FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: jayb on March 03, 2013, 07:44:03 PM
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So over on the CVR water pump thread Harry asked a question about horsepower taken by a mechanical fan. I had some data that I posted on that thread, but it was from 2006, and also it was with the fan just bolted onto the water pump, with no radiator or fan shroud in front of it. When I first did that test I was curious about whether the presence of the radiator and fan shroud would have an effect, but at the time I didn't test for it. The Car Craft test that Bob posted a link to really piqued my interest; maybe the presence of the radiator and shroud could have a big impact on the power taken by the fan.
So this weekend I had several other projects that I could work on, but really didn't feel like working on that stuff. I decided instead to re-run the fan test with a couple of different fans, with no fans, and then with the CVR electric pump. I dug around in my junk and found a Mustang radiator, but wasn't able to come up with the mechanical fan that I ran the test with back in 2006. Who knows what happened to that thing; maybe I was disgusted with it at the time and threw it out ;D Anyway, to acquire a fan or two I called the "local parts department", which is my Y-block pal JC. He keeps everything forever LOL! Sure enough, he came up with a collection of fans that I could test: a clutch fan, a factory fixed blade steel fan, and an aluminum blade flex fan. After paying homage to the Y-block gods, I grabbed the fans and a fan shroud and went back to my shop to try to cobble together a test.
Further searching at my place on Saturday night yielded the Mustang fan shroud to fit the radiator, so I didn't need the fan shroud I got from JC. Here is a photo of the three fans that I tested today:
(http://fepower.net/Photos/Posts/3fans.jpg)
The next task was to cobble together some kind of bracket arrangement to hold the radiator and fan shroud in place in front of the engine on the dyno. I bolted the clutch fan up and used that for fitment purposes. Some angle iron, some square steel tubing, and some steel straps were tack welded and vise-gripped together to get the radiator and fan shroud into position. Unfortunately, the fan shroud was just a little small in diameter for the clutch fan, so I had to sneak the fan right up next to the shroud, but not inside. I was really close though, less than a quarter inch away, so I don't think this had a significant impact on the test. Here's a couple of pictures of the radiator and shroud mounted on the front of the dyno stand, with the clutch fan installed:
(http://fepower.net/Photos/Posts/dynorad1.jpg)
(http://fepower.net/Photos/Posts/dynorad2.jpg)
So, I was ready now for the testing. This was going to be a back to back test on the same day, and I was striving for accuracy, so I made sure to start all the dyno pulls with the same water and oil temperature so there wouldn't be any variations there that could affect the results. First up was the clutch fan setup with the Edelbrock water pump. I have to say I expected this one to do poorly, but I was surprised at how little horsepower loss there appeared to be with this combination. Compared to my previous data with the Edelbrock pump by itself, the clutch fan only cost a few horsepower. Next I changed to the fixed blade steel fan, and this one performed worse than the clutch fan by a measurable amount at the higher engine speed range. But there was none of this 30-40 horsepower difference that the Car Craft test showed. Here is the data for the clutch fan and the fixed blade steel fan:
(http://fepower.net/Photos/Posts/clutchvsfixed.jpg)
Next up was the aluminum flex fan. These things have been sold for years as horsepower improvers, because supposedly the blades will straighten out at higher speeds and save power. My testing did not show that; the aluminum fan was only marginally better than the fixed blade steel fan. Here is the aluminum fan in comparison to the clutch fan:
(http://fepower.net/Photos/Posts/clutchvsalum.jpg)
Next I dismounted the radiator from the dyno and removed the aluminum fan, and ran the engine with no fan on the water pump. Made the same 425 peak horsepower it always seemed to. Here is data from all four of the tests on the same graph:
(http://fepower.net/Photos/Posts/nofanvsfans.jpg)
Finally, I pulled off the Edelbrock pump and put the CVR pump and my adapters back on the engine. I was expecting a significant improvement, which I got, but it also appeared to be an improvement across the entire powerband of the engine, not just from 3800 on up. That was good news. Here is the previous data with the CVR electric pump added:
(http://fepower.net/Photos/Posts/alldata.jpg)
Just for grins I plotted the best and worst power pulls, which were the CVR pump and the Edelbrock pump with the fixed blade fan. There is a pretty significant difference here:
(http://fepower.net/Photos/Posts/bestandworst.jpg)
I also calculated the average torque and horsepower across two engine speed ranges with this data. The first table in the picture below shows the averages across the entire 3000-5500 test range, and the second table shows the averages from 4500 to 5500 RPM, where they are more pronounced.
