Listen up, turbo boys, the blower cars are coming. In just a few short months, the heads-up drag racing scene has witnessed a multitude of new supercharged doorslammers breaking past the 6-second barrier. Conventional wisdom says that it takes a big-block packing a pair of thumpin’ turbochargers to run 6s at the dragstrip, but companies like Vortech are disproving that theory in a big way. Thanks to Vortech’s new V-20 line of race superchargers, racers can now bolt up a supercharger capable of supporting over 2,800 hp and 45 psi of boost. And unlike a turbo combo, there are no wastegates, finicky boost controllers, or custom header fabrication to deal with. To get a better grasp on how such phenomenal performance is capable out of a single supercharger unit, we recently sat Vortech CEO Jim Middlebrook down for a tell-all interview. Here’s what we learned.
V-20 race supercharger
As the adage goes, racing improves the breed. Since Vortech has long been known as an industry leader in street supercharger systems, the desire to push the envelope of supercharger technology inspired the company to develop an all-new line of V-20 race superchargers. “Drag racing is absolutely brutal on the entire supercharger, especially the drive system. So developing the V-20 was a natural progression to prove our designs and technology in the most demanding of environments,” Vortech CEO Jim Middlebrook explains. “At the extreme, the supercharger flows in excess of 300 pounds of air per minute, a boost pressure of 50 psi, and at these levels a supercharger unit carries in excess of 500 hp of load just to operate them. Consequently, the mechanical design of the transmission needed to carry these sorts of speeds and power levels must be very robust, and the modeling of the system can be quite difficult. Also, the ability to understand and resolve design issues on paper presents enormous challenges. As such, we have to rely on considerable controlled testing to aid the development process. It is quite time consuming and costly.”
Vortech’s new V-20 line of superchargers encompasses a broad range of models to suit the needs of both sportsman and professional drag racers. Despite being the smallest compressor in the V-20 line, the V-24 X105B boasts 2,900 cfm of airflow and a 75 percent peak efficiency rating. Those airflow figures are good for up to 35 psi of boost and 1,700 hp. Moving one notch up the ladder, the V-21 XB110 supercharger flows 3,100 cfm at 73 percent efficiency, and is good for up to 35 psi and 1,900 hp. Designed for classes such as NMCA Extreme Street and Drag Radial, the V-24 Xi head unit offers 2,300 cfm of flow at 79 percent peak efficiency. It will support up to 1,600 hp and 29 psi of boost. The big dog in the lineup is the V-28 123 supercharger, which flows over 4,000 cfm at 83 percent peak efficiency. Designed for 6-second Outlaw-style drag cars, it supports over 2,800 hp and 45 psi of boost.
As a clean-sheet design, V-20 superchargers utilize several unique features that distinguish them from both Vortech’s street supercharger systems and other centrifugal units. “The gear cover attaches to the main housing like the main caps on an engine block. The input shaft and gear are also inserted into the housing, and the cap attaches with four bolts,” Jim explains. “Likewise, the impeller shaft is supported by two pairs of super high quality ABEC 9 bearings. The bearings and shaft are secured into a special alloy iron tube with a fixed preload, resulting in a bulletproof design. Furthermore, Vortech’s super robust impeller support system feeds dynamic forces back into the bearing system, thus improving stability. All of these patented features provide the most durable platform available onto which we can mount several different compressor stages.”
When choosing a supercharger unit, the projected horsepower output of an engine is just one of many factors that must be taken into consideration. Horsepower goals are certainly targeted when selecting a racing supercharger compressor stage, but there is much more to the selection process than horsepower alone. Information on the engine’s performance characteristics regarding displacement, airflow, rpm range and intended usage all come into play when determining the supercharger compressor’s pressure and flow requirements. “These requirements are plotted onto various compressor maps in search of the best match. Compressor maps are made from data that are gathered in our SAE J1723 test cell,” says Jim. “It is easy to have a very efficient compressor that should operate at 78 percent that only performs at 55 percent if not properly matched. So clearly, all of these parameters play a very important role in determining overall performance. As a starting rule of thumb, a given power objective dictates an approximate overall airflow requirement, and a general sizing requirement for a compressor stage may then be assessed. From there, engine displacement, operating speed, and volumetric efficiency will indicate what sort of boost level is needed to attain the target airflow; and pressure and flow define an operating point on a compressor map. We use a variety of commercial and in-house codes and tools to make these types of determinations. Nevertheless, the fundamentals remain, and the importance of finding the specific operating conditions on a compressor performance map is essential to optimize any given combination.”
“A properly maintained supercharger will run and run in very difficult environments. However, if they are installed improperly, spun at rates way above our recommendations, or connected to drive units that are not harmonically balanced, the results can be devastating.” – Jim Middlebrook
Considering the substantial loads placed on the impeller shaft in a race application, Vortech goes to great lengths to ensure durability with its V-20 superchargers. Larger compressor wheels require more engine horsepower to spin, placing additional loads on the impeller shaft. This is compounded as impeller shaft speeds are increased in race applications. “The V-20 supercharger units incorporate features such as matched tandem bearing sets, heavier-duty shaft designs, and assembly strategies that enhance the overall rotor stability of the system. These all play a key role in enhancing the ability of the system to carry the necessary support high-power levels and relatively large impellers, all at speeds approaching 80,000 rpm,” Jim explains.
Diverging diffusion technology
Supercharger impellers may all look similar to the casual observer, but they require a tremendous amount of development work. “Diverging Diffusion Technology is our term for the optimization through testing and tuning of the second most important area of the impeller to the designer. This is the area where the velocity energy that has been imparted to the air by the impeller is converted to pressure energy,” Jim explains. “By incorporating certain diffuser designs, we have been able to improve even further on compressor performance—in particular, boost and overall efficiency—but at the cost of operating range. However, this now introduces the ability to better match and optimize a given compressor design to a high-performance application. It allows precisely tuning the entire system so the engine/supercharger combination is operating at the best possible overall efficiency. This, in turn, maximizes attainable performance while minimizing the parasitic drive load at the same time. It is a way of taking DDT technology one step further.”