5.9L Vs. 6.7L Cummins Diesel Engines - Cummins Vs. Cummins

The 6.7L Cummins engine comes equipped with a mass air flow (MAF) meter (arrow A), something not used on the 5.9L engine. However, both trucks do utilize air inlet temperature (IAT) sensors (arrow B).

The 6.7L Cummins engine comes equipped with a mass air flow (MAF) meter (arrow A), somethi

Intake and ExhaustDyno Numbers
We went back to Flash Auto to quantify the changes on the chassis dyno, particularly to see if the horsepower gains on the 6.7L would be as great as the 5.9L since it did not benefit from a full exhaust upgrade. With the Edge Juice in the Stock setting, the 5.9L gained 38 hp and 117 lb-ft of torque, and the horsepower peak rose 300 rpm. The 6.7L was even more impressive, gaining 64 hp and 158 lb-ft of torque with just the intake and exhaust. Clearly there are restrictions on the 6.7L besides the DPF and exhaust catalyst, since they were retained.Advantage: 6.7L Cummins

Performance Module Dyno Numbers
Turning the Edge Juice up to the Tow setting netted another 44 hp and 127 lb-ft for the 5.9L and knocked the horsepower peak down to a stump-pulling 2,200 rpm. The 6.7L gained 30 hp and 96 lb-ft of torque from the Juice's Tow setting. Turning the Juice up to the Extreme setting gained another 35 hp and 106 lb-ft of torque for the 5.9L, and 23 hp and 51 lb-ft of torque for the 6.7L.Advantage: 5.9L Cummins

In order to fit the S&B intake box into the stock grommets, it was necessary to shave the mounting feet with a razor blade. A lubricant such as dish soap or WD-40 would also help with fitment.

In order to fit the S&B intake box into the stock grommets, it was necessary to shave the

Fuel Economy
The 5.9L truck was equipped with a 4-inch suspension lift and 35-inch tires on heavy 20-inch rims, and the owner was only getting 13 mpg in mixed highway and city driving. After the intake and Edge module were installed, mileage improved slightly to 14.5 mpg. When the Silverline exhaust was added, mileage improved to 16.5 mpg. "I had never been able to get 500 miles out of a tank of fuel before the exhaust was installed, but now I can," reported the 5.9L Cummins owner.

The owner of the 6.7L truck was not as scientific about recording his mileage, but he did experience a notable increase in mileage after the intake and module were installed. There also seemed to be another increase in fuel economy from the exhaust. The 6.7L owner was pleasantly surprised by the difference the exhaust made, considering that the factory diesel particulate filter and catalyst were both retained.Advantage: Tie

The S&B intake kit offered excellent fitment on both trucks, wrapping around the battery and feeding cool air from the inner fender.

The S&B intake kit offered excellent fitment on both trucks, wrapping around the battery a

Conclusion
The 6.7L Cummins didn't show the same power potential as the 5.9L, but that's no surprise considering that it's saddled with so many emissions controls. What is surprising was that even with an increased stroke length (4.88 inches versus 4.72 inches), the 6.7L made peak horsepower at a significantly higher rpm than the 5.9L Cummins. The fact that we were able to get so much out of the 6.7L without affecting the DPF or throwing any codes spoke volumes about the quality of parts that S&B, Edge, and Silverline are producing.

As more 6.7L Cummins-equipped trucks hit the roads, we expect even more products to become available for them in the future, closing the gap between the new 6.7L and the trusty 5.9L. While the displacement may have changed, the Cummins B-series engine is still alive and well.