By now, the industry has scrutinized, analyzed and debated ad nauseum the merits and drawbacks of selective catalytic reduction (SCR) and advanced exhaust gas recirculation (EGR).

We also know that Cummins, Detroit Diesel, Mitsubishi Fuso, General Motors, Isuzu, Mack, Volvo, and others are going with SCR, while Navistar is going with EGR.

But what does it mean to the OEMs and body builders? What are the additional challenges in body- and equipment-mounting? What can be done with the diesel exhaust fluid (DEF) tank? What are the concerns about engine cooling and increased vehicle complexity?

Here's a look at seven leading chassis manufacturers and the issues related to mounting equipment on chassis that meet 2010 emissions requirements.

Dodge

Kevin Mets, lead engineer for heavy-duty pickup trucks and chassis cabs, said Cummins' 6.7-liter turbo diesel remains the same. He said Dodge is continuing the mantra it has been espousing for the last few years — that it wants to have the most upfit-friendly truck possible.

“When we designed this 2010 truck, our commercial vehicle team was part of all packaging meetings that went on,” he said.

He said the new parts include lines going to the DEF pump and to the DEF injector, and down to the SCR catalyst. The SCR module, “the brains behind the whole thing,” is mounted on the crossmember underneath the cab.

“With the cab on, most of the components are covered by the cab,” he said. “The tank is mounted under the cab. The filler pack is frame-mounted and is in a 3-inch zone between the back of the cab and the closest possible location we allow the upfit to be mounted. It takes advantage of the curvature of the back of cab.

“The pump is mounted on the frame rail and is inboard of all suspension components, so it's narrow enough that it has no effect on service-body applications or toolboxes off of flatbeds. The [power take-off] packaging area stays the same. All of that is carried over from 2009, so the packaging of the PTO should not be impacted by this new emissions package.

“As wheelbases change, the only thing that grows is the exhaust pipe after SCR. As far as consistency goes, the emissions system is the same no matter what wheelbase the system is mounted on.”

Engineering support manager Walther Bloch said the Sprinter tank is mounted under the cab and outboard of the frame rail. The fill neck is mounted to the frame and forward of the 3-inch plane, with no kit to install. The pump is mounted to the frame inboard of the leaf-spring bracket and there is clearance for service-body upfits.

On the exhaust side: the exhaust pipe between the turbo and diesel particulate filter (DPF) is common to 2009; the PTO environment/mountings also are common; and the SCR location relative to back of cab stays constant.

Sprinter curb weight will increase by 155 pounds for the chassis cab and 144 pounds for cargo. Due to chassis certification, Sprinters under 10,000 pounds gross vehicle weight rating (GVWR) cannot exceed the unloaded vehicle weight (UVW) and inertia weight of 7400 pounds, and Sprinters over 10,000 pounds GVWR cannot exceed the inertia weight of 10,470 pounds.

During tests, the average consumption of DEF for Sprinters was 0.6 gallons per 1000 miles. DEF service intervals are every 10,000 miles or once a year.

New engine performance is 185 hp at 3,800 rpm, an increase of 30 hp; new torque is 325 pounds per foot at 1,400 to 2,400 rpm, an increase of 45 pounds per foot.

Ford

Rob Stevens, chief engineer for commercial vehicles, said that while the fundamentals are the same for all of Ford's emissions systems, the actual hardware can be unique between offerings. Ford's medium-duty truck offerings will have Cummins engines and after-treatments and use hardware similar to the rest of the industry. The modifications allowed are determined by Cummins, and will be about the same for all truck manufacturers.

Ford's light trucks, up through Class 5, use distinct hardware to meet the 2010 emissions requirements.

On light trucks, an SCR chamber has been added to the diesel oxidation catalyst (DOC) and the DPF. Like the 2007 system, nothing in the after-treatment progression ahead of the last device can be modified without affecting certification.

The DEF dosing module is new, and can't be relocated or modified.

The DEF tank includes a supply module, temperature and level sensor, heated reservoir and splashing measures. The supply module recalls the DEF in the supply line when the vehicle is shut off.

The DEF is warmed, as required, to assure that it does not freeze during low ambient temperatures. The DEF spray pattern is optimized in the dosing module to promote mixing, improving the effectiveness of the SCR process. The exhaust sensors monitor the exhaust temperature throughout the process, along with the NOx levels and exhaust pressure. The engine-control modules work together with the various sensors and engine controls to assure compliance and perform system diagnostics.

Typical light-truck DEF tanks with mid-ship fuel tanks on pickups, vans, wagons and box deletes are coupled with the fuel tank to improve storage capacities. The completed-vehicle packages do not provide much opportunity for adaptation. DEF fill kits will be available for chassis cab and cutaway offerings, similar to fuel fill kits.

Typical light-truck DEF tanks for chassis cabs and cutaways are mounted outside of the frame on the right side of the vehicle. DEF fill will be located on the left side of the vehicle across the top of the frame, but can be relocated to the right side of the vehicle to best suit the second-unit body installation. Guidelines for tank relocation are being evaluated to accommodate line constraints.

