Because of its ability to produce an abundance of boost at virtually any engine RPM without any supercharger lag, the twin-screw compressor has become one of the most popular choices for contemporary street supercharging. Former NHRA Top Fuel and Funny Car racer Art Whipple was highly instrumental in introducing twin-screw compressor technology to the world of drag racing. He also went on to popularize the concept with the automotive performance aftermarket by developing a complete series of GM-derived, Lysholm-based Whipple twin-screw supercharger kits.
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Simultaneously, Jim Bell (Kenne Bell, Inc.), long known as the builder of some of the fastest and quickest Buick Grand National cars in the country, began experimenting with the Autorotor-derived twin-screw compressor. The by-product of that grand experiment was the 1.5L Kenne-Bell TS-1500 twin-screw supercharger kit for the 1986 and up 5.0L pushrod V-8 engine Mustangs. But how does the twin-screw compressor design really work?
“The basic engineering philosophy behind the creation of the twin-screw compressor is that the shortest, smoothest path between two points is always best for optimum airflow,” commented Jim Bell.
Bell went on to explain that depending on the application, as air enters through the rear or top rear of a Kenne Bell twin-screw supercharger case, the “male” rotor rotates clockwise while the “female” rotor rotates counterclockwise to internally compress the air producing a much higher VE. This is opposite of the operating principles of a Roots design, which is considered to be a semi blow-through design.
“This was done to avoid pumping air between the rotors and case,” says Bell. “This more efficient method of internal compression also reduces the high turbulence, friction, and heat buildup (known as adiabatic efficiency) inside the case during the process of trapping and compressing the air between the rotors, ultimately producing a lower air-charge temperature. The significantly compressed and cooler air charge is then screwed, or propelled, toward the front of the case, where it’s discharged into the engine.”
Due to its superior design, the twinscrew compressor also requires (depending on the size of the supercharger drive pulley) 10 to 16 less horsepower to drive, a noteworthy reduction in parasitic loss. Of course, the end result is increased horsepower and torque at any operating speed, which equates to increased acceleration for quick starts, straight-line running, passing, towing, or hill climbing. “It’s like having a bigblock under the hood,” says Jim Bell with a huge grin.
Although Kenne Bell offers a total of nine different sizes of self-cooled, self-lubricating twin-screw superchargers, there currently are three different sizes used in their Ford-specific kits. Each of the Autorotor-based Kenne Bell street superchargers is 50-state legal.
There’s the billet-aluminum-cased 1.5L TS-1500, which is capable of producing a 40 percent gain in rear wheel horsepower at boost levels of up to 12 psi max boost. There’s the slightly larger 1.7L billet-aluminum-cased TS-1700 interim compressor, which is capable of producing between 45 and 50 percent more horsepower to the rear wheels in normal trim, and up to 55 to 60 percent more horsepower when intercooled at 13 psi. Then there’s the even larger 2.2L billet-aluminum-cased TS-2200, which Bell and company affectionately refer to as the Blowzilla 2200, capable of producing 70 to 75 percent more rear wheel horsepower at 18 psi max boost!
All three units occupy virtually the same physical space inside the engine compartment of any model 1986 to 1995 5.0L Mustang or Ford F-150, or 1996 to 2004 4.6L SOHC Mustang GT or DOHC SVT Mustang Cobra. Listed below are the specific Kenne Bell Ford applications.
Kenne Bell 1986-1995 5.0L Mustang LX, GT, and Cobra, 1.5L, TS-1500 Twin-Screw Supercharger Kit available in satin, black, or optional polished, rated at 450 hp.
Kenne Bell 1994-1995 5.8L F-150/ SVT Lightning F-150 pickup, 1.5L, TS- 1500 Twin-Screw Supercharger Kit, available in satin, black, or optional polished.
Kenne-Bell 1994-1995 5.8L Ford F- 150/SVT Lightning F-150 pickup, 2.2L, Blowzilla 2200 Supercharger Upgrade Kit, available in satin, black, or optional polished.
Kenne Bell 1998-2001 5.4L SVT Lightning, 2.0L, 96+ hp Supercharger Upgrade, available in satin, black, or optional polished.
