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Beta-Testing the R2.8 Diesel With Cummins

Posted in Features on October 23, 2017
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Photographers: Stephen Sanders

If you haven’t heard the news that Cummins has a brand-new 2.8L diesel crate engine on the market, you need to get your eyes and ears checked. The name Cummins has long been ubiquitous in the light-, medium-, and heavy-duty diesel market and for good reason. Cummins engines deliver durability, power, and efficiency. In our world of off-roading 4x4s and tow rigs, engines like the 4BT, 6BT (AKA 12-valve 5.9L), 24-valve 5.9L, and 6.7L Cummins turbodiesels are second to none when it comes time to do work and make torque. And with this new Cummins crate engine available for $8,999, ready to run (literally, you can start it in the crate with a little fuel and a battery versus all the other à la carte crate engines out there), anyone with a pulse and a love for 4x4s has one on order, or wants to.

How cool is this engine? How easy is it to install? We have firsthand experience in both of these departments. First, the Cummins R2.8 Turbo Diesel we put in the UACJ-6D started right up once everything was in place and has run ever since without so much as a hiccup. As for drivability, now this old hunk of patina’d iron easily hauls oats down the highway at 75 mph all day long while getting 22-23 mpg. That’s amazing given the beadlocks, 38-inch mud tires, our heavy right foot, and the aerodynamic acumen of a rusted brick.

With all the miles we racked up on the UACJ-6D during this year’s Ultimate Adventure (as well as the return trip from Hurricane, Utah, to Peoria, Arizona) the Jeep and its R2.8 Turbo Diesel crate engine were itching for more action, so when the folks from Cummins invited us to join them for some high-altitude testing in Colorado we jumped at the chance. Unlike most of our trips, this one was almost all road-based (until the return trip, and for details on that check out the story “Colorado via UACJ-6D”). But the road miles were by design to give the Cummins engineers on the trip all sorts of over-the-road information, collected with onboard data loggers. In fact, the Cummins data logger in the UACJ-6D has been churning information straight back to the Indiana Cummins headquarters since it was first fired the day before Ultimate Adventure 2017 began.

With all the Cummins R2.8 Turbo Diesel–powered rigs such equipped, the plan was to drive the rigs hard, try to get them hot on long climbs, see how they run at altitudes 12,000 feet above sea level and higher—and then see how they run while compression breaking down the back side of the climbs. The engineers took notes on each rig, and we were all on the lookout for any hiccups or strange behavior, noting when and what happened and more. The trip was a blast, and we got a little bit of info on all of the rigs on the trip just for you. Check it out!