(http://fepower.net/Photos/Posts/fandataaverages.jpg)
So I think it is fairly safe to conclude from this testing that switching from a mechanical water pump and fan setup to an electric pump and electric fans will free up about 20 horsepower. Based on this testing I find Car Craft's results hard to believe, unless there is something about the fans that they tested that caused them to really soak up the horsepower. Finally, it is worth noting that this test was not performed with the car running at speed, and it seems to me that this may affect the horsepower loss results from the fans. But since I can't accelerate my dyno down the drag strip, that result will have to remain a mystery ;D
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Jay,
Great info. However, I have one question. A thermostatic clutch fan would be "activated" by heat. With the radiator not circulating heated water how much of a negative affect would this have on the clutched fan numbers?
Thanks,
Mike
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I have to admit I didn't know that clutch fans were activated by heat from the radiator; I thought it was just internally generated heat. If that is the case, then the clutch fan test is probably not valid, because the radiator wasn't hot. I would assume that the clutch fan would do worse than my results indicate with a hot radiator in front of it. I'm still not seeing a big horsepower loss though, because the fixed blade steel fan did not show a major decrease in power, and the blades look to be about the same as the clutch fan blades, although there are only five of them...
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Would it have been more valid if the water was routed through the radiator then to the water tower, so that the pump was actually forcing the water to the radiator and pulling it from the radiator, etc.? Just a question, in my mind of the work needed by the pump to push water through the engine and to the radiator, might be more than to the tower. I agree about the heat and lockup of the clutch fan, etc. Also, another test would be water wetter vs antifreeze vs plain water, etc. But it is not my dime. LOL. Anytime there is a test, there will always be more questions to be answered. Thanks for any input for improved performance. Joe-JDC.
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Thanks Jay for answering so thoroughly. I need a CVR!
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Would it have been more valid if the water was routed through the radiator then to the water tower, so that the pump was actually forcing the water to the radiator and pulling it from the radiator, etc.? Just a question, in my mind of the work needed by the pump to push water through the engine and to the radiator, might be more than to the tower. I agree about the heat and lockup of the clutch fan, etc. Also, another test would be water wetter vs antifreeze vs plain water, etc. But it is not my dime. LOL. Anytime there is a test, there will always be more questions to be answered. Thanks for any input for improved performance. Joe-JDC.
That's a good idea, Joe, if I had known about the radiator's role in the operation of a clutch fan I could have just routed the water through the radiator before going back to the cooling tower. I don't think the radiator is a big restriction, though; the biggest restriction in most cooling systems is the thermostat. Having said that (LOL!) maybe adding the thermostat into the thermostat housing would make the pump work harder and cost more horsepower. As you said, there is no end to the potential tests...
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My understanding of the thermal clutch is it will partially engaged by engine speed & then further engage based on the temp of air flowing across it from the radiator. Regardless you have proven in your testing the electric undoubtedly frees some HP & TQ.
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Last time I did a belt drive water pump versus an electric water pump I saw a 12 horsepower average gain from 2500-6500. So your data looks pretty consistant to me. Like sooooo many aftermarket legends, the gains have grown in the telling and selling over the years.
