Mazda's Skyactiv-D (diesel) technology

[Diesel_Dave]

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.

[mechman600]

Originally Posted by Diesel_Dave

For example, the particulate levels in 07 caused all the diesel truck makers to use DPFs, but DPFs weren't "mandated" per se.

EPA did mandate some weird rules about DPFs in 07, though. I know certain horsepower engines were required to regen every 8 hrs whether they needed it or not, which is silly in an application that requires a regen, say, every 20 hrs. I suppose it was a way to ensure everything was working properly, but all it really did was burn extra fuel and wear out catalysts faster. I'm not sure if those rules stuck for EPA10+.

After the Navistar debacle of 2010+, I believe EPA now has mandated SCR for HD truck engines.

[cRiPpLe_rOoStEr]

Originally Posted by Diesel_Dave

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.

EGR is more problematic regarding the sulphur contents in Diesel fuel, and is also harder to set to use with alternative fuels.

[WesternStarSCR]

Wow you guys know your diesel technology!!! Thanks for all the details and history, it only helps when looking at the whole picture on those considering the options for themselves with the new Cruze, or Mazda 6, or whatever other diesel comes here to the States soon.

[cRiPpLe_rOoStEr]

I started to get interested in Diesels in '98 after seeing some cars from Argentinian, Uruguayan and Chilean tourists in an island in southern Brazil, heard about biodiesel for the first time in '99 and saw an ambulance with a Mercedes-Benz engine running on WVO in 2001, so I started to get even more interested about Diesels due to their higher adaptability to alternative fuels. Well, having a military dad might also have contributed to my passion for Diesels.

[Diesel_Dave]

Originally Posted by mechman600

After the Navistar debacle of 2010+, I believe EPA now has mandated SCR for HD truck engines.

SCR is mandated per se--it's just basically the only way that's been proven to met the regulated levels. That being said, the '07.5 Cummins in the Dodge met 2010 emissions levels for the pickup versions. They ran a NOx adsorber but no SCR.

Early on Navistar bet the farm on being able to meet the levels with only EGR. Early on they could. Later on, as the levels came down, they ran more and more EGR and still couldn't get the levels low enough. Basically, they refused to eat crow and admit they were wrong. By that point, the EPA was issuing them a hefty fine for every engine they sold (I think it was around $5,000). The nail in the coffin came when the other manufactures (Volvo, Cummins, etc.) file suit claiming that they should be allowed to sell the engines at all, and recently won the lawsuit. Recently they've been buying engines from Cummins while they get their own engines to work with SCR.

[Diesel_Dave]

Originally Posted by Diesel_Dave

DEF/SCR useage doesn't directly have anything to do with DPF regen cycles. DEF/SCR is for NOx, DPF is for smoke/particulate.



No, it's not included. The EPA test is fairly short, and DPF regens typically only happen every few hours.

Actually I found out I was wrong. Regen fuel usage is accounted for by the EPA, at least on heavy duty diesels. The full accounting rules are complicated but there are provisions for it.

[cRiPpLe_rOoStEr]

Wouldn't make sense to not account the Diesel fuel usage for the DPF regen.

[Diesel_Dave]

Originally Posted by cRiPpLe_rOoStEr

Wouldn't make sense to not account the Diesel fuel usage for the DPF regen.

Are you implying that EPA regulations should make sense?

[cRiPpLe_rOoStEr]

Originally Posted by Diesel_Dave

Are you implying that EPA regulations should make sense?

Should, altough they don't.