After getting invited to join Cummins for some road and high-altitude testing, we loaded up in the UACJ-6D and headed towards Flagstaff, Arizona. The rest of the group had been doing high-temp road testing near Laughlin, Nevada. Other rigs the trip were a 2000 Jeep Wrangler Sahara, a 2010 Nissan Frontier SV 4x4, and two “Competitive Test Vehicles,” namely a 2.8L Duramax Chevy Colorado and a 3.0L TDI Land Rover. Also, a 5,000-pound rental trailer was shuffled between the various test vehicles during the trip. Unfortunately not present during the part of the trip we were on were two other R2.8-powered rigs: a Mastodon Motor Company 1967 Scout 800 from Anything Scout (which would meet the group after we left), and a Tactical Application Vehicles 1985 Toyota Pickup (which was having transmission troubles).
After a quick bite of lunch in Flagstaff the engineers from Cummins got right back to work downloading the newest computer calibration to the UACJ-6D’s ECU. All of the test vehicles were equipped with data loggers that would collect info for the Cummins engines via the OBD-II port. Here the guys from Cummins make our fuel filter sensor functional. We weren’t worried, but the system will throw a code if this part is not hooked up. All of the R2.8-equipped rigs also have a Murphy Gauge, which gives info from the engine and has trouble-code reporting capabilities with two check engine lights: amber for small issues like the lack of a fuel sensor, and red for mechanically fatal issues like a total loss of oil pressure.
The three little pigs? From Flagstaff we headed northeast towards the high altitudes of Colorado. This route is familiar to anyone going from the Southwest to Moab, Colorado, or the Four Corners region. We stopped for snacks, a drop of diesel, and a pee break in Kayenta, Arizona, near the beautiful Monument Valley. Three R2.8 Turbo Diesel rigs parked in a row. Being the nerds we are, we quickly guesstimated fuel economy for these rigs at 22-28 mpg, numbers absolutely unheard of for gas-powered rigs with big tires and low gears. Keep in mind that Fred Williams’ Tube-Sock and Hazel’s UACJ-6D are on 38s!
With a whiff of diesel in the air, the second day of our trip started in the beautiful (but expensive) ski town of Telluride, Colorado. Some of us were aching to hit one or more of the many amazing passes in and out of Telluride, but data collection left little room for dallying and we had rigs to drive and a long way to go. Along the way we buzzed past lots of amazing vistas, but also noticed this other diesel-powered rig in a group of overlanders: a left-hand-drive overseas Toyota Land Cruiser. We’re wondering what the story with that rig is.
We wholeheartedly recommend any and all road trips through Colorado in September. It’s a beautiful place and a great time of year. Unfortunately for us, we found that September is also road work season in Colorado and we spent our share of time in traffic. When not slowed for construction, we kept pounding the pavement collecting data for Cummins. Any weird occurrences, like stumbles or puffs of smoke, were noted via radio to one of the Cummins engineers not driving a vehicle.
Fred Williams and his co-dawg, Batman, manned the wheel of the Cummins R2.8 Turbo Diesel/NV3550/NP231/5.38-geared Tube-Sock TJ somewhere in Colorado.
Williams knows where all the best coffee shops are in just about every state. Leadville, Colorado, is an awesome town filled with history and cool off-road trials.
The steep climb up to the tunnel on Interstate 70 just east of Silverthorn, and Dillon, Colorado, and then over Loveland Pass, was maybe the pinnacle of this trip. Lots of OEMs test in this area, and we got to see Chevys, Cadilacs, and even a JL or two getting put through their paces. It’s nice to know that Cummins cares enough about its crate engine repower program to do this kind of testing. In the end it ensures that what you spend your hard-earned money on is a solid product that you can rely on anywhere in the world.
Rain in an open top Jeep is no fun, especially at elevation. Rain-X is your friend, and we desperately needed more!
These Cummins engineers are always engineering stuff.
The end.

Tech Specs

1971 UACJ-6D
Engine: Cummins R2.8 Turbo Diesel
Transmission: SM420 with Advance Adapters Ranger Overdrive
Transfer Case: Offroad Design Magnum Box/Ford NP205
Axles: Dana Ultimate Dana 60, 4.88, Eaton E-locker (front and rear)
Springs & Such: Skyjacker Curt LeDuc Series coilover
Tires & Wheels: 38x13.50R17 Falken WildPeak M/T on 17x9 TrailReady HD beadlock
Other stuff: Lucky rock affixed to front bumper, new custom Ford Taurus fan and shroud
Built By: Petersen’s 4-Wheel & Off-Road

Tech Specs

2000 Jeep Wrangler TJ Sahara
Engine: Cummins R2.8 Turbo Diesel
Transmission: NV3500 5-speed
Transfer Case: NP231
Front Axle: Dana 30, 3.73
Rear Axle: Dana 44, 3.73
Springs & Such: Teraflex 2-inch
Tires & Wheels: Dodge Magnum steel wheels with 31x10.50R17 Goodyear Duratracs
Other stuff: ProComp Bumpers, Bestop frameless soft top
Built By: Axis Industries USA

Tech Specs

2010 Nissan Frontier SV 4x4
Engine: Cummins R2.8 Turbo Diesel
Transmission: Nissan 6-speed
Transfer Case: Nissan 2-speed
Axles: Nissan axles, 3.13 (front and rear)
Springs & Such: 2-inch Calmini
Tires & Wheels: Nissan steel with weld-on rock rings, 33x12.50R17 Goodyear Duratrac
Other stuff: ShrockWorks bumpers and rock sliders
Built By: Cummins

Tech Specs

1997 Jeep Wrangler TJ Submarine Tube-Sock Edition
Engine: Cummins R2.8 Turbo Diesel
Transmission: NV3500
Transfer Case: Advance Adapters Atlas II 4.3:1
Front Axle: Currie Dana 44, 5.38, ARB Air Locker
Rear Axle: Currie RockJock 60, 5.38, ARB Air Locker
Springs & Such: BDS coils, Fox shocks (front and rear)
Tires & Wheels: 38x13.50R17 Falken WildPeak M/T, American Racing Chamber Pro beadlock
Other stuff: Bestop soft top, Custom doggy dishes and sleepy nests
Built By: Advance Adapters, Dave Chappelle, and the Fredling


Cummins Inc.
Columbus, IN 47201

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