Diesel of the Week is presented by
The phrase “more than meets the eye” is something that comes to the mind often when considering diesel motorsports — to the average person, a 5,000 lb. truck looks much more akin to a utility vehicle than a racing machine. Even trucks with aggressive wraps and decals get skeptical looks when they power down the track at breakneck speeds. But even more unassuming are the trucks that don’t look like performance vehicles at all.
“Sleepers” are more common in the car community. Essentially, they are cars that are made to appear completely stock or modest looking on the exterior while housing performance upgrades under the hood. Every so often we find a diesel truck with an impressive sleeper build, and today’s Diesel of the Week is no exception.
Mark Rojee has been working on diesels for around seven years at Mahky’s Performance and Tuning. The small family-owned diesel performance and repair shop is nearly 3,000 sq.-ft., has a four-bay garage, and employs six workers, five of whom are mechanics. His father has owned the shop for 34 years, and Rojee first got into diesel work seven years ago. Before that he spent his childhood racing dirt bikes — Like most racers, he was essentially born into the performance world.
A few years back, he bought his first diesel truck: a 2018 Ram 2500. The 4th-gen truck looks humble on the outside, with a factory white paint job and nothing to indicate anything more than a stock truck. But under the hood, Rojee is hiding a 1,500 HP monster that converts his modest workhorse into a racing machine.
The 6.7L Cummins is an Enforcer series engine, built by none other than the guys over at D&J Precision Machine. The engine platform has won multiple Ultimate Callout Challenge competitions. The engine is based on a cast-iron block that’s been sleeved, fire-ringed, fitted with a deck plate, and equipped with an X-beam rods, cast-aluminum pistons, and a HD girdle. A billet flat tappet cam, Hamilton billet lifters, and 7/16-inch diameter pushrods make up the valvetrain.
The cylinder head is a fire-ringed Stage 3 with oversize valve that flows much better than the factory unit thanks to 115-lb valve springs and titanium valve spring retainers. 9/16-inch Arp head studs torqued to 175 ft./lbs. fasten the unit to the block.
For the forced air, Rojee opted for a S400 compound setup that supplies 110-psi of boost to the factory intercooler, and then to the engine. The atmosphere charger sports a Forced Induction 91mm compressor, a 104mm turbine, and a T6 inlet. The smaller unit has a 72mm billet compressor, an 87mm turbine, and a 1.00 A/R exhaust housing. He uses a single nitrous line running to a single .136 jet on a wide-open throttle switch.
An S&S Diesel Motorsport 14mm CP3 was installed to support the set of 250% over injectors, and the common-rail system is controlled via EFI Live tuning software. Underneath, the 48re transmission was built in-house using mostly Sonnax and Goerend parts.
This summer, Rojee hit his personal best time of 6.42-seconds in the eighth mile. For a 7,645 lb. truck, it sure can move!
Diesel of the Week is sponsored by AMSOIL. If you have an engine you’d like to highlight in this series, please email Engine Builder Editor Greg Jones at [email protected].