Ford's light-truck DEF tanks are sized to meet EPA DEF replenishment guidelines, and tank capacities vary by model to meet this objective.

“Since DEF consumption is dependent on duty cycle and operator behavior, DEF replenishment may be required by the operator under some circumstances,” Stevens said. “DEF consumption is dependent on engine loads, because greater loads consume more DEF — both in terms of absolute consumption and relative to fuel consumption — and on driving conditions because steady operation consumes much less DEF than transient operations.”

Under normal operating conditions, the DEF should not require filling by the operator, per EPA replenishment guidance. For complete vehicles and related applications, the DEF tank and fill are located together, with the diesel fuel tank and fill on the driver's side.

The DEF warning system includes a series of audible warnings and cluster messages starting at 1,000 miles. Inducement of progressive performance degradations begin at “empty.” Similar warnings are used with the detection of unsatisfactory DEF.

Freightliner

Randy DeBortoli, project manager for 2010 emissions for Daimler Trucks North America, said the business class M2-106 and M2-106V have “switchback understep” vertical and horizontal systems. There is a clear back-of-cab solution with a six-gallon DEF tank and 50-gallon fuel tank, the lowest weight medium-duty after-treatment system, multiple available tailpipes and a clear right-hand PTO solution.

The daycabs' vertical tailpipes will have right- and left-hand B-pillars, while the horizontal tailpipes will have a short outlet and right- and left-hand turnouts. The extended cabs and crewcabs' vertical tailpipes will have right- and left-hand C-pillars, while the horizontal tailpipes will have a short back-of-cab (BOC) outlet and right- and left-hand turnouts.

“Although the location of the SCR and DPF systems are set, we will be publishing guidelines for exhaust tailpipe configurations to allow easier body-builder retrofit or modifications to meet our guidelines,” he said.

On the heavy-duty DV 13, a mid-chassis mounted one-box also will be available, housing both the DPF and SCR catalysts, and the mixing chamber for the DPF.

On the M2-106/M2-106V, the vertical ATS system offers a clear below-frame solution, high fuel capacity, a clear PTO solution and similar back-of-cab protrusion to the '07 DPF. A crossover 2HH also will be available for very short wheelbases (sweepers, ambulances, RVs, etc).

On the M2-106, the DEF tank is located aft of the rectangular fuel tanks. The clear back-of-cab solution includes a 6-gallon DEF tank, 50-gallon fuel tank and right-hand understep ATS.

GM

Product manager Mike Eaves said the tank on the G van and G cutaway has a capacity of 5.83 gallons and a flexible fill hose. On van applications, the tank is outside of the frame rail within the body.

The new emissions system means that with tanks full, medium-duty vehicles will carry an additional 180 pounds.

“The good news is that there are no significant changes to the frame, axles, suspension, transmission, cooling systems or fuel tanks,” he said.

Navistar

Chet Ciesielski, chief engineer of severe service products, said EGR is “an easy solution for all body builders” because there are no radical hardware additions; no Urea tanks or worries about availability of Urea; no additional catalysts, sensors, gauges or electronics; no additional fluids required; service technicians understand and know how to service EGR-based products; and truck-equipment manufacturers do not have to re-engineer bodies and functional components to accommodate new hardware and packaging.

In addition, with EGR systems, there are no additional components or weight, and no concerns with Urea distribution. All chassis configurations are maintained, and operational maintenance and serviceability issues are reduced.

Because MaxxForce Advanced EGR handles emissions reduction inside the engine, there's no additional after-treatment equipment that adds significant weight to the chassis. This means customers will not have to reduce their payloads.

On the DuraStar, there are left- and right-side mega brackets to hold a slightly larger cooling module, growing from 717 square inches to 1,045 square inches. The same exhaust options today will be available in 2010.

The WorkStar 7400/7500 features a high cab position that's about 4 inches taller, going to the same height the 7600 is now. The cooling module increases from 1,225 square inches to 1,590 square inches, with the same exhaust options as currently available.

Mack

Addressing concerns that a driver/operator could run out of DEF, Dave McKenna, director of powertrain sales and marketing, said he believed it would take a conscious effort to run the DEF tank dry. Mack has furnished a DEF level gauge in the A panel directly in front of the driver. It works similar to the fuel gauge, with the addition of a low-level indicator lamp and an audible tone for when there is less than 5% DEF remaining. Depending upon engine duty cycle, the operator will get between 220 and 280 miles per gallon of DEF.

Below 25% reserve, a small DEF gauge indicator lamp illuminates. Below 12% reserve, an audible tone sounds, alerting the driver/operator of low DEF.

Mack has successfully been running SCR systems on prototype trucks since 2000, logging more than two million miles on 10 customer vehicles. Mack's parent, the Volvo Group, has logged more than 23 million miles of road testing in Europe. This year began production of SCR-equipped vehicles to meet the Euro 4 standards, which took effect this month.

Rick Weber is the associate editor of Trailer/Body Builders, a FIRE CHIEF sister publication. This article originally appeared in their August issue.

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