Supercharger Description and OperationDescription
The Eaton™ M 62 is a fifth generation Roots™-type supercharger. The supercharger is a positive displacement pump that consists of 2 counter-rotating rotors in a housing with an inlet port and an outlet port. The rotors are designed with 3 lobes and a helical 60° twist from front to back. An air bypass valve is built into the housing. The rotors in the supercharger are designed to run at a minimal clearance, not in contact with each other or the housing. The rotors are timed to each other by a pair of precision spur gears which are pressed onto the rotor shafts. The forward end of the rotors are held in position by deep-groove ball bearings. The back end of the rotors are supported by sealed roller bearings.

The gears and ball bearings are lubricated by a synthetic oil. The oil reservoir is self-contained in the supercharger and does not rely on engine oil for lubrication. This oil reservoir is sealed for the life of the unit and is not serviceable.

The cover on the supercharger contains the input shaft which is supported by 2, deep-groove ball bearings and is coupled to the rotor drive gears. The pulley is pressed onto the input shaft and is not serviceable. These bearings are lubricated by the synthetic oil contained in the same reservoir as the gears and rotor bearings.

Operation
The supercharger is designed to pump more air than the engine would normally use. This excess air creates a boost pressure in the intake manifold. Maximum engine boost is 83 kPa (12 psi). Because the supercharger is a positive displacement pump and is directly driven from the engine drive belt system, boost pressure is available at all driving conditions.

When boost is not desired, such as during idle and light throttle cruising, the excess air that the supercharger is producing is routed through the bypass passage between the intake manifold and the supercharger inlet. This bypass circuit is regulated by a bypass valve which is similar to a throttle plate. The bypass valve is controlled by a vacuum actuator which is connected to the vacuum signal between the throttle and the supercharger inlet. Spring force from the actuator holds the valve closed to create boost, and vacuum pulls the valve open when the throttle closes to decrease boost. The open bypass valve reduces pumping loss thereby increasing fuel efficiency.

The solenoid valve attached to the bypass actuator is an electronically controlled, 3-way valve. This valve, controlled by the powertrain control module (PCM), determines whether pressure from the manifold is routed to the bypass actuator or closed off. The valve allows pressure from the manifold to open the bypass valve and regulate boost pressure during specific driving conditions.

Intercooler
The supercharger has an integrated intercooler. Cooling the air enhances the effectiveness of the supercharger. The intercooler uses conventional coolant in a separate sealed system from the engine cooling system. The intercooler system has a radiator, a reserve tank/filler neck, a pressure cap, attaching hoses, and a pump capable of a 26 liters (7 gallons) per minute flow rate. The pump is commanded ON, by the control module, whenever the engine is running.

 

Boost Control System Description
FIGURE Bypass Valve Open(c)





(1) By-Pass Valve Actuator
(2) Boost Signal
(3) Boost Control Solenoid
(4) Boost Source
(5) Supercharger
(6) Intake Plenum
(7) By-Pass Valve
(8) Throttle
(9) Air Cleaner
(10) MAF Sensor
(11) Inlet Vacuum Signal

Boost Control System Operation
FIGURE Bypass Valve Closed(c)





(1) By-Pass Valve Actuator
(2) Boost Signal
(3) Boost Control Solenoid
(4) Boost Source
(5) Supercharger
(6) Intake Plenum
(7) By-Pass Valve
(8) Throttle
(9) Air Cleaner
(10) MAF Sensor
(11) Inlet Vacuum Signal

Operation
Supercharger boost pressure is regulated to prevent engine and drive train damage. When the engine is operating under high boost conditions, the powertrain control module (PCM) limits boost pressure to 83 kPa (12 psi). The PCM disables boost under the following conditions:

• When reverse gear is selected

• When the engine coolant temperature (ECT) is excessively high

• When drivetrain abuse is detected

• When the vehicle is decelerating

• If an intercooler pump failure is detected

• If the intake air temperature (IAT) sensor 2 becomes excessively high

• Under heavy load in first and second gear at engine speeds above 5,800 RPM

The PCM controls boost pressure by using the boost control solenoid. The boost control solenoid is normally an open valve. Under most conditions, the PCM commands the boost control solenoid to operate at a 99-100 percent duty cycle. This keeps the solenoid valve closed and allows only inlet vacuum to control the position of the bypass valve. At idle, engine vacuum is applied to the upper side of the bypass valve actuator, counteracting spring tension to hold the bypass valve open. As engine load is increased, engine vacuum is decreased, causing the spring in the bypass valve actuator to overcome the applied vacuum, closing the bypass valve and allowing the boost pressure to increase. The bypass valve starts to close when the vacuum measures 250 mm Hg (10 in Hg) and is fully closed at 90 mm Hg (3.5 in Hg). When reduced boost pressure is desired, the PCM commands the boost control solenoid to operate at a 0 percent duty cycle. This opens the solenoid valve and allows boost pressure to enter the bypass valve actuator at the lower side to counteract the spring tension, opening the bypass valve and recirculating excess boost pressure back into the supercharger inlet.

Results of Incorrect Operation
An open boost control solenoid control circuit, an open ignition 1 circuit, or boost control solenoid valve stuck open will cause reduced engine power, especially during wide open throttle operation.

The boost control solenoid control circuit shorted to ground, boost control solenoid valve stuck closed or a restriction in the boost source or signal hoses will cause full boost to be commanded at all times and a possible overboost condition during high engine load situations.

A restriction in the vacuum signal hose to the bypass valve actuator or a stuck closed bypass valve will cause a rough idle and reduced fuel economy.

 

Sorry for the size of the pics LOL I am not sure how to make them smaller.

Sean

 

Great post, I'm assuming you got this from the Eaton web page.
I hope this dispells some of the misconceptions some have about the bypass valve. I recieved lots of flack in the past for stating the an SC does not need a bypass valve.
True, without it you could possibly over boost the engine. However, set-up correctly it is unlikely. The stock set-up in my opinion would not hurt the engine on an SS/SC with the valve disabled. The advantage would be the increase in boost at lower rpm sooner, not to mention the throttle respone would also improve somewhat as there would be no time lapse waiting for the valave to close. Also, with the valve disabled the drive train management system would not be able to release boost if it detects a traction problem.

Yes gas mileage will suffer. Yes the reliability of the SC will be reduced. However you would have boost always, which has many benefits on the streets, roadcourses and autocross.
The great advantage to having a blowoff valve in this application (ss/sc) is you could significantly overdrive the SC and regulate the pressure with a valve.

This is technology that makes an SC on modern autos cost effective and reliable.
The bottom line though is A SUPERCHARGER does not need to blowoff pressure, by design!

On a personal note, my SS/SC is parked for the winter and I miss it