NOx in a car

How is NOx controlled on a vechile w no EGR and a standard valvetrain…

Well first unless there is a defect in the exhaust system it is not going to get into the car. It is a product of combustion. Frankly I don’t know much about NOx emissions other than high pressure and combustion temperatures tends to result in their creation.

It isn’t.

There are two primary ways a car controls NOx.

  1. controlling the cylinder temps with the EGR system, which basically displaces a wee bit of incoming air (and its constituant oxygen) with inert exhaust gas. It’s exectly the same effect as closing the air supply a bit in a woodstive, it lowers the temp. Oxygen is a major requirement for combustion. NOTE: The EGR system also helps prevent premature detonation by keeping cylinder temps from getting too high.

  2. the platnum palladium/rhodium (same family) in the catalytic converter when hot causes the nitrogen and oxygen to seperate, turning NOx into nitrogen and oxygen.

A car with no EGR system and a cat converter could, arguably, be said to be controlling NOx in the exhaust…but not as well as one with an EGR system.

NOx is produced when, under heat and pressure, the nitrogen in the air (77%) bonds with the oxygen in the air (22%).

NOx causes photochemical smog, that dirty brown stuff that hangs over L.A., Denver and a number of other cities that suffer from air inversion. All cars are required to have NOx controls, usually done with EGR and a catalytic converter. Old cars (pre-1975) did not have this equipment and were real polluters. Large boilers and other industrial combustion equipment also need to have EGR to control NOx.

Probably by retarding the timing or some other way to keep combustion temperatures down. It’s the heat that causes the oxides of nitrogen.