The word supercharged may trigger thoughts of a monster truck with a huge Roots-type blower sticking through its hood and flames blasting from its exhaust. However, when discussing superchargers within the pages of Today's SUV, that's not what we had in mind. Our focus is on aftermarket, engine-driven superchargers, which enhance the performance of street-driven sport utility vehicles. These supercharger kits do not require holes in the body, can be installed on an otherwise unmodified engine, do not compromise engine reliability or durability, offer the driveability typical of a production vehicle, and meet federal exhaust emissions rules. This guide will not cover racing superchargers or exhaust-driven turbos.

Blower Basics
Superchargers have been around for nearly 100 years. Historically, they are occasionally used in production vehicles, but except for the current Ford F-150 Lightning pickup truck, they are not currently used in production light-trucks or SUVs. For the most part, truck superchargers have remained aftermarket products.

A supercharger (aka, a blower) increases the density of air (also called charge air) going into an engine by compressing and increasing the airflow. If charge air density is higher, more fuel can be burned. This increases engine output over its normally aspirated or atmospheric level.

How much compression occurs is a measure of supercharger effectiveness. It is often expressed in pounds-per-square-inch (psi) above atmospheric pressure and is called boost. For instance, 5 pounds of boost pressurizes the engine's intake tract 5 psi above atmospheric levels. The maximum boost made by aftermarket superchargers, on production engines burning pump gas, is usually about 5 to 8 pounds. A few superchargers, running in conjunction with intercoolers, might produce around 10 psi.

The effect an aftermarket blower has on an SUV engine can be significant. A 30 percent increase in power is common, and 50 percent is not unusual. Because of many sport utilities' poor power-to-weight ratios, such an increase makes a substantial improvement in performance.

However, there are concerns with blowers, and one of them is cost. A properly developed supercharger kit runs several thousand dollars. Add installation fees and labor and you can arrive at figures at or more than $5,000 fairly easily. In addition, because a supercharger increases both the engine's cylinder pressure and charge air temperature -- two causes of detonation or knock -- blowers mandate the use of at least 91-octane fuel, which also increases operating costs. A boosted engine also produces a higher volume of exhaust gases, and engines equipped with supercharger kits may need a low-restriction exhaust system.

Lastly, expect a reduction in fuel economy; how much depends on how the supercharged engine is driven. If boosted operation is infrequent, fuel mileage will be close to stock. If your driving habits require the engine to be boosted regularly, expect a reduction in mileage.

Today's electronic powertrain controls are complex, and the integration of a supercharger usually calls for changes in the fuel, ignition, and sometimes transmission calibrations of those controls. The best kits include substantial calibration measures to ensure that the engine will perform well, drive smoothly, and not pollute the air.

Well-developed kits alter fuel delivery with changes in calibration, injector flow capacity, fuel pump flow, and fuel pressure, or a combination of one or more of those. Adequately developed kits do this with modified fuel pressure regulators. Before a purchase, contact the manufacturer for information about the kit's integration with existing engine controls.

While engine failures due to the superchargers covered in this article are rare if the blower was installed and used properly, they do happen. By federal law, the presence of aftermarket products not designated by their manufacturers to be for racing purposes only shall not automatically void a warranty, however, a warranty claim can be denied if the aftermarket product caused the problem that prompted the claim. Example: You install a supercharger on your new Chevy Tahoe. A week later, the windshield wipers quit working. It's illegal for Chevrolet to deny the warranty claim for the wipers because a supercharger was installed. However, if the blower malfunctions and the engine fails because of that, a dealer may legally deny a warranty claim for repairs.

Supercharger Types
The aftermarket industry currently offers two supercharger designs: positive-displacement and centrifugal. The blowers draw air into cavities formed by spinning rotors or screws. The moving cavities displace charge air through the supercharger and into the engine's intake manifold. During this process, the air is compressed. An excellent characteristic of positive-displacement superchargers for heavy vehicles such as SUVs is substantial boost at low engine speeds. Positive-displacement blowers come in two variations: Roots-type and screw-type.

Roots blowers were invented in the mid-1800s to force air into blast furnaces. Adapted to automotive use in the late 1920s by European car companies, they've been used on everything from motorcycles to heavy trucks. With a Roots-type supercharger, when the moving cavities are exposed to charge air already in the intake manifold, compression occurs. Because this type of supercharger was designed as a ventilator, it has compromises as a supercharger -- limited efficiency because of leakage, turbulence, and flow pulsations, along with charge air temperature rise. Nevertheless, aftermarket units for gasoline engines have been popular, and the well-developed Eaton supercharger is widely used by OEs, including Ford's Lightning pickup truck.

