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Specifications of the Eaton M90 Supercharger

by Tony Oldhand

Eaton is a large and well-known manufacturer of superchargers, and provides specifications for its M90 series. A supercharger is an air pump bolted to the top of the engine, and driven by the engine's crankshaft. Because it increases air pressure, horsepower is increased significantly. Unlike a turbocharger, no transient time lag exists until it "kicks in," so horsepower increases right from engine idle speed through the engine's rpm range. This is of great value for acceleration from a standstill.

Engine Size

The M90 unit is designed for gasoline engines from 3 liters to 5 liters in size. The M90 may be used in other sizes, depending on the application requirements. It is designed for passenger cars and truck engines. Eaton states that it does not make aftermarket kits, so all its superchargers are made for the OEM (Original Equipment Manufacturer) market. This means you cannot buy an Eaton unit directly for a vehicle, unless it was original equipment. Eaton, does, however, have partners that sell aftermarket kits.

M90 Designation

When an internal combustion engine pulls in air, it loses horsepower because of the effort. A supercharger, being an air pump, pushes air into an engine. The amount of air Eaton superchargers moves is in the name. In essence, Eaton superchargers are designated by the amount of air it pumps. For the M90, it moves 90 cubic inches of air per revolution of its shaft. Suppose an engine is turning at 1,000 rpm. With a pulley, the supercharger might be spinning at 1,500 rpm. Multiplying 1,500 rpm by 90 yields 135,000 cubic inches per minute of air being pumped into the engine.

Manufacturer Uses

The M90 is designed as original equipment on three vehicle types. It is used on the Ford Super Coupe car series, and the General Motors 3800 Series L67 and L32 engines. The engineers at Ford and GM rely upon Eaton's expertise in the design of the M90, and incorporated it into their engine designs.

Oil Recommendations

Eaton states the unit is sealed, and the internal oil should last for the life of the supercharger. If you have to change the oil, use a syringe or other small tool to suck out the old oil. Obtain Eaton oil from the company or authorized representative, and fill the M90. For the Ford Super Coupe, it takes 8.1 fluid ounces of oil. For the GM L67, it takes 7.6 fluid ounces. For the GM L32, it takes 6.9 fluid ounces.

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