It’s pretty cool driving around in a $40 million tractor-trailer. The sum of its parts don’t add up to quite that much, but the figure represents a portion of the funding grant from the U.S. Department of Energy that enabled Cummins and Peterbilt to turn their best and brightest engineers loose in the DOE SuperTruck sandbox.
I recently spent two days in Denton, Texas, with the Cummins-Peterbilt SuperTruck and two of its creators, Bruce Bezner, a project engineer in the vehicle performance and engineering analysis group, and Ken Damon, the manager of Peterbilt’s SuperTruck Project. I learned a lot about the project and the truck from these two, and spent an eye-opening 10 hours driving the truck with them over parts of the same test route they used to prove the truck’s capabilities — U.S. Route 287 in north-central Texas.
This was no ordinary test drive, as if I was evaluating the latest model or trying out some new option. Many of the “new” components on this truck were literally handmade and genuinely one-of-a-kind.
There was very little different about this truck from the driver’s perspective. It was a typical — albeit highly modified — Model 579. The modifications included things like aluminum matrix brake drums and magnesium crossmembers, not things that make glaring impressions on a test drive. The seats were the same, and so was the dashboard, more or less. The handling was as I expected, and the visibility from the cab just fine. That’s the kind of stuff one notices on a typical test drive.
What I couldn’t notice was much of the work Cummins did on the project. The engine team, led by David Koeberlein, Cummins’ principal investigator for SuperTruck, achieved better than 22% improvement in brake thermal efficiency for the engine through improvements in design such as gas-flow optimization, a reduction in parasitic losses, improved aftertreatment, an increased compression ratio, and optimization of the piston-bowl shape. They also slowed the cruise rpm of the engine by about 200, which I did notice. The truck also used a high-efficiency advanced transmission from Eaton, which I’m told, included some “experimental” shift algorithms. I noticed that, let me tell you, and it worked exceptionally well.
The much-touted waste-heat recovery system, I’m sorry to say, was also virtually transparent to me, the driver. I can’t report in detail on that either, except to say it felt good knowing I was operating one of — if not the — most thermally efficient diesel engines ever installed a truck.
Engineers also developed some technology they call the road-load management system. It’s cruise control, of a sort, but far more advanced than what we see today. The system is loaded with GPS waypoints and terrain data so it knows the road profile. The system then runs the trip from origin to destination and bases its decisions on a predetermined trip time. It will give up speed (and time) where it makes fuel consumption sense, knowing it will make up the time at some later point coasting downhill when the extra speed is free. When the driver sets the cruise control (really the cycle efficiency management system) for 62 mph, the truck accepts that as a trip-time benchmark, not a road-speed benchmark.
I suppose if I hadn’t been brought up to speed on how the system worked, I probably would not have noticed it.
I have saved the best for last — the aerodynamics. Bezner tells me the aero package on this SuperTruck reduced its drag coefficient by an astounding 50%. This became abundantly clear to me on the first significant hill we descended on the test drive. I had just been made aware of the road load management system and expected the truck to climb the hill a little slower than usual, which it did. But when it took off down the other side, I asked Bezner why the engine was powering us down the hill when it should have been saving fuel and letting gravity do the work.
Bezner, grinning from ear to ear, pointed out that the truck is so aerodynamic it’s just not held back the way lesser trucks are. It was an astounding moment. I’ve rolled down my share of hills, but never before have I seen a truck gain speed so quickly on a modest grade. The implications are staggering, because it works the same way on flat ground too.
“On our first SuperTruck demo vehicle, while running on flat ground in near-zero wind conditions, pulling 65,000 pounds GVW at 64 mph required about 145 horsepower,” Damon explained. “Our baseline truck and trailer with the same load and speed required about 210 horsepower.”
Under fairly typical conditions, advanced aerodynamics (among other factors) allowed the truck to maintain road speed with 65 horsepower less than the baseline truck. It’s worth noting that in computational fluid dynamics analysis, the aero package on the first demo vehicle showed a 38% drag reduction. The second demo truck, the one I drove, was just under 50% drag reduction.
The Cummins-Peterbilt SuperTruck was the first one to emerge from the program. It exceeded the efficiency targets by handsome margins, and I was impressed – all the more so because the driving experience had changed little. I can’t wait to see what the other three SuperTruck teams put on the table.
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