wolcott wrote:
It's been my understanding that EGR was added because in Los Angeles, Denver, and Reno, and other areas with a lot of sunlight and not much rain, NOx was a significant cause of the brown haze that characterized this type of smog, and helped contribute to ozone (I don't know the chemistry behind this). The technique for curing this was worked out in the 1960's for gas engines, and exhaust gas was recirculated to cut the peak burning temperature, which is when NOx is created. However, it took several years and a lot of effort to get EGR so it worked well for gas engines, the early systems were notorious trouble causers that were best deactivated between smog inspections.
NOx can theoretically contribute to Ozone production, but only in the presence of high VOCs, which EGR valves, ironically increase by a huge factor. The actual chemistry of O3 production is poorly understood and is contradictory based on the authority publishing the info. What has been firmly established is that it does NOT cause acid rain in areas of high Ozone occurrence. An amusing side note to the problem of Ozone smog in Non Attainment cities, is that the incidence of skin cancer is significantly reduced due to the UV absorbing qualities of Ozone.
The EPA seems to be in complete denial of an unusual phenomenon called the "Weekend effect", because it completely invalidates their NOx policy for the past 30 years.
If you have wondered why it is that smog levels in many American cities have gone up within the past 20 years, in spite of a greater than 50% reduction in total NOx emissions in that time period as a result of EPA regulation, you will find the answer here.
http://www.aei.org/publications/pubID.1 ... detail.asp This article references a number of studies by very well respected scientists and Government as well as private organizations. Ironically many of these studies were funded by the CARB and EPA, both of which firmly denounce the findings of some of their own scientists, because the findings are very embarrassing to them.
These findings clearly identify NOx reducing devices and EGR valves in particular, actually raise smog levels. So.. EGR valve = Satan.
Further reading.
http://www.heartland.org/publications/e ... Worse.html
http://www.nrel.gov/vehiclesandfuels/nf ... tions.html
web.mit.edu/aeroastro/partner/reports/hartman/brunelle-yeung-08.pdf -