What started out as an innocent purchase of a 2017 Dodge Challenger T/A quickly became an evil obsession for more power. While the stock Challenger was fun, the 370 crank-horsepower was just not enough. A trip to the dyno showed 330 horsepower to the wheels and that quickly sent us down the road of finding more, reliable power. The goal was to reach 500 rear-wheel horsepower, a sizable gain in ponies.
The dyno is one thing but it really is just a number, what really matters is how the Challenger performs. To find out what the car was capable of, we visited our local drag strip. After four runs down the quarter-mile, our best time was a 13.80, not bad, but how would the Challenger do autocrossing? It’s impossible to compare autocross times as at each event the course changes. Instead of run times, we used our finish in overall Professional Autocross, or PAX. PAX is how the SCCA scores different cars together from a variety of classes by using a set multiplier. This system was used instead of class finishing order as the Challenger will be bumped to a new class after all of the modifications have been completed. Out of 52 competitors, we finished 36th, which is less than ideal.
We decided that based on our application that if we wanted to reach our horsepower goal forced induction was the way to go. A centrifugal supercharger made the most sense based on how it produces power. These superchargers provide instant horsepower with no lag. So, it makes the power curve more linear and that will benefit us on the autocross course and drag strip. It will also make driving the car on the street a lot of fun.
A V-3 Si centrifugal supercharger from Vortech made the most sense for our goals. Vortech’s Dodge Challenger Tuner Kit was the best fit for our build since it could provide us with the horsepower and reliability we were looking for. The Tuner Kit does not include fuel injectors, ECU programming, or a fuel pump booster. This allows customers to fine-tune the set-up based on their application and goals.
The V-3 Si supercharger is a stout unit that can support up to 775 horsepower thanks to the 1,150 CFM of air it can move. Vortech states the V-3 Si can spin up to 52,000 RPM and produce up to 22 PSI of boost. When you mix all these statistics together, you get a supercharger that’s perfect for a street-driven vehicle.
With the supercharger kit ordered, it was time to go shopping for the rest of the parts needed for the build. In order to help the car breathe, we picked up Kooks long tube headers and a Hooker Blackheart header-back 3.0-inch exhaust. To feed our HEMI plenty of fuel, a set of Fuel Injector Clinic 775cc injectors were acquired, along with a JMS FuelMax fuel pump voltage booster. The FuelMax system provides the highest output of voltage and amperage, it is also adjustable, allowing for fine-tuning ramp-in and ramp-out to eliminate fuel pressure spikes.
Since the entire front of the car would be removed to install the supercharger kit, the decision was made to add a Mishimoto transmission and oil cooler. The Challenger, completely stock, saw elevated temperatures when driven aggressively, so with more horsepower coming it made sense to upgrade the car’s cooling capabilities. For good measure, we also grabbed an American Brothers air/oil separator. The final piece of the puzzle was to determine how to tune the ECU. The market is full of options, for us the HP Tuners MPVI2+ and VCM Suite suited our needs since the MPVI2+ allows for endless adjustment and fine-tuning. HP Tuners also has exceptional customer support which as you will read further in this article was very important.
With all parts in hand, it was time to get to work. We took the Dodge to Sutton Auto Tech in Idaho Falls, Idaho. Mike Sutton and his family have been building and racing cars for decades. Everything from MGs to purpose-built race cars, the work they do is exceptional. A lot of work goes into installing one of these kits, but thankfully it’s a fairly straightforward process.
The kit does require the removal of numerous components during the installation process. When it was completed though, it all fit perfectly. Visually, it almost looks like it is a factory unit. While the engine bay was torn apart the headers, fuel injectors, oil separator, and Mishimoto coolers were all installed. The JMS Fuel Booster was mounted in the trunk under the spare tire cover. Placing a fuel booster there allows for very quick and easy access to adjust as needed. With the installation complete it was time for tuning, this is where things got tricky.
When deciding to buy and then build a Mopar, we never thought finding a capable tuner would be such an ordeal. The car was supposed to be a three-week project, cue the Gilligan’s Island theme song. That three-week project plan turned into a 13-week nightmare, minus Mary Ann and Ginger, unfortunately. The first tuner had the car for weeks, and when it was finally “done” the car ran horribly. It sputtered, stumbled, and fell on its face other than when idling or with the throttle mashed to the floor, it was simply not drivable.
Dejected, a number of phone calls were made to HP Tuners and racers around the country that have supercharged 5.7 HEMIs. After countless conversations, we were put in contact with Mario at MI Tuning in Las Vegas, Nevada. Even though he was 700 miles away, Mario worked with Sutton Auto Tech to take a look at the tune. Thanks to how well the HP Tuners software works, he was quickly able to identify a number of issues that the original tuner had overlooked. Before he could get to work on the new tune, we needed a 3-bar MAP sensor and an AEM wideband oxygen sensor. Once those were installed, Mario did his magic fine-tuning to the car. After 12 runs and 12 tweaks later, the car finally ran like the beast it was.
On the dyno, horsepower jumped to 519, a gain of 57 percent over the stock numbers. When we went into this, the idea of getting 50 percent more horsepower to the wheels seemed like a pipe dream, a gain of 57 percent means the only thing we will be smoking is tires.
With the car tuned, it was time to head to the drag strip. It should be noted that our original visit to the drag strip was on a set of OEM tires, when we went back to the track the car was rolling on a set of Nitto NT555 G2 tires that were wider by just over two inches. The increased power was, of course, immediately evident. The car went from feeling like a tame street car that was easy to drive and pretty boring on a track, to a car that requires the driver to focus and take control.
After three runs our new best time was an 11.09, that’s over 2.5 seconds faster than the stock run. Impressed, it was time to go autocrossing to see what improvements our modifications created. For our return to the SCCA autocross course, it should be noted that in addition to the added power, we also gained 150 pounds since we had a passenger riding shotgun during each run. The Challenger improved to a 21st place finish, and honestly, it would have been much higher, but the Challenger is so much fun to drive that overdriving quickly became the theme of the day as we carried four-wheel drifts through the long corners grinning ear to ear.
All in, the build cost us just over $11,000, we gained 189 horsepower and lowered our quarter-mile times by well over two seconds. Now, the Challenger isn’t an ideal autocross car, but it was quicker and so much more fun to drive after the parts were installed. Around town, diving the car daily, the retro looks of the Challenger are now equaled to the driving feeling of a classic Mopar. The car looks, feels, and sounds like a classic muscle car so it was money well spent it.
Text and photos provided by Mike DeFord