When the EGR was deleted the camshaft overlap was changed to trap exhaust gas in the combustion chamber. A jeep 4.0 is not capable of easily passing NOX without some provision for reduction of combustion chamber temp. At least thats the way it was explained to me by the Chrysler engineer that taught the Jeep factory advanced driveability class that I took. While it is true that thermal NOx (or simple NO) is a gas, it is my understanding that the formation of Fuel NOx includes some particulate matter as a result of the combustion of the char portion of the fuel, which is nearly 100% carbon. Goatman and I were just discussing this very topic night before last. The particulars of the gas composition really are inconsequential to the discussion, I was just trying to answer his question, "what would cause the NOX to be so high?" And maybe give him some advice that would help him get it fixed.
Wasn't trying to jerk your chain, you obviously have some excellant training, knowledge and experience to be proud of, I was just trying to teach some basic chemistry / terminolgy, as the term caught my attention, and being a chemical engineer, and hanging out in a tech forum here, it got my attention.
Very interesting to hear that the cam is different between HO and Renix, and at least part of the why! Thanks. I made some comments below in another post about 5-90's tests on live California emissions test equipment that showed equal or lower NOx emissions on the same engine without the EGR, versus with it. It is a pet peave of his, he claims he has even tried to convince the State people that the EGR is more trouble than it is worth on the renix 4.0 at least.
NOx means NO, NO2, and NO3, all of which are gasses. The X is just an algebraic variable, short hand for 1,2 or 3. When measuring a pollutant like NOx, they are only measuring the number of N atoms, that are bound to O (oxygen) atoms by measuring the number of N to O bounds which absorb a specific wavelength of light, and the loss of that wavelength of light (missing photons) passing through a sample is detected to quantify the number of NOx gas molecules in the exhaust.
While the particulate is part of the air pollution story it is not what is measured and quantified in the engine exhaust to my knowledge, and I deal with the chemcal plant end of that sort of lab equipment where they also monitor and measure NOx emissions. The NOx reacts with VOCs (molecules of gasoline are VOCs, and natural VOCs like turpines from local pine trees) and forms particles that are called smog. To my knowledge the particulate formation, smog happens after the NOX hits the atmosphere and cools. The smog (particulate) formation is typical trigger by UV light from the sun hitting an NOx or VOC molecule.
VOC = Volotile Organic Compound
Back on topic, I have been told by several experts, including a local Texas auto emissions tester (*) here in Houston, and 5-90, that running a good cleaner through the intake and gas tank (dual treatment) to clean the carbon build up in the intake, and especiallly the combustion chamber out (*)"has never failed to fix and pass a high NOx only failed vehicle" in his experience. However, the tests in California (LA), are tougher than here so who knows, but if the CAT is working well enough to keep the CO and hydrocabons with CA limits, chances are cleaning all the crap out of the combustion chamber may do the trick for him on NOx.
