AS A RESULT of the Environmental Protection Agency's 2007 emissions requirements, Freightliner's M2 106 and 112 models feature new exhaust systems and cooling packages, modified front frames, aftertreatment devices, and various engine upgrades.
Ivan Neblett, vocational product manager, said Freightliner has gone to a one-piece uni-mount to reduce vibration and noise. It will support the additional weight of the cooling package (250 lb). Castings and crossmembers are new on the front of the chassis for the M2 112.
He said the new engine mounts address the increase in torque and power since 1995 — from a maximum of 500hp and 1650 lb-ft with a fleet rating of 370hp and 1450 lb-ft to a maximum of 600hp and 2050 lb-ft and a fleet rating of 430hp and 1650 lb-ft.
The one-piece assembly provides a larger rubber volume for longer life, and the noise level at the driver's right ear is two decibels below what it was in the 2004 Series 60 engine.
On the M2 106, Freightliner created castings to wrap around the radiator.
On the M2 112, Freightliner elected to do a splayed rail on the front frame extension, while on the 106, the rails carry forward as they had in the past.
Because of the castings up front, the steering gear was moved back inside the tire envelope.
“We had to make up for the change in the intermediate shaft between the steering column and steering gear,” he said. “We had to put in a stub-shaft to correct the angle of the steering gear.”
Cooling system
On the M2 112 cooling system, Freightliner has gone to engine-mounted cooling modules, a radiator-mounted surge tank (except for a high fan center), 3/8" fan-to-shroud clearance, a two-piece fan shroud, manual transmission in-tank cooler, and molded-in drain feature.
On the M2 106 cooling system, Freightliner has gone to chassis- and engine-mounted cooling modules, a cab-mounted surge tank, 3/4" fan-to-shroud clearance, a single-piece fan shroud, automatic transmission cooler in radiator bottom tank, and molded-in drain feature.
Within the cab are warning lights associated with the regeneration process — a DPF regeneration lamp that shows up in the indicator light panel just above the speedometer, as well as a switch for manual regeneration. The DPF lamp is activated only after 12-16 hours of operation with no in-transit regeneration.
The maximum exhaust gas temperatures are unchanged from 2004 emissions for Detroit, Mercedes-Benz, and Cummins systems. Exhaust gas temperatures must be maintained to promote passive filter regeneration. The distance from turbo to the ATD must be controlled within prescribed limits.
“The piping from turbo to the ATD is sacred,” Neblett said. “It's called a sealed unit — it's part of the certification system. The engine is not certified on its own. That piping is a sealed unit in one piece. We have to make sure the heat is maintained in that piping, because the regeneration process needs that heat in order to take place.
“The good news is, that section can be modified within guidelines. The bad news is, that's the hottest piping in the system. During active regeneration, the skin temperatures of the piping could reach 1200 degrees F. That's a part of the system that most of you will be interacting with. Take note of the heat coming out of there, as well as where you exit it.”
The major difference in the exhaust packages from 2004 is that there are no cab-mounted ATDs. On the horizontal systems, Freightliner has a diffuser.
“On a stock pipe, the temperatures on that diffuser have reached 800 degrees F,” he said. “So there was some loss of heat from 1200 degrees at the ATD with that diffuser.”
Engine update
John Gustafson, manager of application engineering for Detroit Diesel, said crankcase breather emissions are also a part of emissions certification of engines for '07. Heavy-duty engines continue to have an open breather with a centrifugal/electrostatic separator. Medium-duty engines have a closed crankcase breather.
“We will be introducing a DPF inhibit switch,” he said. “In a sensitive application, and in a particular operation where you do not want to have the vehicle regenerated with elevated exhaust temperatures, you can push a switch and the regeneration will be inhibited.”
Estimated cleaning intervals: greater than 400,000 miles for the Series 60, 200,000 for the MBE4000 and 150,000 for the MBE900. The MBE900 has grown to 7.2L from 6.4.
New power ratings on the MBE4000 include 370bhp/1250 lb-ft and 450bhp/1650 lb-ft.
On the Series 60, there is a 14L displacement for all ratings — no more 12.8L.
Electrical impact of EPA ‘07
Steve Nadig, business class vocational sales manager, said changes in the wiring mean that it is being routed down the left-hand frame rail. Freightliner also has created an E-rail under-cab location that pulls the wiring up and out of the frame rail so that it comes across to the front wall.
“It makes for a very clean installation,” Nadig said. “It's a benefit for the bodybuilders because it gets the wiring up and out of the way from PTO ports.”
Three mega fuses have been added to the power distribution. An alternator cable is routed to the Mega Fuse Junction Box, not to the starter, which improves wire routing, starting, and reliability.
“The Mega Fuse Junction Box is actually on the frame rail, and we fuse all the power going from there, so there will be a fuse to the cab and to the engine,” he said. “The other benefit is that it drastically improves our starting performance. We only have one wire going over the starter. We used to populate other things over there.”
The standard starter is now an integrated Mag Switch — a high-current relay that provides power to the starter. He said it improves starter control circuit resistance and the performance of the newer “soft-start” starters.
There is an additional powertrain PDM, which is used to house the increased number of circuit protection devices for the powertrain components. The PDM provides: battery power to the ECM and transmission control unit; ignition power to the ECM, transmission control unit, variable geometry and variable nozzle turbochargers, ATD, and fuel heater; and a fused battery sense circuit for the low-voltage disconnect system on a sleeper so that the battery is not run down.
The PDM is located under the hood on the left side of the vehicle, although the exact location varies by make and model.
Nadig said that additional wiring harnesses should be routed on the left frame rail.
He added that if a wiring harness must be routed on the right frame rail: avoid routing it between the engine turbocharger and the ATD outlet; route the harness across powertrain components or crossmembers; maintain a minimum distance of 6” from the exhaust system; use TXL or GXL wire insulation with Teflon that is rated to 257 degrees F instead of the standard cross-linked polyethylene insulation; and use a heat shield or heat wrap over the harness.