Say “Cummins crate engine” and most off-roaders look at you with an eager, inquisitive cock of the head like a dog that just heard the word bacon. With a weight of 503 pounds, developing 161 hp at 3,600 rpm and a meaty 267 lb-ft between 1,500-3,000 rpm, and easily handing down over 20 mpg on the highway, the Cummins R2.8 Turbo Diesel crate engine was the perfect choice to power the official 2017 Ultimate Adventure vehicle. In the scorching desert temps up to and over 126 degrees Fahrenheit, the cool-running diesel’s engine temps never climbed over 180 degrees on the trail. With up to 300 miles of off-road slogging between fill-ups, the economical diesel used roughly one-third the fuel as the gas-powered rigs on the Ultimate Adventure. And when we needed it, there was more than enough oomph to keep the 38-inch Falken WildPeak M/T tires spinning.
Arriving in a big, wooden crate and safely wrapped in plastic, our R2.8 Turbo Diesel package came with the wiring harness installed, including the Engine Control Module, the OBD Service Port, a complete throttle pedal assembly, and a J1939 CAN display Murphy gauge. The diesel oxidation catalyst (DOC) is included, as are the accessories, remote oil filter, turbo, and everything minus an intercooler and ducting. In reality, all you need to do to fire the engine inside the crate is hook up a couple of electrical leads, dunk a fuel pickup tube into a diesel container, and fire it up.
Once next to the UACJ-6D chassis, Tech Editor Verne Simons and ace freelancer Trent McGee dove into what they have since dubbed “the easiest engine swap ever.” Here’s how we added Cummins crate engine power to our JK-chassis’d project Jeep. Check back next time when we will show you the crate axles in more detail and highlight the brake and steering systems.
With a list price of $8,999 and including almost everything required for a smog-legal diesel swap, the Cummins R2.8 Turbo Diesel crate engine is actually cheaper than many turnkey gas engines on the market. For that price you get a brand-new factory-built Cummins turbodiesel complete with a fuel pump, a cam-driven vacuum pump to power your accessories, an internally regulated 120-amp alternator, a power steering pump, a wastegated Holset turbo, a DOC exhaust downtube, EGR and oil coolers, a remote oil filter, and a full wiring harness, ECU, and throttle pedal.
In Part 4 we showed you the Axis Industries bellhousing and flywheel adapters we used to mate our engine to a 4.0L Jeep bellhousing. Axis has since introduced adapters for GM Gen III and IV transmission patterns with more on the way. With the suspension sitting at full bump, we slid the engine into place and positioned it for firewall, hood, and oil-pan-to-axle clearance.
The Cummins R2.8 Turbo Diesel is a pretty good fit inside even a short-nosed CJ engine bay, requiring no cutting of the firewall. The remote oil filter housing was originally mounted to the bellhousing bolts as the engine came out of the crate, but we used a bracket from Axis Industries to mount the filter housing off the bellhousing for driveshaft clearance.
Even with the big Ultimate Dana 60 centersection and a linked suspension we wound up with plenty of oil-pan-to-diff clearance at full bump. We probably could have eked a little more uptravel out of our Skyjacker LeDuc Series coilover suspension but we wanted to maintain a slight margin of safety for the oil pan in case we ever hit hard enough to damage or bend a bumpstop or a bumpstop pad.
With the engine positioned where we wanted it, Simons whipped up some frame-side engine brackets. He began with some 3/16-inch plate and 2x4, 0.120-wall rectangular tubing tacked together with his trusty Millermatic welder.
The frame-side bracket accepts Axis Industries’ exceptionally nice engine isolator. The T-shaped reinforcement plate ties the bracket together and also overhangs the top of the framerail for additional weld surface and triangulation.
The engine-side brackets were built similarly to the frame-side, with 3/16-inch plate and 2x4, 0.120-wall rectangular tubing. The Axis Industries engine isolators are, in our opinion, the finest available and do a miraculous job of damping the little vibrating powerhouse.
A final check of clearances and the engine brackets could be fully welded to the frame. Note the blue hose at the front of the engine, which is the cam-driven vacuum pump. If you’re retrofitting a vehicle with power brakes and other vacuum-driven accessories, this is what you will hook up to.
With the engine mounted we installed the grille and began piecing the puzzle together, beginning with, from Flex-a-lite, a Flex-a-fit direct-fit radiator and a Black Magic S-blade electric fan designed for the 1987-2006 YJ and TJ Jeep Wranglers.
We were able to position the Flex-a-lite fan and radiator in front of the engine just far enough to fit the massive custom intercooler from Axis Industries. Axis is working on direct-fit applications for more popular conversions. Trust us when we tell you the company’s air-to-air intercooler is a work of art.
After the Axis Industries intercooler was in place came the daunting task of actually hooking it to the Cummins turbo and intake. We leaned heavily on longtime UA sponsor Diesel Power Products for the high-quality turbo ducting, elbows, and connectors to make our logistics work. Thought it wasn’t available at the time of our build, Axis now has an intake clocking ring that allows you to rotate the intake without compromising the function of the grid heater, which would have simplified our install.
The Cummins R2.8 Turbo Diesel does not use urea or rely on a complicated diesel particulate filter requiring fuel-wasting regen cycles. It uses a cooled EGR system and a passive engine-mounted diesel oxidation catalyst (DOC) to which your exhaust pipe can be attached. We got our DOC-to-exhaust flange from Axis Industries.
A low-buck reverse-flow muffler and aluminized tubing from Summit Racing Equipment make up our 2 1/2-inch-diameter exhaust system. With a punchy 16.9:1 compression, the little Cummins is not exactly quiet, so the reverse-flow muffler helps tamp down the decibels a little better than a straight-flow muffler.
We used an AFE Pro Dry air filter in front of the MAF sensor, but the extremely dusty conditions on UA2017 required us to remove and clean the filter at least twice a day. We will most likely add a tractor-sourced centrifugal filter soon.