Balance of Power

Take a close look at your needs and wants before saddling up too many horses under the hood.

During a truck show at the Lee High Truck Stop in Lexington, Va., two years ago, a proud trucker parked his long-nosed black Pete next to the lines of shining chrome. Dirty and dented, the owner-operator’s rig looked out of place. But it drew audible gasps when the grinning driver opened the hood to reveal a 900-hp Cummins nautical engine that he claimed could flatten out the Rockies.

How he squeezed the large engine under his Peterbilt’s hood remains a mystery, but the response he received isn’t. Truck drivers have always craved high-horsepower engines that shave hills down to speed bumps and leave RVs and slow trucks in their wakes. Nearly 90 percent of Overdrive’s readers own trucks with 500 hp or less, but 63 percent want engines with more than 500 hp. Engine power ranks second only to price when owner-operators list what they look for in a truck.

A big engine offers convenience and an ego boost, as well as a mixture of efficiency and inefficiency. Choosing the ideal horsepower for your operation requires evaluating your typical weight, the terrain you cross, your driving style and the price of fuel.

Minnesota owner-operator Dave Hein wants a late-model truck to replace his 1995 Peterbilt 379 with a 455-hp Caterpillar 3406. “I’m looking for a combination of power and comfort,” he says. “If I get a new truck, it’ll have a minimum of 550 hp and 1850 pounds-feet of torque.”

It’s not as if Hein needs all the horses for a typical haul; he often gets a truckload rate for 25 feet of cargo that doesn’t begin to approach 80,000 pounds. But on those occasions when he’s leaving Los Angeles with a full load heading east, Hein, like other owner-operators, finds downgearing and losing a lot of speed for long climbs over the Rockies “very aggravating.”

A decade ago, the average new truck had 350 hp. That number rose to as high as 375, but has slipped back to the “high 360s,” says Caterpillar Program Manager Bob Wessels. That drop is probably due to the economic climate, Wessels says. Small fleets, which often spec high-horsepower engines to draw drivers away from big fleets, are having a tough time, reducing the number of trucks on the road with 500-hp-plus engines.

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Large fleets increased average horsepower in the 1990s when the need for quality drivers forced them to spec stronger engines as recruitment and retention perks. Those increases were made possible partly through engineering advances.

“Power density” has increased consistently for years, says Ed Saxman, director of powertrain systems for Volvo. For example, the same block that produced 300 hp a generation ago produces 450 today. That improved power density came as engine makers refined the combustion process, boosting power without increasing stress on the metal.

Other developments, such as air-to-air intercooling, have allowed engineers to improve fuel economy, increase horsepower and reduce engine temperatures simultaneously. Also, better fuel injectors, computer modeling, onboard electronics and advanced turbo chargers have improved engines dramatically.

As fuel prices climbed and freight flattened in recent years, the driver shortage eased. Carriers are less willing to fork out the extra cash for big engines and the extra fuel they consume.

Owner-operators are another story. Many are willing to absorb the costs for the operational edge and emotional boost and have no desire to return to the days of lower horsepower.

“There’s a perception now that you’ve got to be at the 500-hp level,” says Cummins spokeswoman Amy Davis. “I can remember when it was 400 hp. That was not that long ago.”

Karl Zweifel runs four trucks with 550- to 600-hp engines in his Tillamook, Ore.-based hay hauling operation. There’s also an old Freightliner cabover with a 425-Cat, but drivers prefer one of the newer, more powerful Peterbilts. “The guy in the Pete with all the power feels good after a run,” Zweifel says. “But the guy in the COE is whipped.”

Extra power translates to safety: Drivers who aren’t frequently shifting are less fatigued and give more attention to traffic conditions. “If I had a bigger motor with more horsepower and torque, I could go up hills a little faster,” Hein says. “It’s less hassle, and I’m not a hazard. I don’t have to slow down quite so much or so fast.”

Extra horsepower can pay off when it reduces time on the road, says Anton Romulus, an owner-operator leased to Landstar. “Between Kingman, Ariz., and Amarillo, Texas, a good truck driver (with a high-horsepower engine) can cover the distance in 10 hours,” he says. “Without the horses and torque, the drive is most likely to be 11.5 hours. Every hill will set you back a little bit at a time, and by the end of the day, it could cost you 1.5 hours for the 700 miles.”

An extra hour a day can translate to more miles per week. That tradeoff is worth it, says Jeff Hillyer, an owner-operator from Minerva, Ohio, who runs team with a 550-hp Cat C-15. “There is a definite time issue,” he says. “We don’t spend all day climbing hills.”

Another asset of large engines is flexibility. Trucks with 500 hp or greater can haul overweight loads at the same speed that smaller engines can haul 80,000 pounds. Because of that capability, says Cat’s Wessels, “A C-16 is a really flexible piece of equipment.”

Bigger engines also bring more at trade-in, Wessels says. “If you don’t have high horsepower, when you sell it, the truck’s a turkey,” he says.

For all their benefits, big engines come with drawbacks. Initial price is usually the biggest barrier. When Zweifel bought his 600-hp Cat C-16, he paid $8,000 more than he would have on a truck with 50 less horsepower, 200 less pounds-feet of torque and components to match.