Kenne Bell 1996-2004 4.6L Mustang GT, 1.5L, TS-1500 Twin-Screw Super charger Kit, available in satin, black, or optional polished, optional intercooler.
Kenne Bell 1996-2004 4.6L Mustang GT, 2.2L, Blowzilla TS-2200 TwinScrew Supercharger Upgrade Kit, available in satin, black, or optional polished, optional intercooler.
Kenne Bell 1996-2004 4.6L DOHC SVT Mustang Cobra, 2.2L, Blowzilla TS-2200 Twin-Screw Supercharger Kit, 9 psi, available in satin, black, or optional polished, optional intercooler.
These 100 percent bolt-on Kenne Bell supercharger kits look so factory it’s kind of hard to tell that they’re actually aftermarket. Furthermore, K.B. states that their twin-screw supercharger kits are the only kits on the market that allow all the OEM engine accessories to remain in the stock position.
Kenne Bell is also working on a 1.7L, 50-state-legal twin-screw supercharger kit (10 psi max boost) for the 4.6L, 3-valve 2005 Mustangs. “A stock 2005 3-valve Mustang GT is capable of producing around 279 hp at the rear wheels,” says Bell. “With our intercooled 1.7L-equipped R&D mule, we’re currently able to produce 460 horsepower!”
More good news! Kenne Bell also offers a fourth model, the 2.4L Blowzilla 2400, which is capable of operating at an incredible 26 psi max boost. However, the 2.4L Blowzilla is for competition or “off road use only.”
Of course, no matter what the application, actual boost, torque, and horsepower are relative to how quick you turn the compressor, and that is governed by the size of supercharger drive pulley you use.
“A general rule of thumb is that for each 1 ⁄8 inch in diameter, you will produce 1-horsepower while simultaneously increasing PSI accordingly. Remember, a supercharger is a pump. As it tries to pump air into an engine, it (by sheer design) pumps more air than the engine can normally exhaust – the bigger the (cubic-inch displacement of an) engine the smaller the pulley. Depending on the actual application and size of the Kenne Bell Twin-Screw Supercharger being used, we offer over 40 different-sized drive pulleys for Ford small-blocks and Ford mod motors ranging from 17 ⁄8 inches to 41 ⁄8 inches in diameter,” says Bell.
Kenne Bell manufactures these pulleys out of machined steel billet (available in 6-, 7-, and 8-rib applications) because with a friction (belt) drive, aluminum pulleys tend to wear faster. Kenne Bell’s one-bolt feature also makes them easy to remove. For example, you can change pulleys right there at the track with a simple wrench, a socket, and a breaker bar. However, depending on the diameter of the actual pulley, you may need a shorter serpentine belt.
Intercooling is another way to safely increase horsepower, and Kenne Bell offers an intercooler option with all of their Ford modular-engine supercharger kits. “Our custom-manufactured barand-plate designs, air-to-water aluminum intercoolers with custom end caps, are some of the best in the industry. We offer these units for the 1996-2004 4.6L, SOHC 2-valve, and for the 1996- 2004 DOHC 4-valve modular engines, and we’re currently working on an application for the 2005 3-valve modular engine Mustang.”
How effective are these units?
“Typically we can reduce the charge temperature up to 90 percent. The best way to describe it is that it will get the temperature down to 20 to 30 degrees ambient. Aside from the obvious gain in horsepower, an intercooler also represents real value. For example, if you were to install headers, exhaust, and a cold air kit, which represents approximately $1,000 invested, you might gain up to 15 hp at the rear wheels. Our intercooler retails for around $1,200, and is capable of producing 66 hp at the rear wheels. Do the math!”
Although 5.0L Ford small-block owners may be left out in the cold in regard to Kenne Bell intercoolers, the company does offer the larger-sized Flowzilla supercharger inlet manifold as an upgrade over the standard 5.0L/GT40 Kenne Bell supercharger inlet manifold. The GT40-based Flowzilla was designed to complement the larger-displacement 2.2L and 2.4L Blowzilla twin-screw superchargers, producing from 6 to 18 psi. The Flowzilla provides up to a 50 percent increase in airflow, and accepts throttle body sizes up to 90 mm. The unit also features an internal bypass valve, and is EGR adaptable.