The screw-type supercharger was invented by Alf Lysholm, an engineer working at a Swedish company called Svenska Rotor Maskiner (SRM) in the 1930s. Because of high manufacturing costs Lysholm Screw Compressors were not used in automobiles for 60 years. It wasn't until computer-numeric control (CNC) machining processes were introduced that small-screw compressors for automotive use became cost effective. Today, two Swedish companies, Autorotor and Lysholm Technologies, manufacture screw-type blowers.

Screw blowers have two helical screws with unequal lobe counts. Distinctions of the screw design include the fact that it is capable of internal compression, and it creates less turbulence and pulsating flow. As a result, this design has a higher volumetric efficiency and adds much less heat to the charge air. Combine those features with a low-speed boost of any positive-displacement design, and a screw-type supercharger may be the best option for a sport utility vehicle. Recently, Eaton licensed the world OEM manufacturing rights to the Lysholm Screw Compressor. A screw blower will be used on the Mercedes Vision SLR supercar rumored to be going into production in 2002. Expect to see screw blowers gradually replacing Roots types in production car and light-truck applications.

Centrifugal superchargers were originally designed for race cars and high-altitude, piston-engine aircraft. Inside, the blower is a fan-like impeller spun at high speed by overdrive gears and is belt-driven off the crankshaft. The spinning impeller imparts radial force to the air in its channels. The air that spins away from the impeller compresses in the housing and flows into the engine. Some of the advantages of a centrifugal supercharger are that there are few moving parts, simple packaging, high boost, and limited charge air temperature rise.

To a greater degree than positive displacement superchargers, a centrifugal's boost depends on blower speed. However, stock engines on pump gas tolerate only limited boost. For instance, say you want 7 psi maximum on an engine making peak power at 5,000 rpm. If you pick a centrifugal blower with that output, down at 2,000 to 3,000 rpm, where the engine spends most of its time, you would have only 1.4 to 2.1 psi of boost -- not as much of an increase. If you select a centrifugal supercharger that provides a maximum of 23 pounds of boost, it will probably damage the engine. Picking the right centrifugal supercharger takes care. They are best in cases where significant boost at high rpm is desired, the engine accelerates though its rpm range fairly quickly and gross vehicle weight is comparatively low.

Intercoolers, or more correctly, charge air coolers, are common on turbocharged engines. In search of a partial solution to a centrifugal blower's speed-dependent boost, a few manufacturers add intercoolers to their kits. As one manufacturer explained to us, supercharger speed is increased somewhat, but the blower still boosts less at low speeds than at high speeds. The intercooler is more efficient at low flow rates than at high flow and with less tendency toward detonation because of the charge air cooling. The practical result is a flatter boost curve, which might make an intercooled, centrifugal supercharger a wiser choice for SUVs.

If you are looking for more general information on supercharging sport-utility engines for street use, you may want to check Street Supercharging by Pat Ganahl. Contact: CarTech, 11605 Kost Dam Rd, N. Branch, MN 55056, (800) 551-4754.

TRD
Toyota Racing Development (TRD) shapes Toyota's performance image. A Toyota Motor Sales, U.S.A. subsidiary, TRD develops Toyota racing engines and sells aftermarket performance products under two different brands: TRD Sport Parts and Kazuma. TRD Sport Parts has a supercharger kit for V-6s in Toyota SUVs. The kit has the fourth generation Eaton/Magnuson supercharger at its core, with the rest of the pieces, including calibration, done by TRD.

The TRD Sport Parts blower kit is 50-state legal and fits 3.4L V-6s in '96-to-'99 Toyota 4Runners. A unique feature of this blower is that when installed by a Toyota dealer on a new vehicle, the supercharger and the powertrain are covered a TRD five year/60,000-mile warranty that replaces the OE powertrain warranty but does not affect the rest of the new vehicle warranty. If it's dealer-installed on a used truck, the TRD warranty replaces the remainder of the vehicle's original powertrain warranty. Of all the superchargers we researched, this is the only case of full coverage by any warranty.

Products in TRD's Kazuma line are intended to be more aggressive in their performance enhancement. A Kazuma supercharger kit is available for the 4.5L, inline six-cylinder in the '95-to-'97 Land Cruiser. Again, TRD went with the fourth-generation Eaton/Magnuson blower for the basis of the kit then added its own finishing pieces and engine controls calibration. Kazuma blowers are true to their description of being more aggressive. According to TRD, at the rear wheels you'll see 110 more horsepower and 16 lb-ft more torque. The Kazuma supercharger kit is 50-state legal when used in its base configuration. Also available are additional drive pulleys that further increase performance, but they are not 50-state legal. The most aggressive pulley runs the blower at 12.5 pounds of boost and has the engine generating 258 hp at the flywheel. The Kazuma supercharger kit for Land Cruisers is not covered by any vehicle powertrain warranty.

