Eaton M112 Supercharger Guide

The Eaton M112 supercharger is a popular choice for automotive enthusiasts seeking a significant power upgrade. Known for its roots-type design, it excels at delivering strong low-end torque, making it ideal for street applications and enhancing everyday drivability. This guide delves into the specifics of the M112, its common applications, and provides general maintenance insights applicable to similar supercharger models.

Understanding the Eaton M112 Supercharger

The Eaton M112 is a positive displacement supercharger, meaning it traps a specific volume of air with each rotation and forces it into the engine. This design inherently provides excellent low-speed boost, resulting in improved throttle response and a more engaging driving experience. Unlike turbochargers, which rely on exhaust gases, superchargers are driven directly by the engine's crankshaft, ensuring boost is available almost instantaneously.

Eaton's superchargers, including the M112 and its close relative the M90, are renowned for their versatility. They can be mounted in virtually any orientation – flat, upside down, or on their edge – offering considerable flexibility for custom installations. This adaptability, coupled with the availability of different drive lengths and easily repositionable bypass actuators (in 12 possible locations), makes them a favourite among custom builders and performance tuners.

Common Applications of the Eaton M112

The Eaton M112 has found its way into a variety of high-performance vehicles, both from the factory and as part of aftermarket upgrade kits. Here are some of the most prominent applications:

Jaguar Models

Eaton M112 Gen4 superchargers are most commonly found on Jaguar 4.0L V8 engines. Specifically, you'll encounter them in models like the:

• Jaguar XJR
• Jaguar XKR
• Jaguar Silverstone

These vehicles often feature engines designated as AJ26S or AJ27S, equipped with either an OEM Supercharger Kit or a custom Eaton M112 Gen4 Supercharger Kit.

Ford Vehicles

Ford also extensively utilised Eaton superchargers, including the M112, in several of its performance models:

• 1999 and Up Ford SVT Lightning: These iconic trucks featured the M112 supercharger with a top inlet air configuration.
• 2003 Ford Mustang SVT Cobra: This legendary Mustang variant was equipped with an M112 supercharger that had a side (left) inlet air design. For certain custom applications, particularly those with hood clearance concerns, the side inlet design can be advantageous.
• Ford Harley Davidson F-150: Certain supercharged versions of this special edition truck also employed the M112.

Other Notable Applications and Considerations

While the M112 is prevalent in the vehicles mentioned above, it's worth noting that the principles of supercharger maintenance and understanding their operation apply broadly. The information regarding oil changes for the Eaton M90, for instance, is often relevant to M112 owners as well. Vehicles like the GM Pontiac Grand Prix GTP, Buick Regal GS, Chevrolet Monte Carlo SS, and Chevrolet Impala SS have commonly featured the Eaton M90, and maintenance procedures can share similarities.

For enthusiasts looking at custom builds, such as the 1UZFE engine conversions, the M112 (or its larger sibling, the MP112) is a popular choice. The 1UZFE community has seen manifolds developed to fit various roots-style superchargers. However, it's crucial to consider factors like pulley size limitations due to radiator hose routing on certain engine configurations. For the 1UZFE, a 2.50" pulley is often cited as the smallest practical size to avoid belt slippage and contact issues at higher RPMs. Many recommend the larger MP112 for such applications to provide more headroom for future modifications and to mitigate potential issues with smaller pulleys.

Supercharger Oil Change: A General Guide

Maintaining the proper lubrication of your supercharger is critical for its longevity and performance. While specific procedures can vary slightly between models, the general steps for changing the oil on an Eaton M90 or M112 are as follows:

When to Change the Oil

Supercharger oil is not typically serviced on a fixed mileage interval like engine oil. Instead, it's often recommended to check the oil level and condition periodically, perhaps every 30,000 to 50,000 miles, or if you notice any signs of leakage or unusual noise from the unit. Some manufacturers recommend replacement every 100,000 miles, but regular inspection is key.