Kenne Bell’s Boost-A-Pumps will deliver 50 percent more fuel and will support 50 percent more horsepower. Boost-A-Pump’s fuel flow and line pressure can be regulated with adjustments from 1 percent to 50 percent by the turn of the cockpit-controlled dial, which means you’re no longer locked into a fixed flow rating and line pressure setting. You can safely adjust fuel and line pressure for either altitude or for motorsports competition at will.
Kenne Bell’s cockpit controlled Boost-A-Spark taps into your existing OE ignition system and is adjustable in increments from 0 to 50 percent. Kenne Bell’s Long Spark Technology increases and regulates voltage, far more than short-spark CD systems, and the unit automatically adjusts spark to meet engine requirements.
Kenne Bell also offers recalibrated Switch Chips, boost, temperature, fuel pressure and vacuum gauges, calibrated thermostats, and water injection kits. If it has anything to do with twin-screw supercharger technology, Kenne Bell has it.
Kenne Bell Superchargers
10743 Bell Court
Rancho Cucamonga, CA 91730
Phone: (909) 941-6646
Tech: (909) 941-0985
Fax: (909) 944-4883
Other Twin-Screw Superchargers
Allen Engine Development
2521 Palma Drive
Ventura, CA 93003
Phone: (805) 658-8262
Fax: (805) 658-8645
Ford Racing Performance Parts
44050 Groesbeck Highway
Clinton Township, MI 48036-1108
Phone: (586) 468-1356
TWIN-SCREW SUPERCHARGING A CLASSIC
There isn’t a classic Mustang owner on the planet who doesn’t wish that he or she had more power at their disposal – whether they need it, or not. Call it the human condition, but the fact of the matter is Mustang owners just can’t resist extra power!
Of course, you could always go “old school” and add multiple carburetion, a cam, headers, and all the traditional stuff. But then what do you have? A gas-guzzler that’s nearly undrivable and most likely a gross polluter, making it the target of every traffic cop in town. “So, what’s a mother to do?”
In recent years, quite a few classic Mustang owners have stepped up to the plate and gone with 5.0L EFI power, and have been all the better for it. Such was the case with this black-and-whitestriped 1965 Mustang convertible, a.k.a. the Skunk. The Skunk was actually one of the first classic Mustangs in Southern California to be converted over to 5.0L EFI power all the way back in 1992 by the late Jim Madden and famed 5.0L/4.6L expert Mark Sanchez from Advanced Engineering West (AEW).
Already five times removed from box stock, our 5.0L featured a Ford Motorsport B-303 roller cam, a set of SVO 1.6:1 roller-rocker arms, an SVO cast-aluminum Cobra upper intake plenum and GT40 lower intake, a set of Doug’s Headers Tri-Y headers and Magna-Flow mufflers, an Art Carr C-4, and an 8-inch Traction Lok rear end with Currie 3.00:1 gears. Over the years, this combination had managed to keep up with the Camaros and Firebirds, but the Skunk’s owner definitely wanted more power!
A supercharger of some type was the answer. However, with space limitations being what they are with an early model Mustang, deciding exactly what kind of supercharger to use required a little researching. The owner decided on the 1.5L Kenne Bell TS-1500 kit for the 1986-1995 5.0L Mustangs, partially because it was pretty much a straightforward bolton proposition.
At that point, we were pretty convinced, but old Jim Bell had some ideas of his own.
“The 1.5L TS-1500 is okay,” said Bell. “But I know you well enough to know that you’re going to want to eventually hop up that darned thing. What I recommend is that you purchase the base kit, and upgrade the supercharger to one of our 2.2L Blowzilla TS- 2200s. Instead of the 6- to 8-pound range delivered by the TS-1500, the 2.2L Blowzilla twin-screw compressor was designed to provide up to 20 pounds max boost.”
Bell went on to relate that the 2.2L “Blowzilla” twin-screw supercharger is about 50 percent larger internally, and features a more aggressive lobe design. Blowzilla also features a bypass valve, which bleeds off excess pressure when you’re not running at full boost.
