THE NUMBERS ILLUSTRATE the serious nature of the stringent 2007 emissions standards mandated by the Environmental Protection Agency (EPA):
-
The NOx (nitrogen oxides) standard — designed for a 50% reduction — has been revised to 0.20 g/bhp-hr (grams per brake horsepower hour), to be phased in for diesel engines between 2007 and 2010. (The phase-in would be on a percent-of-sales basis: 50% from 2007 to 2009 and 100% in 2010.)
-
The NMHC (no-methane hydrocarbon) standard has been revised to 0.14 g/bhp-hr, to be phased in the same way.
-
The PM (particulate matter) standard — designed for a 90% reduction — has been revised to 0.01 g/bhp-hr, to take full effect in the 2007 heavy-duty engine model year.
-
The certification test fuel sulfur content maximum has been reduced to 15 ppm (parts per million). The diesel fuel regulation limits the sulfur content in on-highway diesel fuel to 15 ppm, down from the previous 500 ppm. Refiners will be required to start producing the 15 ppm fuel beginning June 1, 2006.
-
The EPA estimates the cost of reducing the sulfur content will result in an increase of up to five cents per gallon in the price of fuel, and that the new emission standard will cause an increase of $1,200 to $1,900 in the cost of vehicles.
Numbers. Lots of serious numbers.
But even amid the seriousness, OEMs have been able to find some humor in the byproducts of the standards.
GM's Dan Cutler on the theory that by 2010, the air coming out of the exhaust will be cleaner than the air people are breathing in the cities where the trucks operate: “Basically, we're getting the exhaust so clean that you could suck on a tailpipe and breathe cleaner air than you could outside. I wouldn't advise it, though. It raises heck with a good pair of lips.”
Mitsubishi Fuso's Bob Aquaro on the intense heat that will be generated: “Basically, we're going to light this puppy up for its normal period of routine operation and incinerate anything in sight. Driving down the street, the street's going to melt, tires are going to go flat. It's just going to be horrible … No, it's not really that bad. But you can't take this so seriously, because it'll kill you. You've got to have some humor about it.”
EPA's assessment
The EPA started regulating the gaseous emissions from the heavy-duty highway uses of diesel engines in the 1970s and particles in the 1980s.
The EPA's health assessment concludes that long-term (ie, chronic) exposure to diesel exhaust is likely to pose a lung-cancer hazard, as well as damage the lung in other ways, depending on exposure. The health assessment's conclusions are based on exposure to exhaust from diesel engines built prior to the mid-1990s. The assessment also states that evidence is emerging that diesel exhaust exacerbates existing allergies and asthma symptoms, and recognizes that diesel-engine exhaust emissions, as a mixture of many constituents, also contribute to ambient concentrations of several criteria air pollutants, including nitrogen oxides, sulfur oxides, fine particles, and other hazardous air pollutants.
According to the EPA, the amount of exhaust particulate from on-road engines is expected to decrease 90% from today's levels with the engines designed to meet the 2007 regulations, and the composition of the exhaust particulate matter and the gases also will change.
The emissions standards, signed by the EPA on December 21, 2000, mean major changes for engine makers, which have to incorporate aftertreatment devices such as particulate traps (which collect and burn away particulate emissions) and catalytic converters (which convert damaging pollutants to less-harmful products).
And they mean changes for OEMs and bodybuilders, too.
Freightliner LLC's Steve Morelli said the aftertreatment device — in this case, the diesel particulate filter (DPF) — will “take up some space on the rail, so it's going to be a challenge for Freightliner and all business partners.”
He said that because of the higher level of exhaust gas recirculation (EGR) — an emissions control technique for reducing oxides of nitrogen emissions in the tailpipe, with a small amount of exhaust gas recirculated back into the intake manifold to dilute the incoming air/fuel mixture — Freightliner has to change the entire front end of most medium-duty models to accommodate a larger radiator.
“Rather than mounting the radiator directly to the rail, it's now mounted directly to the engine,” he said.
Cutler: “The biggest thing that will affect bodybuilders is the particulate filter. I've looked at prototype vehicles and layouts, and I can tell you right now that about 95% of all body vocations that are out there will not have a problem with our mounting. You still have PTO clearance down the left side, so that's not going to be affected. We're on track with it. The last thing we want to do is create a problem.”
Aquaro: “All of us are driven by '07 emissions. The bottom line is, if we don't meet '07 emissions, we are out of business. We have nothing to sell. For bodybuilders, the effect will be in heat-rejection issues, and how close they get when they start mounting components. We've taken measurements of various types of bodies on Mitsubishi trucks. We kind of know where we need to put this to be as out of the way as possible. We're trying to keep it as transparent as possible. The difficulty of doing that has a lot to do with the heat we lose from the exhaust manifold to the discharge point of the engine to the inlet point on the DPF.
