front passenger seat, far enough from the engine to keep the temperature down to levels that will not harm it.

Preheating the catalytic converter is a good way to reduce emissions. The easiest way to preheat the converter is to use electric resistance heaters. Unfortunately, the 12-volt electrical systems on most cars don’t provide enough energy or power to heat the catalytic converter fast enough. Most people would not wait several minutes for the catalytic converter to heat up before starting their car. Hybrid cars that have big, high-voltage battery packs can provide enough power to heat up the catalytic converter very quickly.

Catalytic converters in diesel engines do not work as well in reducing NOx. One reason is that diesel engines run cooler than standard engines, and the converters work better as they heat up. Some of the leading environmental auto experts have come up with a new system that helps to combat this. They inject a urea solution in the exhaust pipe, before it gets to the converter, to evaporate and mix with the exhaust and create a chemical reaction that will reduce NOx. Urea, also known as carbamide, is an organic compound made of carbon, nitrogen, oxygen and hydrogen. It’s found in the urine of mammals and amphibians. Urea reacts with NOx to produce nitrogen and water vapor, disposing more than 90 percent of the nitrogen oxides in exhaust gases .

Turn Off Your Engine! (studies & links within article)

Turn Off Your Engine! (studies & links within article)

December 19, 2007 | Posted by Mel Peffers in Automobiles & Fuels

This post is by Mel Peffers, Air Quality Project Manager at Environmental Defense.

Many people idle their car engine in winter because they think it needs time to warm up. Not true! Today’s fuel-injected engines don’t need a warm-up period, and idling for long periods can lead to excessive engine wear.

Worse, cars idling for over 10 seconds use more gas and create more global warming pollution than simply restarting the engine. Surprised? It’s true. The 10-second rule has been proven empirically.

The 10-second rule was originally published by the Canadian Office of Energy Efficiency – Idle-Free Zone. Their results were replicated by the American Society of Mechanical Engineers, which found that restarting uses the same amount of fuel as idling with the air conditioner on for 6 seconds.

Besides contributing to global warming, diesel engine emissions can cause a whole host of health problems – asthma attacks, impaired lung function, heart problems, and even death. (See this CARB report on health effects for details.)

Idling is a significant problem in large cities like New York and Los Angeles where people are often stuck in traffic. A car in gridlock emits up to three times the pollution as one in free-flowing driving conditions.

Environmental Defense is working with the City of New York on reducing traffic congestion (see allchokedup.org). We’re also working with Mayor Bloomberg on tougher enforcement of the existing idling law, which has been in effect for five years. Plus we are working on a no-idling policy for school buses in Texas, and Truck Stop Electrification (TSE) expansion so truckers won’t need to idle overnight while sleeping. Our GreenFleet initiative helps fleet owners reduce emissions.

Avoiding pollution and engine wear aren’t the only benefits to not idling. You also can save gas and money. Here are some studies that demonstrate it:

Edmonds.com – “…you can drastically improve your gas mileage.”

Homemade Hybrids – “I kicked the idling habit and saved a gallon of gas per tank.”

With this Cost of Idling worksheet [PDF] from Argonne National Laboratories, you can calculate the savings for your own vehicle. For more tips on clean driving, visit Car Talk’s “Driving Tips for Tree-huggers“.

Not idling is good for the environment, good for your wallet, good for engines, and good for health. Everyone wins by simply shutting off an idling engine.


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