Anatomy of a 5.90 Index Diesel Drag Truck
Believe it or not, some of the best side-by-side action you’ll find in diesel drag racing is happening in its newest class: 5.90 Index. Added to the Outlaw Diesel Super Series’ menu for 2018, the goal is for drivers to run an elapsed time (E.T.) as close to 5.9 seconds in the eighth-mile as possible without going any faster. Officially coined the Outlaw 5.90 Class (and sponsored by Firepunk Diesel), it’s a category strategically designed to bridge the gap between the Pro Street and 6.70 Index fields. In creating 5.90 Index, a host of highly talented drivers immediately began piecing together trucks to compete with.
Some 16 racers were signed up in the ODSS 5.90 field for 2019, all of which were trying to get their 1,300-plus horsepower, full-size diesels down the track as smoothly as possible. Figuring out the perfect launch strategy, finding the chassis’s happy place, knowing when to let out, when to brake and which ECM calibration gets you as close to that golden E.T. as possible is all part of the learning curve. Although the primary means of propulsion for 5.90 Index is Cummins power, some trucks sport multiple turbos while others prefer big singles and nitrous. Some competitors even choose mechanical injection as opposed to the electronically controlled common-rail systems that’ve begun to dominate diesel drag racing.
For a closer look at what exactly goes into a 5.90 Index truck, along with some of the class’s heaviest hitters, keep reading.
5.90x Vs. 5.90x
Competing in 5.90 Index means a 5,000-pound truck will need to bring more than 1,050 hp to the table (and that’s at the wheels). However, just as is the case in other index classes many trucks are packing enough power to obliterate their dial-in, but are de-tuned enough to click off 5.90s on a consistent basis. Racers race on a 4/10 pro tree and need an NHRA Class 6 ET (type A or B, depending on wheelbase) license to compete. Starting line aids such as delay boxes, trans brakes, four-wheel line locks and throttle controls are permitted as well.
Mindy Jackson
Fresh off a Pro Street title in 2018, the “Old Hustle, New Flow” Cummins-powered ’94 Ford Lightning returned to the ODSS circuit as a 5.90 truck in 2019—and with Dustin Jackson’s wife, Mindy Jackson, behind the wheel. She wasted no time taking advantage of the truck’s proven chassis, placing fourth at the season opener and then taking a second at the following event. By round 4 she had things dialed in and won three out of the remaining four races on the season schedule. Without a doubt, Mindy was the most feared 5.90 racer this year, and her class title is well-deserved.
I.I. Cummins, Stainless Diesel Windmill
The Cummins power plant under the hood of Mindy Jackson’s Lightning is no longer equipped with the triple-turbo arrangement it used to be, but the single charger setup provides more simplicity and reduced stress on the engine, not to mention the weight savings. A 5-blade charger from Stainless Diesel more than gets the job done, and the waterless Shredder series Cummins from Industrial Injection held strong all season.
Paul Cato
One truck that competes in a substantially de-tuned state is Paul Cato’s ‘98 Dodge. His second-gen has been as quick as 5.41 at 134 mph in the eighth-mile (more than 1,500 hp at the wheels), but to keep from breaking out on race day he pulls a few hundred ponies out of the equation electronically. A seasoned, skilled drag racer, Paul obtained wins at the ODSS season opener in North Carolina (Rudy’s) and round 6 in Florida (Hardway Sunshine Showdown) and ended up second in points for 2019.
Big Single, Full Bottle
Paul Cato’s second-gen is powered by a common-rail Cummins with a single 85mm S400 from Stainless Diesel coined the Godfather. His second turbo checks in in gas form (i.e. nitrous oxide). However, even more important than his engine setup and its power adders is the fact that, as the owner of Maverick Diesel, Paul is able to perform his own tuning. This is huge for tweaking the ECM calibration until things are just right.
Rick Fox
One of the more interesting things in 5.90 is that, due to it being an index class, no weight limitations exist. Rick Fox took the approach of going as light as possible with his build (less weight means less horsepower is required to run that 5.90 number, which correlates to less stress on the engine). While the appearance of the original 2000 model year Dodge remains, a tube chassis was built using 1-5/8-inch chromoly tubing. The truck is also front and back-halved, along with being four-linked front and rear.
D&J Common-Rail with Compounds
For a proper foundation, a Cummins put together by D&J Precision Machine sits at the front of the truck’s tube chassis. It’s force-fed plenty of air thanks to a 72mm/85mm compound turbo arrangement. The atmosphere charger is a Stainless Diesel S485 (again the Godfather), while the high-pressure unit is an S472 bolted to a polished Stainless Diesel exhaust manifold. At the conclusion of the 2019 race season, Rick yanked the engine for a new racing venture and sold the truck as a roller.
Mandatory Safety Equipment
At this level of competition, a cage isn’t a suggestion, it’s a requirement. The funny car roll cage in Rick Fox’s Dodge is certified for 8.50’s in the quarter-mile, which of course means a full SFI rated fire suit is required to sit inside it and pilot the truck. While some 5.90-intended rigs have been converted from roll bar trucks into roll cage trucks, it definitely pays to start with a fresh cage build rather than modify or add to an existing bar.
Brett Marcum
Brett Marcum entered the 5.90 Index fray with a bang in 2019, grabbing the win in round 2 (his first race) and backing it up with a W at the very next event. Having competed in this year’s Ultimate Callout Challenge, where he ran a 6.22 in the eighth-mile and finished 10th Place overall, Brett’s third-gen Dodge went 5.96 right off the trailer when he joined the ranks of 5.90. His standard cab Ram is powered by a common-rail Cummins built by Freedom Racing Engines and uses a Garrett/BorgWarner compound turbo arrangement to build boost.
Austin Doidge
After seeing success in the 6.70 Index class, Austin Doidge reworked his second-gen Dodge and bumped up to the 5.90 field in 2018. And although most trucks in 5.90 make use of common-rail mills, Austin has stuck it out with his mechanically injected 12-valve—a 6.4L Cummins with a nasty, 13mm P7100 hanging off the side of it. The healthy P-pump routes fuel to truck-pull-ready 5x0.025 injectors from Infinite Performance, and breathes through a pair of Reaper turbochargers, also from Infinite Performance. Austin finished sixth in points in 2019.
Select photography provided by Amy Gilbert of Stainless Diesel
Looking for something faster? Check out the Anatomy of a Pro Street Diesel Drag Truck piece we put together here.
