Quote:
Originally Posted by wankel7
Don't forget its ok for that loaf of bread to be delivered via a semi truck that has no emissions controls on it too....
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Apparently, you haven't been around diesel engines in semi's for many years.
The latest several
generations of diesel engines from Cat, Cummins, Detroit, which are the predominant over the road powerplants, are all using the latest electronic/computer controlled fuel injection systems. These powerplants are used throughout the diesel powered range of vehicles, which include semi's, school buses, public transportation system buses, delivery vehicles, etc.. Most all are turbocharged/intercooled, which greatly helps with volumetric efficiency and cleaner running.
This industry result has been for the same reasons that everyone else in the transportation industry/business has "cleaned up" their act: vastly improved fuel efficiency with cleaner exhaust emmissions.
The fact is that on ULSD, mandated by the EPA for all over the road diesel use, these motors burn cleaner with fewer emissions than the current generation clean gasoline motors. Fewer NOX, less CO, and without all the particulates from the older mechanical diesel fuel injection systems that could not be as closely regulated per injection stroke and were frequently "over fueled" in an attempt (generally successfully) to get the maximum horsepower out of a diesel motor.
You simply don't see trucks spewing black smoke out the stacks anymore, because the operators now get optimal fuel injection delivery ratios and the maximum power out of their motors without having to resort to overfueling. That black exhaust represents a lot of money going up in smoke with $4.00/gal diesel fuel, which few can justify from an economic standpoint, let alone from a pollution standpoint.
Similarly, the mid-range diesel motors in city delivery service have been "cleaned up". Again, economic factors as well as federal pollution standards have been at work to extract maximum fuel efficiency and economy of operation. The federal pollution standards are more stringent here than on gasoline motors, too.
When you see a modern diesel vehicle with visible exhaust smoke, it's way out of tune or has been tampered with ("performance chip" or "overfueled") to defeat the pollution controls designed into it. There's simply no benefit to the operator to have excess fuel burning in the exhaust gas stream instead of burning it in the combustion chamber where it can generate horsepower.
There's also "particulate traps" in the exhaust system, which are the diesel equivalent to "catalytic converters" in gasoline powered vehicles. And there's crankcase ventilation controls, exhaust gas recirculation controls for idling, etc., on the diesel motors. If you don't know your electronics for diagnostics, you can't work on the modern diesel motors any more than you can work on a gasoline powered car today ... they both require computerized diagnostic test equipment.
At the rate most commercial vehicles put on miles and are retired today, there's very few of the older type diesel motors on the road anymore in fleet service. They're simply too low in HP and efficiency to be economically viable, where the old "standard" was around 250 to 325 HP and 12-16 speed transmissions, now most trucks have 400-600HP and fewer number of gears, delivering fuel economy similar to the older units. That "extra" horsepower and less shifting means a trucker can keep up his roadspeed a lot better, which means better labor efficiency ... it's all about making and keeping money.
Serious diesel exhaust emission technology hit the streets in the USA starting about 1982. By then, all the major manufacturers had introduced better fuel injection/injectors, better combustion chamber designs, better cam timing, better induction/exhaust systems, and so forth ... in an effort to get more HP per cu inch and better fuel efficiency along with cleaner running. Turbocharging had just about become "standard" in the diesel industry by 1985, and mechanical fuel injection systems were well on their way out by the mid 1990's.
It's truly unfortunate that the myths and misperceptions about diesel technology persist in the USA marketplace ... although a number of car and truck manufacturers helped create this problem with some very poorly designed vehicles a few years ago. The European marketplace, especially, has been using highly fuel efficient commercial diesel motors for many years, and they've been well accepted. Had they been brought over to the USA, we'd have been able to be much more fuel efficient, too. And not all the cars are "pokey and smokey" ... even Alfa Romeo has a diesel powered sports car that is quicker and faster than their gasoline powered stablemate. We've rented diesel Peugeot's and they're pretty nice drivers, and got close to 40 mpg in highway driving with a fully loaded down car. Here at home, our family has been driving diesel MB's since 1968, and my current 1982 300Dturbo sedan still delivers 28 mpg around town, my 1971 220D (now repowered with a 2.4 motor) gets 32-34 mpg on the highway, down a mile or so per gallon from the 2.2 motor (but worth it with the extra midrange torque to maintain roadspeed in the mountains). All of our family's diesel Audi's, Peugeot's, VW's, and Volvo's had fuel economy ranging from a low of 34 mpg to a high of 50 mpg in various road conditions, although all of those cars were not as durable as the MB's, so those were all retired with low six figures on the odometer.
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