lionelhutz

I find the claims that you're stuck somewhere or need a tow if the electric fan fails rather funny. I'm not worried at all about getting stuck somewhere if the electric fan fails. The car is fine unless it's stopped. As long as I can get rolling 20-30mph again before the temps climb too high it will cool back down just fine.

AboveTheLogic

I had my junkyard electric fan fail, made it home 10 miles away with no issue. As a precaution, I killed the engine and coasted as much as I could. I could have gone farther. I didn't have the courage to try to get on the freeway, though.

aussiejohn

G'day,

lionelhutz, diehrd and AirBusPilot between them have provided the correct answers to the OP, which is what he asked for in the first place. While some of you have given your own opinions WITHOUT any real data to back it up, the three members above have.

It's a bit like the argument about the two main types of steering; almost every manufacturer of highway cars has followed the post war Morris Minor and switched to rack and pinion steering. Is it better than worm and sector? Who knows, but most serious off road cars or SUVs plus ALL trucks and buses have stayed with W&S. R&P is generally lighter, more compact and CHEAPER to manufacture than a W&S steering box.

Regards from Down Under.

aussiejohn

hugie82

This is my 82 with the old style Flex o lite dual fan set up. Now summit sells it under their name. The clutch fan does suck a good amount of torque when hot but it's more how fast the engine revs is where you notice it the most. When you here of guy switching to aluminum flywheels, it's very similar to there results. You will feel it off the line, a much quicker punch when you hit the gas and burn outs will be easier. The stock alt is 82 amp and it's good enough to work but it can be over taxed in situations. A heavy rain on a hot day with the AC , wipers , headlights, blower and hitting the breaks in traffic. Your volts will drop to 11 volts. A newer CS130 amp alt conversion is common and is easy to fit DB electronics is a good source. Durangoboy had a good thread on it but he was kicked off here awhile ago. His thread might come up in a search. I haven't done it yet but when this alt goes, I will.

69427

I disagree on multiple points.

Every fan test I've ever seen was done when the engine was going ZERO mph. All I care about when the engine (and obviously the car) is going zero mph is cooling ability.

Secondly, those of us who track our car think in three dimensions. The fan weight (whether mechanical or electric) has to be accelerated, decelerated, and cornered. Electric fans, and the larger alternators to drive them are generally heavier than mechanical fans (My alternator weighs 7 pounds, my mechanical fan weighs about 12 ounces IIRC, and the shroud is a couple pounds additional). I have more than enough horsepower. What I don't have in excess is cornering or braking ability. My vote is for the lighter components, as the fan system isn't doing any cooling contribution at speed anyway.

Thirdly, what's the dynamic drag/load of the fan at speed? An electric fan just coasts, causing a rotating obstruction to the air trying to go through the radiator, potentially reducing the efficiency of the radiator. A mechanical fan is turning, and also farther away from the radiator, which should cause less dynamic obstruction of the airflow.

What's the power required to turn a mechanical fan at high engine speed while high speed/velocity air is intersecting it? I don't believe anyone knows. If the air exiting the radiator is going faster than the fan "pitch", then the air is putting energy into the fan, and it is a net power increaser. Does this happen? I don't know. It's possible in correctly designed aircraft cooling systems for the air to exit the radiator at accelerated speeds. If the fan is turning "faster" than the air, then the air gets accelerated backwards (consuming power from the engine, a negative), but the accelerated air is thrust, and the fan helps pull the engine (and car) forward. Is this amount significant? Again, I don't know. What I do know is that no one tests fans in a real world situation. It's always at zero engine mph.

My point is I don't believe there's a single correct answer for every car and every situation.

lionelhutz

Both the claims the fan could be a net power adder or that it adds thrust to the car are rather funny....

I'd think not using HP to drive the fan and applying the HP to the rear wheels instead would be a much more efficient use of the HP than expecting the fan to pull the vehicle down the road.

69427

Can you quote a law of physics that says any of the previous statements or questions are invalid?

lionelhutz

How about you provide any proof it happens in a vehicle. You're the one making the silly claims about what a fan could do in a vehicle, so you are the one responsible for backing those claims up. You can't throw out a silly theory and then require someone else to prove it's not true.

69427

I didn't invent any theories here. (And I don't care what you think is funny. I'm an engineer, not a comedian.) I just related common instances of what happens in different aero situations. I'm still waiting for an example of what I posted that was a violation of any law of physics.

Do you disagree that NOT ONE fan test published in any car magazine takes into account that the car (and engine/fan) actually moves against relative air motion/velocity when on the road/track, and that sitting still in a dyno is an apples to oranges comparison?

Gotta go run some errands. I'll check back in later.

lionelhutz

The fan being a "net power increaser" violates the first law of thermodynamics making it a completely ridiculous claim.

You still want to claim the fan will help pull the car down the road or track better than just using the engine power directly coupled to the wheels?

ajrothm

I've tested this on a chassis dyno. A 7 blade fan with a Hayden 2799 clutch killed 15rwhp with the water temp at 180*. That was making 3 pulls with the fan and 2 pulls without the fan.

I agree an electric fan WILL eat up some power due to the load on the alternator, however much of the time, the fan will not be on. Drag strip action, fan won't likely be on (if you cooled the engine down the way you should have), highway rolls- the fan won't likely be on. Electric is definitely more efficient, it cools better and makes the car much easier to work on.

Lincoln MKVIII fan is my fan of choice.

slickfx3

why the extra fan, i just saw it it looks big enough, what is it for?

69427

I don't recall anyone saying that a fan is a better method of motivation than the rear wheels. However, on occasion when I do an autocross for amusement it's been my experience that any engine horsepower over 300 is essentially a waste in that endeavor. With the low speeds and torque multiplication of the lower gearing used, it's impossible to get two rear tires to fully use all the power that a high perf engine might have. I'm more than happy to use up some of that excess horsepower in any fashion that will help accelerate the car. If the fan helps in any way, I'm happy.

Again, my earlier point was that there are no credible tests of what power is consumed in a mechanical fan in actual use (when a car is actually going down the road), nor do I see much discussion of what power it takes to accelerate the added mass of a higher output alternator and electric fan, nor the impact of having to decelerate and change direction of the car with this added mass up front.
For a DD or show car, none of this matters. For those of us who like to track our car, it does matter.

As I mentioned earlier, there's no single right answer for every application.

terry82

if motor over heats it kicks on .when you have ac on, in traffic, on a hot day you may need that extra fan.

speedreed8

but the sensor was set at around 238°.

terry82

you can buy lower temp sensors or put in a switch.

slickfx3

i know i can't going into the file and adjust the temps to turn on, i can't buy different rated sensors?

so you are saying bypass the sensors and manually switch it on?

how about removing the manual fan and have the aux fan perform all the cooling duties?

Haggisbash

Does the under hood temp increase with a fan that is sometimes off? the engine compartment gets so hot I figured the mechanical fan was a help to keep the air moving under the hood. do those that run electric fans that cycle on-off notice any difference in the engine compartment heat?

terry82

put in lower temp sensors or put in a switch .if you run just the fan its very loud .

jb78L-82

GM added the auxiliary electric cooling fan to the 79 L-82 AC heavy duty cooling cars since the 78 L-82 AC cars like mine ran routine temps of 225 with no AC on and 240-245 with the AC running. They had to do something about the extremely high coolant temps and the auxiliary electric fan was the solution in conjunction with the mechanical fan and used through 82.