Volume 3 Issue 4 - Diesel Articles

Diesels seem to be the rage today. Just about every American manufacturer has one. When you consider the price at the pump, its really not surprising.  The American public wants fuel economy. The EPA is demanding fuel economy. It stands to reason, then, that automakers are searching for ways to boost mileage and diesel driven vehicles are giving them a way to do it. Although the purchase price is usually higher, the range and power afforded by these virtually indestructible engines gives them the road worthy staying power drivers need in order to recoup those more sizable initial investments.   

As a young driver in the late '70s and early '80s, I never looked twice at a diesel vehicle, except, maybe, with disdain. They were noisy, smelly, filthy, smoky beasts. Yeah, and they were ugly, too. Styling left a whole lot to be desired.  Although Mercedes was out there marketing a fairly successful line of diesels, I never paid them much attention, except when one of my better heeled, college chums offered to run some of us out for midnight burgers or pizza in his.

But todays diesel vehicles owe more to my friends stylish, well-engineered Mercedes than to the embarrassing excuses for vehicles that American:

  

and even some German:

manufacturers were hawking back in those early days. During a debilitating oil crisis, these offerings, at least from GMs flagships, Oldsmobile and Cadillac, allowed those with a penchant for the large and luxurious to keep their gunboats yet ease their consciences with gas mileage ratings of upwards to 30 MPG. Torque and acceleration were minimal, but so were visits to the pump.

Mercedes, however, had the right combination in its 200D:

 and (later) 300D:

models and those who could afford them cruised comfortably past the filling station in German-crafted luxury and have continued to do so in the intervening years.  But because many of the Mercedes lower priced competitors couldnt come close to matching its power and performance,  Americas fascination with the concept waned quickly, and production of American diesel cars evaporated along with the oil crisis.

The one segment of the consumer diesel market that HAS remained strong throughout the decades is, of course, the heavy duty work wagon:

or pickup truck:

Through the years, owners of these vehicles have opted for diesel engines—as one might expect—because of their power, economy, reliability and longevity. Now, with technological advancements of the past three decades making it possible to incorporate  those quadruplets of desirability into a family vehicle or luxury or sports sedan, its a whole new ball game and nearly every major manufacturer is lining up in front of the American consumer for their time at bat.

Diesel for the Auto Illiterate and Mechanically Challenged…

Yes, Im eventually going to talk about the Chevy Cruze Turbo Diesel, but before I do, theres something you should know. Im not an auto expert. I dont have facts, figures, equations or formulas on the tip of my tongue. Whatever information you see here has come from research and not years of experience. So, engineers, mechanics or auto aficionadi, you may find yourselves bored with much of what you read here. Sorry about that. Feel free to cut to the Cruze-specific stats later in the article.

BUT, for those of you who may have stumbled onto this magazine—and this article— (by mistake? Oh, no…) and who find yourselves scratching your heads at all this high level diesel talk, take heart! This piece is for you!  I didnt know squat about diesel engines, either, when I started this story, and any understanding of the subject and the technology has been hard won, I assure you.  So fasten your seat belts and get ready for a crash course in diesel. Hopefully, after youre through, should you consider a diesel powered vehicle for your next auto purchase, youll be able to walk into the dealership with, at least, a modicum of understanding of what the salesman is saying and of the value of the technology youll be purchasing.

Conventional vs. Diesel: Whats the Big Deal?

First of all, diesel produces more usable power than gasoline and is much less volatile; for example, under pressure, diesel burns while gasoline explodes. Hmm. A couple of very good reasons to consider it, I think. In chemical composition, its similar to heating oil, jet fuel or kerosene although by the time it gets to the pumps, most of its characteristic polluting sulfur has been refined from it.  Diesel powers over 50% of the cars and trucks in Europe due, in part, to a 20-40% greater efficiency and greater power achieved. It can, however, add upwards to $2000 a vehicles purchase price, but because Europeans tend to keep and maintain their cars FOREVER, the cost amortizes nicely. They end up with a comparatively economical vehicle (comparatively—since the average European can pay between $6 and $10 MORE per gallon of fuel than we do), with a much more durable engine.  

Diesel fuel and conventional gasoline are both refined from crude oil, but the process employed for diesel is simpler. This means that diesel fuel is cheaper and easier to produce than standard gasoline (think about this next time you compare prices at the pump). As a result, at some point it needs to be cleaned of more pollutants in order to lower emissions. At the same time, because diesel is more efficiently combusted in vehicle engines, greater energy is produced with fewer CO₂ emissions. This is one of the reasons diesel vehicles are generally more fuel efficient than conventional gasoline-powered vehicles.

The engine differences center around the mode of combustion. Pistons in traditional engines pull air and fuel into the combustion chamber on the downstroke, then require the spark plug to ignite the fuel in order to create a small explosion.  A diesel engine does not use spark plugs as the combustion chamber is already full of hot, compressed air when the fuel is injected.

Whats DEF, SCR, NO_x, N₂ and H₂0 Got to Do With It?

The “clean” diesel process depends on DEF, or Diesel Exhaust Fluid. This is an aqueous urea (yep, its what you think it is) solution of 32.5% high purity urea and 67. 5% de-ionized water. Urea is normally used as a Nitrogen source in pastures and is sold as a powdered fertilizer for about $412/ton. For clean diesel use, it is liquefied, sold for about $7.50/gallon and can be found at auto parts stores and even discount and general purpose stores like Wal-Mart and Sears.  

