There is one supercharger that outnumbers all the others by a wide margin for a number of good reasons. Automotive giant Eaton Industries developed the Eaton supercharger, with the assistance of veteran supercharger legend Jerry Magnuson. Numerous incarnations of this small but amazingly efficient supercharger have appeared on a wide variety of factory installations, ranging from the 3.8L ’89 Ford Thunderbird Super Coupe to the 4.6L 2003 and 2004 SVT Cobra. In fact, Eaton Industries supplies 98 percent of the domestic and international OE supercharger market, making them the largest supercharger manufacturer in the world!
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Over the years, Magnuson has had a fruitful and continuing relationship with Eaton, and offers high-performance upgrades or variants based on Eaton supercharger products, which some people refer to as an “Eaton with an Attitude.” As of this writing, Magnuson Products, Inc. is the only Eaton-authorized repair station, and Jerry works extremely hard to keep that distinction.
During the early 1980s, Eaton responded to a subtle industry call for a compact supercharger design that possessed extremely high volumetric efficiency, the ability to operate quietly, and the durability to outlive most of the engines it would be mounted on. Magnuson, who had manufactured his own brand of supercharger (Magna-Charger) of ingenious, hybrid-rotor Roots-type superchargers for many years, was recruited to work with Eaton engineer Kris Berry, who was assigned to the task of reinventing the supercharger to meet OE demands.
The two eventually arrived at a design that looked somewhat similar to a Roots blower, but a closer look revealed an entirely different animal. The most significant differences are that the Eaton’s rotor speed is remarkably high, and its intake charge enters the unit and exits under pressure from one or the other of its flat faces (front or rear), which is the area you would expect the supercharger drive gears to be located. These various exits have been optimized for installations on vehicles like the second- generation Ford SVT Lightning pickup, 2003-04 SVT Mustang Cobra, and a variety of GM production vehicles.
According to Magnuson, one of the drawbacks to the Roots design can be found in a shift in VE as its drive speed increases with engine RPM. A typical Roots design can only muster a VE level of about 75 percent, unless it has been very carefully fine-tuned. That performance ceiling comes mostly because there just isn’t time to fill the rotor voids. The air must travel quite a ways down between the rotor vanes, and the large rotors require case clearances that allow an unavoidable amount of leakage. This adds up to a VE that is livable, but not what Eaton was after.
Eaton needed a minimum of pumping losses, which can be reduced by more precise clearances. However, in the real world, exacting tolerances and the possibility of dirty air filters don’t get along. The solution to this particular demand came in the form of better dynamic sealing through a novel rotor vane shape, mixed with some applied experience on the part of Berry and Magnuson.
The two engineers began with a clean sheet of paper, open minds, and enough Eaton engineering capital to do the job properly. Bringing the intake air charge into the unit at one end of a pair of computer-optimized smaller rotors offered many advantages over the Roots “down and around” airflow design. Most significantly, Eaton’s new design allowed much longer rotor-port timing than was ever possible with the Roots design. Using a smaller case and rotor diameter meant tighter rotor-case sealing. Finally, the ability to turn the rotors at speeds that would cause a Roots to explode brought about some surprising advantages.
One of the most remarkable improvements turned out to be the unit’s response to energy in the inlet waves near to and surrounding its inlet port. A careful look at the inlet and outlet port shapes on any version of the Eaton reveals shapes and profiles that are anything but accidental, and distinctly unfriendly to the manufacturing process. They are in a word – bizarre. Developed in part through computer modeling and refined through thousands of hours of flow-bench time, the appearance of the ports is totally alien to anything that has appeared on a Roots before. This shape appears in a more extreme manner on the heavily modified units that come from Magnuson’s West Coast “pump works.”
To put it bluntly, these units like to be turned at ridiculous RPM, and they come back at you with a wall of energy. At a rotor speed of 5,000 rpm, the VE is in the neighborhood of 85 percent. At 10,000 rpm, the VE rises to about 89 percent. And at 15,500 rpm, the VE is close to 97 percent! In the interest of long-term reliability, the OEMs use pulley size to regulate a maximum operational limit of about 12,000 rpm. Jerry feels that his Eaton/Magnuson units are good for at least 15,000 rpm, and he isn’t usually wrong about these kinds of things!
The high VE numbers mean you’ll waste very little power trying to turn the supercharger into its sweet spot. This is the major difference from other, earlier supercharger designs. A very high pumping efficiency also results in cooler air, because the air isn’t lingering around the rotors. This turns out to be a critical improvement in performance potential.
