I can't remember seeing a car with a belt driven fan (in recent years)! I h ave a 20yr old Saturn and a 13yr old Buick...they both have electric motors that are only on if the car idles for a long time. Personally, you are not the kind of person that can let things go...you like to beat it to death.. .you need another hobby or possibly a woman/man.
Back in trade school in the early seventies we had a dyno - at4500 RPM a Slant Six made 11 more HP to the rear wheels with the fan removed (and a big box fan providing wind-tunnel-like airflow to cool the rad)That was a rigid steel fan with something like 5 blades. What you need to remember about the belt is it just has to handle TORQUE. 15 ft lbs at 4000 rpm is 11.5 HP, and it is a VERY wimpy fan belt that will not transmit 15 ft lbs of torque. At 2000 RPM that is only 5.7 hp
At anything over about 20 MPH most vehicles will cool adequately without a fan unless you are working them hard like pulling a trailer. I don't think the fan was on for more than 20 minutes driving the loaded PT cruiser from Kitchener to PEI and back with 4 adults and a load of luggage.
240Z had them for sure. There were a few other models too - I'm sure at least one high output American beast.
Just did a little bit of investigating, and assuming 4000 cfm (heavy duty cooling fans will often excede this), and 14" static head at 80% efficiency, the fan WILL draw 11 HP according to the calculator at
I am not talking about those homeowner models, I mean a real commercial air compressor. (hence saying 240v @ 30a )
First question is, did that fan have a hydraulic clutch? If not, then it's forced to run a full engine speed, with no slip, which makes a huge difference.
Why 4000 CFM? The electric fans that the gear heads are using to replace mechanical fans are generally about half that. So, what basis is there to use 4000 CFM for a typical auto fan? Where did the 14" static pressure come from? Seems extremely high, probably an order of magnitude off for a fan/radiator combo. It's not driving air through some long duct work. And also at 60MPH, air is being rammed into the fan by the movement of the car, which would drastically reduce the HP required to turn it. As it would in your static car test.
Here is what a 5HP fan looks like:
The issue I brought up is people are doing these fan conversions to cars *today* that have smaller, plastic fans, hydraulic clutches, etc. And they are using the alleged 5 to 15hp numbers to justify it.
some info here..
Also some interesting test results here
If I'm reading his write up correctly, at 4500 rpm a bolt on super HD mechanical fan can take 40 HP !!! A flex fan takes only 20 at 4500 rpm. On presumes that at slower rpm the HP drain is much less and goes down/up as the square of speed. So I'd presume at 2250 rpm the respective draws would be 10 hp and 5 hp, which seems in line with "normal" engine speeds and what people tend to think these fans draw in "typical" use.
That was a good find. It's the first actual real test data that I've seen. Some observations:
The HP required actually varies by the cube of the speed, not the square. So how fast the fan is actually spinning is critical. From what there is in the test description, it appears that only one of the fans had a clutch. He describes it as a Yearwood 9189N thermo clutch, I couldn't find anything on that. So, we don't know is it a relatively recent hydraulic clutch or an old design? I would think newer clutches might attempt to limit the top speed of the fan? He also says it was behaving erratically, IDK what effect that had on the test. But you can see the effect a clutch and what it does can have on the results. The clutch reduced the HP used when cold to 19hp from 35hp when it was hot and presumably fully locked up. If a more modern, better clutch also limited the high end, so the fan can't run full speed at 4500, that would make a big difference. I haven't seen anything definitive on what clutches used in later year cars actually do, if anything to limit speed. Everyone seems to agree that they have a lot of slip when cold, less slip when hot. How they perform versus speed, I couldn't find anything.
Also a major difference in this test versus the real world, is this was stationary. A car doing 2500 RPMs would typically be cruising at highway speeds. In that case, air is being forced into the fan. I would think it would act like a windmill. Windmills don't need power to run, they generate power.
I still don't know what to make of this. Most of us have an idea of what 20 or 40hp is, what a motor that size is, what it can do, etc. It just doesn't compute to me that it could take anywhere near that much to run an auto fan with a decent hydraulic clutch. It also doesn't compute that auto makers have been struggling for decades to get mileage up to meet CAFE standards and to make their cars more competitive. Switching to an electric fan is almost trivial. It's hard to believe that you had this huge, low hanging fruit there and it's only in the last decade or so that you've seen a big move to electric fans. Case in point, the discussion that involved this was BMW X5s, they used a mechanical plastic fan with a hydraulic clutch until 2008.
Doubt automakers are doing much research on better fan clutches. Aside from your example, mot are using electric for the past 30 years. Every car with FWD and transverse mounted engine uses electric. I had an '83 Mercedes 300D and it had electric.
If a fan can use 40 hp, it is no wonder the used air cooling for the 36 HP Volkswagen. Oh, wait, it had a blower whee.l
I doubt they are today either. But you would think in the 80's through
2000 when they were still widely used, if the fan was using 20 -40hp, they would have. And it's still an issue today, some SUVs, many pickup trucks apparently still use them.This 20/40hp thing is just astonishing. The HP to keep a car or SUV going at 55MPH is what? Maybe 50hp? I just find it impossible to believe that those fans were/are sucking up 10/20/40 hp. If they were you could have gotten ~2x increase in fuel economy in 1980 by going to electric. That's HUGE. Instead the transition took decades, while they were squeezing .1mpg out of small stuff, desperately shaving a pound off here and there?
Aside
You recollection is different than mine. I recall cars replacing mechanical fans with electric during the 90s. With many cars, those probably not the majority, still using them in the early 2000s.
Every
You might want to check your memory on that....
They list a fan clutch for the 83 300D. Are you confusing the auxilliary electric fan with the mechanical one? That car had both.
Talking about air cooling - the fan on a Corvair, which is actually a centrifugal blower, not a fan, consumes 14 HP at 4000 RPM pushing about 1450CFM at 7" water pressure through the cooling fins. The horsepower goes up significantly when the speed is increased to 4800 RPM and higher.
What memory? I remembered the electric since it had to be replaced.
I had a '62 Corvir Monza and it would have been nice to have that 14 HP at times. Fun car to drive though.
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.
OK, let's start with the basics. There is no 1983 Mercedes 300. They only made the 300 series in diesels, they were the 300D, 300CD, 300SD,
300TD. Which car did you have? And all of those used the same 5 cyl diesel engine with a mechanical fan and hydraulic clutch. Did you look at the parts link? I ask again, are you confusing the auxilliary elec fan with the primary mechanical cooling fan? Those cars had both.
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.
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.
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