maxbraketorque
NAXJA Forum User
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Here are some airflow rate numbers for two different fan clutches.
Testing conditions:
NAPA 272318 XJ 4.0L fan clutch. This is not the ZJ fan clutch. The 272318 is the same as the Murray 2625 fan clutch available at O'Reilly and Advance Auto. I've been using this fan clutch for about a year now.
I wish I had performed more airflow measurements of the NAPA fan clutch to make a better comparison at lower rpms where fan speed is going to be more important. But that aside, the USMW clutch still clearly much pulls more air at lower rpms. Probably from 1000 rpm upward, the USMW 22148 significantly outflows the NAPA 272318.
I have not tested the NAPA ZJ fan clutch because it won't fit with my Cold Case radiator. However, if I were to guess, I'd say that the USMW creates as much air flow as the ZJ fan clutch at 1000+ rpm. At idle, the ZJ fan clutch likely flows more.
Testing conditions:
- Kestrel 1000 anemometer.
- Front grill removed.
- Hood closed.
- Anemometer placed against A/C condenser at the same location for each measurement. Location roughly corresponds to mid-height of the radiator and about mid-distance between the base and tip of the fan blade extent. I can post a photo if anyone wants to see the location.
- Engine up to full temperature for at least 15 minutes prior to all measurements.
- About 70F ambient air temperature.
NAPA 272318 XJ 4.0L fan clutch. This is not the ZJ fan clutch. The 272318 is the same as the Murray 2625 fan clutch available at O'Reilly and Advance Auto. I've been using this fan clutch for about a year now.
- Idle (about 670 rpm): 560 ft/min.
- 2000 rpm: 1150 ft/min.
- Idle (about 670 rpm): 520 ft/min.
- 1500 rpm: 1300 ft/min.
- 2000 rpm: 1750 ft/min.
I wish I had performed more airflow measurements of the NAPA fan clutch to make a better comparison at lower rpms where fan speed is going to be more important. But that aside, the USMW clutch still clearly much pulls more air at lower rpms. Probably from 1000 rpm upward, the USMW 22148 significantly outflows the NAPA 272318.
I have not tested the NAPA ZJ fan clutch because it won't fit with my Cold Case radiator. However, if I were to guess, I'd say that the USMW creates as much air flow as the ZJ fan clutch at 1000+ rpm. At idle, the ZJ fan clutch likely flows more.