Because the 600-hp engines make more torque, they require more expensive drivetrain components. The cost rises so much with a 600 because not only do the components take more time and labor to manufacture, the production volumes are lower, making the economics less favorable. Because the 600-hp engines generate more heat, they also need more cooling capacity.

“When you specify a 2050 torque rating, you’ve got to get a big, really expensive transmission,” says Volvo’s Saxman. “You’ve got to get bigger rears, too. Your truck is expensive and heavy. That last 50 hp comes with a weight premium. You can add 350 pounds when you go from 12- to 15-liter engines – enough to drive a weight-sensitive person from one component to another.”

The components and extra power of a 600-hp engine can easily cost an owner-operator $10,000 more than a conventional 475 to 550-hp engine does.

While more powerful engines tend to burn more fuel, a smart driver can limit that extra cost because most of the extra fuel is burned to achieve high speeds.

“Higher horsepower engine operating costs are generally affected by the operator’s right foot,” says Detroit Diesel engineer Chuck Blake. “If you drive a big engine conservatively, you can get the same or nearly the same fuel economy as a smaller engine. If you use it only when you need to, that’s great.”

That “if” is a big one, though. “When it’s available, drivers use it,” says Cummins’ Amy Davis. “Fleet operators recognize that. Premium fleet operators have started backing off, and even owner-operators started to back off, ordering high-horsepower engines.”

Owner-operator Zweifel says he can coax as much as 5 mpg from his 600-hp Cat. “I’m not unhappy with it,” he says. “I get the same mileage out of my 600 as my drivers get out of their 550s. I’m not thinking about how fast I can go because I’m paying the bills.”

Fuel efficiency is one reason why Anton Romulus won’t buy a truck with a bigger engine. “Unless they develop an engine that can deploy more horsepower with the same fuel consumption, I do not need more horsepower than the 500 I have,” Romulus says. “If the fares don’t pay for a 600-hp engine, why do I need it?”

Higher fuel costs are starting to hurt sales of bigger engines, especially at the fleet level, says Mack’s David McKenna. Furthermore, many truckers don’t realize how great the fuel economy penalty of idling a larger engine to power air conditioning and heat can be. “These engines, during spring and fall, get very good fuel economy. But averaged out over a year, the fuel efficiency is not acceptable.”

Finally, truckers who spec big engines often can’t get extended warranties and might pay more in the long run not only for fuel, but also maintenance. For truckers like Hillyer, the extra expense is worth it.

“I tell myself it’s worth the money, but I haven’t put a calculator on it,” he says. “I come from the old school – you can never have too much horsepower. It’s nice after years and years of driving old trucks to drive something powerful. ”


Karl Zweifel, owner of a 2001 Peterbilt 379 with a Caterpillar C-16, will be the first to admit he likes what his 600-hp engine will do. “I bought it because I wanted it for days like yesterday. I was climbing one of those hills at 105,000 pounds,” he says. “When a heavier truck like mine can pass a truck loaded at 80,000 like the log truck I passed, it irritates the heck out of them.

“It’s a cheap thrill,” he says. “Well, it isn’t cheap, by any means.”

Whatever the cost, for many truckers the emotional payoff alone is worth it. Anyone who has ever coveted a sports car or a large sport-utility vehicle has experienced the same rush, truck makers say.

“Where a 400-hp engine would be good, owner-operators buy a 600,” says David McKenna, a marketing manager for Mack. “I should be driving around in a Celebrity, but I’m driving around in a Suburban.”

“They buy their truck much like I would buy a sports car,” says Caterpillar’s Bob Wessels. “The things we thought about when we developed these engines are the same things that truckers think about – does it feel good to drive it? We built it to make sure that it will make them smile.”

Furthermore, owner-operator personalities and business needs vary considerably, says Volvo’s Ed Saxman. “There’s technically astute and emotional and everything in between,” he says.


More horsepower requires more torque. Torque ratings that ranged only as high as 1650 pounds-feet 10 years ago now reach 1850 and 2050.

Volvo’s Ed Saxman says the relationship between the two can be difficult to understand. “Torque is really how much grunt an engine has,” Saxman says. While horsepower expresses work done over time, “torque is an expression of strength.”

High torque provides more power at lower rpm, which makes a big difference when climbing a hill. Engine makers say it’s important to consider the torque curve of an engine when spec’ing power in order to understand the difference. For instance, an engine with 1650 pounds-feet of torque at 1000 rpm has the same hill-climbing ability as an engine rated at 1000 pounds-feet of torque at 1650 rpm.

Unless spec’ed properly, a high-hp engine could have power available only at high rpm, which will burn too much fuel. But, higher torque ratings require heavier duty drivelines and transmissions.

Getting the right torque for the job is essential when spec’ing big engines. “Torque is the big deal,” says Detroit Diesel’s Chuck Blake. “Torque will pull a high-horsepower engine down into a fuel-efficient area. Generally, bigger horsepower translates to bigger torque. You can get big horsepower and little torque – which looks good on the rocker cover, but won’t run very well.”

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