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Heavy-duty action is heating up in the pickup arena. Each of the Big Three is fielding a new or revised diesel engine, beefed up to grind it out in the marketplace.

All are powerful and capable, but Dodge believes its new 6.7 liter Cummins inline six-cylinder turbo-diesel, available in 2007 Dodge Ram 2500 and 3500 models in January, stacks up well against its formidable competitors. The engine also marks a big evolutionary step from the 5.9 liter turbo diesel it replaces.

Displacement is a key advantage in the diesel battle, said Don Altermatt, Chrysler Group senior manager for diesel engine engineering, with the Cummins’ 6.7 liters trumping the GM Duramax’s 6.6 liters and Ford Power Stroke’s 6.4 liters. The greater displacement is achieved by increasing bore and stroke. Cylinder bores are enlarged from 102mm to 107mm and the stroke increases from 120mm to 124mm.

Output is significantly boosted with the 6.7 liter’s 350 horsepower at 3,013 rpm trumping the 5.9 liter’s 325 at 2,900 rpm. More importantly, peak torque is upped from 610 ft.-lbs. at 1,600 rpm to 650 at 1,500 rpm. The lower the engineers can get the rpm torque the more low-end power the pickup has to do work, he said.

“From 1,500 to 2,800 rpm it has a flat torque curve,” said Dennis Hurst, Cummins executive engineer for midrange engines. “It produces more torque over a broader range than competitors.”

Some competitors peak at higher low-engine rpm and then decay, Altermatt said. Bottom line for the serious trucker is that there’s more torque available to launch, and to do it quickly.

Punctuating how far the Cummins diesel has evolved since it was first dropped in the 1989 Dodge Ram, idle torque is 10 percent higher than the peak torque of the original.

The 6.7 liter diesel comes with a new six-speed automatic, which is designed to handle torque demands beyond the engine’s 650 lbs.-ft., and helps the engine deliver improved fuel economy and performance. Tow rating for the powertrain is 16,400 pounds and payload capacity is 5,020 pounds.

“It will be a noticeable improvement in capability over the 5.9 liter at the same loads,” Altermatt said.

Another component contributing to engine performance is a variable geometry turbocharger. It’s a Cummins patent, Hurst said, and the first application of this technology on a Dodge pickup. Unlike the swinging-vane type others use, the VGT is a sliding-nozzle unit. It has the capability to precisely match boost pressure to optimize engine performance.

“With the capability of varying the turbine end we can get a more responsive turbo,” Altermatt said. “And on the low end you can change the ratio of turbine-compressor speed. Then you can back it off and have the benefits of a larger standard turbo by opening up the turbine on the high end.”

The VGT turbo also controls Exhaust Gas Recirculation flow rate and helps the engine achieve more torque at high altitude. The cooled EGR system also is responsible for reducing particulates and decreasing nitrogen oxide emissions. It allows the 6.7 liter to comply with all 50 states’ 2007 heavy-duty emission standards.

The turbo’s tendency to produce high-frequency noise is quelled via blade-path noise reduction. This is one of a long list of measures taken to reduce noise, vibration and harshness.

“Compared to the current 5.9, if you look at noise levels – sound-pressure levels, dBA of noise level – the overall noise level of the 6.7 liter engine is reduced by 3 dBA,” he said. “That doesn’t sound like much – except if you understand how sound is added, one source to another. That’s like cutting the sound levels in half.”

There is also “good noise,” a throaty exhaust sound courtesy of an integrated exhaust-brake option, which is an integral part of the VGT. It comes with a switch to engage it and the software necessary to operate the brake in harmony with the transmission.

The exhaust brake is especially useful when pulling a heavy load, such as a big horse trailer or RV. It adds to braking efficiency and can reduce the amount of time a driver has to use the vehicle’s brake.

“It’s a deeper exhaust sound, not the irritating noise you hear with a Jake brake,” Hurst said.

Cummins customers like the big-rig feel and are in tune with the company’s heritage, he said. “This inline six fits with Cummins’ Class A truck legacy.”

 

Now, if 'they' can come up with chip to trump the chipped 5.9s all will be well with the 6.7 owners.

 

The 6.7L sounds pretty good, especially the VGT. Do they all come standard with an exhaust brake?

 

It has to be enabled by the dealer... it's integrated into the turbo.

 

does that mean you have to pay $1,200 bucks to have it enabled??
how much do they charge you to enable a function like that??
if it is already on there then it should already work IMHO

Mark

 

I stopped in at the dealer last week to get some info on the 6.7's. He gave me a tech letter sent to dealers about the new engine. Exhaust brakes are now standard on these trucks. I think it said a $300 rise in cost or something like that. But if you order one now, you'll get an exhaust brake standard.

 

I got the same info about the exhaust brake, they will be standard def on the 08's

 

Exhaust brakes are standard on all 6.7 engines built after the end of december 06'. Nothing to enable, just get in and go.

 

I live in Louisiana and when Katrina hit us we had no fuel for a while and we got a "pass" to use "farm" diesel. It was a big help. I heard these engines will fry if you use "regular" diesel in them. My only apprehension is that what happens when the nation has trouble for what ever reason and we have a hard time to make this new fuel? And now all these new trucks are sitting around, useless. I think I will stick to my 06.

 

The only difference between farm fuel and the new ultra low sulfur fuel will be the dye and in a few months it will be all you can get . Around here that is all were using already but I do not know about the rest of the country there may be some old fuel still out there .

 

The part about "these engines will fry if you use regular diesel in them" is not correct. For what it is worth, my 6.7 now has over 19,000 miles on it and it has had 11 tanks of the ULSD run through it. It is not available in my area. I get it when I find it, but the closest to me is 87 miles away. It won't hurt the engine, the only thing it "might" to is fill the particulate filter up quicker than normal. (don't know what normal is) I make my living with my truck and although I probably shouldn't, I don't have a choice about what diesel I run. As many miles as I run, I'll will more than likely be the first to find out about the particulate filter. I also believe that most of the diesel now is actually the ULSD. According to most oil company web sites, they will tell you that they haven't made any LSD since June of 06.

To sum up my thoughts on the subject, I don't believe you will hurt your engine but you will probably put a little more soot into the air, (most everyone seems to want to do that anyway) and you might be filling up the particulate filter a little quicker than normal.

 

Except for the fact that it will kill the new Piezo Fuel injectors a lot faster than the ULSD...It doesn't matter to me who uses what fuel, but just thought it should be out there.

 

Again, nothing I can do about it. ULSD is not available in my area.

 

What makes you think it isn't?

I thought that all Diesel produced for the past few months has been ULSD...

 

Talked to a tanker yanker the other day. He said he just started in the middle of December delivering only ULSD in my area.