OT: Car radiator fans and HP

Page 3 of 3  
On Sunday, August 31, 2014 3:42:13 PM UTC-4, snipped-for-privacy@snyder.on.ca wrote:

Did the Corvair have a hydraulic fan clutch or is it direct drive? I was raising the point about a hydraulic fan, in which case, the fan isn't connected directly to the engine and *forced* to an unrealistic speed that isn't needed. The hydraulic clutch slips and if the load gets greater, I think it's going to slip more, limiting the top RPM.
If auto fans used such huge horsepower, why do you think the auto manufacturers the world over were so slow to move to electric fans? From what I recall, most cars continued to use them into the 90s Most cars converted over in the 90s, but many still had them past 2000. BMW X5 had it until 2008. Why do some SUVs, many light trucks still use them? If they use 10, 20, 40 hp why didn't the auto makers yank them all out in the 80s? I think it only takes around 50hp to keep a car moving at 55mph. 5, 10, 14 hp is HUGE compared to that. And most of them had auxilliary electric fans in the cars already. Yet all these auto manufactuers the world over, with all their dynos, wind tunnels and far more sophisticated test methods than any hot rodder, no one stood up at a meeting and said I can take MPG from 15 to 25 by removing the fan? We can meet CAFE standards for the next 20 years without spending $5bil to make all kinds of little changes that add up to 1mpg? It just seems to me if it was that big of a hog in typical cars, you would have seen a sudden converion circa 1980. Instead it went on 20 years and in some cases is still going on today? That part just doesn't compute for me.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It probably cost a couple of dollars more for the electric motor than a fan. Gas prices were not that bad. Most of the time the engine was running at 2000 rpm or less , so at slow speeds the fan was not taking that much HP. As it go up with the cube of the speed, it mainly sucked up the large HP at the higher (racing) rpms.
--
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, August 31, 2014 6:23:10 PM UTC-4, Ralph Mowery wrote:

The auto manufacturers were all desperately spending billions to increase MPG to meet CAFE standards that went into effect in the 70s. They were retooling all kinds of stuff, switching to plastic, shaving ounces off of metal parts. So, it's still hard for me to fathom that many cars still had mechanical fans into the 90s and even past 2000 if they used a significant share of HP.
Most of the time the engine was running at

I agree. That's why I've asked about whether those tests, numbers etc were done with say a 1990s era hydraulic clutch, or just a fixed fan with no clutch. I would think there would be a big difference between the two, because the one with a clutch probably won't go to 4500 where the power escalates. It has slip and if it gets harder to turn, you would think it would slip more and not go up as much in speed. It might max out at some much lower speed. Which is kind of what I recall working around cars. If you revved the engine with the hood up, you noticed a pickup in fan speed, but it doesn't seeem to me like it went from 800 RPM to 4500, ie 6X.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 31 Aug 2014 06:01:00 -0700 (PDT), trader_4

From what I read of fluid fan clutches they don't let the fan spin any faster than about 2300 rpm. So that's going to limit the maximum HP draw. The 40 hp does seem like a lot but remember, this is at 4500 rpm so that mechanical fan is really spinning. And if as you say, things go up cubed instead of squared, a direct coupled fan of 5 HP at 1500 is going to be pulling a heck of a lot of HP at 4500.
Just as a reference point, I read from a semi-authoritative source that the old heavy duty GM Turbo-Hydromatic 400 could take as much as 40 hp off the engine output on a dyno. So imagine the drain on power of an older car with the TH400 and a hd mechanical fan when it's at full throttle.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I had a '60 with powerglide and the 80 hp engine. It would have been super nice to have any extra hp, even 5 !!! It was a heck of a nice car though.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 31 Aug 2014 14:32:41 -0700 (PDT), trader_4

Trader, keep in mind that the 40 hp was for a super hd mechanical direct connect fan. Almost NO automakers used such a fan on typical cars. These guys were using it to see what the most hp drain might be. Back in the day almost all non ac cars just had a crappy stamped steel almost flat 4 blade fan if a 6 and a crappy 5 blade fan if a v8. If they had AC they usually had either a fluid clutch (GM and Chrysler) or a flex fan (Ford). And except for when you were "gunning it" to pass or the stop light grand prix these engines were only running 1800 to 2500 rpm unless you got a performance axle ratio. So they might only be pulling 5 - 8 hp most of the time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sunday, August 31, 2014 8:11:58 PM UTC-4, Ashton Crusher wrote:

