Fluid-injection for NOx reduction

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Diesel exhaust f uid

Fluid-injection for NOx reduction

By Mike Mavrigian (Photos by author except where indicated)

If your shop doesn’t routinely service diesel-equipped vehicles, you may not be fully aware of the use of DEF (Diesel Exhaust Fluid). DEF consists of a mixture of high-purity urea and deionized water. Controlled by a “dosing” module, DEF is injected into the diesel engine’s exhaust stream. DEF consists of a mixture of 32.5% high-purity synthetic urea and 67.5% deionized water.

DEF dosing is controlled by the engine’s ECU. When heated, DEF splits into ammonia and carbon dioxide, which is then atomized and vaporized. Once DEF enters the exhaust, the water in the DEF vaporizes, leaving ammonia molecules to travel to the catalytic converter where it neutralizes NOx molecules. This reaction converts NOx to harmless nitrogen and water, substantially cleaning up diesel emissions.

The EPA has mandated that all on-road diesel-equipped vehicles manufactured after January 2010 must reduce NOx emissions. The most common method to achieve this reduction is by injecting DEF into the exhaust path. All diesel-equipped vehicles that feature an SCR (Selective Catalytic Reduction) system utilize DEF injection.

The use of SCR systems reportedly

A “typical” SCR (Selective Catalytic Reduction) system (the Delphi system is shown here). This illustrates the basic layout of an SCR system, where the heated DEF solution is injected (dosed) into the exhaust stream, based on engine operation.

An example of Ford’s SCR system. After the exhaust stream leaves the diesel oxidation catalyst, the selective catalytic reduction stage kicks in (on demand), at which point the exhaust stream is further purif ed by a diesel particulate f lter. provides an additional benef t of a 3% to 5% increase in diesel fuel economy. This is a result of enhanced combustion as exhaust temperature rises, especially in the heavyduty applications. Cummins reportedly has gained substantial mileage improvements with their SCR system.

DEF usage rate

A “typical” DEF capacity on a full-size light truck should provide a driving range of somewhere in the neighborhood of 5,000 to 7,000 miles or so (depending on the make, model, size of the DEF tank, driving habits, etc.). The SCR system in Chevy and GMC light trucks uses DEF at a reported rate of about 1% to 1.25% of the vehicle’s diesel fuel usage. Citing the Chevy Silverado HD as an example, a full tank of 5.3 gallons of DEF provides a driving range of about 4,970 miles.

When the DEF on-board tank is approaching empty, the vehicle’s onboard warning system will alert the driver with enough lead-time to replenish the DEF tank. Using the Chevy Silverado as an example, the f rst warning will occur at a remaining range of about 1,000 miles with additional warnings at the 300 mile and 0 range. Below a range of 300 miles, the warning (possibly along with a speed limiting warning) will appear every time the engine is re-started.

Again, using the GM vehicle as an example, if the DEF tank is allowed to run empty, at the next engine start, vehicle speed will be reduced to a maximum of 55 mph and eventually to a miserable 3 mph to 5 mph. If the DEF tank is not ref lled, no damage will result from running the DEF tank empty.

If the DEF tank is run dry, according to GM, when ref lling, more than one gallon of DEF must be added to release the speed limitation. You must then wait about 30 seconds with the engine at idle for the exhaust f uid message to clear.

If the vehicle is driven before the message clears, the speed limiting may remain in effect. If the exhaust f uid empty message clears while driving, the vehicle must be brought to a complete stop in order to release the speed limitation.

Ford diesel vehicle SCR design is slightly different. An alert is illuminated when the system determines an 800-mile-to-go status (Ford claims that their system requires a ref ll every 7,500 miles). If the DEF tank runs dry, about a 50% loss of power will be realized during that drive cycle (not just after the next ignition-on cycle).

Instead of (or in addition to) ref lling DEF tanks when an early warning is provided, it’s wise to top-off a DEF tank at the same time that the engine oil is changed (for example, every 3,000 to 4,000 miles). In

other words, you need to keep on top of the DEF level status. Running the system dry will result in severe driver inconvenience, in terms of entering a limp mode (either loss of power or severely limited vehicle speed).

