1985_K5_Silverado
1/2 ton status
I'll just let that last one stand on its own.
CK5
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Shroud or no shroud
- Thread starter Kyle Strong
- Start date
Quackaddict
1/2 ton status
forget it
Wasn't trying to start a problem or be dumb. Guess it depends on your alternator output and what kind of battery you are running. I don't know I was just trying to put an urban myth to rest or see if it was true. I am obviously not the only one who has heard this. forget I said anything.
Wasn't trying to start a problem or be dumb. Guess it depends on your alternator output and what kind of battery you are running. I don't know I was just trying to put an urban myth to rest or see if it was true. I am obviously not the only one who has heard this. forget I said anything.
chevyin
1/2 ton status
IMO its most likely true. The mechanical fans draw a load on the motor that's constant (well almost, clutch changes things) and is always drawing a load on the motor, whether it needs it for cooling or not, where as an electric fan has the battery to draw from in peak conditions and the alternator can make up the difference once the peak draw is lowered. Electric fans generally work off of a thermostat, hence they only work/draw a load when the extra cooling is actually needed (more efficient over time). Have I ever tested this theory? No. But I wouldn't just assume an electric fan draws the same amount as a mechanical unit.
It's been proven that a clutch fan takes less than 5HP to spin. (I'd have to guess this is not engaged, either way it's not much) I guarantee a good set of electric fans can suck that much out of the alternator. 
The key is to stick with a CLUTCH fan, and not a flex fan, and that the clutch is locking and unlocking as it should.
The key is to stick with a CLUTCH fan, and not a flex fan, and that the clutch is locking and unlocking as it should.
chevyin
1/2 ton status
Seems strange then that drag racers who want as little auxilliary drag on their motors as possible tend to run as much electric as possible (including electric water pumps). Are they just not running alts and recharging the batteries between each pass?
It also seems weird an electric unit, which only runs when its actually needed, would end up being less efficient over time.... unless you have a grossly over-sized electric fan setup, which isn't the fault of it being electric. Even a grossly over sized mechanical fan would draw more HP than is necessary. Also, with the clutch disengaged, a mechanical fan still takes some draw off the engine. When an electric fan is off, there is zero draw on the engine.
Again Im not sure, not trying to be the expert here, just seems logical to me.
It also seems weird an electric unit, which only runs when its actually needed, would end up being less efficient over time.... unless you have a grossly over-sized electric fan setup, which isn't the fault of it being electric. Even a grossly over sized mechanical fan would draw more HP than is necessary. Also, with the clutch disengaged, a mechanical fan still takes some draw off the engine. When an electric fan is off, there is zero draw on the engine.
Again Im not sure, not trying to be the expert here, just seems logical to me.
I know that circle track racers run electric fans with no alt. Drag racers can and probably do, but a more likely reason is that they can turn them off when they make a pass, eliminating any losses from the alternator (or a clutch/flex fan) powering them, yet still have cooling after and before the next trip down the track.
There is no question that OFF the electric fan would take less energy from the motor, but if a clutch fan is as effective (and more in some cases) without any wiring, and a power drain of 5HP, an application where you are talking tenths and hundredths of a second is the only way you would notice the difference.
Other problem is that without extensive cost (testing) how do you determine the perfect amount of fan for your motor? No one knows what the factory fan moves CFM-wise, so it's pretty hard other than to just go overboard on the electric fan size to make sure you don't have too little cooling.
Note that many people just wire up the electric fans to stay on all the time, whether needed or not, so the efficiency aspect there is wasted.
Also note that all GM trucks to my knowledge are STILL clutch fans, while cars are not, and haven't been for some time. Even in this day and age of penalties for economy, emissions, and factory power rating wars, clutch fans still have a place in trucks.
There is no question that OFF the electric fan would take less energy from the motor, but if a clutch fan is as effective (and more in some cases) without any wiring, and a power drain of 5HP, an application where you are talking tenths and hundredths of a second is the only way you would notice the difference.
Other problem is that without extensive cost (testing) how do you determine the perfect amount of fan for your motor? No one knows what the factory fan moves CFM-wise, so it's pretty hard other than to just go overboard on the electric fan size to make sure you don't have too little cooling.
Note that many people just wire up the electric fans to stay on all the time, whether needed or not, so the efficiency aspect there is wasted.
