The Ultimate Cummins Commuter
As if bone-stock diesel pickups aren’t capable enough right out of the box these days, thousands of enthusiasts are doubling their horsepower while continuing to tow or haul anything they need to. On top of that, they’re practically transforming their trucks into show pieces by bolting on big, offset wheels, stretched tires and de-badging them. Jake Bosie’s ’12 Ram 2500 blends in perfectly with the modern diesel landscape. His sleek, silver Quad Cab short bed sports 22x12-inch American Forces on 33x12.50 Nitto Ridge Grapplers, a stout set of rear traction bars and only the Cummins badges on the front quarter panels remain.
But how did he effectively double the truck’s factory horsepower? Believe it or not, with a 6.7L Cummins under the hood it was fairly easy to to pull off. What’s more is that the valve cover has never been removed, the injectors and injection pump are stock and the factory automatic transmission has gone untouched. The majority of the performance gains came by way of EFI Live tuning from Motor Ops, but the addition of a fixed geometry, BorgWarner S400 turbocharger paved the way for the 520hp wall to be broken. Then to ensure ample low-pressure fuel supply is always on tap for the factory CP3, a PowerFlo lift pump was installed.
Below, we highlight each mod that helped take Jake’s fourth-gen to the next level—and even explain why the factory 68RFE automatic is still alive and ticking with four-digit torque on tap.
Fixed Geometry Turbo: What Every 6.7L Cummins Needs
Although no internal parts or injection system changes have taken place on Jake Bosie’s 105,000-mile ’12 Ram 2500, upon popping the hood it’s apparent that the 6.7L Cummins’ factory Holset VGT has been replaced. In fact, the OEM exhaust manifold, air intake and turbo downpipe have all been done away with in favor of a second-gen swap kit from Fleece Performance Engineering. By fitting a second-generation Cummins style exhaust manifold and a larger BorgWarner S400 fixed-geometry turbo onto the engine, the failure-prone VGT is eliminated and the horsepower wall it brings with it can be breached. Thanks to the 6.7L engine’s displacement advantage over the previous 5.9L, spooling an S400 is extremely easy with aftermarket ECM tuning.
Larger in every way, the fixed geometry S467SX easily outflows the factory VGT. It sports a 67.7mm inducer cast compressor wheel that can move 90 lb/min (approximately 1,285 cfm). On the exhaust side, a 74mm exducer turbine wheel with an 83mm inducer exists inside a spool-friendly 0.90 A/R exhaust housing. A 4-inch diameter downpipe transitions into a 5-inch exhaust system just beyond the firewall. With the right amount of fuel in the mix, this turbo can support 750rwhp or more in the 6.7L Cummins application.
High-Flow, One-Piece Exhaust Manifold
The second-gen style exhaust manifold is a key reason why Jake’s 6.7L retains good drivability despite having a much larger turbo feeding the engine. Made by Steed Speed and offered with the Fleece second-gen swap kit, it centrally locates the turbo on the manifold and features a T4 divided flange (vs. the non-divided T3i factory flange). Thanks to the improvement in exhaust flow and efficiency, the S467 is quick to light—even with the factory injectors and CP3 still in the mix.
Electronic Exhaust Brake
Like many 6.7L Cummins owners, Jake’s decision to pursue more horsepower by adding a fixed geometry turbocharger left him unable to use the truck’s factory exhaust brake function. However, with the inside line on a groundbreaking new electronic exhaust brake from Fleece Performance Engineering, he was able to bolt a pre-production system onto his truck for testing. Now, he has the best of both worlds: the added reliability and power provided by the S467 charger and the use of an exhaust brake to help slow his 7,400-pound missile down.
In-Tank Lift Pump Upgrade
Although it’s impossible to see here, Jake opened the Fleece Performance Engineering catalog once more and added one of the company’s in-tank PowerFlo lift pumps. Unlike external, chassis-mounted aftermarket fuel systems, the PowerFlo pump resides within the tank, seamlessly integrates with the factory wiring harness and provides vastly quieter operation. On top of that, it utilizes an active fill bucket so it can never suck air or be ran out of fuel. The PowerFlo pump can also support as much as 800rwhp—peace of mind for anyone planning for future CP3 and injector upgrades.
Finely-Tuned Factory Automatic
As for the 68RFE six-speed automatic, it’s stock for now. While many consider pushing 570rwhp and 1,140 lb-ft of torque through a stock 68RFE transmission living on the edge, Jake opted for transmission control module (TCM) tuning when he had the folks at Motor Ops calibrated the ECM for more horsepower. Thanks to the TCM tweaks, the slushbox’s optimized shift schedule, increased line pressure for firmer shifts, and improved torque converter lockup strategy, it's stayed alive for more than 10,000 miles so far. To be sure, Jake isn’t living in fantasy land. He knows the ‘68 could let loose at this power level any time, and when it does he plans to tear it apart and beef it up himself.
ECM Tweaks & On-the-Fly Tune Changes
Motor Ops was also responsible for extracting every ounce of power from the stock injectors and CP3, and after Jake’s Ram cleared the aforementioned 573rwhp and 1,140 lb-ft on the dyno there was little doubt he’d chosen one of the top names in the Cummins tuning game. Five custom tuning calibrations, created via EFI Live, are available on the fly thanks to this CSP5 switch mounted on the dash, to the left of the steering column.
Tired of half-worn mud terrains howling down the highway but not yet willing to run an all-terrain, Jake found a happy medium with the Nitto Ridge Grapplers. Like so many others that’ve made the switch to Nitto’s hybrid terrain tires, he reports that the Ridge Grapplers provide a quiet ride, more-than-adequate traction when off the beaten path, even wear and are quick to eject rocks. The Ridge Grapplers aboard his Ram measure 33x12.50R22LT.
Setting the truck off, cosmetically, while simultaneously keeping pace with today’s big-wheel craze is a set of American Force B02 Trax SS wheels. The polished, one-piece eight-lug 22x12-inch wheels feature a -40 offset and 4.93-inch backspacing. With a 3,640-pound load rating, they’re also built to allow eight-lug trucks to carry on with their usual, hefty workloads.
Controlling Axle Wrap
With 1,140 lb-ft of torque to grapple with, it doesn’t take long for the rear AAM 1150 to wrap and the leaf springs to twist into an S shape. To get the rear axle and suspension under control, Jake installed a set of pre-load adjustable, single tube traction bars from Flight Fabrications. Both the frame and axle mounts are made from ¼-inch thick, laser-cut steel, the traction bars themselves are made of 1.75-inch diameter DOM tubing and greasable forged-steel Johnny Joint rod ends from Currie Enterprises are employed. The rear U-bolts have also been upgraded from the ½-inch factory pieces to 5/8-inch diameter units.
Looking to add a fixed geometry turbo to your 6.7L Cummins? Start your search here!