For those who have changed their fans, how much mileage and power have you gained from stock solid 4 blade fan.

1. clutch fan ?
2. electric fan ?


And for the clutch fan, what's the height from the mounting flange to the fan blades (radiator side) ?

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

I never really did check for a milage differance when going to an electric fan. I could feel an increase in power though.
I think I gained about a tenth in the 1/4.

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1. clutch fan netted 2 mpg better
2. electric fan netted another .5 mpg better and allot more power

Before installing the electric fan I put my four blade back on and drove it two weeks. That is a about 500 miles, and the mileage dropped 2 mpg.

I think the little 1920 one barrel jetted lean (#55 jet) is right on the edge and any drag on the motor makes a big difference. My car weighs 3380 lbs with a full tank, 3580 lbs with me in it. Book specs show up to 3180 lbs. In 1974. However, added 5 leaf springs and a 8 3/4 rear end.

I think there are other advantages to the electric fan besides drag such as better mixing on the number one runner since air is not being blown over it all the time. In the winter and cooler months the plugs run the same color now. The front plug was always a shade or two darker from the other 5.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

H'mm. The improvement stated is very much higher than can be supported by appropriate calculation, and is also very much higher than found in scientifically-conducted fuel economy research (by actual researchers) going back many decades. I wonder what other changes you might have made at the same time that would account for the bulk of this improvement.
No.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I swapped out the cast iron intake and replaced it with an aluminum intake in March. You also said that doesn't make any difference in an earlier post.
You also said the same thing about my heat deflector/isolator to keep the gas from boiling in the carb.

I keep a very accurate log book and drive over 130 miles a day. The figures were taken with the current configuration this year using a #57 jet. I put the old stock fan on just for fun to see what would happen and those are the results.

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

No, I said it can't make as big a difference as you claimed. See here.
Nope, I didn't. I've recommended heat deflectors & isolators similar to yours many times; why would I say it doesn't work?

Don't get me wrong, I'm glad your car's running well and you're continuing to make it run better, but the results you're claiming for your mods just don't reckon, and some of the theories you're using to try and explain the differences you report don't have a sound basis. There are sound reasons why your car runs better with the manifold swap — primarily it's by elimination of vacuum and/or exhaust leaks that existed with the previous manifold. I'm sure you're keeping accurate mileage records, and that you're not trying to deceive anyone here...it just remains to figure out where the bulk of that 2mpg gain is coming from. It's not coming from the fan swap.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Dan,
I am going to go out on a bit of a limb here.
I have no problem giving you credit as one of the most knowledgeable /6 enthusiasts on the planet. However, you seem to be a little soft in taking the discussion, person, and situation into context some times.

Ted is not a new member, he has shown to have a very solid knowledge, and well tuned combination. I believe that his input warrants consideration, and I believe it should carry weight above that of an unknown. It appears he is well versed in tuning, and he has a solid foundation for which to make the recommendations.

As such, if he says he swapped to the fixed fan, and saw the decrease in MPG, or gain with the flex versus the fixed, I believe what he has to say.

It seems you are solid in your beliefs, so much so that the opinion of others with excellent "creditials" cannot be "right" if their opinion is in contraction of your opinions. Said another way, instead of your posts offering a different opinion, they tend to "discredit" the other post.

No malace, or anger intended, just a suggestion in how you present in your posts, at least to me. You appear incredibly knowledgable, but a little "strong"

Hopefully this comes out right.....

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1976 Dart Lite /6 3 Speed

I have no interest in discrediting Ted. I have no doubt he swapped fans, and I have no doubt his mileage records are accurate. The grey area is causality. The cardinal rule of science (which is a word that means "knowledge") is that correlation does not imply causation. "A" happened, and "B" happened, but it's problematic to say that "A" caused "B", for the numbers are highly unlikely.

"Belief" has nothing to do with it. This is not a question of faith, it's a question of science and fact. What we think we see is very often not what we're actually seeing, and it takes careful observation to sort out what's actually going on. Reality has a nasty habit of punching ugly holes in beautiful theories, and that's not a matter of opinion (mine, Ted's, yours, or anyone else's). Things work the way they work, which is not necessarily the way we imagine them to work. There's no getting something for nothing in this universe, which often doesn't work the way our common sense or intuition suggests it should. And things are often not as they seem. This has been discussed many times here on the board, often with respect to "miracle" fuel economy gadgets and "engine treatment" additives, and "magic" engine modifications.

