Knowing how fast the alternator is spinning can be very important
with the low idle speeds on modern vehicles. To figure this out you
need to determine your pulley ratio. This ratio is the diameter of the
crankshaft pulley divided by the diameter of the alternator pulley.
You'll need your alternator pulley diameter and your crankshaft
pulley diameter that the drive belt contacts.
To help you figure this out, all PennTex alternator pulleys have the
part number etched on the front of the pulley. That part number
is the "PX" number listed in the alternator pulley diameter column.
Once you know your pulley ratio, multiply that number times the
engine RPM to get the alternator RPM. For instance, an engine
with a PX-1128 (2.3") alternator pulley and a 6" crankshaft pulley
equals a pulley ratio of 2.61. 2.61 times an engine speed of 700
RPM equals 1827 alternator RPM. Match that number with the
alternator rotor RPM charts in the alternator section to see which
PennTex alternator will be best for your application. For further
information, call us at 877-590-7366.
|
Pulley Ratio Chart |
|||||
|
Alternator Pulley Diameter |
Crankshaft Pulley Diameter |
||||
| 6" | 6.5" | 7" | 7.5" | 8" | |
|
1.9" (PA-4008) |
3.16 | 3.42 | 3.68 | 3.95 | 4.21 |
|
2.0" (PX-1353 PX-1346) |
3 | 3.25 | 3.5 | 3.75 | 4 |
|
2.2" (PX-1238 PA-4024) |
2.73 | 2.95 | 3.18 | 3.41 | 3.64 |
|
2.3" (PX-1128, PX1129, PX-1130 PX-5570) |
2.61 | 2.83 | 3.04 | 3.26 | 3.48 |
|
2.35" (PX-1155) |
2.55 | 2.77 | 2.98 | 3.19 | 3.40 |
|
2.4" |
2.5 | 2.71 | 2.92 | 3.13 | 3.33 |
|
2.5" (PX-1355) |
2.4 | 2.6 | 2.8 | 3 | 3.2 |
|
2.7" |
2.22 | 2.41 | 2.59 | 2.78 | 2.96 |
|
3.0" |
2.0 | 2.17 | 2.33 | 2.5 | 2.67 |
|
3.25" |
1.85 | 2 | 2.15 | 2.31 | 2.46 |
If you find that the alternator speed at idle speed RPM may not be enough
to keep your batteries charged, consider a PennTex High Idle system.
It automatically raises your engine RPM when it senses low voltage
at idle with the vehicle in Park.
Click For Printable Pulley Ratio Chart
©2006 PennTex Industries, Inc.