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For nearly two decades, the gearheads at DiabloSport have been hard at work finding ways to maximize the performance of late model Dodge, Jeep, and Ram vehicles. That’s put more a lot more power and control in the hands of wide range of enthusiasts over the years, but perhaps the biggest gains have been bestowed on those who’ve put a 6.2-liter supercharged Hemi in their garage.
First introduced for the 2015 model year under the hoods of top-spec Dodge Challenger and Charger SRT models, the 707 horsepower Hellcat engine was the most powerful V8 ever put into production at the time. It also went on to spawn even more powerful variants like the 797hp Hellcat Redeye, the 807 horsepower Hellcat Super Stock and, of course, the 840 horsepower Demon, the latter of which remains the burliest production power plant ever installed in a road-going factory muscle car.
In the years since the Hellcat’s debut, FCA (now known as Stellantis) also saw fit to bring this boosted pushrod fury to other vehicles in the company’s portfolio, spawning models like the 707hp Jeep Grand Cherokee Trackhawk, the 702hp Ram 1500 TRX, and the limited-production, 710hp Dodge Durango SRT Hellcat. But while each of these machines put unprecedented levels of power in the hands of the Mopar faithful, hot rodding tradition has long dictated that it’s only a matter of time before gearheads are ready for more. And knows DiabloSport how to deliver it.
“We had support for the Challenger and Charger Hellcats within a few months of those cars landing in showrooms back in 2015,” says Powerteq and DiabloSport calibrations manager Brian P. McMahan. “What we discovered early on was that the 6.2-liter is a very, very durable engine – we’ve had a tried and true tune for it since the beginning that makes a solid 30 horsepower, and that thing runs like a Swiss watch. There’s even more to be had, but erring on the side of caution made sense ensure that we would deliver a solid product that does exactly what it says it does in a wide variety of different conditions and situations.”
McMahan points out that it would be easy to tout even bigger gains under very specific circumstances, but that’s not how DiabloSport rolls. “Conditions change all the time, so we utilize pretty much all of the different parameters that the factory uses to compensate for those changes. These cars will run everywhere that they were originally designed to run with that additional horsepower.”
While this tuning is certainly one of the first steps in building a competitive machine for the drag strip or the road course, it’s not just for hardcore racers, and that point is exemplified by DiabloSport’s recently-added support for the Jeep Grand Cherokee Trackhawk. “There’s something for everyone here – it’s all-around tuning,” he tells us. “People are using these SUVs for everything, whether that’s dropping the kids off at school or laying down fast ETs at the track. At the end of the day it’s still an SUV, and we still do different things for the different driving modes offered in the vehicle. So we try to keep the ‘normal’ modes generalized so the vehicle is still easy to drive on a day-to-day basis, then ramp things up further with the Sport and Track modes.”
McMahan explains that while Challenger and Charger Hellcats are very closely related in terms of their drivetrains and associated components, the Jeep was a slightly different beast. “That was our first time working with the HP95 ZF eight-speed automatic transmission, which is full-time all-wheel drive, and it uses a totally different controller, so there was a lot of work to be done there to develop that to level where the Hellcats are. Overall they’re pretty similar, though – it just takes time to reverse-engineer some of that stuff. But sweating the details really helped us understand the evolution of the code and what the factory calibrations are doing. It gives us a better perspective on the engineering mindset that they’re using.”
Putting more power to the ground is certainly one of the most compelling benefits of tuning a Hellcat Hemi, but DiabloSport’s tuners also allow you to do quite a bit more than that. For instance, did you know that when you disable traction control, it’s not *really* off?
“Even with a long-press of the button, there’s still some things that are still active when you’re using the factory software,” McMahan says. “For instance, the ABS system pays attention to the lateral acceleration of the car, and it will try to keep the chassis in line by pulsing the brakes at various corners of the vehicle. But with these tunes, we’re basically telling it to truly disable everything that might dial the power back. And that’s something you might need while you’re running the car on the dyno or at the drag strip. Or just because you want to have some fun with it. When you disable traction control this way, there’s no acceleration intervention by the system whatsoever – it’s going to give you full power the entire time.”
DiabloSport tuners also allow you to manually set temperature targets for the engine cooling fans, which can be useful if you’ve changed thermostats, as well as adjust parameters for the idle speed, rev limit, the top speed governor, and the tire size, the latter of which compensates for non-factory tire sizes to provide accurate gauge readouts. These tuners also allow you to adjust throttle sensitivity to preference and, for more adventurous users, there are wide-open timing and fueling parameters on that can be tweaked as well.
These tunes also dial up the performance of the eight-speed automatic transmission, too, providing quicker and firmer shifts. “It’s steadily more aggressive through the modes,” says McMahan. “So that means enhanced shift times and better shift feel, and the more aggressive mode you choose, the more aggressive it will be. We focus on making sure that the shifts are clean, quick, and sharp, but not so harsh that they’ll upset the chassis.”
These tuners also improve the Hellcat engine’s transition into boost. “These engines aren’t on boost all the time,” McMahan points out. “But instead of using a vacuum-actuated bypass valve, which are common in non-factory blower setups, there’s an electronic bypass valve. The software is designed to bleed off boost when you aren’t asking for a ton of power, and it can also reduce or completely take away boost if the system senses trouble. So what we changed here is how the throttle request is delivered relative to the RPM range. The factory puts limitations on this, and we’ve adjusted it to provide more mid-range and low-range throttle without running the risk of harming anything. And that provides a lot more super-cool blower noises as well as more tip-in torque, which delivers a much different driving experience.”
Diablosport offers three methods for customers to get a tune-friendly PCM: they can purchase a spare PCM that's ready to go; they can send in their vehicle's PCM for unlocking; or they can swap their PCM for an unlocked PCM.
DiabloSport’s inTune i3 and Trinity T2 handheld tuning devices support all of the factory supercharged Hemis up to the 2021 model year, including the Durango SRT Hellcat and Ram 1500 TRX. The standard versions of these hand-helds are 50-state emissions legal and can support multiple licenses, which allows you to tune several different vehicles using the same device.
You’ll also need to get the vehicle’s PCM to play nice with the tuning device in order to get a tune installed, and DiabloSport offers three different ways of doing that. “You can get a spare PCM as part of one of the kits that we offer – you send us your information and we send you a pre-programmed PCM that’s ready to go, along with the tuning device,” McMahan says. “You also have the option of sending us your factory PCM, which we would modify and then send back. And we also do a swap option – we send you a modified PCM with a call tag for your stock PCM, which you’d send to us once you’ve installed the modified one in order to minimize down time.”
Both the inTune and Trinity tuners come pre-loaded with everything you need to hit the ground running, and older devices can be updated free of charge with DiabloSport’s recently-added calibrations for the latest vehicles via the software update agent. “Keeping these devices updated is a good idea anyway,” McMahan adds. “We’re always adding cool new stuff, so you never know what might pop up.”