Quote:
Originally Posted by compu_85
VWs TDIs have had cooled EGRs since the 1997 model year. Cooler gas = less NOx. Our Passat has 2 EGR circuits, and IIRC 2 coolers 
IMHO NOx isn't that big of an issue. Adding a cooled EGR to a 603 probably make a huge difference. The major pollutant on these engines is probably HC and particulate matter.
-J |
Your understanding of Diesel emissions is incomplete.
Diesels actually make little HC (or CO) and the PM is only a concern because PM carries non-particulate bound organics which are carcinogens. Lower PM and you lower the organics. The part you see is just carbon.
You are right that cooler gas = less NoX. But NoX IS a big deal. It's the catalyst in photochemical smog and is REALLY toxic. Diesels make a ton of it. NoX is a formed by temperature, pressure, and time. Diesels have high combustion chamber temps, LOTS of pressure, and relatively longer times due to the relatively low engine RPMs compared to Otto-cycle engines. Much of the development in the Diesel engine field has been aimed at reducing NoX for those reasons.
Just FYI - I'm retired from the EPA where I was a tech working on Diesel aftertreatment development as well as EGR applications.
Dan