Surprising as it may seem, running these units at such an elevated RPM does not make them any noisier. The rotor vane shapes (modified involutes), the extremely precise balancing and manufacturing processes, and the unusual intake and exit port shapes allow the Eaton to operate without making much more noise than the normal accessories on a modern vehicle.
Every OEM installation of this design has incorporated a bypass valve located in the intake ducting. This valve is positioned at the inlet of the supercharger, and is operated by a combination of Electronic Control Module (ECM) and manifold pressure actuators in almost every instance. The purpose of this valve is to lighten the engine load under cruise conditions and allow a clean mode-switch as the driver stomps on the throttle. Under cruise conditions, the valve is open, allowing the intake manifold to receive inlet air without any involvement of the supercharger or intercooler (if there’s an intercooler). As the engine demand calls for boost, the bypass valve closes, diverting intake air through the supercharger and into the intake manifold. This means that under cruise conditions, the supercharger is just freewheeling, without any significant power drain on the engine. With its small rotors, the unit doesn’t make large demands on an engine in any case, but every little bit helps.
Eaton and Magnuson use the same general airflow-based scheme to identify their products. These callouts are usually 60, 90, or 120, referring to their ability to pump a certain volume of air in a single rotor revolution. Magnuson typically recommends his Ford Model 90 for small-block Ford engines displacing 351 ci or less. For much smaller engines (Ford’s 260 and 289), Magnuson leans toward the Model 60 for street applications. In many instances, Jerry will make recommendations leaning more toward a more basic unit, either unaltered or with only slight internal modifications. He explains that although this may seem paradoxically wrong, a smaller unit – turned very fast, indeed – will provide incredible throttle response, and will keep up with any mildly-modified small-block. With a more modified engine, especially if the cylinder heads have been seriously ported, Magnuson recommends his Model S-90, which is a worked-over Fifth-Generation Eaton.
As mentioned earlier, these superchargers take advantage of the inlet tract wave energy to almost completely (up to 97 percent) fill the voids between the rotor vanes. This effect is nearly identical to what happens in a properly designed tunnel-ram intake manifold with carburetors. Air is obviously a compressible medium. As such, a column of air pulled into a tube, then suddenly halted by a valve of any kind (in this case, the rotor timing and inlet port of the supercharger) will slightly compress at its leading end. This creates a wave, or pulse, that travels back toward the initial source of the air. When the valve (or port) reopens, a negative wave is created in the tube (slight vacuum), and the air begins to flow through the valve again.
The intensity, speed, and frequency of those waves are determined primarily by the volume of the tube, the valveopen/closed frequency, the volume of air ingested for each valve cycle, and the valve area. In a tunnel-ram intake, the idea is to optimize these factors by changing the manifold’s runner volume and length to suit what the carburetors need to stay under control, and to hopefully have a nice, firm pressure wave heading toward each intake valve when the time is right for it to open again.
With the insanely high rotor speed of the Eaton design, the wave timing is actually based more upon a harmonic of the actual valve-open frequency, but the effect is the same. A harmonic is a little like a playing card fanning against bicycle spokes instead of slapping the tire once per revolution. It is related to a recurring fundamental frequency, but typically in smaller increments that are equal divisions of that fundamental frequency.
The inlet of the Eaton supercharger is located relatively far from the intake manifold that, allowing for the generally springy nature of air, makes a nice, hard wave coming back from the valves difficult to use. However, there is enough of a wave available from the engine to exploit it around the inlet of the blower. This is one of the considerations you should make in deciding whether to go for the stock Eaton supercharger model or one of Jerry Magnuson’s breathed-on Eaton/ Magnuson high-performance units. Both superchargers will turn at about the same RPM, they’re both ridiculously efficient, and neither is noisy. A Magnuson-modified Eaton unit is optimized toward a more specific operating range in terms of engine RPM than is the unmodified Eaton.
Either unit is designed to operate over a wide range of RPM, of course, but if you were to drive the same Mustang, for example, while conducting an A-B comparison of the two superchargers, you’ll see a softer power curve over a slightly wider RPM range with the basic Eaton. The Magnuson-modified unit provides more intense power and a higher peak output. In most cases, that difference is hard to describe with a word like “dramatic”; perhaps incredible might be a better choice!
The Eaton and Ford Alliance
Ford was one of the first (if not the first) domestic automobile manufacturers to incorporate an Eaton supercharger on a production model. The Eatonsupercharged and intercooled 3.8L V-6 Thunderbird Super Coupe appeared in 1989, with a very creditable 210 hp and 315 ft/lbs of torque.
