Hitting the Road With EGR
HDT editors test-drive more new engines.
STEVE STURGESS, SENIOR EDITOR &
JIM WINSOR, EXECUTIVE EDITOR
To this point, we have driven Detroit Diesel (HDT, April 2001), Cummins (HDT, May 2001), and Mack (HDT, January 2002) cooled EGR engines in various truck models. Early in the evolution of EGR in heavy duty diesels was the Series 60, then came an early Cummins prototype for the ISX. Several other opportunities to drive the ISX have been presented, including a back-to-back comparison of pre- and post- 10/02 ISXs.
The Mack E7 was a near-production engine that we touched on briefly in the magazine.
Now we have completed the suite with the Volvo V-Pulse technology on what will eventually be designated the VE D12D engine.
Cat's interim-technology "Bridge" C-15 isn't included in the driving roundup. However, since Caterpiller's advanced combustion emissions reduction technology (ACERT) is going to rely heavily on aftertreatment devices along with fuel system and in-cylinder combustion changes, the performance and driveability — and external appearance of the engine — are likely to be much like today's C-15.
We will drive them and revisit Detroit Diesel and Cummins models in an upcoming issue.
Taking Volvo's V-Pulse
Volvo's exhaust-gas-recirculation solution to the emissions requirements for EPA '02 is a little different from the other engine makers who are on target for the October deadline. In its V-Pulse technology, Volvo is using exhaust pressure generated at the exhaust valve to drive exhaust gas through the cooler and into the inlet stream.
Routing the exhaust through the cooler in two separate paths and inserting a couple of additional valves makes good use of this available exhaust pressure. By doing so, Volvo engineers do not have to resort to the complexity — and cost — of a variable geometry turbocharger (VGT) that Cummins, Detroit Diesel and Mack have chosen.
For the driver who does his pre-trip and includes checking engine levels, there is a surprise: the oil check and fill has been moved to the inlet side of the Volvo engine, away from the additional heat surrounding the turbo and the exhaust-gas coolers.
That's not to imply there is any significant danger on the hot side of the engine though. For the most part, the additional components, plumbing and wiring are all tight to the engine, where they don't intrude.
However, they are reasonably easily serviced and have the additional advantage of being up high where they benefit from the cooling air through the radiator. Nevertheless, Volvo says it anticipates underhood air temperatures to be 5 degrees higher than currently.
The starter sounds quite different as it is a smaller, geared starter — a change that trims a couple of pounds off the engine weight to compensate for the added EGR components.
Once running, the engine settles to its usual quiet idle. From then on, from the driver's perspective, that's the end of the story. There is little to distinguish the post '02 Volvo engine from its predecessor. The comparison chart on page 42-43 shows the ratings that will be available; our evaluation VN day-cab had the 435/1,550 rating.
Since it avoids the complexity of the variable geometry turbo, the Volvo engine also doesn't show any of the unusual turbocharger activity associated with that device. The other three EGR engine manufacturers with VGT technology all claim a boost in driveability (see below), but the VE D12D is indistinguishable in its throttle response — at least in my memory — from the existing engine.
The test VN was running at around 68,000-69,000 pounds gross. Backing up the engine was an overdrive 10-speed Eaton Fuller with a "C"ratio set and the rear ends had a 3.73 ratio. Tires were 22.5 low profiles, gearing the truck to about 1,500 rpm in top gear at 60 mph or, cruising at 70, the tach showed just about 1,700 rpm. The route was from Volvo's Greensboro headquarters just off I-40 at junction 210 to a turnaround at the Wilco truckstop in Wytheville, Va., a little over 100 miles away.
This meant we could run the grade at Fancy Gap, a 7% climb I have made many times in the past when testing Volvo new introductions. It is a good test of the engine's pulling power and on this occasion the VN ran all the way up with just a single shift to 9th, pulling the steeper sections at a steady 1,300 rpm and 45 mph. At this engine speed there was still 200 rpm in hand back to the torque peak of this 12-liter engine. The engine pulled more strongly than its 1,550 pounds feet of torque would have suggested. However, there's no significant change to the torque rating with the EGR change.
