Sisu, an AGCO company with the diesels used in many of AGCO brands (Massey, Challenger for 2) started using DEF for Tier 3, primarily for the fuel economy advantage. By using DEF and Diesel Oxygen Catalyst, they can run hotter combustion temperatures which results in high NOX, but they take care of that with the DOC and urea in the DEF to convert the NOX. They can apparently run hot enough to burn off the particulates but Deere says it can't be done without sacrificing something so you find the big JD diesels having both the DPF and using DEF. Some say they can get by with super high injection pressures and precise controls. Kubota's newly announced engines all add ATAACs to engines that didn't previously use them and with them precisely measured and controlled air inlet temp - inlet into the cylinders. That is pretty basic emissions technology but comes with complexity and cost. So when an engine company announces they are introducing a line of engines with a different configuration to meet customer demand, you need to know what that demand is. Did they screw up in the first place and now have to backpedal (like Navistar - now switching to DEF because they could not reliably meet emissions with their announced low cost simplified design). Are the new engines higher installed cost, the reason Kubota didn't use them on their tractors? The challenging solutions are in the larger diesels (not super large diesels - medium and large ag tractor size). The smaller diesels are still allowed to be very dirty because they don't get a lot of hours and their total pollution is insignificant. But new changes may still be in order gown the line. Health studies are now focusing on what particle size is the primary cancer causer and new European standards specify limits on different particle sizes. In the US the EPA has not yet said anything about following the European standards but... Europe may have more concern because of the higher traffic density and the high percentage of diesel cars in much of Europe.
