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Delphi Introduces New High-Pressure SCR Systems for NOx Treatment; Initial Target Passenger Cars and Light Commercial Vehicles

Components of the Delphi SCR system. Click to enlarge.

Delphi has introduced a new selective catalytic reduction (SCR) NOx control technology for diesel engines that improves the performance, packaging and long-term reliability of the SCR system as well as reduces vehicle CO2 emissions by up to 1 g/km over any comparable system, according to the company.

By injecting aqueous urea solution into a SCR system at up to four times the pressure of previous systems—which allows the catalyst to be close-coupled to the engine—Delphi says it has solved many of the issues associated with other SCR systems.

Currently applicable to passenger cars and light commercial vehicles, the technology is also being developed with higher flows to suit medium- and heavy-duty diesels. The system consists of three basic modules:

  • The SCR doser (an injector with integrated high pressure pump) is mounted in the exhaust line just ahead of the SCR catalyst and injects the urea solution at 20 bar (290 psi) directly into the exhaust stream.

  • The solution is supplied to the injector by a low pressure pump within the Urea Delivery Module (UDM) in the remote urea tank.

  • The third element of the system is the electronics and software used to control the dosing subsystem.

The high pressure of the dosing injector, combined with an innovative insulation arrangement, prevents the urea solution from boiling within the doser, allowing its tip to be directly exposed to the hot exhaust. This architecture puts more energy into the urea spray which requires less mixing energy from the exhaust and eliminates deposit formation at the nozzle tip. It also ensures consistent spray performance over the entire life of the system.

The performance of the Delphi doser allows exhaust designers to move the SCR catalyst closer to the engine which in turn reduces CO2, as catalyst heating and light-off strategies can be reduced.

Unlike alternative systems that use timed injector opening, the Delphi system uses a positive displacement solenoid pump that delivers an accurate, metered quantity of urea through the injector, regardless of supply pressure, throughout the lifetime of the system.

As an experienced diesel fuel injection supplier, Delphi has the ideal combination of design and high-volume precision manufacturing expertise necessary to develop this new system. In total, we now have 52 SCR patents and another 20 applications pending.

—Peter Spadafora, Delphi product team leader, SCR Systems

Additionally, the Urea Delivery Module (UDM) can be customized to integrate the functions of urea level sensing, lifetime filtration, heating for defrosting in winter and a delivery pump, packaging conveniently into the base of the tank. The delivery pump is only required to pressurize the urea solution to prevent boiling in the feed lines.

The modular architecture of the main system elements simplifies installation into the vehicle and offers flexibility to individual vehicle manufacturers. Depending upon customer preference, Delphi can provide either a Dosing Control Unit, a simple Heater Control Module or just the software and electrical interface specifications to control the dosing sub-system. Where required, Delphi can also provide system services to specify and calibrate the dosing sub-system.

Delphi’s high pressure SCR dosing system will help vehicle manufacturers meet stricter NOx requirements such as EU6, Tier 2 bin 5 and corresponding Japanese regulations while improving CO2 emissions and minimizing overall system cost.

—Peter Spadafora

The first production application of the Delphi SCR system is scheduled for introduction in 2012.



Amazin. Our typical gas guzzler's CO2 emission could be reduced from 293 g/Km to 292 g/Km with this new system. A 5-star to Delphi for this outstanding achievement.


"aqueous urea solution" seems to be code for "ammonia" which, of course, is stored on-board in it's own tank.

That means these SCR equipped vehicle now need an MPG rating for the Ammonia they consume. The Delphi press release conveniently fails to mention this rating.


I don't know why the knee jerk reaction against reducing CO2 emissions from Diesels.

I understand that the vehicles will be given an MPG rating that equals the average (diesel fuel MPG plus urea MPG divided by 2).


So, HarveyD, what did you expect? Should a more or less "passive" aftertreatment component be able to reduce CO2 from 293 to 193 to qualify according to your standards? What other type of "can" could do that? It is amazing that they can get any reduction at all.

The final result depends on what you compare with. The difference compared to other NOx catalysts (e.g. NOx adsorbers) is much greater than 1 g/km, although not mentioned by Delphi. Delphi compares with other SCR systems. They also use smilar amount of urea. Of course you need to include urea consumption in the MPG rating. However, one should note that the energy required to produce 1 kg of urea is less than to produce 1 kg of fuel. Simply adding the two consumptions is not fully correct.

More important that the reduction of fuel consumption, however, is that they can move the catalyst closer to the engine. This should reduce cold start emissions; a very important issue for SCR systems.



The world deserves more than a 1g/Km reduction. Using low resistance tires could do more.


Mercedes developed a similar system to clean up diesel exhaust some time ago. The urea consumption is such that it needs to be replenished when its time for an oil change.


The world deserves more than low resistance tires. A emissions compliant Diesel does MUCH more.


tenneco - gillet gmbh has such a solution since years in Europe...


TT: You may put as many bandages as you may find over liquid fuel ICE vehicles and they will still consume imported oil and pollute the planet. Electrification + clean energy power plants (Nuke + Sun + Wind etc) is the best way out. The sooner we start the transition, the sooner we will get there.

Henry Gibson

The governments have mandated the use of renewable fuel why not then mandate cheap plug in hybrid cars. Force auto companies to produce cheap plug in hybrid cars and force people to buy them regardless of price. And by the way, speeds can be reduced on roads to get a very big increase in operation efficiency. Politicians believe they can avoid the laws a physics by mandating renewable fuels to avoid the unpopular step of mandating lower speeds. Mandating freight traffic to travel on more efficient rails instead of roads is also possible. WalMart has a big truck distribution warehouse in Utah on I15 when it should have been in Nevada near Las Vegas along the Railroad tracks and I15. ..HG..


HarveyD, if you want to get a great reduction, you have to add the contribution from many different sources. If SCR can offer an improvement, why not embrace that small contribution. There is no single soution to all our problems. Sun and wind is not cannot cover all need and Nuke power has its specific problems. Besides that, why are you building more and more coal plants in the US? Use that marginal electricity in BEVs and they will be worse than gasoline cars.

Henry: Your government could do the same as the EU. You could consider BEV and plug-in in electricity as a renewable fuel. In fact, the EU Commission actually already favours electricity more (better incentives) than biofuels but that is a different issue... If BEVs are better than biofuels, BEVs will win the race. But... you cannot give them unfair incentives or mandates.

Mandates can be good but you must give enginees some freedom to come up with inventions, too. Mandates on electric propulsion alone might not give us the best solution for the long-term future. I sounds like Soviet Union policy to me.

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