I'm reminded of the guy on Usenet years ago who swore he picked up 15mph additional top speed in his '75 Valiant by swapping from a 7¼" rear axle to an 8¼" rear axle. Both rear axles were in good condition, and both were non-Sure Grip 2.76s. His explanation was that the 8¼" has vastly less internal friction than the 7¼". That's wrong, no matter how much he wanted it to be right: Fact is, if his 7¼" rear axle really had enough internal friction to slow the car's top speed by 15 mph, it would've melted into a smoking heap of slag in minutes. What's the actual explanation? Donno. Probably the two axles weren't actually the same ratio, or there were other changes he wasn't talking about, done at the same time as the axle swap. The point is, he was absolutely sure of his explanation, even though it could not possibly be correct.

I have no problem with people believing what they will. I do have a problem with guesses and impossibilities being presented as facts and explanations. That's not me trying to stamp out all opinions other than my own, it's me trying to figure out what's actually going on when presented with an implausible explanation or a seemingly contradictory set of observations.

I'm also not on a proselytising crusade; it'd be pointless because those who really, really wanna believe in 15 mph worth of friction reduction by swapping to an 8¼" rear axle, or improved #1 combustion due to an engine bay airflow phenomenon that's not actually happening and wouldn't affect combustion if it were, or 2mpg from going to a clutch fan, are probably going to carry on believing in their pet ideas and imagined explanations, no matter what I or anyone else has to say. I do, however, chafe when magic and faith are taught in place of knowledge to those who don't know enough about the topic at hand to separate the one from the other. My goal is to get at correct information, that's all. I understand that some people will misconstrue that effort as a personal attack. That's understandable, but regrettable. I'm not on an attack mission. (You may believe it or not, as you choose. )

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

No it isn't. We are adults here and we should be able to have a civil discussion. What Dan is saying is absolutely true and he hasn't been unecessarily strident, rude or condescending. It is totally appropriate for him to air his views in this manner so that those reading can analyze the information on both sides and come to their own conclusion. This is a discussion about well known and measurable effects; it is not a religious conflict.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Anyone else with input regarding this?

I was thinking off fitting a flexalite fan - not the wing fan mind - but the sturdier version that need not be replaced every so often.

I have One I have tested it but it is very noisy. so I took it of. But if I can realize a MPG saving I will reconsider or go electric.

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Regards,
Fanie Gerber
It's never junk, it's just a part you're not currently using

http://www.valiant50.co.za
Just say I own a few Mopars

If you get a Flex-a-lite fan or one of the many imitators, be sure that it has steel blades and a steel hub. The ones with aluminum hubs were known to crack and fail catastrophically.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

Me, I don't like flex fans. See flex fan discussion.

See also this discussion of a clutch fan that fits in tight A-body engine compartments.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It has been a while, but I recall about a 1.5 mpg gain going from a Flex-A-Lite 19" steel flex fan to an electric at 75% highway driving. I kept very accurate mpg records.

Mitch

Car Craft Feb 2002 - "Electric Fan Dyno Test. Yes, it is worth power. Real power"

I can't find the actual article on line but seem to remember the power loss with using the factory solid fan being pretty staggering... 35-50 HP on the dyno mule.

I'll see if I have the article still.

This is another study from carnut.com on the same subject. Sorry for the bad spacing

http://www.carnut.com/ramblin/dyno.html

The testing was to determine the CFMs at idle (800rpms) and at a slow engine speed (1600 rpms) and hp losses at 4500rpms as well as, and this is an interesting catagory....engine spin-up time from idle to full throttle at 4500rpms (a test that measures the ability of the engine to spin itself up to the given rpm and is directly proportional to the stuff you have hanging out front....this would tell give us a torque expenditure that is dedicated to doing nothing but getting the fan mass up to speed!). A figure of 100% was used for the engine with no fan or accessories involved. We checked all the fans for balance and corrected where necessary! The figures below for this measurement reflect an additional time taken per apparatus!...... And awaaaaaaaaaaaaaaay we go!

FAN TYPE IDLE (800) IDLE (1600) HP LOSS (4500) TIME LOSS %
_____________________________________________________________________

BB18 1680 2355 40.8 8%

BB18C(heat) 1580 2205 35.6 13%

BB18C(COOL) 1104 1400 19.3 11%

SKIPPER 1503 2020 31.5 7%

FLEX 17 1420 1814 20.2 5%

______________________________________________________________________

Having presented this here, I want to say one thing. It isn't a perfect scientific test...but I think it represents a close proximity to real world.

