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

Comparing The 6.7L And 5.9L Cummins Engines

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A lot has changed since the 5.9L Cummins B-series engine was first offered in '89 Dodge pickups. The injection systems, cylinder heads, emissions equipment, and turbos have all seen dramatic improvements over the last 20 years. However, the one thing that Cummins has never altered was the displacement. During the same time period, General Motors upsized its diesel from 6.2L to 6.5L, and then to the current 6.6L engine for the Duramax. Ford sold 6.9L, 7.3L, and 6.0L in the past, and currently sells 6.4L Power Stroke engines, continually improving in order to meet various performance, fuel economy, and emissions requirements.

Yet while the number of valves and injection systems have been updates on the Cummins B-series, the engine has always displaced a consistent 5.9 liters. Of course, all of that changed last year when Cummins revised the B-series in the face of increased emissions controls for diesel engines. The new 6.7L B-series engine has 12% more displacement, advanced electronics, a variable geometry turbocharger, and is saddled with an EGR cooler and diesel particulate filter.

5.9L VS. 6.7L On The Dyno
We wanted to see how the 6.7L stacks up next to the proven 5.9L, so we rounded up two stock Dodge trucks equipped with four-wheel drive and automatic transmissions. The 5.9L Cummins truck was an '06 Quad Cab shortbed, and the 6.7L Cummins was an '07 Mega Cab. We began by putting both trucks on Flash Auto's chassis dyno in Albuquerque, New Mexico, to see how the real world power figures compare to Dodge's advertised numbers. As we were generating power numbers, the differences in emissions controls became immediately obvious. The 5.9L made plenty of smoke under load, even in stock form. By contrast, the 6.7L was squeaky clean during our dyno pulls. Advantage: 6.7L Cummins

Stock Power Numbers
The 5.9L-powered truck put down 269 hp at 2,550 rpm and 594 lb-ft of torque at 2,300 rpm; and the 6.7L-equipped Dodge put down 259 hp at 2,850 rpm and 487 lb-ft at 2,750 rpm. Runs were made in direct drive for both trucks-however it should be noted that the 5.9L Cummins was backed by the 48RE four-speed automatic transmission and the 6.7L used the new 68RE six-speed automatic. Unfortunately, the 5.9L Dodge used in our test had 35-inch Toyo tires on 20-inch Eagle Alloy rims. In order to limit the variables between the two trucks, the stock tires and wheels from the 6.7L truck were swapped onto the 5.9L truck, resulting in 10 additional peak hp and 10 lb-ft of torque. Advantage: 5.9L Cummins

Installing Performance Air Intakes
After getting stock power figures, we installed some typical aftermarket components on both trucks to see how they responded to the modifications. We began at the front of the trucks by installing S&B intakes (5.9L P/N 75-5033 and 6.7L P/N 75-5015). Both S&B air intake kits used large-diameter, smooth, molded tubes and multi-layer cotton gauze filters that meet ISO 5011 specifications. The only real difference between the intake kits for the different engines was the installation of a mass air flow (MAF) sensor to the intake on the 6.7L Cummins in addition to the air intake temperature (IAT)sensor used on both engines. The S&B intakes were designed to route cool air from the stock air duct in the fender, and included detailed instructions complete with color photos. Minor trimming was necessary to get the feet of the new airbox to fit in the locating grommets on both trucks, but this was a small price to pay for an intake that costs a fraction of other competitors' products and delivers just as much horsepower and superior filtration.Advantage: Tie

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241 comments
Cam Robison
Cam Robison

Dillon Zellhuber FYI ram does not own cummins lol

Ricky Amezcua
Ricky Amezcua

why hate on gas? we should be hating on prius and outback owners. my 460 can pull 70ft mobile homes so why go there?

Randy Bahl
Randy Bahl

Umm last I checked Cummins is there own corp business. Dodge buys there engines from Cummins. You can find your cute 12 valve Cummins in a case IH tractor

Randy Bahl
Randy Bahl

Umm last I checked Cummins is there own corp business. Dodge buys there engines from Cummins. You can find your cute 12 valve Cummins in a case IH tractor

Billy Underwood
Billy Underwood

Ford was bailed out by dodge? Wtf? Bought shares of ram so they could use cummins? Lmao! Ram don't own cummins.

Hunter Llewellyn
Hunter Llewellyn

Ford was bailed out by dodge awhile ago...needless to say they bought shares of ram and used the cummins motors in their heavy duty trucks such as their 450's and up

Zach Self
Zach Self

2010 an up 6.7 idk about the 07.5 to 09

Brandon Wood
Brandon Wood

Ryan Milliken do you see what I see on those license plates!?

Manuel Venzor
Manuel Venzor

The 5.9L is better! The 6.7L is ok. It would be a lot better if Chrysler designed a transmission to be able to handle it. The Cummins QSK45 sounds pretty gnarly right Patrick Hoisington?

Josh Fox
Josh Fox

WaaaaaaaaaaaaaI have toyotas! All over!

Craig Welch
Craig Welch

5.9 junk 6.7 is bigger better and beast

Steven Seeley
Steven Seeley

Joel Case Sr. Yea 9 sec on stock turbo and stock injectors dummy so try again

David Hubbard III
David Hubbard III

I gotta say I love my 1999 5.9..had to put the egde comp box and a better tranny but like I say when u see the smoke shes doin work..oh and its 197k on it

Joel Case Sr.
Joel Case Sr.

I worked for a ford dealer for years as a mechanic been a mechanic 20 some years have worked on damn near every make and model but the biggest p.o.s I've ever had the misfortune to come across is the 6.0 powder choke

Joel Case Sr.
Joel Case Sr.

Jacob Nikolas Aaron Mirlin u got a ttb ford and u got the balls to talk about a junk frt end what u been smoken

Joel Case Sr.
Joel Case Sr.

Got a first gen and third gen the 5.9 is as dependable as a hammer both of mine run there ass's off my 03 will smoke a new M3 its fn hilarious gets about 20mpg I sled pull drag race and regularly tow over 15, 000lbs

Trevor Myers
Trevor Myers

Both 05's I think but ima have to go with the 5.9

Walt Slover
Walt Slover

I recently got to see a 6.7 with a window rite next to #6, the rod fell out the hole onto our driveway!!!!

Jack Stout
Jack Stout

I think they ask these types of questions just to laugh at some of the ignorant posts.

Eric Salas
Eric Salas

5.9 wanna of dodge cummins best engines!!

Cody Simoncelli
Cody Simoncelli

If you hate a dmax perhaps you should stay away from diesels all together

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