Sorry, that did sound a little terse. I'm very much used to listening to people blast about how "filthy those damn diesels" are, and they always seem to come back to a small handful of reports that used very poor control methodology to support their points. Two of those reports originated with CARB, which is not known to be very... objective... when dealing with studies of diesel emissions.
Anywho. There are several common misconceptions about diesels, trucking, and industrial applications. For instance, what most folks don't know is that the average OTR (Over The Road, semi, tractor-trailer, "big rig") truck has an anticipated service life of ten years. MOST are replaced before that time; for instance, it has been reported that major companies such as WalMart, UPS and FED-EX try to turn their fleets over every ten years, often by replacing trucks after only 5 years of service. As a result, the average age of a truck on the road is closer to 8 years; the oldest ones still running as parts of small fleets are only dating to the mid-90s by now, with only the rare OO truck (owner-operated) featuring an older age. Delivery vehicles, such as the ubiquitous UPS-type trucks, have a similar lifespan, and are typically replaced at 6-8 years of service. City buses are usually rated at a 12 year lifespan (by what moron, I don't know...) and are usually turned over at 8-9 years. School buses are not typically rated for service life; depending on your region and relative funding of schools, they can be anywhere from averaging 2 years of age to averaging 15. Diesel engines in big trucks have typically lead the innovation curve for the past 2-3 decades: they were the first to receive computerized injection (as far back as the 80s the Bosch corporation had a functioning, marketable system to control fuel injection on a pump-injected or unit-injected industrial diesel; they were marvelously more efficient but also not terribly durable, and did not sell well). Common rail fuel injection made its debut back in the late 90s, well before cars were even considering direct injection to be a viable option; modern CRTD engines support 7+ injection events per cylinder per cycle, including pre and post burn for emissions regulation. As early as 2000, Mercedes Benz was advertising a diesel engined heavy truck wherein the truck's exhaust was cleaner than the air going into the engine, when measuring VOCs, HC, CO, PM and other non-NOx, non-CO2 pollutant values. The latest offerings from Cummins and Detroit. are making similar claims, though their NOx values are added to the "lower out than in" category. Often the biggest issue when poor maintenance is encountered is not the laziness/greediness/ineptitude of the owner/operator/maintenance department so much as availability of parts. This is an issue that has gotten dramatically worse in recent years with the sudden heavy push to get cleaner, more technology packed engines into service. Engine families are receiving shorter and shorter production runs, and older engines are being phased out rapidly. This makes it hard and expensive to find parts to do the long-interval maintenance on some of these vehicles. Take, for instance, the Cummins ISB series engine, specifically the ISB5.9. Essentially, this is an "industrial" version of the venerable Cummins 6BT engine. When it debuted, it featured direction injection controlled via DBW -drive by wire- and utilizing an inline or rotary injection pump. The original 6BT was rolled out into agricultural service (with a mechanical injection pump and no electronics, 2v/cylinder) in 1984, found its way into trucks in 1989, and essentially remained unchanged barring the occasional back and forth between a rotary pump and an inline pump for fuel delivery. The ISB rolled out in 1998, featured an electronic IP and 4-valves per cylinder. It was quickly adopted into service through the coach and light truck lines of production to replace the 6BT. After only /5 years/ they dramatically overhauled it again, creating the ISB2 engine and introducing common rail injection and reworked electronics, as well as a plethora of new sensors. Finding parts for an ISB engine is becoming very difficult; we have four 2003 models in our fleet of 26 buses. One of them smokes like a freight train because the $900/each injector assemblies are NLA/find what you can (Yeah, that's $5400 parts alone just for the injectors, plus other consumables to get there). Cummins has already replaced the ISB2 with the ISB6.7 after a mere 7 years of service; it's already becoming expensive to find ISB2 common rail injector assemblies ($1800+ each parts, 10+ hour job to replace). Notice, both most recent ISB engine production runs have not even lasted the full expected lifespan of the vehicles they were placed into. Engines are being superceded and discontinued at a rate similar to that of a consumer automobile, but with vehicles that are supposed to last /much/ longer. I can't really comment on the lifespans of industrial applications, but I do know that industrial diesel engines are some of the cleanest internal combustion engines on the planet, both in fuel consumption and emissions profile. Stationary engines have had emission controls long before most on-road engines had them, owing to the narrower operation profiles, constant high-load states and the fact that most of them are never freaking shut off. Designing emission controls to work well with their duty profiles is /simple/ and often even done voluntarily. Diesel Oxidation Catalysts are commonplace, high EGR for part load applications common, and charge cooling is typically much better than on-road setups. Mobile Ag/Construction equipment, not so much, but even at the height of the construction bubble their fuel usage was a small fraction of that used on the roads, rails and in stationary applications. Anyway. Another issue is purely one of perception. We, almost as a rule, do not notice when things are running well. Everything is going as it should, why should we notice? It's when stuff goes wrong, such as a car blowing blue smoke or a diesel spitting the black, that we notice. The general consensus is that there are a -lot- of mismaintained heavy trucks on the road, but a survey of vehicles actually traveling on the roads would bear out that falsehood; poorly serviced trucks are quite definitely a very small minority on the roadways. Meanwhile, we obsess over CO2 while ignoring sulphur compounds from cars (gasoline can be 90+ppm sulphur vs ULSD @ 15ppm), nano and microparticulates from all vehicles, which are presently under study for their impact on the health of inner city residents; the proportion of diesel to gasoline exhaust there is very, very small, and the tight spaces make it inevitable that you will partake of high quantities of these miniscule, damaging particles. VOC emissions from refueling are also rarely considered; having a vehicle that gets better fuel consumption will mean lower VOC release per unit driven; a motorcycle would fare better than a car, here, despite more frequent fueling stops. Also, to judge the "green" score of a motorcycle vs a car, you would have to look at such things as initial energy investment, congestion effects, the roadway needs for transit, blacktop space for parking, and so on. I agree that arguing over who is "best" is likely futile, as the statistics can (obviously) be made to say whatever you want them to say, and if you focus on one aspect, such as the incredibly low CO2, CO, HC and VOC emissions from a diesel, someone else is going to scream at you for another aspect, such as diesel's PM and NOx emissions (interestingly enough, if you look at Particulate *count*, PM_count, you actually have worse particulate emissions from the average modern gasoline car vs. an untrapped diesel. If you're looking only at particulate *mass* the diesel loses again). Long post is long, peace out folks. -Kurt On Thu, Oct 6, 2011 at 3:04 PM, Allen Thomas <[email protected]> wrote: > Don't take offence Kurt, I didn't mean any. And true Gas just like anything > that burns something creates pollution, and a discussion of what is worse is > probably futile since its all bad. They say by grilling meat you are adding > carcinogens. I read somewhere that lawnmowers are the largest contributors > to urban smog. Supposedly coal fired power plants are the largest > polluters. I was just chiming in on a discussion about the pollution values > of vehicles, and I feel that the small polution values of motorcycles pales > in comparrison. There are a lot of poorly maintained "dirty" diesel engines > out there, more so than pre FI/Catalyst car engines because they are > built for commercial usage, not only by trucks, but virtually all heavy > equipment. BTW, congress passed a law in 2005 to force retrofitting diesel > scrubbers, but it was never funded. From what I understand is that they are > forcing better refinement of the fuel to remove the sulfides. > > > -- You received this message because you are subscribed to the Google Groups "Nighthawk Motorcycle Lovers!" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/nighthawk_lovers?hl=en.