For more information, contact: TRD, Dept. TSUV, 1382 Valencia Ave., Tustin, CA 92780, (800) 688-5912, www.trdusa.com.

Kenne Bell
One of two companies marketing screw-type superchargers in North America, Kenne Bell Performance Products has developed and sold supercharger kits for Ford and DaimlerChrysler applications for a number of years and has just started a product line for GM V-8s. Kenne Bell relies on the Autorotor supercharger for the core of its kits but does the rest in-house. The screw-type's advantages, paired with Kenne Bell's engine control work, makes these kits outstanding choices for a variety of different SUVs.

Kenne Bell was the first to put a blower kit on the market for the '01 Ford Escape and the Mazda Tribute. Kenne Bell blower kits are also available for '87-to-2000 Ford fullsize, sport utilities with 4.6L, 5.0L, 5.4L (16- and 32-valve versions), and 5.8L engines. The flagship Kenne Bell Ford kit fits the 2000-to-'01 Excursion with the 6.8L V-10 and is good for 410 hp at the rear wheels.

Kenne Bell's Dodge coverage starts with the 4.7L V-8 in the '99-to-2000 Jeep Grand Cherokees. The company also has kits available for the 5.2L engine in the '98-to-2000 Durango.

Destined to be one of Kenne Bell's biggest volume products is its new supercharger kit for the Vortec 8100 V-8 in the 2001 2500-series Chevy Suburban and GMC Yukon XL.

For more information, contact: Kenne Bell Performance Products, Dept. TSUV, 10743 Bell Ct., Rancho Cucamonga, CA 91730, (909) 941-6646.

ATI Procharger
Accessible Technologies is the only manufacturer of centrifugals with widespread availability of charge air coolers as an integral part of its blower kits. Another ATI distinction is its P-1SC self-lubricating ProCharger, which eliminates oil lines to the engine.

ATI has blower kits for 5.0L, 5.3L, and 5.7L engines in '88-to-'01 General Motors fullsize SUVs along with the Vortec 7400 engine in '96-to-2000 Suburbans and Yukon XLs. All of these kits include intercoolers. ProCharger also offers a blower kit for the 16-valve 5.4L V-8 in '96-to-'01 Ford Expeditions and '98 Lincoln Navigators. Lastly, ATI offers kits for the Dodge Durango.

Some ProChargers are 50-state legal and others are not legal for street use in California. For more information on ProCharger kits, contact: Accessible Technologies, Inc., Dept. TSUV, 14801 W. 114th Terrace, Lenexa, KS 66215, (913) 338-2886, www.procharger.com.

Powerdyne
Made by Powerdyne Automotive Products, an innovative manufacturer of centrifugal superchargers, the Powerdyne is unique with its Gilmer belt transmission. Called SilentDrive, it eliminates gear noise as well as the need for lubrication. Powerdynes also use a curved-blade impeller, said to improve low-speed boost.

Powerdyne is unique in that it offers a kit for the '96-to-2000 4.3L V-6-powered GM compact SUVs. It also supports '96-to-2000 5.7L V-8s in GM fullsize utilities. Powerdyne has kits for fullsized '88-to-2000 Ford SUVs with 4.6L, 5.0L, 5.4L, or 5.8L engines and for '96-to-'99 V-8 Ford Explorers. Lastly, Powerdyne supports Dodge SUVs with the 5.2L engine.

Powerdyne tells us all its kits are 50-state legal. For more information, contact: Powerdyne Automotive Products, Dept. TSUV, 104-C East Ave., Ste. K-4, Lancaster, CA 93535, (661) 723-2800, www.powerdyne.com.

Vortech
Established in 1990, Vortech (not to be confused with GM Vortec engines) was at the leading edge of growth in centrifugal supercharger sales during the '90s. Today, Vortech Engineering is one of the largest makers of centrifugals.

Vortech blowers fit '88-to-2000 General Motors fullsize sport utilities having 5.7L engines and '88-to-'95 7.4L engines. Additionally, Vortech does kits for 4.3L V-6s in '96-to-2000 GM compact SUVs. Vortech has blowers for '87-to-'99 Ford sport utilities with 4.6L, 5.0L, 5.4L (16-valve only), 5.8L, and 7.5L engines. It has kits for Ford '91-to-'94 Explorers with 4.0L V-6 engines. There are also Vortechs for Jeep Grand Cherokees with 5.2L V-8s.

About the time you read this, Vortech will have available a blower kit for the 2000-and-later GM SUVs with the 5.3L and 6.0L Generation III V-8s along with a supercharger setup for the V-10 in the Ford Excursion.