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That's great stuff Jay. Agree that running hot water through the rad may have made somewhat of a difference with the heat-activated clutch , but your testing should still hold up quite well. Interesting too why the CC test showed some greater hp gains between types yet, based upon the captioned pics, they did not run a radiator on their dyno tests. Kudos, as always, for all your efforts!
p.s. I've wondered about the hp loss from running a OEM type mechanical fuel pump versus an electric pump. But, like Joe said, not my time nor $!
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through the center of the radiator would possibly activate the thermal section of the clutch fan. Im thinking a 5-8" diameter tube aimed with the heat dumped into it aimed at the clutch area through the radiator could concentrate synthesize the heat.
I find it interesting even the demonstrated "loss" with the clutch fan for "by the book" at speed and ambient temp it should be "free-wheeling" . I really wonder if different manufacturers and models of clutch fans and the condition of clutch (150,000miles etc) fans effects their lock-up /free-wheeling?......Id expect some clutch fans could almost be "smart" if the thermal control matched the application.
One thing on the electric fans and electric water pumps is it seems no one ever hooks up an alternator and a weenie-battery to make sure that the engine/alternator is indeed making the electricity/power that is required to run the water pump and fan(s). Running them off an external battery is inherently wrong in a test for power loss. It would be like plugging in an electric motor and using it to turn the supercharger vs belting it up to the crank. Obviously a drag-racer can run on nothing but battery, but not so a street car or open track car. My feeling is turning a fan/water pump directly has to be by-the-book more energy efficient then driving an alternator, to make electricity and then using said electricity to power the fan/water pump.
Now here's a hint I picked up back when I had JD Larson as a neighbor: Never store a fan-clutch laying down store them vertical as if mounted in the car. Supposedly this keeps them sealed up and working in the long run.
BTW: Is the mentioned CAR CRAFT MAGAZINE test on line?
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One thing on the electric fans and electric water pumps is it seems no one ever hooks up an alternator and a weenie-battery to make sure that the engine/alternator is indeed making the electricity/power that is required to run the water pump and fan(s). Running them off an external battery is inherently wrong in a test for power loss.
I don't agree, since at the track the alternator can be switched out or disconnected. Also, power required to run the electric fans and water pumps is stable at all engine speeds, because they run at a speed determined by battery voltage. So, your mechanical water pump has to pump enough water to keep the engine cool when it is idling in traffic, and it will just take more and more power to run, unnecessarily in most cases, as the engine speed increases.
Here's some math to think about. 1 horsepower = 750 watts of power (conversion from English to SI units). An alternator delivering 14 volts and 10 amps to run the electric water pump is delivering 140 watts. (Power = Volts X Current). If the alternator is 50% efficient at converting rotational power to electrical power, then it is taking 280 watts, or 0.37 horsepower, to drive the alternator and deliver the power required by the electric water pump. Bottom line - the power loss, even with the alternator connected, is in the noise...
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A fan clutch is a wet clutch that is activated by the bi- metal spring on the front. It spins some from friction naturally and engages fully when hot air passes over it. Newer ones have been made more efficient by using lighter materials but at low or idle rpm are still susceptible to overheating. HP is not my only reasoning for an electronic pump, cooling efficiency is another purpose. Also keeping the engine cooler can give good gains too.
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Also keeping the engine cooler can give good gains too.
I wonder...?? Yes, a cool, dense intake charge is good, but the NASCAR boys run their engines hot with good results. I also seem to recall that, theoretically, if the engine is hotter it loses (transfers) less heat away from the combustion process and converts more of that heat to energy, improving overall thermal efficiency. Do I recall that correctly (at least in theory)?
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I could be wrong, but I think the Nascar engines run hot because it allows them to use a smaller air opening and radiator, for less drag. They gain more from the reduced drag than they would with a lower temperature coolant. Maybe?
paulie
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nice work jay..
I run a clutch fan on mine and I never hear it. stays cool all the time (190-200) My durango has a clutch fan (same style) and that damn thing will activate and sound like a tornado !
