Electric fan or not?

22A x 12V = 264 Watts = 0.35HP, call it a 1/2 HP with losses.

If the mechanical fan requires more than 0.5HP the difference is FREE HP

Here is a quote I found regarding a chassis dyno test with a mechanical fan
"First, when I worked for GM, we discovered, on a chassis dyno, that a mechanical fan can draw up to 26 horsepower. Usually something like a seven bladed fan on a clutch, that is...Once the clutch engaged, the hp dropped sometimes as much as 26 hp."

Here is the link:
Two Guys Garage Forum - electric vs mechanical fan


26HP seems very high to me, can't wait to hear from someone who has done a dyno test. Most articles I found indicate 12-15HP

Good link Jeff..Lots of excellent points made for the electric fan there..

I had a look for a wiring diagram. No luck I used a flex a light thermostat fan control with a sensor that goes in the upper rad hose. It had a diagram on the package. Fairley easy. Just depends on the fan controler you choose

Originally Posted by jeffstar

22A x 12V = 264 Watts = 0.35HP, call it a 1/2 HP with losses.

If the mechanical fan requires more than 0.5HP the difference is FREE HP

Here is a quote I found regarding a chassis dyno test with a mechanical fan
"First, when I worked for GM, we discovered, on a chassis dyno, that a mechanical fan can draw up to 26 horsepower. Usually something like a seven bladed fan on a clutch, that is...Once the clutch engaged, the hp dropped sometimes as much as 26 hp."

Here is the link:
Two Guys Garage Forum - electric vs mechanical fan


26HP seems very high to me, can't wait to hear from someone who has done a dyno test. Most articles I found indicate 12-15HP

That is Dynamic Loss. Sustatained loss is much less.

But I agree. I said previously, that you can accelerate the engine quicker with an electric fan.

Any item from a dead stop or low RPM accelerating to a higher RPM at a fast pace will also show a loss of power, or performance. Even an electric fan does not get up to operating speed in 1/4 of a second. It often takes 3 - 5 seconds for an electric fan to get up to speed.

A Chassis Dyno Test is acceleration testing. Yes there is a momentary loss from acceleration. If that loss is averaged out over several minutes, it is barely noticable.

The real test should be, sitting at a constant throttle position, then deactivate the mechanical fan and see if you can measure the differance. My guess is the dyno will not be able to see any differance, but is probably near 2 - 3 HP of operating power at 2500 RPM's (or highway RPM's)
This also depends on the fan type.

This is what clutch fans do, but they have a huge amount of mass. A flex fan does not.

If you have a marginal cooling system, then a mechanical fan is the only way you will be able to cool your engine. and the HP loss is something you must accept.

Another thing that is not taken into consideration, mostly because on a dyno, there is not air movement infront of the engine....

The in-rush of air from a vehical traveling abouve 35 MPH, aids in the rotation of the fan, thus subtracting the amount of power the engine must use to rotate the fan. So that 5,000 - 10,000 CFM'c of air hitting the blades is converted to mechanical energy aiding in the rotational energy.

Think of it like a wind turbine. The wind pushing the blades rotates the blades, thus converting wind energy to mechanical energy converted to electrical energy.

man, mike, almost everything you just said is wrong, haha.

"But I agree. I said previously, that you can accelerate the engine quicker with an electric fan"

This is the one thing you had right, it is accelerating quicker because there is less mechanical drag on it, and there fore it is putting out more horsepower at the same rpm.

" A Chassis Dyno Test is acceleration testing"

Dynos test power output, not acceleration. They have nothing to do with acceleration. You can put a car on a chassis dyno and let it idle, and it will tell you the HP, no acceleration of anything needed.

"If you have a marginal cooling system, then a mechanical fan is the only way you will be able to cool your engine"

My electric fan turns out more cfm than my mechanical fan ever did, and it does this independent of engine rpm. My electric is full speed at engine idle and moving tons of air. My mechanical is at 700 rpm at idle, and moving little air. If you have a crap radiator you will overheat much faster at idle with a mechanical fan. the same is true at speed. My electric fan is spinning faster and moving more air than a mechanical. If I cruised at 10,000 rpm like an indy car, a mechanical might work......

"The in-rush of air from a vehical traveling abouve 35 MPH, aids in the rotation of the fan, thus subtracting the amount of power the engine must use to rotate the fan"

This is true, But I race from a dead stop. At 35mph the amount of air coming through the grill, through the radiator and to the fan blades may help a little, VERY VERY little. hang a big heavy steel engine fan out your window at 35 and see it turn about 20 rpms. If your engine is at 1500rpm at 35, it still has to push the fan to 1480. With an electric fan, mine almost never runs if I am going above 35 and just cruising, so at speed I have ZERO fan to worry about. And if we use your reasoning, my electric is turned off at speed, but the wind is turning it, and a DC motor that is forced to trun is a generator, and you said electricity is power, so my fan, according to your ideas, is making HP, just like your wind generator......

I saw a great mag article online a while back with dyno tests for several different fan setups, stock, flex and electric, but I can't find it now.....

But then again, who the hell am I, I could easily be wrong too.... I doubt either of us is a rocket scientist or physicist. Let the mud fly....

So odd ball what typ of gas mileage are you getting from that Psycho Fairlane

The real beauty of the electric fan is that it is divorced from engine speed. This means that you can have a slow, burbling idle while stuck in traffic and still move plenty of air. This also means the fan can stay off when you are headed down the road and don't need the fan to move air through the radiator. Since (hopefully) you are moving down the road most of the time, you save gas and have more power available most of the time with an electric fan.