Full Speed Ahead

Jim Park

Try to imagine the challenge in affecting change on the magnitude of 90 percent in whatever it is you do. It’s enough to make you roll over and go back to sleep.

But that’s what was required of engine makers to meet EPA’s ’07 emissions reduction mandates — and that’s on top of the 80-percent reduction in emissions already achieved since the mid-1980s. Detroit Diesel Corporation (DDC), in February, invited journalists to Freightliner headquarters in Portland, Ore. for an ’07 progress update, and to sample first hand the progress engineers are making on the Series 60 engine.

I’m here to tell you they’re coming right along.

With more than five million test miles logged on 58 trucks, and thousands of test-cell hours clocked before that, DDC is into the final phase of testing; a.k.a., the D-level phase of reliability growth vehicle testing. They’ve ironed out the final kinks in the design, and they’re preparing for full-scale in-service customer testing — set to begin in April.

All the engines have been running 15-ppm ultra low-sulfur diesel fuel, and prototype CJ4-category engine oils, just like they will in real life.
DDC has replaced its troublesome swinging vane turbo with an electronically controlled, water-cooled, variable geometry [VGT] Holset turbocharger. The boost pressure from this unit runs about 45 psi, down from the 52 psi of the ’02 version. The ECM-controlled electronic actuator on the turbo permits very precise airflow management — the heart of the exhaust gas recirculation NOx-reduction concept.

The cooling package for the 455-hp engines has grown by nearly 300 sq in. Freightliner is using a rad that’s 10-in wider and about an inch taller. The wider rad rests in a pair of side extenders bolted to the front of the frame rails. The rad is actually mounted solely to the engine in order to achieve closer fan-to-shroud clearances for optimum cooling.

The water pump has been optimized for ’07, providing a higher rate of coolant flow at lower engine speed. On our short trip — even when pulling a two-mile, eight-percent grade, the coolant temp never went above 205 F.

Out back, of course, is the diesel particulate filter (DPF) — a new fixture on all EPA ’07-compliant engines [See accompanying story on DPFs on page 45 of this issue]. Freightliner says it’ll be using a frame-mounded horizontal DPF on all sleeper cabs, and cab-mounted vertical DPFs on short-wheelbase day-cabs.

“All in all,” says Al Pearson, Freightliner Test Engineering’s director of vehicle testing, “the EPA ’07 requirements have added about 250 lb to the weight of the Series 60 engine, including the DPF.”

Slightly larger and heavier than a regular muffler, the DPF
on most OTR tractors will be frame mounted like this

Along with the external changes, the Series 60 sounds and runs different too. The multiple injection events change the sound of the engine a little, but it still has the characteristic metallic knock unique to the big-block Detroit. The Holset VGT is responsible for a much livelier throttle pedal, and the torque curves have been flattened considerably compared to previous models. Together, these changes render the engine a real pleasure to drive.

Getting the Job Done

Three-hours of stick time isn’t much as far as reliability testing is concerned, but I got a good taste of how DDC is progressing with the new product. The 140-mile trip took us west from Freightliner HQ in Portland to a restaurant called Camp 18 in Seaside, Ore. The route was mostly hilly and twisty two-lane following U.S. Rte. 30 and U.S. Rte. 26, along with about 20 miles of freeway driving getting in and out of Portland.

I was lucky enough to drive two trucks while in Portland, one with nearly 180,000 miles on the clock; the other with a mere 4,500 miles showing. The older was of the C-level generation, the first of the on-road test engines. The second — a D-level engine — will be running in a customer’s fleet by the time this issue comes off the press. The differences between the two weren’t significant.

Both engines felt pretty much the same, suggesting engines didn’t need much tweaking between design generations. There were a couple of software glitches on the older engine, but nothing on the newer one. I had the pleasure of Al Pearson’s company over in the right seat-one of the top dogs in the test engineering group — to talk me through the changes DDC made going into ’07.

Optimum engine speed is between 1,400-1,500 rpm. Peak torque of 1,550 lb ft lies at 1,150 rpm, leaving the driver a fair bit of lugging room before needing a downshift. Pearson told me the Series 60’s torque curves have been flattened a bit, which gives the engine a different pulling personality.

The Holset VGT makes the throttle pedal really sensitive in the low gears. That might take a bit of getting used to, especially for drivers who prefer to make their shifts at low rpm. If you can make the shift before the turbo kicks in, you’ll make smoother take-offs. This characteristic works more to the driver’s advantage in the top side of the gearbox: after an upshift, it takes only the slightest touch on the pedal to get the boost pressure back up to premium again.

On the way back from Seaside to Portland, we ran the truck through an active regeneration cycle — to remove the accumulated soot from the DPF. Normally the “regen” event would happen on its own accord, requiring little more than the push of a button by the driver to acknowledge the event was about to occur. We also had the benefit of a laptop computer sitting on the dash to monitor the progress of the cycle. It took about 20 minutes to complete the cycle, and if I weren’t watching it on the computer, I’d have never known the difference.

Operating Costs

These active regen events require fuel, but very little of it in the grand scheme. Tim Tindall, DDC’s program director for EPA ’07, told us that users could expect — on average — to burn about one liter of fuel per 1,000 miles for active regen events.

Tindall says fuel economy is proving to be the same or slightly better than previous versions of the engine. “We actually showed some gains when running 500-ppm diesel,” he says. “But the ULSD fuel knocked us back a little. It looks like we’ll be doing about the same as we are now.”

Oil drain intervals are not going to change.

Freightliner and DDC remain tight-lipped about the price, but what I can tell you is that driving the Series 60 won’t be any chore at all. The new torque curves and the snappy throttle response make the engine feel bigger than it is. While nobody is looking forward to 2007, Detroit Diesel fans, at least, won’t be rolling over and pulling the covers back over their heads.

Jim Park

Jim Park was a CDL driver and owner-operator from 1978 until 1998, when he began his second career as a trucking journalist. During that career transition, he hosted an overnight radio show on a Hamilton, Ontario radio station and later went on to anchor the trucking news in SiriusXM's Road Dog Trucking channel. Jim is a regular contributor to Today's Trucking and Trucknews.com, and produces Focus On and On the Spot test drive videos.

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