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Big Power: The largest truck engines are sometimes a necessity

Posted: December 13, 2018 by Jim Park

Bigger loads can require the heftier power of bigger truck engines.

TORONTO, Ont. — Big is a relative concept when talking about truck engines. Within the span of my career in the industry, “big” has crept upward from 350 hp back in the early 1980s to 600 hp today.

The first trucks I drove in the late 1970s and early 1980s were sub-300 hp models like the Mack ENDT-676 I learned on — it generated 285 hp and a dizzying 1,080 lb-ft of torque — and the “Shiny 290s” I drove at Liquid Cargo Lines. We hauled three- and four-axle tankers with those Cummins NTC 290 engines. Some of the senior drivers at the company had 350-hp engines, but other than bragging rights, there wasn’t much difference between the two.

There were bigger engines around at the time, like Caterpillar’s 3408, which was actually a marine and industrial engine. Some owner-operators managed to shoehorn those V8s under their hoods and went down the road with up to 800 horsepower under foot — at little more than two or three miles per US gallon.

Mack’s E9 V8 engine was also around at the time, officially cranking out up to 500 hp, but there are accounts of some of these putting 650 hp or more to the wheels … after a few adjustments. Driving back then on hilly Interstate 81 between Syracuse, N.Y., and Scranton, Penn., I spent a lot of time behind a 290 staring at the four-way flashers of other guys with their 290s and 318s. The big dogs with their 500- and 600-hp Cats and Macks would roar by out in the hammer lane, leaving us under clouds of black smoke, wishing we had a little more juice.

Wishing we had a little more and actually needing a little more are two different things. It would be hard to argue than any 40-ton American load needs 600 hp. You can build a better case for Canadian trucks that weigh 55,000 kg and more.

Drivers gravitate to bigger power, but is it necessary? Sometimes the answer is yes.

TORONTO, Ont. — The debate over big power has been raging for years. Do big engines burn more fuel? Is 600 hp and 2,050 lb-ft more efficient or productive than 500 hp and 1850 lb-ft? Do big engines improve productivity? Are they necessary?

We have asked numerous engineers these questions over the years, and the consensus seems to be that the laws of physics demand a certain amount of power to move a certain load at a certain speed. Cruising along a flat section of road at 100 km/h will require X horsepower, let’s say 200, but it’s probably less with today’s advanced aerodynamics. If you travel at 110 km/h you might need 225 horsepower. At 90 km/h, you’ll need only 175. It doesn’t matter how big the engine is, it will still produce only what’s needed to maintain the desired speed.

If you increase the weight, you’ll need more power to maintain that speed. If you’re pulling a hill, you’ll need more power to keep the truck moving at that speed. At some point, after dialing in several variables, you run up against the limits of the engine’s ability to maintain road speed on a hill. That’s when the 450s and 500s start losing ground to the 600s. You only pay for the extra power when you use it. Maintaining 100 km/h on a hill with 600 hp will require more fuel than a 450 that can maintain only 80 km/h.

Engine power in the real world

So much for physics. In the real world, if you have the power, you’ll use it, and yes, fuel economy will suffer. On the other hand, underpowered trucks are frustrating to drive, and might even be dangerous if they impede the flow of traffic.

“Try running Hwy. 138 between Sainte-Anne-de-Beaupré and Sept-Isles on Quebec’s “Cote du Nord” with a B-train and a 475 engine,” observes Pierre Aubin, owner of L’Express du Midi, Delson Transport, and Transport Audet, of Ste-Catharine, Que. “You’ll be crying.”

All of Aubin’s highway trucks are 600 hp and 2,050 lb-ft Cummins X15s, and he make no apologies for his choice of powertrain.

“If it wasn’t working for me, I wouldn’t be doing it,” he says emphatically. “We haul heavy loads here in Quebec and you need that power. Do we need 600/2,050 in the U.S.? Of course not, but for equipment utilization, I’m not going to buy two separate fleets of trucks, one for Canada and another for the States.”

Next, consider his business case. Overall, his spec’ – a Kenworth W900L with 86-inch studio sleeper, 600/2,050 X15, Eaton 18-speed manual transmission. and generally beefed up frame, crossmembers, driveline, for the heavy work — costs him about $25,000 more up front than a more “typical” spec’. But he claims that comes back two-fold on resale.

“I have people calling me from all over Canada wanting to buy my used trucks,” he says. “I never have any problems getting my price because they know the trucks will last 20 years. And drivers love them, which is pretty important today.”

In the same vein, Rod Olyowsky, operations manager of Regina-based heavy-hauler Cara Dawn Transport, runs a fleet of 30 heavy-haul trucks, mostly tri-drives, powered by Cummins X15 600/2,050 engines. While about half the work the company does is in the 50-ton range, the rest of it involves big loads, 100- and 150-ton loads into mine sites. For that work, big power is an absolute necessity.

