Exhaust Valves Set

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Do you live in an area where you car has to meet inspection requirements? Normally your vehicle will also have to pass emissions requirements. This article will help explain what emissions are, and how to fix a possible problem your vehicle may have.

Emissions are simply the exhaust or leftovers of combustion coming out of your vehicle's engine. An emissions test is normally done with a probe placed into the exhaust tailpipe. The emission sampler will "sniff" or sample the contents of the exhaust coming out of the tailpipe. Every road going vehicle produced, has certain clean requirements that it is required to meet. This requirement is specified by EPA to limit the amount of pollutants exiting the vehicle.

Most emission samplers are five gas analyzers. That means they "see" or measure five types of gases. The five gases that will be measured are HC, NOX, O2, CO, and CO2. We will start with HC or hydrocarbons. HC's are simply another term for unburned fuel that makes it through the engine and out the exhaust. HC's cause smog and and are not good to breath. NOX means oxides of Nitrogen. NOX is a by product of highly heated and compressed air that has nitrogen in it. NOX is another bad emission to breath at high levels. O2 is leftover unburned oxygen in the exhaust. Although O2 is obviously not bad, it is tested for to look for people trying to cheat the test.

The percentage of oxygen in the exhaust will also tell the fuel ratio of the engine as it runs. CO and CO2 is carbon monoxide and carbon dioxide. CO is odorless and will give you headaches and eventually kill you by robbing O2 from your body, if in high quantities. CO2 is present in the air but large amounts contribute to global warming. Before doing any emission test the check engine soon light, should never light up or it will cause the car to fail. HC's are usually the worst problem for cars that will have to pass the test.

Many things can produce high HC's such as too much or even too little fuel, not all cylinders firing, advanced timing, bad catalytic converter, or an air pump that isn't working. These are the most common causes. Tune up's can prevent most emission problems. NOX is generally worse on higher compression engines. All engines produce NOX but the use of EGR valves will cool and slow down the burn rate of the engine's combustion. This considerably lowers NOX values.

O2 levels are controlled by the fuel ratio being correct from the fuel injection. If there is an exhaust leak all the test numbers will be low and incorrect except the high O2 numbers which will void the test. CO has to do with the efficiency of the burn in the engine and also is highly effected by the fuel to air ratio of the engine. CO2 is also an indicator of the engines set up. The HC's and NOX are by far the largest problem areas. Catalytic converters scrub or clean the majority of the emissions and need to be replaced when they break internally causing a loss in power and no longer clean the air.

Jerry Lemke is the webmaster at http://www.freeengineinfo.com A site focused on engine information for repair, troubleshooting, performance, upgrades, and new technologies for all types of vehicles.

Diesel Engine Principles For Beginners

Diesel engine principles are pretty straight forward for the experienced mechanic but what about regular everyday people who have never taken the time to find out more about a diesel engine and how it works?

I am going to explain in layman terms the basic principles of a diesel engine.

What is the difference between a gasoline engine and a diesel engine?

The first thing you should know is a gasoline engine and a diesel engine are totally different. A gasoline engine is constructed much lighter than the heavier built diesel engine. The gasoline engine runs on a air and fuel mixture combined with a high energy spark that is timed to ignite inside each engine cylinder at the precise time creating power and torque turning force which drives your vehicle.

A diesel engine uses high compression intake air that is compressed into a very small space inside each cylinder causing extreme heat. This is called heat of compression which ignites a very fine high pressure mist of diesel fuel that is injected into each cylinder at the exact time.

So you now know that a gasoline engine needs a high energy spark to run while a diesel uses heat of compression. The four stroke principle in all engines run on four strokes or four cycles, both these terms mean the same.

Here is how the four stroke diesel engine operates. The four strokes are intake, compression, power and exhaust.

The pistons, valves and injectors work together in each cylinder in a set sequence over and over.

Intake stroke. Intake valves in the cylinder head open allowing pressurized air to enter each cylinder while the piston is traveling downward. The pressurized air supply is made possible by the turbocharger which pushes air into the intake system giving the diesel engine a boost of air to keep up with instantaneous injection of fuel.

Compression stroke. When the piston starts to move upward the valves close which traps the intake air in the cylinder and allows compression to take place. The heat of compression is reached when the piston reaches the top of the cylinder, the diesel fuel is then injected into the cylinder at the precise time.

Power stroke. After injection takes place an explosion occurs in the cylinder because of the combination of heat and atomized diesel fuel. This causes the piston to be forced downward which produces torque and the horsepower required from a typical diesel engine.

Exhaust stroke. After the power stroke the piston moves upward once again while the exhaust valves open allowing the previously ignited gases to escape to the atmosphere out the exhaust system.

As mentioned before each cylinder goes through this exact sequence over and over in a set firing order. For instance, a 6 cylinder diesel engine has a firing order 1 5 3 6 2 4 This is the order that each cylinder goes by, following the 4 strokes mentioned above.

This sequence has been engineered to allow the diesel engine to run smoothly with no imbalance.

Here is some diesel engine trivia on high performance diesel engines. Fuel passes through the injector at speeds of nearly 1500 miles per hour, as fast as a jet plane at top speed. Fuel is injected into the combustion chamber in less than 1.5 milliseconds, the same time it takes for a camera flash to go off.

The minimum amount of fuel injected into a diesel engine is one cubic millimeter, about the same volume as the head of a pin. Volkswagen has developed a one liter diesel powered car that got 100 kilometers out of .89 liter of fuel, 60 miles on less than one quart of fuel.

There is much to learn about diesel engines and a ton of information online. If you have ever considered buying a vehicle with a diesel engine you have my blessing.

The extra cost will be to your benefit, so I recommend finding out more about diesel engines before you decide which one to choose.

I hope you have found this information on diesel engines helpful.

About the Author

John Whelan is a certified Heavy Duty Mechanic with 30 years experience and enjoys sharing tips and resources on school buses and other related mechanical systems.
Check out his Website for free tips, photos and information.

crank shaft cam shaft timing marks? I have a 1927 chevy four cylinder, I am replacing the cam shaft and crank?

So I lined up both timing marks and am trying to set the timing. and seems like maybe i put the crank shaft 180 off crank shaft is half the size of cam shaft. At what point of the # 1 valves going up and down should the cylinder be at TDC to set timing? I watch the valves exhaust opens closes intake opens and closes at that point #1 cylinder is at the bottom not the top ???? does that mean my crank shaft is 180 off?? Any extra info would be appreciated. When I try to start it it is forcing itself to turn over, pull the plugs out and it turns easy I have a fully charged battery

When the piston is at the top of it's compression stroke both intake and exhaust valves should be closed, or there wouldn't be any compression. Put you finger over the #1 hole and when you feel it push your finger off, you are at the top of the compression stroke.

2005 Alfa Romeo GT 2.0 JTS from UK and Ireland - Comments
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