Pontiac G6 -LZ9 3.9L V6 Alternator Isolator Decoupler Pulleys PDF Manual

More and more OEs are recognizing the performance gains achieved with Isolator Decoupler Pulleys (IDPs), and designing them into their vehicles to connect or couple the engine’s alternator to the accessory drive belt. Never use a solid or overrunning alternator pulley on a vehicle designed with an IDP. Downgrading the original IDP will compromise performance and may lead to accessory drive problems. For OE quality and performance, RotoRx® is the only true aftermarket IDP available.

IDPs provide unique levels of vibration isolation within the accessory drive belt system. This results in quieter and smoother performance particularly in more torsionally active engine applications. With its unique internal clutching mechanism, the RotoRx® IDP is able to effectively isolate vibrations through absorption. The clutch mechanism also includes engineered internal damping elements to further control vibrations
and resonances that would otherwise be felt within the vehicle’s passenger compartment. IDPs also include a decoupling feature that enables the alternator to coast freely if the belt speed is suddenly and rapidly decreased, such as during engine shut down or transmission shifting. Besides quieter performance, IDPs allow manufacturers to use narrower belts with lower output tensioners. The lower system tension means the alternator, water pump, and other accessory bearings will last much longer. Here’s how IDPs stack up against other pulleys: The Solid Alternator Pulley used to be the industry standard and has been around for many years. It has evolved from the V type to the V-ribbed type (serpentine belt). Its only purpose is to drive the alternator via the belt. If your alternator has a solid pulley, only replace if damaged, rusted, or worn.

The Overrunning Alternator Pulley (One-Way Clutch) has a simple one-way clutch inside the pulley. This internal clutch allows the rotor of the alternator to coast to a stop when the engine is shut down. This “overrunning” feature eliminates “chirp” sounds that occur when the engine decelerates quickly, causing the belt to slip (engine shut down or transmission shifting).

The Isolator Decoupler Pulley (IDP) not only has a one-way clutch inside, it also incorporates a torsion spring to absorb energy. The effects of the internal clutch are the same as mentioned above; however, the patented internal torsion spring design is the key to the much higher level of function associated with the IDP. The internal spring is tuned (engine specific) to absorb base engine vibrations (cylinder firing pulses) before they reach the alternator rotor and negatively affect the accessory drive. With the IDP installed you will see much less tensioner motion, reduced noise, vibration, and harshness and an all around more robust accessory drive.

What to look for… IDPs should rotate freely in one direction and have a “spring feel” in the other direction. Service life of the IDP is also dependent on the duty cycle, driving conditions (city vs. highway), and seasonal temperature variations. Since these conditions are generally
unknown when rebuilding the alternator, you should always install a new IDP at this time. This will ensure a quality rebuilt alternator and help
eliminate field failures. Never substitute a solid alternator pulley or a simple Overrunning Alternator Pulley in place of an IDP. The vehicle manufacturer has designed the vehicle with this higher level of function for a reason! Substituting a different alternator pulley may cause damage to accessory drive components. IDPs should always be checked when replacing any accessory drive component or every 40,000 miles (65,000 kms).

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