Look's like the clutch fan don't cost me mush hp,So I think it will stay.
thanks Jay ...
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Intresting test results Jay. I always heard the aluinium flex fans freed up HP over the yrs. Your results left me thinking. By the way did no one catch Jays mule engine is running the dreaded FRAM filter! LOL
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Car Craft fan test results, a 13 year old article now. While one can draw some conclusions, I'd stick to Jay's more real-world results.
http://www.network54.com/Forum/215655/message/1066184641/Car+Craft+Cooling+Fan+Dyno+Test
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Intresting test results Jay. I always heard the aluinium flex fans freed up HP over the yrs. Your results left me thinking. By the way did no one catch Jays mule engine is running the dreaded FRAM filter! LOL
Actually, the "dreaded" Fram filter is the PH8A. Those things are junk. The Fram HP1 filters are actually pretty good.
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Maby its not relevant for this test. But i
noticed when i lost a belt on a car if i drove
faster than 65 mph the fan actualy rotated
the waterpump enough to cool the engine.
Just a thought regarding acelerating the
dyno down the dragstrip.....
The speed helping with turn the fan but
the fan also causing aerodynamic drag ??? ???
I gues someone have to do some realworld
fieldtest to realy figure out how to get that
last 0.?hp gain ;D ;D
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This is a tad off-topic but I believe it was Car Craft magazine that years ago also ran a test of a '72 or '74 (forget which) big block Chevy Chevelle at the dragstrip. The test only involved adding aero devices to the body to see if making it slicker would improve e.t. and mph. The car IIRC was a high 9 second racer and the tests (not all of which I can now remember!) were a whopping success and a hell of a lot cheaper for the $ spent than adding more hp.
After some baseline runs, they added a under-the-front-bumper OEM type lower spoiler, then a really big front spoiler that almost touched the ground, then some belly pans under the seating area, a big sheetmetal pan that covered the gas tank area right up to the edge of the back bumper, a top mounted rear deck lid spoiler, etc. Amazingly, IIRC the car did pickup 6-7 mph in speed, mainly due to the big front spoiler and the gas tank bellypan. Don't remember how much the e.t improved but there was improvement all be it not as much % decrease as the % mph gain.
Anyway, the moral of the story was do all one can to prevent air from getting under the front of the car and where one can't, make the bottom as smooth as possible.
Btw, this is NOT the CC article as it's not on-line but this HR article speaks of the same ideas.
http://www.hotrod.com/techarticles/body/hdrp_0609_aero_tricks_tips/viewall.html
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Interesting results. I have to admit I was kind of skeptical about the Car Craft test because for years we were fed the idea than a clutch fan was trash and the flex fan was best. That theory seemed to make sense if for no other reason that the flex fan was lighter. Your numbers verify Car Craft's results. Goes to show that the auto engineers knew what they were doing! If they could have substituted a cheaper flex fan for the clutch fan, they would have.
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Hi Jay,
I gotta get over here more often, this is great stuff.
Do you recall the diameters of the crank pulley and waterpump pulley?
Also, I cant tell from the picture, Ford make some thick-blade fans (about same thickness as the basic 4-blade crossed fan) that would not flex, and some thin-blade fans that would flex, was your test the thick one?
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Werby, where have you been? ;) As measured at the outside, the crank pulley diameter is 6.75", the water pump pulley diameter is 5.75", and the fan blade was one of the thick, non-flex ones.
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:-\ Thanks Jay... and yes I read your book - Excellent thank you! As for the water pump/Fan issue, I think I'll stay with the stock unit with electric fans since I already have. If I were heavy into drag racing, I'm sure I would go for the extra HP. I'm mainly going to be cruising and hope to get some time down the strip later this year.
Something else to consider, I'm sure I would gain some ET just dropping about 50-75 lbs. off my fat X@# which would also help my health and easier on the bank account!
Anyways, thanks for the information!
Tim