“When Ford first started talking about installing a 3.8L supercharged engine in these vehicles, Jerry (Magnuson) was recruited by Eaton Corporation as a consultant,” said Magnuson Products Sales Manager Bob Roese. “Rumor has it that before the Eaton engineering team ever bolted a supercharger onto a 3.8L Ford pushrod V-6 engine, they had over 25,000,000 dollars worth of development money invested in the project. Because of the federally mandated emissions rules and regulations, Ford required that this supercharger had to require zero maintenance!”
Although they weren’t production vehicles, Eaton/Magnuson superchargers made an appearance on the 4.6L DOHC Mach III Mustang show cars (there were two) built in 1992. Not officially recognized as legitimate concept cars by some of the hierarchy at Ford, the Mach III concept cars were really a backburner inter-department engineering exercise conducted by Team Mustang, then spearheaded by Will Bodie and O. J. “John” Coletti. These vehicles were specifically intended to whet the whistle of new-car-starved Mustang enthusiasts worldwide before the longawaited introduction of the exciting new SN-95 1994 Ford Mustangs.
The Lincoln Mk VIII-derived 4.6L DOHC engines that powered the Mach III Mustangs would ultimately be used in the SVT Mustang Cobra production models, with a considerably more refined Eaton-supercharged version actually making an appearance in the 2003 SVT Mustang Cobra. However, the Mach III engines, rated at 450 hp, featured flexfuel, clean air-engine packages, a feature the SVT Cobra wouldn’t have. This allowed them to burn 108-octane M-85 fuel, which is a mix of 85 percent ethanol and 15 percent premium gasoline.
The Ford-Eaton alliance moved forward in 1995 with the introduction of the second-generation SVT Lightning pickup. Powered by a 5.4L Triton V-8 with 8.4:1 compression, the Gen II Lightning featured an Eaton Gen-IV supercharger with water-to-water intercooler. This package produced a whopping 440 ft-lbs of torque and 360 hp, and was capable of propelling the Lightning from 0 to 60 mph in 6.2 seconds, and earning quarter-mile times of 14.6 sec onds at 97 mph. With a top speed of 140 mph, the Lightning quickly became the fastest production pickup in the world.
Next up was the aforementioned Eaton supercharged and intercooled 4.6L DOHC 2003 SVT Mustang Cobra. Considered to the epitome of late-model Mustang performance, the SVT Mustang Cobra knocked out 390 hp and 390 ft-lbs of torque – although many who’ve driven the car swear it’s more like 425 hp.
Magnuson Products, Inc.
1990 Knoll Drive
Ventura, CA, 93003
Phone: (805) 289-0044
Fax: (805) 677-4897
Private Label Eaton/ Magnuson Supercharger Systems
Allen Engine Development is located in the heart of supercharger country, just a stone’s throw away from industry giants like Vortech, Paxton, and Magnuson. Eaton supercharger buffs will be happy to learn that Allen Engineering offers a total of nine (9) air-to-water intercooled supercharger packages for Ford’s 4.6L and 5.4L SOHC and DOHC modular V-8 engines for Mustang, Thunderbird, Crown Victoria/ Grand Marquis, Explorer/Mountaineer, and F-150/F-250/Expedition models. These kits are all CARB certified and 50-state legal.
All of Allen Engine Development’s modular engine supercharger systems feature the Eaton/Magnuson third-generation M90s supercharger as the centerpiece. They also come complete with a cast-aluminum supercharger intake manifold, an air-to-water intercooler, mechanical water pump, billet-aluminum fuel rails, supplemental fuel system regulator, electrically activated supercharger bypass valve, and all the necessary brackets, belts, hoses, and hardware to complete an OEM-quality installation.
Allen Engine Development thoroughly dyno tests all their Eaton/Magnuson Ford kits on Super Flow engine dynos using the Digi-log Data Acquisition System to achieve 100 percent accurate test data. So when you buy one of Allen’s street supercharger kits, you know you’re getting the real deal.
Allen Engine Development, Inc.
2521 Palm 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: (810) 468-1356
Irvine, CA 92618
Phone: (800) 888-8945
Roush Performance Products
28156 Plymouth Road, Suite Z
Livonia, MI 48150
Phone: 1-800-59 ROUSH
Local: (734) 466-6222
Fax: (734) 466-6940
Written by Bob McClurg and Posted with Permission of CarTechBooks