Dodge Ram diesel light trucks feature an 8.2-gallon DEF tank. According to Chrysler, the anticipated usage rate is about one gallon of DEF for every 50 gallons of diesel fuel used.

The Ram early-warning system initiates when there is about two gallons of DEF remaining in the tank. A “Low DEF Ref ll Soon” warning is displayed, along with an audible chime. When only one gallon of DEF remains, a message will be displayed that says “Ref ll DEF — Engine Will not Start in XXX Miles” (the number of miles displayed is calculated by the system’s controller). If the warnings are ignored and the tank runs

DEF f ll points for commercial/utility vehicles can vary. This utility box truck features a DEF f ll on the left side box wall.

Ford F-Series trucks feature the DEF f ll point alongside the diesel fuel f ll point (green cap for diesel and blue cap for DEF).

Ford F-Series trucks (model 2010 and later) share the same quarter panels in both gas and diesel applications. Shown here is a gasoline-powered Ford F-Series fuel f ll point. Notice the plugged-off (unused) location to the right of the fuel cap. Industry-wide, all DEF f ll points are easily identif ed by a blue cap, labeled for diesel exhaust f uid. It’s a good idea to remind customers not to confuse the blue DEF caps for windshield washer solvent locations.

dry, a “Ref ll DEF — Engine Will Not Start” message appears. This indicates that the engine will not start on the next key-on cycle. At least two gallons of DEF must be added in order to re-start the engine.

DEF tank f ll location

Location of the DEF f ll point varies depending on the make and model of the vehicle. On the Chevy/GMC models, the DEF f ll point is located next to the fuel f ll point on full-size vans; and underhood on the passenger side of full-size trucks. DEF f ll points are identif ed with a blue cap. On Ford F-Series trucks, the DEF f ll point is located adjacent to the diesel fuel f ll on the driver side.

Commercial/specialty vehicle DEF f ll locations can vary widely, depending on the model. Utility box trucks may feature a DEF f ll at any convenient location, usually on

an exterior wall of the box area. Tow trucks might feature the f ll point behind the cab. For any diesel vehicle that falls outside of the “normal” consumer light truck or van, you may need to search (or look in an found in auto parts stores/retailers.

All DEF f ll caps, regardless of make or model, should be light blue in color and should be labeled “DIESEL EXHAUST FLUID.” When f lling the commonly available in one-gallon and 2.5-gallon containers. I’ve seen one-gallon containers going from anywhere between $7.74 to as much as $12.25 (with the higher prices usually found at car dealerships). NOTE: I purchased one gallon of Peak’s BlueDef at a local parts store for $7.96 on April 30, 2013. Freezing

Once DEF temperature reaches approximately 12 degrees Fahrenheit, it will freeze. However, this won’t leave the vehicle

Photos courtesy Peak

Typical consumer size DEF one-gallon containers are the most common size

stranded. The engine is able to start, and the vehicle may be driven normally. As owner’s manual).

Dodge Ram DEF f ll locations are found underhood. engine coolant warms, the DEF will thaw and will once again f ow properly. While there have been claims that urea will become toxic at 118 degrees F, this isn’t so. Actually, urea isn’t toxic at any temperature. If it becomes too hot, the shelf life may simply decrease (as ammonia begins to form).

DO NOT add any additives, such as antigel, to any DEF tank. DEF will expand by about 7% when frozen and will revert to a liquid state when heated during engine operation. DON’T treat DEF as you would diesel fuel. You don’t need, nor should you ever add, any modif - ers/additives. Keep the

DEF tank, DO NOT Home-brew alteroverf ll. In freeznatives? ing temperatures For f eet convenience, 50-gallon drums of DEF are also available. The large tote containJust because the DEF the DEF mixture ers (shown at right) provide added convesolution is comprised will expand when nience for larger f eet operations. of a mixture of urea frozen. DEF tanks and water, this does are designed to accommodate this expannot mean that you can whip up your own sion, but only if you f ll to the advised batch. The urea used in DEF is a very highlevel. If a DEF tank does become damaged purity synthetic, and is not urine. Also, the and leaks, there’s no real hazard, since it’s water used in DEF must be extremely pure not toxic or f ammable. It’ll just make a and deionized. The bottom line: no, you stinky ammonia-smelling mess. can’t make your own DEF by mixing urine DEF prices designed specif cally for SCR systems.

