Roots/screw-type systems that essentially swap out the original intake manifold) can be installed relatively quickly with little impact on the rest of the vehicle’s components or systems. The quicker the installation, the lower the labor cost at a professional shop.
Installation Impact on the Vehicle
Assuming all turbocharger and supercharger systems employ an intercooler, the Roots/screw-type supercharger systems generally require the fewest compromises and/or fabrication modifications during installation. Because they install in place of the intake manifold, few changes are required at the front of the engine or in the engine compartment. Consequently, they offer the most integrated, factory-looking appearance under the hood. Centrifugal superchargers require a mounting bracket on the front of the engine that can require moderate modification, removal, or relocation of factory components.
With bolt-on turbocharger systems, the installation of the exhaust manifolds, turbochargers, and associated plumbing typically require considerably more fabrication, modification, and relocation of stock parts than supercharger systems. An intercooled turbo system can also take up more real estate under the hood, particularly when using larger turbochargers. That can induce a number of fitment challenges that require additional fabrication to overcome.
Installation Cost
Again, because of the extra equipment associated with them, turbocharger kits are generally more time consuming to install, and therefore, there are more labor costs.
So, while a turbo kit offers greater performance potential, the cost involved with this investment may steer some toward a supercharger. In fact, there are other factors to consider before ordering a system for your car.
For one, the tight confines of the engine compartments in Corvettes, Camaros/Firebirds, and GTOs/Monaros make packaging and installing a turbo kit very difficult. This not only makes the installation a painstaking and difficult procedure but can make future servicing all but impossible without an extensive teardown of the vehicle’s front end.
There is more room in the engine compartments of full-size trucks, SUVs, and TrailBlazer SSs; but stuffing a turbo system can be a challenge in a regular street car.
My opinion is that turbocharging is great for vehicles destined to spend equal time on the street and strip; but for typical, street-driven vehicles, a supercharger system is the easier and more economical method to build power. Many tuners and manufacturers that fall on the turbo side of the argument will undoubtedly disagree; but when it comes to bolt-on, forced-induction kits, superchargers are easier and cheaper to implement with less maintenance.
Understanding Boost (Including PSI Versus Bar)
Whether it is a supercharger or a turbocharger system, the measure of pressurized air fed into the engine is referred to as “boost.” It is the difference between the ambient air pressure and the increased air pressure that the boost-producing device generates at the intake manifold. Boost is the opposite of vacuum, which is what a nonboosted engine makes during normal operation.
When an engine isn’t running, it generates no vacuum or boost (negative pressure), meaning the pressure in the intake manifold is the same as the ambient air pressure: about 14.7 pounds per square inch (psi). At idle and low-throttle conditions, an engine generates vacuum, indicating the pressure in the intake manifold is lower than the ambient pressure.
In a supercharged or a turbocharged engine, boost is created as more throttle is applied and the boost-generating device forces air into the intake manifold at a higher pressure than ambient (positive) pressure. The air pressure at the intake manifold swings from negative to positive; that’s why high-performance boost gauges indicate both vacuum and boost measurements.
Boost is generated when the supercharger or the turbocharger creates air pressure greater than ambient when it is introduced to the engine (at the throttle body). Supercharged engines generate a small amount of boost whenever the engine is running, even at idle. Turbocharged engines require higher RPM to generate boost.
In North America, boost is generally measured in PSI, while bar is more common in other countries. When measuring in psi, the ambient air pressure is regarded as the base, or 0 pounds of boost. The positive pressure builds on that base with 1 pound of boost indicating 1 psi greater than ambient pressure.
With bar measurements, bar is roughly the equivalent of ambient air pressure. Technically, 1 bar is equivalent to 14.7 psi, not 14.5 psi, but many enthusiasts equate it to the normal atmospheric pressure, so a 0.5-bar pressure reading is roughly 7.25 pounds of boost. A full, 1-bar reading would indicate 14.5 pounds of boost.
Drag Racing
Turbochargers are common among Outlaw-type drag racing classes, where the virtually unlimited boost potential from increasingly larger turbos has enabled tremendous power levels. Simply put, superchargers haven’t matched turbos for boost capability. That is changing with a new generation of larger, higher-flow superchargers, led primarily by ProCharger.
With the weight breaks offered to supercharged cars in many classes, the boost capability of the latest blowers puts racers on par with turbocharged competitors. Racer Tom Kempf, who has driven a turbocharged 10.5 Outlaw Firebird for more than a decade, is ready for the change.
“I’ve had a lot of success with turbochargers, but that has come with a number of compromises,” Kempf says. “First and foremost is these big, powerful turbo engines are very hard on transmissions, when it comes to staging and building boost at the starting line. That’s not an issue with a supercharger.”
Supercharger systems are much less complex than turbo systems with far less plumbing. That reduces fabrication time during the vehicle’s build and makes it easier to do between-round maintenance. The bottom line is turbochargers are still the power adder of choice for most racers, but the tide is turning.
“Turbo cars may still be running the quickest times,” says Kempf. “But it seems that, more and more, the blower cars are winning the races. If we can get the boost we need from a blower, I’m ready for the change.”
A new generation of centrifugal superchargers is challenging the boost capability of turbochargers that have long ruled Outlaw-type drag racing, offering comparable boost capability with less plumbing complexity and reduced stress on the transmission, particularly when staging.
LS Performance Potential
Simply put, the performance potential of a boosted LS engine is almost unlimited. Whether simply adding a bolt-on kit to an otherwise unmodified engine or building an engine from the ground up to support a larger horsepower goal, the parts are available to do it all, including dedicated performance cylinder blocks designed to withstand nearly 30 psi of turbocharged boost and more than 2,000 hp.
Realistically, most enthusiasts and builders are aiming for something more modest in a street-driven or street/strip car. But the already high power levels of stock LS-powered vehicles (from the 305 hp of the 1998–2002 LS1-powered F-Body cars to the 505 hp of the LS7-powered Corvette Z06) means the return on a supercharger or turbocharger investment will be impressive.
In most cases, a standard street-based bolt-on supercharger or turbocharger kit adds approximately 100 to 125 hp. Bolt-on twin-turbo systems can approach or exceed 200-hp gains, but extreme care must be taken with