I could see where an electric could be worth a few MPG especially on a small engine like a slant 6.

That's a really good article. Their testing setup — while limited by the constraints of simulations like this — is technically sound, and one of the fans they tested is from a slant-6 F-body, helping to make the results at least partially relevant to our cars. Taking a look at the link (because the data table is readable there — it's not readable here due to spacing issues) a few interesting things are apparent.

The (disengaged) clutch fan takes ~39% less power to spin at 4500 rpm than the standard slant-6 fan. The 4500 rpm speed at which the horsepower demand was measured is significant, because most of us with street-driven slant-6s — especially those of us concerned with fuel economy — don't spend much time at 3500 rpm, let alone 4500. With common-upgrade 205/70R14 tires and relatively extreme 3.55 rear axle and non-overdrive transmission, we're spinning 2830 rpm @ 60 mph or 3300 rpm @ 70 mph. With original-replacement 185/80R13 tires and relatively extreme 3.55 rear axle = 2904 rpm @ 60 mph, 3388 rpm @ 70 mph. With midsize 185/75R14 tires and common 2.93 rear axle = 2370 rpm @ 60 mph, 2766 rpm @ 70 mph). We're spending most of our time way below 4500 rpm. That's going to reduce the horsepower demand of any/every engine-driven fan very substantially, because air resistance increases as the square of velocity: at 3000 rpm, the drag against which the engine must spin the fan is only 44% of the drag at 4500 rpm. Fortunately for our effort to interpolate from the data in the linked chart, virtually all the fan's power demand comes from wind resistance. That 39% power demand difference at 4500 rpm is going to approximate a much less significant 17% power demand difference at 3000 rpm, and the actual demand will drop from 19.3 hp for the disengaged clutch fan and 31.5 hp for the solid fan, to about 9 hp and about 14 hp, respectively.

The figures above tell us how much power we're putting into spinning the fan at various engine speeds with the car standing still and the transmission in neutral. With the car moving along at any road speed above about 40 mph, the vehicle's forward motion itself creates enough airflow through the radiator that the fan is superfluous. More importantly, this pushed air greatly reduces the resistance encountered by the fan blade. The exact road speed at which the fan's air drag drops to insignificance will vary depending on vehicle and fan configuration, but it's a pretty safe bet that's the case at 60 and 70 mph with most any fan one would care to run. In this operation mode, the difference in power required to turn a solid vs. clutch fan will be unmeasurable or nearly so.

The acceleration time loss measurement is an interesting one; as they note, the clutch mass actually works against us in that test: it takes the engine significantly longer to accelerate with a clutch fan than with a solid fan, no matter whether the fan clutch is engaged or disengaged. Here again, while the numbers are interesting, the practical magnitude of the actual effect will be much, much smaller. That's because most of us don't spend much time accelerating our engines immediately from idle to 4500 rpm in Neutral. We accelerate our engines much more slowly and to a much lower RPM in gear.

We also need to look at their info for the clutch-engaged condition. In that case, the clutch fan consumes 13% more power than the solid fan — this isn't due to the clutch, but due to the larger diameter, higher blade count and steeper pitch of the clutched fan blade compared to the solid fan. Applying our correction to get from the test speed of 4500 rpm to 3000 rpm, that difference drops to a little under 6%. We spend less power on the fan when the clutch is disengaged, but more power on the fan when the clutch is engaged, so we have to average it out to figure out what we're spending overall. Let's assume that during operation when the fan is relevant (see above), we see a 50% duty cycle for the clutched fan (i.e., the clutch is engaged half the time and disengaged the other half). Averaging the engaged- and disengaged-clutch numbers gets us 27.45 hp consumed at 4500 rpm (12 hp @ 3000 rpm). Comparing that to the solid-fan numbers (31.5 hp @ 4500 rpm, 14 hp @ 3000 rpm), we have an overall difference of about two horsepower at 3000 rpm. That is not sufficient to affect fuel mileage by 2mpg.

The quality of the data is just one half of what goes into science. The quality and relevance of the interpretation of that data is the other half. If you just look at the numbers presented in the article, it's easy to conclude that a solid fan on the front of your slant-6 is gobbling up enormous amounts of power, maybe even enough to make 2 mpg difference. But when you apply the data to the context of our real-world application of fans and engines, that conclusion fails for lack of support.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.