For light truck applications, DEF is Allowing impurities such as calcium,

DEF pure! and tap water. DEF is a sophisticated blend

On-road emergency f lls can also be provided with the use of 500-gallon mobile units, which may be ideal for over-the-road truck/tractor mobile service operations.

Circle 107 on Reader Service Card

copper, magnesium, etc. (which would/ could be present in urine and tap water), would introduce impurities that can kill active sites in the catalytic converter (the ammonia itself won’t harm the sites). Continued use will eventually make the converter inoperative, requiring converter replacement.

Also, and this is IMPORTANT to know and to relate to your customers: DO NOT add ANYTHING to the DEF tank except actual DEF. If someone, by accident or ignorance, dumps diesel fuel treatment/booster into the DEF tank, this will kill the entire SCR system, resulting in a repair bill of thousands of dollars. PAY ATTENTION. You wouldn’t add orange juice to your fuel tank or Pepsi to your cooling system, so don’t add anything but the correct f uid to the DEF tank.

Along the lines of DEF purity, consider the quality of the DEF. The major brands (Peak’s BlueDef, ACDelco, Motorcraft, etc.) offer the highest quality both in terms of purity and proper urea-to-water percentages. However, there are a few bargain-priced brands out there that feature a higher water content,

Misco offers digital refractometers. Their model 201 refractometer offers a single-scale readout, ideal for most shops. which isn’t as eff cient and won’t last as long as anticipated. In other words, stick with the major brands.

Vehicle manufacturers have designed DEF f ll ports at a smaller-diameter size in order to prevent accidental introduction of diesel fuel into the DEF tank. While the standard diesel f ll point (for light trucks) accommodates a 22 mm nozzle, the DEF f ll point is sized for 19 mm.

Keep it clean

Whenever handling DEF, the f uid must be kept clean. If a funnel is used, it must be absolutely clean and free of any contaminants. It’s best to dedicate a funnel (and label it) for DEF only. Spare DEF should be stored in its original container, with the lid/cap secured, to avoid airborne contaminants in the shop. Do not transfer DEF to another container that previously held anything else (oil, windshield wiper f uid, coolant, etc.). Avoid cross-contamination! It doesn’t take any extra time to handle DEF properly.

FYI: Urea is corrosive to metals such as copper and brass. DEF systems are typically plumbed with high density polyethylene.

Verifying DEF quality

All API certif ed DEF will feature an API symbol on the container. Use only API certif ed DEF.

The concern with DEF quality (beyond API certif cation) is the potential for water dilution. Just as water can enter a fuel system, it is possible for water (moisture) to enter the SCR system and slightly dilute the DEF. One indication that the DEF has been diluted is when the vehicle uses more DEF than normal (beyond the mileage use specif ed by the vehicle maker).

An easy f eld test to check for the purity of DEF is with the use of a hand-held refractometer. A refractometer that is designed for testing DEF will easily allow you to verify the water content.

A refractometer is a precision optical instrument designed to measure the concentration or mixture of water-soluble f uids. It measures refractive index, which

is the speed at which light passes through Tips on refractometer use a liquid. The more dense the liquid, the Keep the refractometer clean. Make sure slower light will travel through it, resulting it’s clean before using, and be sure to clean in a higher reading. it after use and before storing. Be sure

Applying a few drops of the vehicle’s DEF to clean any accessories such as dropper, to the refractometer is all that’s needed. extraction device, etc. DEF refractometers (those units capable of Wait until f uid and tool temperature are measuring urea concentration) are available stabilized at ambient temperature before with single scale or dual scale readouts. taking a reading. The single scale provides a percentage of urea by weight. A dual scale unit also provides a refractive index scale readout, which is primarily used by manufacturers and distributors of DEF (a quality control aid). For shop technicians who simply want to check for water dilution, a single scale unit will suff ce.