Tools and Materials Needed

• Supercharger oil (specific type recommended by Eaton or the vehicle manufacturer – do NOT use regular motor oil)
• Syringe or pump for oil extraction and filling
• Wrench or socket set to remove the supercharger unit (if necessary) or access plugs
• Gloves and rags
• Drain pan (if draining the unit)
• Manufacturer's service manual for your specific vehicle and supercharger

The Oil Change Process (General Steps)

1. Locate the Supercharger: Identify the supercharger unit on your engine.
2. Access the Oil Fill/Drain Plugs: Depending on the supercharger's mounting, you may need to remove other components to gain access. Some units have separate fill and drain plugs, while others might only have a fill plug, requiring the unit to be tilted or drained from the fill port. Consult your service manual.
3. Drain Old Oil: If a drain plug is present, place a drain pan underneath and carefully remove it. If not, you may need to use a syringe to extract as much oil as possible from the fill port.
4. Refill with New Oil: Using a clean syringe or pump, fill the supercharger with the specified type and amount of supercharger oil. The correct oil type is crucial; using the wrong oil can damage the internal components. Typically, around 6-8 ounces of specialized supercharger oil is required, but always verify the exact capacity.
5. Replace Plugs: Reinstall any drain or fill plugs, ensuring they are tightened appropriately.
6. Check for Leaks: After running the engine briefly, check around the plugs and the supercharger casing for any signs of oil leakage.

Important Note: If you are unsure about any step, or if your supercharger requires removal from the vehicle for service, it is highly recommended to consult a qualified mechanic or refer to a detailed service manual specific to your vehicle.

Performance and Upgrades

The Eaton M112, particularly in its 4th Generation Magnuson variants (MP90 and MP112), is known for delivering a significant power increase, often in the region of 40% or more. This boost in performance comes with the benefit of maintaining original equipment quietness and reliability, without a substantial impact on fuel economy under normal driving conditions. For those looking to push the boundaries further, smaller supercharger pulleys can increase boost pressure, but this often necessitates supporting modifications such as upgraded fuel systems, intercoolers, and potentially lowering the engine's compression ratio to safely handle the increased cylinder pressures.

Frequently Asked Questions

Q1: Will an Eaton M112 supercharger fit my vehicle?

A1: Fitment depends entirely on your specific vehicle's engine and the available space. While M112s are found on certain Jaguars and Fords, custom applications require careful consideration of mounting brackets, intake and outlet positioning, belt alignment, and hood clearance. Researching specific swap kits or consulting with performance specialists is recommended.

Q2: What kind of oil does an Eaton M112 supercharger use?

A2: Eaton superchargers require a specific, high-quality synthetic supercharger oil. Do not use conventional motor oil. The exact type and quantity can be found in your vehicle's service manual or by consulting Eaton or a reputable supercharger specialist. Using the wrong oil can lead to premature wear and failure of the internal components.

Q3: How much boost does a stock Eaton M112 produce?

A3: The boost pressure generated by a stock Eaton M112 varies depending on the application and the pulley sizes used. However, typically, they operate in the range of 6-10 psi for most factory installations. Smaller pulleys can increase this figure, but it's essential to consider the supporting modifications required.

Q4: Can I use an M90 instead of an M112?

A4: Yes, you can often use an M90, especially for milder performance gains or if space is a constraint. The M90 is generally suited for smaller displacement engines (3.0L to 5.7L) compared to the M112's typical range (4.6L to 6.0L). However, if you plan on running higher boost levels (above 8-9 psi) or intend to lower your engine's compression ratio for more aggressive tuning, the M112 or MP112 offers more potential and is a more robust choice.

Q5: Where can I buy a used Eaton M112 supercharger?

A5: Used Eaton M112 superchargers can often be found on online auction sites (like eBay), automotive forums dedicated to performance parts, or through specialist salvage yards that focus on performance vehicles. Expect to pay anywhere from $500 to $1000 USD for a used unit in good condition, depending on its origin and mileage.

In conclusion, the Eaton M112 supercharger remains a potent and versatile forced induction solution. Whether found in a Jaguar XKR or fitted to a custom project, its ability to deliver substantial low-end torque and overall power gains makes it a desirable upgrade for many automotive enthusiasts. Proper maintenance, particularly concerning lubrication, is key to unlocking its full potential and ensuring reliable performance for years to come.