Also note that all GM trucks to my knowledge are STILL clutch fans, while cars are not, and haven't been for some time. Even in this day and age of penalties for economy, emissions, and factory power rating wars, clutch fans still have a place in trucks.
mouse
1/2 ton status
Back when I was drag racing every weekend, I would turn the cooling fans off as I was staging the car. The air over the rad during the run would be sufficient. While waiting in line for the burn out box, a friend would use a bug sprayer to spray the rad with a mist of water, and when the engine ran the fans would be turned on as well. If I had run an electric water pump, I would not have used it during the race, only staging and the return trip after the race.
chevyin
1/2 ton status
While many people may do this, its certainly not as intended, or correct. Its not really fair to compare a clutch fan to an electric fan when the electric fan is installed improperly (always on). It would be like comparing to a clutch fan with a seized clutch.dyeager535 said:
I really dont have any evidence to back up my opinion that electric fans are most likely more efficient, just seems logical to me. So I'll just say we can agree to disagree until I see some evidence one way or the other.
Im heading off to see the g/f now, but maybe tomorrow ill do a little research on the subject and see what I can find out.
1985_K5_Silverado
1/2 ton status
Here's how we used to hash things like this out many years ago, in engineering college, before we actually hung numbers on everything.
We can use an engine
to drive a belt
that drives a clutch fan
which pulls air through a radiator to cool that same engine.
or
We can use an engine
to drive a belt
that drives an alternator
which creates electricity
that drives an electric motor
that drives a fan
which pulls air through a radiator to cool that same engine.
Then we'd go about hanging numbers on those things, which would include comparative cost of building the systems, in addition to operating and maintaining them. That can get pretty complex, and I'm not motivated to do it.
We can use an engine
to drive a belt
that drives a clutch fan
which pulls air through a radiator to cool that same engine.
or
We can use an engine
to drive a belt
that drives an alternator
which creates electricity
that drives an electric motor
that drives a fan
which pulls air through a radiator to cool that same engine.
Then we'd go about hanging numbers on those things, which would include comparative cost of building the systems, in addition to operating and maintaining them. That can get pretty complex, and I'm not motivated to do it.
If we talk about efficiency (the same thing as "power lost"), the question is how much total energy each setup requires, assuming that both setups get the job done. This depends on the weather, so an electric setup wins big in cold climates.
Being that 1HP is 745W, 5HP is like a draw of 275 Amps from the alternator. Does this put things into perspective?
The drag from a mechanical fan depends on temperature, clutch condition and engine speed, so there's no way we can assign it a fixed number. What we need is some kind of average based on weather.
While the electric wastes some energy in the conversion from mechanical to electric power and back again, there is probably more waste in the mechanical clutch. It is transmitting some torque and also slipping, which is going to produce a lot of heat (waste energy).
For a given airflow (cfm), it should take about the same amount of energy, regardless of the fan technology. However, the electric fan will always have an efficiency advantage since it can run only when needed. It also gives you better cooling at idle (i.e. cold A/C air at stoplights). At higher engine speeds, the mechanical fans are generally MUCH more powerful.
Being that 1HP is 745W, 5HP is like a draw of 275 Amps from the alternator. Does this put things into perspective?
The drag from a mechanical fan depends on temperature, clutch condition and engine speed, so there's no way we can assign it a fixed number. What we need is some kind of average based on weather.
While the electric wastes some energy in the conversion from mechanical to electric power and back again, there is probably more waste in the mechanical clutch. It is transmitting some torque and also slipping, which is going to produce a lot of heat (waste energy).
For a given airflow (cfm), it should take about the same amount of energy, regardless of the fan technology. However, the electric fan will always have an efficiency advantage since it can run only when needed. It also gives you better cooling at idle (i.e. cold A/C air at stoplights). At higher engine speeds, the mechanical fans are generally MUCH more powerful.
1985_K5_Silverado said:
Cost is always a good question. If you save .1MPG (or whatever the number is), how many miles do you drive to recover the $500 from a nice flex-a-lite dual high-speed fan/shroud combo?
chevyin
1/2 ton status
The big flex-a-lites Ive seen/bought cost about 400, not 500, and come with a built-on shroud. But yeah, its a large expense.
Thanks for the insight Blue85, yes your comments help put things into better perspective. Only thing Im wondering is how we could determine how engine speed affects the mechanical system's cfm abilities. The flex-a-lite I installed on my dad's truck a while back is rated at 4600 cfm. Id be surprised if a mechanical could do that much, even at higher RPM's. But then again, it comes down to is that much even really necessary too.
