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TJ cooling: A discussion

Jeep Cooling Systems...a question of balance

That said if you have any cooling issues the e fan may or may-not help. Especially if we assume the mechanical fan/clutch is working properly to begin with.

As for horsepower gains, well not really. There is no gain just a freeing up of what is already there. BUT, there is NO free lunch, remember it takes electricity to run the fan and the more required the harder the engine has to work to generate it.

E fans draw Amps and a quick look at the Flex-a-lite lineup of e fans shows the max amount of amps for any e fan at 28 amps.

 1 horsepower = 745.69 watts

If the e fan draws 28 amps then it takes about .45 HP to run it, which certainly could free up some HP over a mechanical fan. But if the m fan is clutched so as it can free wheel when not needed then the savings drop dramatically.

The m fan (clutched) does not run unless the temp raises enough to lock up the fan, yes the e fan does same so that is a wash. On the other hand the e fan does not require as much HP as it takes to drive the m fan, but then the m fan will cool quicker since it draws more air.

What we don't know is the cost (HP) of the m fan and how much CFM it can pull...suffice to say, it is LOTS! In fact far more than the e fan.  But that is ONLY when it is engaged, which should be a fairly rare occurrence.

Conclusions: 

The e fan will most likely, under most circumstances cool as well as the m fan, free up a few HP and often result in a small increase in MPG.

If cooling needs are heavy duty then its the trusty m fan to your rescue. Yes you may need to up the ante by going to a 7-blade setup and a HD clutch but you can bank on the m fan to keep you cool when e fans cannot.  The e fan just cannot pull the CFM under extreme heat loads whereas the m fan can.

E fans are very inefficient under load. Electrical motors have 100% of their torque at "0" rpm and it drops off from there. The m fan, when locked via the clutch is going to pull some serious CFM under load, as it is engine driven rather than electrical. Flex-a-lite offers an entire line of of HD and "racing" grade m fans and as we know, Flex-a-lite is just not blowing hot air.

Finally as many of you know and gave me advice I wrestled with this issue for the first 2 years I lived in the Phoenix area. My Jeep ran hot regardless of highway or city, rock crawling or not. I had to drive sans AC and run 91++ octane and even then I had pre-det on the highway.

My research and speaking with a lot of folks told me e fans were not the solution. But the answer was a 3 part one:

*  Remove headlight trim rings

*  Install hood vents: 

 *  Install the OEM 7 blade fan and HD clutch:

PROBLEM SOLVED! AC on, burning 87 octane while pulling a loaded trailer highway or off road.

The E fan:

Model 485 Flex-A-Lite.

Fan RPM @13.5VDC. 2450.

Airflow-Cu. Ft./Min. at 0º Static Pressure, 3300.

Amp Draw. 18.

Now for the "rub". The fan pulls 3,300 CFM at ZERO static pressure. But the pressure in a fan shroud and pulling air across the fins of a radiator reduces this by some amount. The result is the CFM is reduced thru this parasitic loss. The e fan depends on your vehicle going down the road at speed to off set this parasitic loss. In other words if you are not jamming air into the radiator the e fan is gonna let you down.

Remember max torque for the e fan is at zero rpm and goes down from there. The belt driven fan which pulls its CFM has very little parasitic loss since it is engine driven and in the case of a Jeep has access to a couple of hundred lbs of torque/HP which it shares with other requirements.

But lets not forget that the majority of autos today use electric fans, there is a reason for this. Better mpg, more hp-less drag on engine and better-designed cooling systems.

I would say that no matter how you view it the e fan (meaning a good quality unit like a Ford Taurus or the Flex-a-Lite) will give you little more more bang for your buck than a mechanical one.  But only you can decide if it is worth the extra money involved.

That said I feel if you are battling heating issues like I have and really need some serious CFM flow then the OEM 7 blade w/HD clutch is your answer...But I would not add it if I didn't have a problem.

Click here for Page 2>

Further reading:  OEM 7 blade fan/clutch install>

and Cold Air Fab Parts I & II>

and Hood vents install>

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