“The beauty of this blower is that due to its size, you can run 6 to 8 pounds boost on the street (using the 31 ⁄8-inch pulley) running on unleaded high-octane pump gas. Then whenever you go to the track, you can change out the pulley to something like a 21 ⁄8-inchdiameter drive pulley in less than 10 minutes, time. With 100+ octane gas in the tank, you can run between 17 and 18 pounds boost!”
The 2.2L Kenne Bell Blowzilla twin-screw supercharger also features the Flowzilla air inlet that flows like gangbusters. For this application, we selected one of Accufab’s 70-mm polished billet-aluminum throttle bodies with EGR spacer plate, along with one of the company’s calibrated throttle position sensors.
Of course, with the bigger blower and more boost, the stock 19-lb/hr stock injectors wouldn’t come close to getting the job done. In their place, we substituted a set of Bosch 30-lb/hr units, which, when working in conjunction with our 22-gallon Fuel Safe fuel cell and 230-lph Bosch electric fuel pump, certainly won’t be starving our 5.0L for fuel! We also upgraded our mass airflow meter (MAF) to a 90- mm K&N-filtered Kenne Bell MAF (as used on the SVT Lightning) to provide our 5.0L with a bigger gulp of fresh air.
Now that we had the kit, the next step was installing it. Once again, Mark Sanchez and his son Vincent (who as a young boy had helped his father originally install the 5.0L engine in the Skunk) were slated to do the work. A mere 4 hours from the moment we pulled through the door, Team AEW had the engine up and running, and ready to deliver to Doug’s Headers shop. Once there, Doug and the boys installed a set of his ceramic-coated 15 ⁄8- inch diameter primary Tri-Y headers and a custom-fabricated 21 ⁄2-inch exhaust including one of Doug’s ceramic-coated X-pipes. From there, the spent gases exit through a pair of 4 x 9 x 18-inch Magnaflow stainless-steel mufflers, and out through a pair of 21 ⁄2-inch ceramic-coated tailpipes. It’s a real nice system, and it should help out considerably in the horsepower department.
With our ’65 back at AEW, we drove over to Kenne Bell’s facility where Dynamometer Technician/Product Engineer Brent Morris was waiting to get with the program. Fuel mapping and overall engine programmings are both important parts of the process. Just prior to dyno testing, engine systems programmer Ken Christley burned a “30-lb chip” (for our 30-lb/hr injectors) and installed it in our computer. Then, with 20 degrees of advance in the distributor and 116-octane Sunoco unleaded in the fuel cell, Morris conducted a series of three pulls, with our best being the second pull, which registered the following data at 12 psi:
308.2 hp at 4,900 rpm and 434.4 ftlbs of torque at 2,600 rpm
Now that’s pretty darned good for a slightly warmed over, 55,000-mile 5.0L small-block. Of course, the most noteworthy gain was in the torque department. We’re really going to have our hands full when all 434.4 ft-lbs of torque kick in.
Could we have extracted more horsepower and torque out of our 2.2L Kenne Bell-supercharged early-model Mustang? Yes and no. Actually, we tried to run more boost, but that proved counter productive. Technician Brent Morris changed out the drive pulley from 31 ⁄8 inches to 27 ⁄8 inches, and the engine started to come alive during the third pull. Unfortunately, the OE ignition system began crapping out and started dropping sparks at high RPM. The addition of an MSD 6BTM electronic ignition set up to retard timing under full boost while controlling detonation would certainly help. And Jim Bell had a few ideas of his own.
“Had this been a stick (due to parasitic loss from the torque converter), we would have realized another 60 horsepower right off the bat. And since this is also a non-lock-up torque converter, you easily lose an additional 30 horsepower throughout the entire power band. Had we been able to regain that lost horsepower, we would have had ourselves close to a 400-horsepower blown Ford small-block!”
So what’s in store for this Kenne Bell-supercharged Skunk? Well, now that we know what this system is capable of, we’re going to build up a fresh small-block using an Authorized Engine Remanufacturing (AER) 5.0L roller cam block as the foundation. After installing another B-303 cam inside, we’re going to drop on a set of Holley System Max bigvalve aluminum cylinder heads, Extrude Hone the intake, install the MSD 6BTM, and a few other goodies. But for the time being, we’re more than happy with what we already have. And really, who wouldn’t be?
Written by Bob McClurg and Posted with Permission of CarTechBooks