Again, thanks for the comments, I think you hit the nail on the head for the most part.
Thanks for the insight Blue85, yes your comments help put things into better perspective. Only thing Im wondering is how we could determine how engine speed affects the mechanical system's cfm abilities. The flex-a-lite I installed on my dad's truck a while back is rated at 4600 cfm. Id be surprised if a mechanical could do that much, even at higher RPM's. But then again, it comes down to is that much even really necessary too.
Again, thanks for the comments, I think you hit the nail on the head for the most part.
mo
1/2 ton status
the stock dual electric fan setups on my camaros will keep the temp down if you make them run when you want them to, either through chip mods or adjustable fan relay. These cars have always ran hot in my experience and i don't see why they would not work perfectly fine in a blazer as long as your cooling system is in decent shape. This setup would pry set you back $25 from P&P, well worth the attempt atleast in my mind before spending 4-500 on a flexalite setup...
adjustable fan realy is $50-60
adjustable fan realy is $50-60
dyeager535 said:
The fact that GM cars now run electric fans while trucks use mechanical may have more to do with transverse vs longitudinal engine mounting. The cars with longitudinally mounted engines have other packaging issues that make the electric fans desirable as well. This seams to point in favor of the mechanical fan, but proves nothing.
broc944
1/2 ton status
I have had this for about a week now.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLX%2D290&N=115&autoview=sku
It runs only for a very short period of time, drops the temp like a rock, almost to much in my opinion. I read a ton of stuff on electric fans. I do not have any hard numbers on gas mileage or horsepower, I am just glad I did not go the junkyard route with the electric fans.
If you can afford this setup I would try and go with it. I have the capability to have the fan controller automatically run the fans, or I can shut them off for high water crossing, or I can turn them on manually (The only reason I can think of this would ever be needed is if the temp. sensor fails) Yes this setup cost some money, but not only are you getting powerful cooling fans, but you are getting Variable Speed Controller that takes the headache out of the whole system.
They also make the coolest ass sound when they start up and shut down, sounds like a X-Wing fighter from Star Wars
.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLX%2D290&N=115&autoview=sku
It runs only for a very short period of time, drops the temp like a rock, almost to much in my opinion. I read a ton of stuff on electric fans. I do not have any hard numbers on gas mileage or horsepower, I am just glad I did not go the junkyard route with the electric fans.
If you can afford this setup I would try and go with it. I have the capability to have the fan controller automatically run the fans, or I can shut them off for high water crossing, or I can turn them on manually (The only reason I can think of this would ever be needed is if the temp. sensor fails) Yes this setup cost some money, but not only are you getting powerful cooling fans, but you are getting Variable Speed Controller that takes the headache out of the whole system.
They also make the coolest ass sound when they start up and shut down, sounds like a X-Wing fighter from Star Wars
.
chevyin
1/2 ton status
Yep, that's the same setup I installed in my dad's truck. I was very impressed with all the highlights you just mentioned, and am now planning on buying one for the K5 and the chevelle. The way I look at it, I have alot of money invested in the engines (especially for the velle), paying some bucks for an almost fail-safe cooling system is like buying insurance and longevity for the drivetrain.broc944 said:I have had this for about a week now.
http://store.summitracing.com/partdetail.asp?autofilter=1&part=FLX%2D290&N=115&autoview=sku
It runs only for a very short period of time, drops the temp like a rock, almost to much in my opinion. I read a ton of stuff on electric fans. I do not have any hard numbers on gas mileage or horsepower, I am just glad I did not go the junkyard route with the electric fans.
If you can afford this setup I would try and go with it. I have the capability to have the fan controller automatically run the fans, or I can shut them off for high water crossing, or I can turn them on manually (The only reason I can think of this would ever be needed is if the temp. sensor fails) Yes this setup cost some money, but not only are you getting powerful cooling fans, but you are getting Variable Speed Controller that takes the headache out of the whole system.
They also make the coolest ass sound when they start up and shut down, sounds like a X-Wing fighter from Star Wars
Its fun watching the temp gauge drop so fast you can see it move. Dad's rarely runs more than 10-15 seconds, and that's only at 60%.
garlicbreath
1/2 ton status
Look into the electric fan setup from a 98+ Panther IE crown victoria, grand monkey, town car. They are by far the biggest factory electric 2 speed fan I have ever seen. Keeps the bacon cool while waiting for speeders in 110 degree heat with the AC on.
