Written by Jason Reiss
Photography by the Author and courtesy of Vortech Superchargers
There is no secret in the automotive community regarding the performance capabilities of the centrifugal superchargers manufactured by Vortech Superchargers. The company has been whipping up gear-driven centrifugal supercharger units for the better part of three decades.
Although the company made its name with Ford’s Fox-body Mustang, founder Jim Middlebrook and his team took their collective talents and applied them across the landscape of modern performance cars to provide reliable and powerful performance increases to many late-model vehicles. The subject of today’s discussion is the 6.4-liter Hemi engine under the hood of the 2018 Dodge Challenger, boosted with authority by one of Vortech’s V-3 Si-Trim superchargers.
There are two ways you can buy a Vortech supercharger kit for the Challenger —complete, or as one of Vortech’s well-known Tuner-style kits. The latter systems omit the ECM calibration and fuel components so that the builder/tuner can select the best setup to suit the needs of a particular build.
Here we’re primarily discussing the complete kit, although we have some dyno results from a build that utilized one of the tuner kits calibrated by a well-known tuner on the East Coast.
The V-3 Si-Trim supercharger is Vortech’s most popular unit, and for a good reason: it’s capable of achieving 775 horsepower and 26 psi boost pressure while remaining well-mannered under the hood of a street car. With its self-contained internal lubrication system and helical-cut gears, the Si-Trim reaches 78-percent peak efficiency in Vortech’s test laboratory, which utilizes the SAE’s J1723 testing standards.
There are strict requirements for the laboratory equipment, testing accuracy, conditions, and presentation of the results. We could go on and describe some of the engineer-speak that’s involved in executing the proper testing, but let’s rest assured that Vortech is testing its superchargers using these standards to ensure they meet performance goals.
Follow along with the captions for some of the installation highlights and read on for the details of why this system is groundbreaking.
The 6.4-liter SRT Hemi engine found in the engine bay of several of Dodge’s performance cars is an excellent platform for performance; its 392 cubic-inch displacement is on the larger side for a production V8, with 485 horsepower and 475 lb-ft of torque available for motivation in factory trim. With a 4.090-inch bore, 3.720-inch stroke, and 10.9:1 compression, the 6.4-liter Hemi takes full advantage of the most important feature of these engines: the deep-breathing, twin-plug cylinder heads that feature Dodge’s signature hemispherical combustion chambers.
“The piston design does not allow for even the slightest error, which is why we took two-and-a-half years to perfect our production tune. It literally cannot be stressed strongly enough — the tune is everything on these cars,” Vortech’s Brian Ellis explained.
Further discussion with Ellis reveals that the Hemi’s cast pistons — which feature a ring land that’s located right at the top of the piston — won’t tolerate boost if the calibration is not spot-on.
“If there’s any detonation at all, the whole top of the piston comes off,” says Ellis.
Calibration Is Key
Back in 2009, Dodge started locking the PCM with encryption on some of their models, which meant that a new tune file couldn’t be loaded consistently. The difficulty of working with this configuration pushed Vortech to step away from building kits for the Hemi platforms for several years because the PCM just couldn’t be flashed properly for a production-level supercharger kit format.
Not coincidentally, there is one crucial caveat to the Hemi’s operation: when it’s equipped with a supercharger and power is boosted significantly, you must pay careful attention to the engine tune. That last part hasn’t always been a workable process, though. Reliability and durability were the chief concerns when it came to the development of the system; Vortech has built its reputation for street-style superchargers upon those tenets and the 6.4 Hemi kit is no different. It is no secret that the Gen III Hemi in boosted form is no picnic to calibrate properly.
So, to maximize the performance of the Hemi platform when equipped with the V-3 Si-Trim supercharger, Vortech’s engineers worked countless hours to develop its out of the box, 50-state-legal tune, which produces a whopping 730 horsepower and 645 lb-ft of torque at the crankshaft, using 7 pounds of boost pressure.
Although at first glance the Si-Trim blower might seem small for this particular engine combination, he says it’s perfectly matched to produce the most reliable and safe maximum horsepower suited for the factory stock engine. For those guys who eventually decide it’s time for a built engine with forged pistons and the like, the charge cooler will support 1,000 horsepower, while the bracketry will hold most of Vortech’s head units, up to and including the YSi-B, which is capable of far more performance than the Si-Trim blower included with the kit.
According to Ellis, there’s more to consider.
“In addition to having the PCM unlocked, what’s significant about our kit is that it has the capability of tuning properly for the boost. The current software out there, any of the main names that you know, they have the capability of tuning just fine for naturally aspirated vehicles, but none of them even have the parameters available to them to create a safe, ‘out-of-the-box’ tune file for boost. Virtually every other ‘complete’ forced-induction kit out there is band-aiding the tune. They turn the knock sensors completely off or dumb them down to the point that they don’t see any knock, and with the ring land right at the top of the piston, there is no limp mode. Your first notification of a problem is a blown engine, which is unacceptable,” he emphasized.
The system is calibrated to make 7 psi of boost pressure. With forged pistons, one can run more, but in factory configuration with 91-octane fuel (the best you can get in California), that’s about all you can get safely. When the Vortech team performed its research, 7 psi was determined as the safe limit on a stock engine with the supplied tune. With good, 93-octane fuel, maybe 8 psi is the absolute limit, according to Ellis.
Since Vortech’s calibration team was able to dig into the PCM software and unlock several more calibration tables, they can tune nearly on the same level as the OEM, with all of the factory safeguards in place to ensure the engine remains tuned safely. With help from Dan Millen and his team from Livernois Motorsports, Vortech was able to provide a complete tuning solution that is simple for the end user.
“We didn’t just accept what was available and go with that. We made it so that it was safe to our specifications, and until it was capable of being done, we just didn’t do it. It took a long time and a lot of painstaking research and development, and we’re super proud of the product. They work, they’re safe, and it’s up to the standard that people would expect from Vortech,” says Ellis.
High Horse Performance