Have seen many places here the accolades of replacing mechanical clutch cooling fan with high volume electrical fan. Just bought one yesterday (Imperial). Got to thinking about real vs. percieved benefit. Please clear me up. If the primary purpose of a cooling fan is to cool down the radiator fluid. Then there is no benefit to replacing mechanical with better cooling electrical. The thermostat controls fixing the temperature at 196 F. So it will open/close to maintain that temperature. If the primary purpose is to cool the engine block and accessories, then I see a direct improvement over the mechanical clutch fan(especially at low speeds i.e. idle). Also, claims have been made that there is a 2 - 3 HP gain by replacing mechanical with electrical. I disagree with this. Nothing is free. Either you draw engine power away from torque losses of turning a mechanical fan off the engine, or you draw engine power away from drawing more load off the alternator. If you don't think using all electricals (lights, fans, ....) draws power, open the hood and watch the RPM drop when you turn everything on. The only other benefit to increasing cooling under the hood could be in terms of the a/c evaporator working better with higher rate of air drawn thru it. But I have never really had a problem with cool air.

So.....with all that. Please justify spending $60 - 70 bucks and the time to cross over to a electrical fan.

TIA

The other's have pointed out the pointers, so no need for me to reiterate. However, the cheap route would be to yank one from a GM, as outlined in Turbobricks (link below).

I've done this in both of the wagons ... it helps most on the A/C. I'll be pulling the one out the '86 soon, though, as I'll be selling her.

-- Kane ... who's got some de-Puffinizing to do also ...

The biggest benefit is that when you are moving down the road then you really do not need any fan. Therefore when you go electric, the alternator IS NOT working any harder.

The load on the Waterpump is another good point. That's about it, I don't know if it justifies $60 bucks.

I'm about to do the same... I just hate the damn fan noise. It reminds me of those older rodeos/explorers/etc that sound like they were powered by a box fan instead of an engine. If it does put any more drain on the alternator, I seriously doubt that it would make more of an impact on your horsepower than a mechanical clutch fan.

Also, you know when you rev above 5000rpm, and it just almost stops accelerating? You can really feel this in 3rd/4th. There is too much rotating mass and resistance from the air for the engine to spin any faster. Its almost kind of a mechanical rev limiter :)

Anyway, I'm still gonna keep hunting for the right fan. Does anyone know of a good brand to go with that is really quiet but still cools well? I'm not looking for much improvement over the stock fan, I just want the noise to go away. Far away.

Robin Roemisch

bitjockey@hotmail.com

Asheville, NC

'89 744tic m46 12psi

Matt: Another benefit from going electric is when you ditch the regular fan, the engine noise level drops a lot. i rmn & etc.. Jim A.

In general I agree (no free rides), but I converted when my fan clutch began acting strange. I didn't have some whopping power increase, only a slight power increase at lower RPM, on the other hand I'm going on my third year with no problems. I guess the main thing is when huffing it down the highway and electric fan is off you plain ass are spinning less "wasted mass" (short for less energy used to turn less mass)....

I'll just add one reported beni: supposed to be easier on the water pump without the rotating mass of the fan and clutch...dunno if true but my water pump is still good!!

There is no need to replace your fan clutch with an electric fan. In fact, the clutch fan is more powerful than most electric fans.

The clutch fan is more efficient than the non clutch type fans. Most late model Volvos had the clutch type fan. Horsepower loss is significantly reduced when the clutch is not engaged.

There is still some accessory drag, however. When the engine is making 115 hp at 5500 rpm, it is not very noticeable. When the engine is making 30 hp at 1500 rpm, it is noticeable. Free up 3 hp at 1500 rpm, and you have gained 10% at that rpm range. 10% is about what most people can feel.

When the clutch fan is engaged, the drag would be greater. Probably along the lines of running the AC. Most people can feel the AC compressor sap power.

Plenty of articles in magazines over the years have proven the small power improvements that come from removing the AC belt. There have also been articles on removing the mechanical fan and replacing it with an electric one.

If you want to do some math, you could probably figure out how much power your alternator consumes given your current power needs. Increase that by 15 amps for the fan and recalculate the loss. The extra draw to run the fan will probably amount to about 1 hp at most. You can rig up an alternator cut out that is triggered either by a vacuum/pressure switch or by full throttle. You will run off the battery when it is triggered, but your battery should have a 1 to 2 hour reserve time, and I doubt you could spend more than 2 minutes in boost or at full throttle even under the most exceptional circumstances. If you do regularly make 10 mile top speed runs or climb the Rocky Mountains, you might want to add an over ride switch (and buy a more powerful fan than that $70 Imperial).

I go by the amps on the motor. Anything less than about 12 amps is not very powerful. Look at the heavy duty fan that Volvo used when it converted to primary electric fans in 1992 on the 740/940. It is a two speed fan, but even on low it would handily outperform that Imperial. The Imperial may work for you, particularly if you have the secondary electric pusher fan. There are plenty of people using relatively low power electric primary fans that have not reported cooling problems. Yet, anyway.

Philip Bradley

My 84 UK spec has a conventional fan, no clutch, direct drive. I monitor every drop of fuel and removing the fan, adding an electrical one, manually opperated, made no difference that was measurable. I have left the electrical fan in place as well as the mechanical as extra cooling when towing, not that it needs it.

However the car was noticably quieter without the mechanical fan.

Chris