GS Motorsports' Hemi Paxton Blower - Forcing The Issue

Normally aspirated engine performance choices, all of which rely upon atmospheric pressure providing the airflow through the engine, are well-known to Mopar fans. Typical mods include high-flow heads, camshafts with larger specs, high-compression pistons, and a revised induction. these mods have a place and definitely get the job done, however, with new production vehicles already fitted with the hot Hemi engines, it takes a fanatic to pop the hood and start replacing core engine parts. Forced induction opens another chapter in engine performance--the force coming in the form of supercharger packages. What's the upside? Think of the potential to dramatically ramp-up engine output without having to break the seal on that brand-new mill under the hood. With the addition of boost, the same basic engine package can deliver radically increased output without compromising drivability or utility, all the while keeping the engine internals intact.

What exactly does a supercharger do? In a normally aspirated engine, a descending piston on the intake stroke is chased by air propelled by the pressure differential of the outside air and that inside the cylinder. In a supercharged powerplant, air is forced into the cylinder under pressure from the supercharger, resulting in a cylinder packed with more air. More air will support the burning of more fuel, and, taken together, the result is more power. What's the potential for improvement? It depends upon the level of boost, or the pressure delivered by the supercharger system. Atmospheric pressure is about 14.7 psi. Running a supercharger with 14.7 psi of boost will double the force filling the cylinder, potentially doubling the engine's output in a theoretical ideal situation. More boost can create even more power, although there is quite a difference between theoretical potential and practical application in the real world. From a practical standpoint, a more restrained application of boost can reliably produce tremendous gains, while remaining nearly transparent in normal street driving.

Various centrifugal supercharger kits have been available for specific engine packages for years, and the concept is well proven. GSMotorsports has brought the centrifugal blower to the new Chrysler Hemi by developing packages to install and integrate a Paxton supercharger unit to the production engine package. These supercharger systems are specifically designed and engineered for Chrysler Hemi applications.

What actually distinguishes a centrifugal supercharger? All superchargers utilize some form of compressor to supply the engine with air, with the two most popular types being positive displacement and centrifugal. Both of these utilize an accessory beltdrive from the crankshaft to drive the supercharger unit; the difference is in the way they actually compress the air. The positive displacement type shares its principles with the wild Roots-type blower seen on dragsters. A positive displacement supercharger actually works as a pump, capturing a fixed quantity of air with each revolution of its internal rotors, and forcing that fixed quantity into the engine. A centrifugal blower is more analogous to a fan, only spinning at an extreme speed, creating pressure in its specially shaped housing as air is blown in under high velocity. The physics of a centrifugal blower creates boost in a smooth, progressive manner, building boost pressure as the engine's rpm increase.

Centrifugal blowers have proven to be very successful at increasing power, with these compact units mounting in a forward accessory position on the engine, directing their bounty of pressurized air into the engine via a system of ducting. The actual compressor unit is more comparable to a turbocharger in function than the positive displacement supercharger, but rather than utilizing hot exhaust gasses to provide the drive, it relies on a beltdrive system. To obtain the high impeller speeds required for efficient boost production, the drive speed is stepped up internally in the supercharger unit, typically via a high-ratio gearset. Centrifugal blowers can be very flexible in terms of boost output capacity, with a given unit capable of a relatively wide range of practical boost output, dependant upon the drive ratio.

It's also a fact of physics that the act of compressing air creates heat, which is contrary to power production. To increase the efficiency of the blower, a means of cooling the induction charge pays dividends big-time in charge density and detonation tolerance. Charged cooling systems come in a variety of arrangements, but all use heat exchangers to discharge induction heat either directly to the ambient air or by a liquid-to-air system, which in turn rejects heat to the air via a secondary heat exchanger. The GSMotorsports systems favors the latter, for the more direct induction tract and the more compact heat exchanger. Heat transfer is accomplished by a liquid-to-air heat exchanger between the blower discharge and the throttle body's air intake. Cooling is provided by a closed water circuit, which dissipates heat via a second heat exchanger mounted at the front of the vehicle. This system has been highly refined as a direct and comprehensive bolt-on installation into Mopar late-model Hemi-powered vehicles.

So what's the horsepower bottom line? The basic GSMotorsports' Stage 1 5.7 Hemi kit is claimed to provide a real-world gain of 135 hp and 130 lb-ft of torque to the rear wheels. While that may seem like more power than the typical street machine could harness, GSMotorsports has components for custom installations or race applications with seemingly even more power at hand. If your goal is to seriously step up the power of your late-model Mopar, the GSMotorsports supercharger kit can supercharge your machine to supercar status with a single bolt-on power adder.