That was kind of one of my points, that the "test" numbers some are using to justify these high fan HP are not representative of the type of fan under discussion, ie one in 2000 - 2007 BMW X5 or similar. It sounds like some of the companies selling electric fans and the proponents of them may have glommed on to those numbers. The problem is, I haven't seen any test numbers for say a 90s era car or current SUV, light truck that use modern hydraulic clutch fans.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 31 Aug 2014 16:14:20 -0700 (PDT), trader_4

No, they top out at about 2300 rpm.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 1 Sep 2014 05:53:18 -0700 (PDT), trader_4

The only great value I see to electric fans over mechanical with clutch is that they can run at MAX when the car is idling. For some cars that's important, for others it's not. On my 69 firebird I have an electric fan off a big Lincoln. It just runs hot and this works better overall then either the original style fan and clutch or a flex fan.
One of the things I think some people are failing to recognize in their comparisons of electric industrial fans versus these car fans is the industrial fans are not pulling the air thru a honeycomb of a radiator. There is a fair amount of resistance to pulling the air thru that and just as the hp required for the fan being cubed as speed increases, I'm pretty sure the resistance of drawing air thru a honeycomb increases faster then a linear rate as the CFM's increase as the fan speed increases.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

A mechanical fan with clutch is always turning - always. There is no free-wheeling. The electrics in my car hardly ever go on in the winter. The only reason I can think of for using a mechanical fan is the auto manufacturer didn't want to change engine controls, or electrics couldn't keep it cool enough. I don't know how much HP the fan uses. The dyno results I've run across are all over the place. But there's a HP difference in favor of electrics. I never had either type fail.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Sep 2014 18:03:37 -0500, Vic Smith

Yeah, I was only thinking of teh HOT side of things, like a McDonald's DLT.
I've had both fan clutches as well as electric fan motors wear out.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tuesday, September 2, 2014 7:22:00 PM UTC-4, Ashton Crusher wrote:

I agree with Vic and I think you do too. An electric fan can be controlled so that it only runs when necessary, which is only a fraction of the time. I've seen people claiming they have taken out mechanical fans and not replaced them with anything and the vehicle doesn't overheat. I for sure wouldn't do that, but when the car is moving at road speed, winter, etc, the fan isn't needed and the electric can stay off. I also agree that another advantage is that the elec fan can run at max speed when the car is idling. I never doubted that an electric fan could have some advantage, only questioning, like you, how many HP it really adds up to.
Now for an example of how you can go too far, here's what BMW does with their existing auxiliary fan on the E53 series X5. Instead of making it a simple on/off fan, they made it variable speed, with the variable speed electronics in the fan motor. Great idea. Put electronics in a fan that's in one of the worst possible spots, ie heat, road spray, etc. And then they send it a PWM control signal. So now, if the fan isn't working, there is no easy way to diagnose it. You can't just put 12V on it, see if it spins. Neither can you put a VOM on the incoming wires to see if the system is telling it to spin. And for a final good measure, they supplied it with 12V all the time. One of the failure modes is for the miracle fan to create a parasitic draw that drains the battery overnight. It's great for the BMW dealership though, those fans are $500 and a couple hours labor to put in.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 02 Sep 2014 18:03:37 -0500, Vic Smith

Well, you can call that luck. I've had customers' clutches sieze up - so they run full tilt all the tome. I've had then fail that they don't drive and overheat. I;ve had them get so sloppy the fan came off and went through the rad.. I've had flex fan blades crack and come apart. I've had rivetted fixed pitch solid fans loose blades (and come through the hood). And I've had electric fans get so stiff they've burned out the protection fusible link, I've had them totally sieze, and I've haf them get so sloppy the rotor ground away the magnets, as well as having them just plain burn out. I've also seen them get so hot they melted the plastic blade right off at the hub.
That said, Istill prefer the electric fan. (after 46 years experience as a mechanic)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload


have

flex

I put a new fan clutch in my Aerostar a few months ago when I replaced the radiator. Worked fine for a few weeks, then started overheating when idling on a hot day - not every time, just when I'm not watching the gauge. Sure enough, it was failing already. It's such a bear to swap it out, I wouldn't mind putting an electric fan in there this time. I can see wiring fun though. But I wouldn't mind if it ran all the time.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Tue, 2 Sep 2014 21:09:48 -0800, "Guv Bob"

No problem wiring it at all. power wire direct from battery positive, through fuse to relay to motor, and to ground. a temp switch on the rop rad hose if you can't find a place to thread one in (they make them for this purpose) and run power from switched ignition to the relay coil, and from the relay coil to the switch and to ground. Less than 10 feet of wire in total will do the job. You really do NOT want it running all the time. You can connect a second feed to the relayelay, to run the fan when the AC is on (or add a second fan controlled by the AC)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.