Quote:
Originally Posted by mechman600
The FE increase of the SCR engines had little to do with regen cycles. EPA07-09 require in-cylinder NOx control, using ridiculous amounts of EGR and retarded timing, causing poor efficiency. Because EPA10+ engines take care of most NOx with aftertreatment (SCR), EGR flow can be reduced and timing/fuelling tuned for much better FE. Regen cycles did not change a whole lot for EPA10.
Aftertreatment fuel usage in the Cruze will depend largely on duty cycle. Low load city driving will require more aftertreatment fuel. Mostly highway usage will require much less aftertreatment fuel because of naturally higher engine out exh temps.
Typically in on-highway truck applications, overall aftertreatment fuel usage is only a couple percent of total fuel usage.
|
The EPA didnt mandate what technology be used per se (in-cylinder vs aftertreatment). The EPA just mandated the levels of the different pollutants and it was up to the manufacterers to decide how to do it.
That being said, sometimes the level pretty much determines the technology. For example, the particulate levels in 07 caused all the diesel truck makers to use DPFs, but DPFs weren't "mandated" per se. NOx has been more different. Even in the Dodge diesels there was variety in 2010-2012. The pickups didnt use SCR but the cab chassis trucks did (pickups vs cab chassis run different cert cycles). The 07-12 pickups used EGR and NOx adsorbers. To make things more interesting some European diesel truck manufacturers (Euro 5 & 6) are getting rid of EGR completely and using only SCR for NOx.