Turbo boost was at maximum here, but there was only a very distant turbo whistle. With no boost gauge there was no way to tell the pressure generated, though likely less than other cooled EGR engines. I did notice the fan cycled more frequently than with previous Volvo engines on this climb.
The cooling system is substantially unchanged, though it does, of course, have the exhaust cooler and the EGR valves in the circuit. To move the additional heat, the engine now has a 13-blade fan instead of the previous 11-blade one. The fan, though, is efficient, running in its engine-attached fan ring, and it's not at all intrusive.
Of the drives I have done with cooled EGR engines, this was certainly the least eventful. There's nothing about the Volvo EGR execution that would cause a driver to even comment and without lifting the hood, I would say it would be impossible to distinguish a pre-EPA '02 from a new-emissions engine.
That's probably good for Volvo. The engineers consider the avoidance of the potentially troublesome VGT a big plus for the Volvo solution for cooled EGR. With concerns among fleets about the reliability and durability of EGR, this undoubtedly gives Volvo an advantage. But without the performance boost possible with the VGT, it also trades off any potential gain as well.
Mack Shows Its ASETs
We didn't know it back in December of last year when given the opportunity to drive the cooled EGR Mack E7 that Mack was pursuing two distinct EGR paths for its different profile of customers. Included under the Application Specific Emissions Technology (ASET) is a cooled EGR using a VGT, EGR valve and cooler, designated C-EGR and intended for over-the-road applications. This is the technology we drove. For on-/off-highway and vocational customers, Mack has a less complex, lower cost option of internal EGR, or I-EGR. This relies on careful design of the air-flow through the engine and an extra bump on the exhaust cam to bleed appropriate amounts of uncooled exhaust gas back into the cylinder. The design of the cylinder head and the speed of the flow through the exhaust vary the amount of EGR without the need for EGR valves.
This surprisingly simple system has a potential trade-off: fuel economy. However, the vocational Mack customer is less likely to be concerned about the small loss than an over-the-road, high-mileage operator.
Mack C-EGR
Under the hood of the daycab CH was a 427 Econodyne, rated at 1,800 rpm and with 1,460 pounds feet of torque coupled with a 9-speed transmission and rear ends for vocational application, likely down at around a 4.33 ratio. We were pulling a loaded trailer.
The CH Mack tractor was built to the Tyson chicken fleet spec for daycabs, and had recently been repowered with the latest version of Mack's pre-production E7 C-EGR engine with the 427-hp rating. The engine packaging sported a brightly colored fan shroud indicating that this was a pre-production piece. The shroud is closely fitted to the fan to enhance air flow when maximum cooling is required.
Jim Winsor took the 77,000-gcw rig for a couple of laps around Mack's Engineering and Test Center track in Allentown, Pa., particularly to see how the EGR engine would pick up the load from a start on the 17% grade test hill. It was a non-event. With V-MAC electronics and the variable geometry turbo sensing the heavy load at clutch engagement, the engine barely labored as it accelerated to 1,800 rpm and he was able to grab second gear with no problem, a very positive first impression of how the engine performs.
With me at the wheel, we headed over to nearby I-78 heading east to New Jersey. The entrance ramp is close to the climb up South Mountain, about a 7% two-mile grade. Starting in at 52 mph at 1,400 rpm, I quickly had to grab a gear as the torque peaks at 1,300 rpm on this EGR engine, 100 rpm higher than the previous E7. However, that was it for the climb, staying in 8th all the way to the top and cresting the hill at 35 mph sitting right on the 1,300 rpm torque peak.
We stayed in the same ratio on the downgrade, where the retarder held the truck back nicely, aided no doubt by the additional boost from the VGT.
After a pause for some picture-taking, Winsor took over for the run back to Allentown and the climb up South Mountain in the opposite direction, which is about a two-mile climb. Like me, Winsor felt the engine was more responsive, had more bottom-end acceleration as he went up through the gears and merged into the I-78 traffic. There's no question that the engine is very driver friendly with improved performance, especially in the 1200-1500 rpm range. Winsor got a good run at South Mountain at 62 mph before the grade started unwinding rpm's and reports he dropped only one gear but topped the mountain at 40 mph, very impressive, indeed.
More Power 2002
The High Cost of Clean Air
Pre- and Post-October '02 Engine Availability
