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. 
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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.
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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.
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 (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
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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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