Citing two examples of DEF-capable refractometers, MISCO U.S. offers a digital single-scale unit (their DEF-201) that retails for around $350. The reading will provide a precise level of water content to OTC (Bosch Automotive Service Solutions) offers an affordable, +/– 0.1%. The dual-scale high quality DEF refractometer with their model 5025. unit (DEF-202) retails for around $435. Either model is powered by a Storing DEF pair of AA batteries. Storage temperatures need to be held at

OTC has released their OTC-5025 DEF refracbetween 12 degrees F and 86 degrees F. tometer, which retails for around $114. The According to sources, this maintains optikit includes a refractometer, dropper, lens mal shelf life for up to two years. If DEF is wipe cloth, instructions, screwdriver and allowed to freeze, once thawed, its eff - storage case. The refractometer features a ciency returns to normal. Prolonged storage reticle (scale) that is enlarged through an above 86 degrees F will cause hydrolysis to eyepiece to measure light. The values on the occur, reducing shelf life. scale have been established to specif cally evaluate DEF condition. OTC’s unit features Availability 0.5% line graduations, with a scale range of DEF is available in a variety of volumes, 15% to 40%. including one-gallon containers, 2.5-gallon

Regardless of the brand you choose, a containers, 55-gallon drums and 275-gallon DEF-capable refractometer is a useful and totes. must-have checking tool for any shop that DEF is also available at the pump, primarservices diesel-powered vehicles. This elimiily at truck stops and diesel repair facilities. nates guesswork with regard to the quality As time progresses, we’ll see more at-the(in terms of water dilution) of customer DEF pump DEF availability. tank contents. Our understanding at this time is that

The DEF f ll point for GMC and Chevy light trucks is located underhood adjacent to the passenger-side f rewall. DEF is sold in North America as DEF, Peak’s BlueDef, Valvoline’s Airshield, C-Blue, TerraCair and Air1.

The use of DEF is here to stay, with the number of applications increasing at a very steady rate.

If your shop services diesel engineequipped vehicles, model year 2010 and newer, you’ll need to stock DEF, and you need to understand the need for storage and transfer cleanliness.

We offer this brief article as a primer on SCR systems and the use of DEF. So, the next time a customer asks for “muff er juice,” you’ll know what he’s talking about. ●

SUPPLIERS OF DEF

ACDELCO

6200 Grand Pointe Dr. PO Box 6020 Grand Blanc, MI 48439 (800) ACDelco (223-3526) www.acdelco.com

BRENNTAG NORTH AMERICA

(TerraCair Ultrapure DEF) 5083 Pottsville Pike Reading, PA 19605 (877) 363-5843 www.brenntagdef.com

KRUSE NORTH AMERICA

(BlueSky/AdBlue DEF) 3511 Silverside Rd. Suite 203 Wilmington, DE 19810 (877) 221-7335 www.krusena.com

MOTORCRAFT

16800 Executive Plaza Dr. Dearborn, MI 48126 www.fordparts.com

PEAK

(BlueDEF) Old World Industries 4065 Commercial Ave. Northbrook, IL 60062-1851 (877) 845-0333 www.BlueDEF.com

VALVOLINE

(Airshield DEF) 3499 Blazer Pkwy. Lexington, KY 40509 (859) 357-7777 www.valvoline.com

DEF REFRACTOMETERS

MISCO U.S.

3401 Virginia Rd. Cleveland, OH 44122 (216) 831-1000 www.misco.com

Models: DEF-201 & DEF-202

OTC BOSCH AUTOMOTIVE SERVICE SOLUTIONS

655 Eisenhower Dr. Owatonna, MN 55060 (800) 533-6127 www.otctools.com