Smog time in California, test only

[gofstbuick]

CaPPY
I'm back at work now. regarding the water injection system, it is a category 1 (Items not of concern).

 

[tom h]

generally 2-way and 3-way cats can look identical on the outside.

http://www.howstuffworks.com/catalytic-converter2.htm

Most modern cars are equipped with three-way catalytic converters. "Three-way" refers to the three regulated emissions it helps to reduce -- carbon monoxide, VOCs and NOx molecules. The converter uses two different types of catalysts, a reduction catalyst and an oxidization catalyst.

The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the NOx emissions.

The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning (oxidizing) them over a platinum and palladium catalyst. This catalyst aids the reaction of the CO and hydrocarbons with the remaining oxygen in the exhaust gas.

The third stage 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 is. 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

 

[gofstbuick]

tom h:
That is pretty much true. As the computer adjust the A/F ratio, during rich mixtures (14.4-14.6:1) the absense of O2 in the cat puts the mixture out and controls NOx. It is the absense of O2 that cools the mixture and reduces Nox; during lean mixtures (14.8-14.2:1), the O2 is stored in the sustrate material and released during oxidation to convert HC and CO to CO2 and H2O (perfect combustion of the internal combustion engine yield carbon dioxide and water). For those that remember their chemistry class, the catalyst basically changes one compuond to another. The change creates heat, and that is why the temp is hotter at the rear of the cat as opposed tho the front.As stated, the O2 sensor is key, and a properly working O2 sensor should respond from full lean (0-150mv) to full rich (850-1000mv) in less than 100ms. Even though the GN computer is not that fast, the response of the O2 is key to good emissions control. I recently tested my O2 using a digital storage oscilloscope and reponse was 40ms for the sensor to move form 100mv to 900mv.