DEF is used as a consumable in the process of SCR, or Selective Catalytic Reduction, where the toxic polluting emissions, NO_x, or Nitrogen Oxides, are broken down into N₂, or Diatomic Nitrogen and H₂0. The DEF is injected into the exhaust pipeline where the liquid urea vaporizes into ammonia and carbon dioxide. The CO₂ dissipates as a gas, leaving the ammonia which, then, reacts with and reduces the Nitrogen Oxides into water and Nitrogen gas (N₂)—both harmless—and releases them through the cars exhaust.

Are We There Yet? On to the Chevy Cruze Turbo Diesel

The engine used in the Chevy Cruze Turbo Diesel 4 cylinder engine was conceived in Torino, Italy, and created in Kaiserslautern, Germany. Far from being new to the international marketplace, its been used in Opel Astras and other GM vehicles across Europe for years. In fact, diesel powered vehicles accounted for more than 55% of all new vehicle registrations there in 2012 (about 6 million) with GMs share of that market hovering around 400,000 vehicles sold.

The downsized Duramax system in the Cruze uses a particulate filter and urea injection to reduce (see above, for those of you who skipped the previous few sections) Oxides of Nitrogen. The spare has been supplanted by a 4.5 gallon urea tank on the trunk floor and has been replaced by a can of “fix-a-flat.” Under normal driving conditions, a tank of urea should last about 10,000 miles. Topping it off is recommended at each oil change or about every 7,500 miles.

The European version had to undergo several alterations or enhancements to address driving conditions and manufacturing requirements unique to the US:

• One-hundred-twenty degree Death Valley heat
• Minus 40-degree Minnesota Winters
• 14,000-foot Colorado mountain passes and
• Tweaks to accommodate higher levels of exhaust gas recirculation and
• Different exhaust after-treatment hardware.

The engine has a Euro standard, 4-cylindar iron block, aluminum head and pistons, steel crankshaft and a compression ratio of 16.5:1. The diesel fuel is pumped in at just over 28,000 PSI from a common fuel rail and Piezo injectors. Torque peaks at 264 pound-feet (lb.-ft.) at 2600 RPM. Two hundred fifty  lb.-ft. is available from 1750  to 3000 RPM. A burst of gas brings 280 lb.-ft. of over boost for up to 10 seconds—the diesel version of an Indy cars “push to pass.” A six-speed automatic is the only available transmission. The fuel tank has a 15.6 gallon capacity.

Its clean diesel reduces emissions without sacrificing power. Its ECOTEC 2.0-liter, turbocharged clean diesel engine boasts an SAE (Society of Automotive Engineers)-certified 151 horsepower and 264 lb.-ft. of “low end” torque. This produces 90% fewer Oxide emissions over older, previous generations of diesel engines. The result? 55 mpg on the highway. Thats 858 miles on a tank of fuel.  Not too shabby.

Chevy says the Cruze is the first car in its class with 10 standard airbags, giving it a 5-star overall vehicle rating for 2014 from the NHTSA (National Highway Travel Safety Administration). In case the above isnt enough to sway buyers, to sweeten the pot, Chevy includes:

• Free oil and filter changes (for the first two years or 24,000 miles, whichever comes first)
• Free DEF changes every 10,000 miles for the first three years
• Free roadside assistance for five years (or 100,000 miles)
• Four-wheel tire rotation
• 27-Point vehicle inspection

At first glance, you may be hard-pressed to tell the difference between the Diesel and Chevys gasoline powered Cruzes. In fact, the only thing distinguishing its appearance are 17” aluminum wheels and low rolling resistance tires. The grill opening, shutters and underbody aero panels all appear to be borrowed from the Cruze Eco. There are other differences to consider. Because the diesel weighs in at about 3,500 lbs., 300 lbs. heavier than its heaviest gasoline siblings, it requires larger, stronger brakes. In addition to the comfortably stylish heated leather seats, there are the comfort modifications. Youll find a different dash mat and hood blanket to deaden the (almost indistinguishable) engine rattle. As mentioned earlier, the diesel engine is 20% to 40% more efficient than a regular internal combustion engine, but may cost upwards to $2,000 more.

Whats the Bottom Line?

So, why should a consumer buy a Cruze Turbo Diesel instead of, say, Chevys Cruze Eco? The Ecos gasoline engine boasts improved efficiency and is rated at 33 mpg and all Cruze models will burn about $1,750 of fuel in a typical 15,000-mile year.  But EPA stats on the diesel assume a 45/55 mpg city/highway ratio. True, diesel fuel burns more efficiently, but, at least for now, costs about 15% more per gallon. The Eco costs about $4,000 less than the diesel, but half of that difference comes from fewer standard and safety features.  The diesel has more power, more torque and runs 200 miles further on a tank of fuel.  Also, diesel drivers statistically spend two-thirds of their time behind the wheel on the highway.

So, does the Cruze Turbo Diesel performance and longevity justify the expense

Absolutely. Faced with the choice between a less expensive vehicle with fewer options, a less secure and responsive engine and fewer miles per gallon, Id choose the heavier, more powerful, more responsive, and, eventually, more economical ride anytime. Even if I didnt spend 2/3 of my time on the highway, when I did find myself on one, Id love the ultra long cruising range.  Id know that the money payoff would be there eventually, as long as I kept the car awhile, which, I could easily do because of engine durability.    Faced with the choice, Id say its a no brainer.

But what do I know? Im not an engineer, mechanic or that other thing…