01 August, 2008
The Mysterious "Black Box"
In my line of work as a diesel mechanic, I talk to many truck drivers and I am asked many questions. Almost every conversation winds up being about engines. "Motors" is the word most commonly used, but "engine" is the correct word. Motors are electric. Anyway, I've noticed a trend among truck drivers through my many conversations with them. They're afraid of technology when it comes to engines. I should explain big rigs to those of you unfamiliar with them. They are, by far, old technology when compared to cars and it's been said that big trucks are about twenty years behind cars. I believe it. One example would be the brakes on a big truck. They're predominantly drum brakes. DRUM BRAKES! When was the last time you saw a car that had drum brakes on all four wheels? The late 1960's? Air operated disc brakes do exist, but I've only seen them twice. Once on a motor home and the other time it was a tour bus. What I'm leading to in this post is the technology found on diesel engines. In the mid to late 1990's electronic engine controls were starting to appear regularly on heavy duty diesel engines in an effort to reduce the bad stuff coming out of the exhaust pipe. It was nothing special, but the electronic control module, or ECM (sometimes called a powertrain control module or PCM, it depends on the manufacturer) was almost unanimously not trusted by truck owners and drivers. "Why" you might ask? Because they didn't understand how it worked. Prior to the use of ECMs on diesel engines, the fuel metering was done by a mechanically operated injection pump. Injection pumps are big pieces of metal, make whirring noises and have fuel lines coming out of them. If you've ever heard of someone "turning up" a diesel, they're referring to a mechanical fuel injection pump. What a "mechanical diesel" has over an electronic diesel is reliability and simple operation. Technology-wise, a diesel engine with a mechanical injection pump is on the same level as a gasoline engine with a carburetor on it. A person could understand how mechanical injection worked and could tinker with it themselves a little bit. Fuel is delivered to the pump, the pump distributes the fuel to the right cylinders at the right times and smoke comes out the stack. That's where mechanical diesels are bad. Smoke. For reasons I can't understand, some people will equate smoke with power. They think it's cool to have smoke pouring out of the stacks (usually without mufflers). I see wasted energy and money coming out of the stacks, because that smoke is unburned fuel. I've talked with drivers, who in just a few minutes of conversation, bitched about high fuel prices and then praised mechanical diesels. Umm, I don't get it. I've even heard of people wanting to swap out an electronic diesel for a mechanical diesel. First of all, that's probably the most stupid thing I've ever heard and secondly, if they complain about poor fuel economy now, just wait until that mechanical engine goes into the truck. Moving on. In the early 2000s, heavy duty diesels were equipped with EGR (Exhaust Gas Recirculation) systems to comply with emission regulations. Simply put, EGR systems put some exhaust gas back into the cylinders and is mixed with fresh air/fuel mixture. Exhaust gas will have unburned fuel in it and by putting it back into the engine, that unburned fuel gets burned and isn't wasted. Well, the EGR systems were put on in a hurried fashion to existing engine designs and it caused all sorts of problems. The engine manufacturers were the first to be blamed, then the EGR systems were declared "crap" by the drivers/owners and eventually they figured out the EPA was to blame. The EPA wasn't really at fault, their goal was good, but I think they gave an unrealistic deadline that was too short. After the first couple of years with EGR systems, the manufacturers got the problems straightened out, but the drivers/owners still didn't trust the system even though the car or pickup they drive has an EGR system on it that works just fine. In fact, cars have had EGR systems on them since the early 1970s! The latest thing to spook drivers/owners is the 2007 diesel engines and ULSD (Ultra Low Sulfur Diesel) fuel. First came the ULSD, which was to replace Low Sulfur Diesel at pumps by the fall of 2006. ULSD is not as good a solvent as low sulfur diesel and when it appeared at the fuel pumps, fuel filters started clogging with alarming regularity. Low sulfur diesel will break down a lot of impurities that find their way into fuel tanks. Think of how salt dissolves in water, now imagine if those salt crystals didn't dissolve. That's the problem with ULSD, particulates don't dissolve. Guess where all that non-liquified crud ends up? That's right, into the fuel filter where it belongs. There was a huge problem in the fall and winter of 2006/2007. Our shop was changing fuel filters for customers so much that we went from keeping one each of the most common filters on our service trucks to keeping CASES of the common filters on our trucks. There was a point where we had trouble finding fuel filters because demand was so high. Again, the drivers didn't understand why their filters clogged, they just knew it was because of the switch to ULSD. The filter problem was a non-issue by the spring of 2007, but the effect will last for years. But the fun doesn't end there. Beginning 1 January, 2007, all new production diesel engines were required to meet another new set of emission standards. The engine manufacturers knew of the new standards well in advance this time and were ready for it. So now we have electronic engine controls, EGR systems and *gasp* Diesel Particulate Filters (DPFs). It's an exhaust filter. Particulate matter (i.e. soot) gets trapped in the DPF and every so often the DPF does something referred to as "regeneration." In a nutshell, what happens during regeneration is this. A small amount of raw fuel is injected into the DPF causing the thing to heat up to the point where the trapped particulate matter is burned off. The only thing left is a small amount of ash. The stuff coming out of the stacks is super clean, probably cleaner than a car's exhaust. But, there is a price to pay. DPFs will have to be cleaned on occasion to remove the ash trapped inside. The truck manufacturers have suffered for their brilliance. Since nobody trusts this "black magic", sales of trucks with 2007 engines plummeted. What I hear on my end is this frequent phrase from drivers "... that emissions shit." They don't understand it, therefore it's shit. Even though it's a good thing. Lower exhaust emissions, what's not to love? I'd like to see each person who complains about the "emissions shit" spend a day in a shop with running mechanical diesels. Just starting a mechanical diesel in a shop will instantly fill the place with eye burning smoke. It is not pleasant at all, even with a good ventilation system. If you fear something because you don't understand it, what's keeping you from learning about it? Use Google, read a book, read the trade magazines. Knowledge is power.