Most Vortech kits are 50-state legal, but some are not legal for use in California. Consult Vortech for specific information on exhaust emissions compliance. For more information, contact: Vortech Engineering, Dept. TSUV, 1650 Pacific Ave., Channel Islands, CA 93033-9901, (805) 247-0226, www.vortechsuperchargers.com.

Magna Charger
The Magna Charger is the aftermarket implementation of the Eaton, Roots-type supercharger offered by OEs. Its manufacturer, Magnuson Products, has been the aftermarket distributor of Eaton blowers in North America for many years, and its experience in developing Roots superchargers for light trucks is extensive.

Magna Charger has kits for 5.3L and 5.7L Vortec engines in '96-to-2000 GM SUVs. You can get Magna Chargers for the 4.6L and 5.4L (16-valve only) engines in '97-to-2000 Ford fullsize utilities. The Ford kits have intercoolers.

Some of these kits are 50-state legal and some are not legal in California. Consult Magna Charger for specific information on exhaust emissions compliance. For more information, contact: Magna Charger, Dept. TSUV, 3172 Bunsen Ave., Ste. D, Ventura, CA 93003, (805) 298.0044, www.magnacharger.com.

Paxton
The old Paxton division of the McCulloch Corporation sold aftermarket and OE centrifugal blowers as far back as 1953. Remember the Paxton supercharged '57 Thunderbirds? Today, the name is owned by the Paxton Automotive Corporation and current Paxton superchargers trace their heritage back to those old T-birds. Paxton is notable for being the only blower maker supporting both the Dodge and Ford V-10s. It's also one of only two companies doing blowers for Lincoln Navigators with the 32-valve engine. Paxton kits are also available for '97-to-2000 Fords with the 4.6L and 5.4L V-8s.

Paxton has blower kits for 5.2L engines in '93-to-'97 Cherokees. Paxton supports '88-to-'98 General Motors SUVs with the 5.7L or 7.4L engine. Paxton states that all its kits are 50-state legal. For more information, contact: Paxton Automotive Corp., Dept. TSUV, 1250 Calle Suerte, Camarillo, CA 93012, (805) 987-8660, www.paxtonautomotive.com.

Jackson Racing
Jackson Racing, known to sport compact car enthusiasts for its performance-enhanced Acura and Honda automobiles, recently focused on SUVs with a supercharger kit for the Honda CR-V. Said by its manufacturer as being responsible for a 60 percent increase in power at 6,000 rpm, it is an adaptation of the Eaton/Magnuson blower and includes Eaton's bypass feature that improves unboosted driveability and fuel economy.

For more information, contact: Jackson Racing, Dept. TSUV, 440 Rutherford St., Goleta, CA 93117, (888) 888-4079, www.jacksonracing.com.

Holley
Holley Performance Products is a newcomer to the blower business in a roundabout way. Twenty years ago, Roots-blower expert Jerry Magnuson sold his first supercharger brand to B&M, which, in turn, sold that business to Holley in 1999. While the brand name is new, Holley's design has been around for decades and is proven in its reliability. Holley markets its 144 Powercharger kit for SUVs on a limited basis. Holley currently offers a supercharger kit for GM '88-to-'95 fullsize SUVs. This blower kit is 50-state legal.

For more information, contact: Holley Performance Products, Inc., Dept. TSUV, Box 10360, Bowling Green, KY 42102-7360, (270) 782-2900, www.holley.com.

Whipple
The second of two companies marketing screw compressors, Whipple's greatest assets are product development and the screw compressor itself. In its Whipplecharger kits, engine control calibration for good driveability gets strong emphasis. Currently, Whipple markets blower kits for General Motors' engines and is developing them for Ford and Chrysler engines. It uses Lysholm Technologies twin-screw superchargers for the core of its kits. The rest of the hardware is developed in-house.

Whipple has supercharger kits for all '89-to-2000 General Motors fullsized utilities using the 4.8L, 5.0L, 5.3L, 5.7L, 6.0L, and 7.4L V-8 engines. Additionally, Whipple has a brand-new, state-of-art blower kit for the Vortec 8100 in the '01 2500-series Suburban and Yukon XL. Whipple's data shows these kits use 6 pounds of boost to increase power at least 48 percent.

Whipple also has entered the Ford SUV blower market with a kit for the 5.4L 16-valve engine in the '98 Ford Expedition and Lincoln Navigator and a kit for the 6.8L V-10 in the 2000-to-'01 Excursion.

The company also has a kit for the Chrysler PT Cruiser and, as of press time, is working on a blower for the Mercedes-Benz ML320. All Whipplecharger kits are 50-state legal.

For more information, contact: Whipple Ind., Dept TSUV, 3292 N. Weber, Fresno, CA 93722, (559) 442-1261, www.whipplesuperchargers.com.