HOHN

There are a couple companies making the catalysts. Cummins Emissions Solutions makes some.

I've heard BASF makes some of the substrate material. The real advancement in SCR tech involves the switch from an iron-zeolite base to a copper-zeolite base. For some reason, it's a LOT better..

patdaly

Justin, any chance you guys could license Honda's Cat?

It sure would be nice to get away from adding the Urea.

HOHN

I haven't a clue. Anything's possible I suppose. Does Honda have some special cat?

johnny5.9

This doesn't mean much to me but I'm sure it does to you. This info was pulled from diesel power magazine's write up on clean diesels.

1) Honda DPF system during lean-burn operation, the NOX adsorbent in the lower layer of the catalyst adsorbs NOX from the exhaust gas.
2) As needed, the engine-management system adjusts the engine air/fuel ratio to rich-burn, where the nitrogen oxides in the NOX adsorption layer react with hydrogen obtained from the exhaust gas to produce ammonia (NH3). The adsorbent material in the upper layer temporarily adsorbs the NH3.
3) When the engine returns to lean-burn operation, NH3 adsorbed in the upper layer reacts with NOX in the exhaust gas and reduces it to harmless nitrogen.

patdaly

As Johnny5.9 has posted, Honda's new Cat requires no Urea to produce Ammonia.

Sure would seem a better solution, unless it cannot produce enough Ammonia for larger engines.

72dart

And with all these new and improved emission devises, how much will it add to the cost of the engine option? When I bought my truck, the engine option listed at $5550.00 and when the 6.7 was introduced it jumped over $1500.00 to over 7K. Will this new one be 11K+? As these new designs come out, to keep up with the EPA, they are more expensive, less reliable, higher operator cost, and the list goes on. Keep it! The truck in my signiture will be my last diesel pwered HD. I will sell it in a few years to buy a new gas powered truck. I do get a kick out of the manufactures having to up the stock power ratings to lure buyers (idiots). I would think the the engineers at Dodge would offer the four cylinder Cummins in its 3/4 tons for increased milage. But I suspect that most of these stooge's drive Honda Accords and have no real valuable input for the needs of the heavy duty truck buyer in the first place!

XLR8R

Urea-catalyzed emissions reduction has been around for a while (mostly in Europe), and I got the impression that Cummins was developing the tech for it based on it's proximity to MB through Daimler-Chrysler... at least that's what they seemed to be trumpeting in my issue of Machine Design early last year.

Nobody likes new & improved technology more than I do - but like most of us, I detest how it gets forced upon us... not Cummins fault - but the EPA's, and that of those who hold elected office in government (hope we all remember that in November!)

Using SCR & EGR together makes sense based on the principle of diminishing returns; as you approach 100% effectiveness with either scheme, the drawbacks are simply prohibitive. Hopefully, the benefits from increased fuel economy and reduced sooting (and thus maintenance costs) in the intake tract will outweigh the added complexity, expense & inconvenience of yet another vehicle "system" to deal with.

Presently, there's definitely too much EGR in the 6.7L
SCR-only systems would probably have OTR truckers stopping to pee in their urea tanks!

Justin, does switching to copper zeolite catalyst reduce the amount of slip in the exhaust to insignificant levels? Are you guys working with Delphi's ammonia sensors? If you tell me do you have to shoot me?

HOHN

A-ha! This Honda system is technically not considered SCR. That technology is called a NOx Absorber.

I'm under the impression that these aren't used yet because 1) they don't have a demonstrable service life long enough for HD truck use, and 2) they can't reduce NOx as efficiently as SCR can.

jh

hoot

Can't we just pee in our tank?

HOHN

As you noted, the levels of EGR currently run on the 6.7L are just a tad high. It's unavoidable though, because so many CTDs are used as grocery grabbers that SCR isn't nearly as practical.

For those who don't know, NOx emissions are highest when the engine is run at light loads and lean mixtures. Since pickups are far more likely to be run at light loads (on average) than big trucks are, the proportional consumption of urea would be much higher. Early indications from other companies SCR systems is that a HD truck will have urea consumption of about 3% of fuel consumption. In a pickup truck, that number goes up as high as 10%-- meaning your urea tank has to be a lot bigger and your cost per mile is much higher.

Generally, the more EGR you run, the less SCR is needed and vice versa. By using SCR, you can scale back the amount of EGR run to where both the EGR and the SCR are more efficient.


Oh, and XLR8 to answer your question, I'm pretty sure there will be some kind of feedback in the SCR system to address the slip issue. "Slip" for you other folks is when there's more ammonia in the system than can be consumed by the SCR catalyst-- you don't want raw NH4 coming out the pipe, though it might help your crop grow better.

Copper zeolite is more efficient-- I don't think the slip issue is why they went copper-based, I think it has to do more with actual reduction efficiency. More sites, smaller pore size, something like that.

1-5-3-6-2-4

HOHN, So how does Detroits DD15 size up in this big picture? they seem to be well seated in the OTR game with the Series 60, but is the DD15 going succeed without SCR chambers? any thoughts on that?

HOHN

Turbocompounding is nothing new, as DD mentions on their site-- Cummins built turbocompounded N14s 20 years ago.

Ultimately, turbocompounding is not the best solution. For one, the massive amount of gear reduction is pretty inefficient. It's also tough to make the gearbox reliable with such high reduction ratios (often up to 75:1).

The absence of SCR means they are running a lot higher levels of EGR to keep engine-out NOx levels under control. Inevitably, that means sacrificing fuel economy. It's almost axiomatic that better mpg means higher NOx output and vice versa. Since they can't have higher NOx coming out of the engine (to let SCR deal with), they have to sacrifice mpg to get it down.

The injection pressure on the Cummins engine is higher too. The XPI system being jointly developed by Cummins and Scania will have the highest injection pressure ever on a heavy duty diesel engine.

Still DD has a solid engine that will deliver good performance and plenty of power. Rating for rating though, the Cummins will pull stronger off idle and let you hold a gear longer before downshifting (which helps mpg a bunch) and the SmartTorque ratings give you an extra boost.

If you want a GREAT truck for mpg, get an International ProStar with the 450hp SmartTorque rated ISX. This setup is the mpg king of HD trucks.

Look what FedEx and Wal-Mart are buying for new trucks-- it's no accident that the Prostar/Cummins setup is what they are ordering. MPG rules in this modern day.

JH

SpitterGuy

Wow, that's quite a big tank (comparatively to a 2500/3500). That would require more than just picking up a jug at the nearest pitstop. That would have to be offered at the pump. It surely would have a big impact on stowage space in a HD Ram. About how much urea is required per gallon of diesel consumed? Or is the urea load based (e.g. lighter engine load requires more urea or vise-a-versa). I'm just trying to figure out how much attention this added system will need.