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Text and Photography C.Asaravala. Illustrations by Jon Mikelonis.


New technology is cool. Applying new technology to old applications is even cooler. This is especially true with muscle cars. Whenever you take a newer, better, faster, stronger and lighter part and adapt it to an older Ford, you've got to be pleased.

A while back we showed you how to upgrade to a higher output alternator, with the help of a PA Performance 3G alternator conversion kit. (Refer to Keeping Current: Alternator Upgrades in the Ignition section of the Tech Department.) Well PA Performance has another worthwhile modification for your street or strip Ford; the lighter, more efficient, PMGR starter. PMGR stands for Permanent Magnet Gear Reduction, which is different from the Positive Engagement type of starter found on most Ford V8's up to 1993. More on the differences later.

Ford and many other auto-manufacturers started using these high-tech starters in the 90's, in order to achieve a multitude of benefits, including faster starting, less weight and space, and simply a better, more reliable, design that does not demand as much battery power as the older starters.

Positive-engagement Starters (Stock type)
Positive-engagement starters use the armature windings of the starter motor to engage the drive gear. The high starting current is controlled

View a cutaway illustration showing how a stock starter works.
by a starter relay mounted close to the battery. When you crank the motor, the circuit in the relay is then closed, and current flows through the drive coil. The drive coil creates an electromagnetic field that attracts a moveable pole shoe. The moveable pole shoe is attached to the starter drive through the plunger lever. When the moveable pole shoe moves, the drive gear engages the engine flywheel.

While these starters are highly reliable, they are heavy (19-20 lbs. for a typical 302 starter), and they are bulky in size. With long tube headers they can heat soak and not function until cooled. They also demand a large amount of current, which means a hard starting motor can easily drain the battery after a few crank attempts. These starters do not work well with high compression engine due to the lack of torque output from the gear drive.

Permanent Magnet Gear-Reduction (PMGR) Starters
The permanent magnet starter design provides for less weight, simpler construction, and less heat generation as compared to conventional field coil starters. The starter is activated via a heavy-duty, three-terminal, 12V solenoid which draws less current.

Because there are no field coils, current is delivered directly to the armature through the commutator and brushes. The permanent magnet starter also uses gear reduction through a planetary gear set. The

View a schematic of how a PMGR starter works.

planetary gear train transmits power between the armature and the pinion shaft. This allows the armature to rotate at greater speed and increased torque.

The planetary gear assembly consists of a sun gear on the end of the armature, and three planetary carrier gears inside a ring gear. The ring gear is held stationary. When the armature is rotated, the sun gear causes the carrier gears to rotate about the internal teeth of the ring gear. The planetary carrier is attached to the output shaft.

The gear reduction provided for by this gear arrangement is 4.5:1. By providing for this additional gear reduction, the demand for high current is lessened. The electrical operation between the conventional field coil and PMGR starters remains basically the same. Special care must be taken when handling the PMGR starter. The permanent magnets are very brittle and are easily destroyed if the starter is dropped or struck by another object.

 

(Installation)

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In This Article
We discuss the technology behind Permanent Magnet Gear Reduction starters, better known as "mini starters". Also in this article is detailed how-to instructions for installing a PA-Performance min-starter.

Also See:
Keeping Current: 3G Alternator Upgrade
 

PA Performance has PMGR starters for just about any Ford vehicle. At $135 this starter is well worth the weight (8lbs vs. 20lbs) and space savings. Price includes wiring kit and a lifetime warranty.

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