Originally Posted By: artificialist
Originally Posted By: Nick R
Originally Posted By: FirstNissan
Not bad at all. Im liking the improvements in Chevy over the past few years. Im waiting for the cruze diesel. If it comes, I will be No.1 in line to get it.
Well better get in line now
http://www.insideline.com/chevrolet/cruze/chevrolet-cruze-diesel-coming-in-2013.html
Numerous cars were coming to the USA with a diesel, but then got cancelled mysteriously.
I will believe it when I see it.
One reason the VW Jetta TDI is great is because it uses no DEF. Will the Cruze diesel (If it ever happens) use DEF?
DEF is a selective catalyst reductant (SCR) used to control NOx emissions.
Just like gasoline engines, diesel engines use EGR to control NOx emissions. Inert exhaust gasses are rerouted to in intake charge, displacing some of the combustable mixture in an effort to lower combustion chamber temperature, thus reducing NOx emissions. Diesels typically take this one step further and introduce an EGR cooler to the system, giving further capacity to reduce combustion chamber temperature.
To be sold in California, vehicles (including diesels) must meet LEV II emissions. This is equal to the EPA's Tier 2 Bin 5 emissions and limits NOx emissions to 0.05 g/mi.
The long and the short: A 2.0L engine doesn't require an SCR to meet those emissions numbers. Cooled EGR is all that's needed to keep NOx emissions in check. These small diesel engines don't use DEF in Europe and they'll likely not use them here either, being that Europe's emissions standards are *more* restrictive than ours anymore.
Larger engines, like those used in light duty pick-ups and heavy duty over-the-road trucks, are a different story altogether. Figure that the smallest of the pick-up diesels was the older Ford 6.0L Powerstroke. That's three times larger than the 2.0L in a VW or Cruze! Three times more air gets sucked in and expelled during each combustion cycle.
More displacement requires more EGR is required to dilute the incoming air charge. At it's peak, some truck diesels were running as high as 35% EGR dilution to keep NOx emissions under control. EGR in itself generally reduces effiency and the massive amount of EGR required to keep emissions in check caused some reliability problems, mainly in the form of clogged EGR valves and EGR coolers (Ford 6.0L and Cummins 6.7L are both known for this).
SCR in the form of DEF is really what saved the light duty pickups as we know them. The addition of SCR takes a lot of the burden off EGR for controlling NOx emissions, leading to a much more reliable and efficient engine operating model.