“For each inch of pipe on the exhaust system, you have heat loss. You can lose as much as 50 degrees C for every inch of pipe. So how far away the DPF is from the discharge port of the exhaust manifold to the inlet of the DPF has a huge impact on the operation of the DPF. You can't move this thing around in '07, because as soon as you try to move it somewhere else, you will have violated every emissions law there is. So bodybuilders are going to have to depend a little on us. It's a huge concern for everybody. There's a lot of science going into it.”
A look at the system
Morelli laid out the science behind the new system:
As the truck rolls down the road, particulate matter is regenerated, or broken down. If the particulate matter builds to the point where passive regeneration can't keep up, then the truck is forced to go into active regeneration, which means the temperature inside the aftertreatment device will have to reach 600 degrees C — a process that takes about 40 minutes.
The DPF will collect ash, which needs to be cleaned occasionally. The device is taken apart and the filter is removed and cleaned.
Caterpillar is going in a different direction with its ACERT technology, which includes series turbochargers, variable valve control, a high-pressure multiple injection fuel system, Cat electronics control systems, and an oxidation catalyst. Cat engines feature an enhanced combustion process called clean gas induction (CGI), closed crankcase ventilation system, and DPF filter system with active regeneration.
The Cat diesel particulate filter uses a wall-flow filter technology. Regeneration is necessary to activate a process of oxidation that eliminates the soot that collects along the inlet walls of the filter. To aid the regeneration process, the exhaust gas is heated by auxiliary means. Regeneration only takes place when needed, which optimizes fuel economy. Engines with 500 hp or less will require one DPF; engines with 550 or more horsepower will require dual filters.
The primary process for achieving additional NOx reduction includes the elements of ACERT Technology with Clean Gas Induction (CGI). CGI draws clean inert gas from downstream of the particulate filter and then puts this clean gas into the intake air system.
On the system Morelli originally described, the aftertreatment device takes the place of the muffler. Unfortunately, it weights 50 to 60 pounds more than a muffler.
“The bigger the horsepower, the bigger the device,” he said. “Cat's running a bit lighter because they opted not to go with diesel oxidation and only use a diesel particulate filter.
“With exhaust-gas temperatures, the distance between the turbo and the aftertreatment device is critical. No longer will we be able to just move the exhaust system as we're used to doing. Maintaining exhaust-gas temperatures necessary to promote passive regeneration requires that distance to be static. You can't just move it anywhere you want, because you need to maintain the heat and exhaust flow from the turbo to the aftertreatment device. Because we're filtering and collecting soot, we're increasing, at times, the bad pressure on the engine, which means the tailpipe becomes more critical. We need to control how the exhaust pipe itself is run from the end of the device to the exhaust.
“In an attempt to control the exhaust-gas temperatures, we are developing some fusers. The exhaust gas is up to 1200 degrees F. As it is dumped into the atmosphere, we want to keep the temperature as low as possible. No longer will we be mounting the muffler/aftertreatment device to the cab. They're just too heavy. We're not going to be able to modify the exhaust system the way we used to. Bodybuilders are going to have to work with our engineering department to design or pre-design an exhaust system that will work with their bodies.”
Said International's Greg Sale, “In spite of their size, we're planning to offer all of today's current exhaust-system locations. The big difference is that it will be more difficult to just cut and relocate them. But we still want to be able to offer that functionality. Proximity to the engine is important to maintain the heat into them. There are also pressure sensors across them, so any change in the exhaust is important for us to keep track of. Bodybuilders will want to have our engineers OK the moving of the exhaust system, because the EPA will be checking up on us.”
Misconceptions
Sale and Aquaro cleared up some misconceptions regarding the new systems.
Sale: “One fear a lot of people have is that it will be easy to miss-fuel their vehicle and mess it up. The reality is no. By the time '07 comes, there will be only one fuel available. Low-sulfur fuel is an enabler for your aftertreatment. Sulfur attacks the catalysts that are going to be in the particulate filters. If you put in a fuel that has 500 ppm sulfur, you'll destroy your filter at 30 times the rate you would have. If you go 1,000 miles on new fuel and miss-fuel with the wrong stuff, it'll be like using up 30,000 miles of the life of the filter. What about old trucks? Will they be OK with the new fuel? Yes. Fuel refiners will be adding agents so new fuels won't mess up the injection equipment on old trucks.
“Another fear people have: I've heard questions such as, ‘If the filter gets plugged up, will the engine speed up and generate extra heat to burn off the trap?’ The answer is no. The whole purpose of the engine is to provide the speeds and torque the operator wants. The whole goal of this is that the operator is never going to notice a difference in driving or in any mode of operation.”
Aquaro: “There are people talking already about having to change the DPF every time you change the engine oil. No, that's not true. We're saying that the DPF in trucks in most applications, using the correct engine oil — which is low ash, which is not even available on the market yet — should last the life of the truck without having to be serviced. In some cases, we'll have to service it, which means cleaning it out.”