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Delphi’s On-Board Diesel Reformer for Emissions Control

Cut-away illustration of the Delphi Diesel Fuel Reformer shows the reforming catalyst. Click to enlarge.

At the recent Engine Expo in Stuttgart, Germany, Delphi provided an update and some test data on its development of an on-board diesel fuel reformer for emissions control. (Earlier post.)

The on-board reformer will allow a Lean NOx Trap (LNT) to meet more stringent current and future emission regulations such as Euro 6 and EPA Tier 2 Bin 5 without major engine modifications or additional fluids, and at a lower cost than urea SCR.

Unlike catalysts, which continuously convert NOx to N2, LNTs (or NOx adsorbers) are materials which store NOx under lean conditions and release and catalytically reduce the stored NOx under rich conditions.

This process can perform well at high exhaust temperatures, but historically has demonstrated poor performance at lower exhaust temperatures. Low exhaust temperatures represent a large portion of vehicle operating time, particularly for medium- and light-duty diesel vehicles (including cars and SUVs) used in cities.

On-board reformer design

Through a catalytic partial oxidation process, the Delphi Diesel Fuel Reformer System converts diesel fuel into a hydrogen-rich stream of gas (reformate). The reformate is injected directly into the vehicle’s exhaust system to achieve optimal regeneration and desulfation of a Lean NOx Trap aftertreatment system and improve its emission reduction performance. The reformate is also used for diesel particulate filter regeneration.

Diesel Fuel + Air Reformate
CH2 + 0.5 (O2 + 3.8 N2) H2 + CO + 1.9 N2 + Heat

The hydrogen generated on-board can also be used to serve other purposes, such as ammonia generation. This could eliminate the need for an external reductant such as urea when using a Selective Catalytic Reduction (SCR) System.

Applied in a Silverado full-size pickup truck, the reformer device helped reduce NOx emissions to 0.023 g/mi—well below the Tier 2 Bin 5 target of 0.05 g/mi.

2004 Silverado LD FTP Emissions
Fuel Econ.
Fuel Reformer System Average 0.3035 0.161 1.786 0.023 16.3
System efficiencies 86.3% 88.7% 96.4%
Std. Dev. 0.065 0.043 0.695 0.008 0.329
Tier 2 Bin 5 Standard n/a .075 – .09 3.4 – 4.2 .05 – .07

Delphi is currently targeting production for the device in 2010.




might this technology help VW and others (I guess Mercedes would be the only other) selling diesel engine passenger cars (not trucks/SUV's) meet the new emissions standards which are, currently, likely to prohibit model year 2007 passenger car sales in the United States? If so, then why the heck are they waiting until 2010??? This product, if it would allow vehicles to meet the new Tier 2 requirements set to begin in 2007 (no?), seems like a significant breakthrough that really should be on the market immediately (or as soon as humanly possible).

Rafael Seidl

Exactly which variant of the 2004 Silverado as used as a testbed? It is not possible to discern excactly how much additional fuel is burnt to facilitate the frequent purges.

Besides, it is quite important to know if the tests used regular or ULSD, since NOx traps are highly sensitive to sulphur poisoning. This translates to higher activation temperatures, sulphur purge cycles and poor life expectancy due to thermal fatigue.


Avoiding the need for carrying another fluid (urea) seems like a big advantage. Paper says fuel efficiency impact may be as low as 1.5%. If costs are reasonable, this looks like a winner.


A small turbo-BioDiesel could carry four passengers and get 90 - 100 mpg.

I could live with that if gas gets to $5 per gallon.


It strikes me that they could reduce (or not increase) emission standards in rural states. Then people in Montana who might have long distances to drive could get the benefit of diesel vehicles. [ Everyone in Paris does ]

BTW Lucas, there is no reason that I know of that you cannot hybridise a diesel (or plug in hybridise one).


Mahonj - Search Google for William Lucas Jones hybrid.

See if you recognize anything.


Lean burn GDI CVT HEV with LNT...

Sweet dream comes true.


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reasons to not hybridize diesel engines:

1) diesels are already more expensive than petrol for the same performance
2) diesels already have high torque. electric is nice w/ petrol b/c the high torque from the electric compliments the low torque from the petrol


While the NOx reductions are impressive, I hope something can be done about the relatively high NMHC and CO emissions. Actually, something HAS to be done since the NMHC emissions exceed Bin 5. Am I missing something?

Reducing NOx at the expense of higher HC and CO emissions is NOT a good thing from an air quality perspective.

Rafael Seidl

Carl -

Moreover, a diesel's engine-out NMHC and CO emissions are substantially lower than those of a gasoline engine. all diesels (at least in Europe) have long featured an inexpensive oxidation catalyst anyhow. Your concern seems unfounded.

If a reformer were deployed, it will operate only during the recuperation period of the NOx trap, when you need elevated CO levels to achieve the chemical reduction. Ergo, the device will not lead to significantly higher levels of CO (nor of NMHC if it's operating properly).


Rafael - thanks and please forgive me, I'm not an engineer (air quality meteorologist actually), so I guess I'm not sure what the chart above represents. Are you saying these are the emissions measured only during operation of the reformer?

Actually, I'm aware that diesel engine-out CO and NMHCs are inherently very low. That's why I hope these NOx reduction devices don't cause an increase in the CO and NMHC emissions (not a good trade-off in my opinion).


2010? No wonder Delphi is going under, seems this product could receive some more attention and increased funding, to "fast" track it into the (US) market... at least for school buses and big rigs



Reasons to hybrid a diesel vehicle:

1) Yes, a diesel is marginally more expensive but increased production will bring costs down. Bosch et. al. are getting very good at making the expensive injectors etc. By the way hp will be same peformance but torque will be double for the diesel, this is the useful grunt that makes the difference

2) Which brings us to the other point, yes the torque is higher on the diesel, but a hybrid will still allow you to crawl through the urban jungle without the engine on. Surely thats the whole point!
In any case through higher gearing who say's you could'nt add more torque with the motors to the diesel engine.


Plz...dont make me cut,splice or weld my Saab turboD on moms Civic hybrid. Diesels are 2-500 less in EU.

Prabhu Manickam

It's good to see things developing in diesel engine to reduce pollution. I am for India where the diesel engine as used more in passenger cars, so in case of implementing this into the passenger car model will be good but capital cost,modification cost, along with diesel cost will it be fruitful.


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