“We don’t even worry about weight or fuel economy,” he says. “This business is the polar opposite of the freight business. They fret about things like that, we buy the trucks we need to do a job.”

Like Aubin, Cara Dawn could maintain a fleet of lighter trucks for the less-demanding jobs, but it’s hard to make that work on paper. Olyowsky says fuel costs are always a concern, so the company focuses on things they can manage, like idle reduction. “There’s no point worrying about fuel efficiency when you’re pulling 200,000 lb.,” he says. “We can attack that in other ways.”

Added truck revenue

Meanwhile, at Winnipeg-based Paul’s Hauling, the engine spec’ is very important for a different reason. That company hauls petroleum products in B-trains, and every liter in the tank is money in the bank. They run 13-liter Mack and Detroit engines at 505/1,850 rather than the 600/2,050 Cummins engines because of the weight savings.

“We load to gross and every 100 lb. is worth so much in revenue at the end of the year,” says maintenance director Trent Siemens. “Every pound counts. We’d be giving up 400-500 lb. on every load with the bigger engines.”

Over the past few years, the company has upped the ratings on its 13-liter engines, going from 485 to 505 hp on some models. Later this year they’ll take delivery of a few Peterbilts with MX13 engines at 510/1,850.

That said, Pauls’ spec’ now includes 70-inch sleepers, fridges, and other amenities that drivers crave, and everyone knows how difficult it is to find drivers.

“We do consult our drivers on future truck spec’s, and of course they’d love an 550 X15. But they understand the weight issues,” Siemens says. “Given a choice between the bigger sleeper and a bigger engine, they’ll take the sleeper every time.”

On the owner-operator front, has anyone ever met one who didn’t want more power? That may not be a fair assessment, but sensible ones will match their equipment to the job, like former highwaySTAR of the Year Rene Robert. He recently spec’d a new Peterbilt 587 for a job hauling magnesium chloride in B-train tanks around Manitoba and Western Canada. His spec’ included a 605/2,050 X15 and an UltraShift MXP automated 18-speed.

“There wasn’t much to talk about when I bought the truck. I knew I needed the 605/1,850,” he says. “I have been hauling trains for years and I know what works. I still have a 20-year-old Freightliner with a Cat C15 550 engine. It worked well for me all those years on trains and it’s still in good enough shape to keep and put a driver on. That work is hard on an engine, so you need a big block that will stay together.”

He says all things being equal, the fuel economy on the truck is decent, 4.5 mpg (52.3 L/100 km) at 62,500 kg, and the truck does the job well. “I’m not sure what advantage there would be in spec’ing something smaller, even an X15 at 550/1,850. I’d always be wishing I had ordered the bigger one.”

Engine spec’ing philosophies

Thankfully, there are many different philosophies on how best to spec’ a truck and run a trucking company. Some are steeped in the full-aero fuel economy mindset, while others see trucks strictly as a means to an end and will buy whichever model and powertrain makes the most money. Somewhere in all that is the need to match the spec’ to the job. And if the job requires 600 hp, so be it. If a 700-hp engine were available, they’d probably eschew the 600 and buy the bigger one.

“Not many fleets spec’ trucks the way I do, and believe me, they should be free to spec’ their trucks anyway they want,” says Aubin. “But I have been doing it this way for 38 years. If it’s the wrong way then I should have gone bankrupt a long time ago.”

The line separating big engines from the others is blurring. When you can get more than 500 hp and 1,850 lb-ft from a 13-liter block, there’s not much space between those and the big-block engines delivering 100 additional horses and 200 extra pound-feet. All the newer 13-liter engines on the market now deliver Super-B pulling power, and a surprising number of fleets are successfully using them in just such applications.

But as some are fond of saying, “there’s no replacement for displacement.” Currently only two engines deliver the extra power heavy-haulers need, the Performance variant of Cummins’ X15 and Detroit’s DD16. Once you exceed 62,500 kg, as most heavy-haulers do, the need for the addition torque and horsepower is legitimate. It’s no longer a luxury like it might be for the Texas bull-haulers who just like the left lane.

Here’s a list of some of the big power options currently available:

Engine                        Disp.            HP                        Torque               Dry weight (lb./kg)

Cummins X15 Perf      15.0L             485 – 605               1,650 – 2,050       3,152 / 1,430

Cummins X15 Econ     15.0L             400 – 500              1,450 – 1,850       3,152 / 1,430

Detroit DD16               15.6L               500 – 600              1,850 – 2,050       2,837 / 1,287

Detroit DD15               14.8L               400 – 505              1,250 – 1,750       2,718 / 1,233

Detroit DD13               12.8L               350 – 505              1,250 – 1,850       2,487 / 1,128

Mack MP8                   13.0L               425 – 505              1,560 – 1,860        2,597 / 1,177

Volvo D13                    12.8L               375 – 500              1,450 – 1,850        2,605 / 1,182

Paccar MX13               12.9L               405 – 510              1,450 – 1,850        2,600 / 1,179

 

 

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