[1971WARBIRD]

i found this for someone the other day and thought others might be interested in seeing it.

okay found it.i was right and i was way wrong.here are the numbers from the carcraft/may/2000.
fan power test:45HP
all test used alternators and the fans are Flex-a-lite brand."flex-a-lite.com"they either came from jegs or summit,with flex-a-lite part numbers.

test was done with a near 500 hp small block.in a separate test the 63 amp alternator pulled 1 hp.test was done by Marlan Davis....
.................................................. ...................max power rpm/3500-5000avg/3500-6500avg/overall avg
496 hp no fan............................................... .....................6,300 rpm/316.3/462.2/388.8
494 hp electric fan (jegs)150......................................... .......6,300/312.7/460.0/385.9
487 hp thermal clutch (summit)5718 fan 5555 clutch.................6,300/311.6/453.3/382.0
485 hp non thermal clutch(summit)5718 fan 5255 clutch............6,300/306.8/450.0/377.9
476 hp heavy duty thermal clutch(summit)5718 fan 5655 clutch..6,300/303.3/444.5/373.5
476 hp high performance flex (summit)1308.............................6,300/304.9/443.8/373.9
473 hp stock 4blade rigid (factory used)..................................6,200/301.9/437.6/369.3
466 hp low profile flex (summit)1018...................................... ..6,200/302.5/435.0/368.3
460 hp 0ne piece plastic flex (summit)418.................................6,100/301.7/432.6/366.7
449 hp OE 6 blade rigid (jegs)1718........................................ ...6,100/297.9/423.4/360.1

as you can see my memory isn't what it used to be,45 not 100

the best flex to electric is only 18 hp,i totally missed that 476hp before.hope this helps.
__________________
FREEDOM ISN'T FREE

[Half-Inch Stud]

Were the fans messing with the carb mixture?

Yea, I can see how mech fans take more power to turn than elec fans. Do you have the RPM that these HP values were stated? Crank Pulley//Fan pulley diameters or were they 1:1?

[1971WARBIRD]

i went back and added the rpm numbers that were in the article,and it looks like they used the same pullies for the whole test,but didn't give a size.not a ton of power to be had,but if you have a good cooling system,it's free horsepower.
here is quote from the article;

"keep in mind that none of these test measure a fans cooling ability in a real car.due to pressure drop throught the core,radiators significantly affect a mechanical fan's efficiency,both in terms of flow capablity as well as horse power it takes to drive them.on the other hand,for a marginal cooling application,a mechanical fan still out-performs an electric fan when it comes to peak cfm.just like the engine,you should design the cooling system to work together as a complementary team."

[Steve C.]

Numbers were generated using a 496hp small-block Chevy at 6,300 rpm.

Read this: With a direct drive fan the amount of HP used is pretty much in direct relationship to engine speed, ie it uses less HP at lower RPM because it isn't drawing its design air flow thru the blades.
With an electric fan you loose the 30% generating loss in the alternator.


Mention of that article came up in a similar discussion here about fan & alternator losses in this post:

http://forums.maxperformanceinc.com/...r+Craft&page=2

[Firebob]

I've tried both clutch and flex(actually all three including elect). The thing that got me was the weight difference between the clutch and the flex. All that extra weight hanging off the front of the motor. I went back to my flex. No real difference in cooling. Don't know how much the hp difference is offset by the weight.

Robert

[Half-Inch Stud]

I try to keep me motor below 5500RPM. Yet that had been exceeded (on the top of 2nd gear), and promptly broke both V-belts.

[1qikta]

Joe,

I have had a lot of fun with this thread.

About the time you posted it I was looking for some frontal weight loss and freeing up a little more recipro weight. Up to this point I have been running a stock cast water pump, stock pulleys,my correct 7 blade fan and a HD fan clutch for an AC car.

For the '09 season(off track) I plan to run the 5718 six blade fan and 5555 clutch... and for the track a non thermal (fluid drilled/drained) clutch with a 5 blade GM aftermarket new fan. According to your test results above it will yield some power.In addition I bought a aluminum water pump and a set of the Billet RARE aluminum pulleys. Total weight savings will be about 10-11 total lbs at the track...4-5 lbs of which will be reciprocating.

Prior to any track time, I will hit the chassis dyno to get you some real numbers...with and without the 1.65 HS rockers.All compared to October's dyno pulls.

From what I understand some FS guys have even cut down or totally removed some water pump vanes off their impellers to cut their power loss...I dont know if I will go that far.

[Schurkey]

Keep in mind that the weight of the fan and clutch can't be considered "rotating (not reciprocating) weight" in the same way a crank or flywheel is, because it doesn't rotate at the same speed as the crank; AND under heavy acceleration, the crank is free to accelerate while the fan and clutch slip.

Removing five pounds of fan isn't like removing five pounds of flywheel.

The horsepower required to turn those fans isn't realistic. The test was poorly done and proves NOTHING.

In "real life" those fans would have a considerable air flow restriction in front of them; at higher engine speed they'd either "stall" (solid-mounted fans) or the clutch would slip more; either way they'd take much less horsepower to turn.

[1971WARBIRD]

Hi Jay
it will be interesting to see real numbers that can be compared.your car runs close enough that small changes should show up and be believeable.

[GOAT8U2]

I thought when I ditched my stock fan it weighed 14 or 15lbs, I could be wrong.

I'd assume the initial test was a chasis dyno, which 45whp is really hard to believe on just a belt to electric fan swap.

[1971WARBIRD]

test was done on an engine dyno.shows how small changes can make a difference.people have made big money selling smaller pullies over the years,because they help out with a couple HP.

it will be interesting to see what Jay comes up with as his car is dailed in close enough to be able to spot small changes.

[Cliff R]

A few years ago we track tested an electric fan against a thermal clutch fan, no measureable difference in ET or MPH. The electric fan pulled enough current that the alternator draw offset any gains over the thermal clutch unit. I went back to the clutch fan, as the electric fan kept killing my battery between rounds....FWIW....Cliff

[72blackbird]

I've run an electric fan with a small shroud for over 12 years now, after my fan clutch took a dump and took out the OEM shroud and radiator. Most of you don't think it makes a difference, but I noticed right away the engine revved much easier and I had greater piece of mind knowing it wouldn't happen again.

It may not make a difference in drag racing, but in road race/ autocross it really makes a difference- very few V-8 racers run a stock cooling setup.

Geno

[1qikta]

My fuel delivery upgrade,frontal engine drive and additional Carb CFM are the last areas I have to improve on. If I dont put the effort in I will never know if there are gains to be had.The 496 should respond to it all though.

It certainly will squeeze out what power is left.

[lust4speed]

Both the thermal and standard clutch fan engage by silicon fluid between the outer vanes and the inner vanes inside the clutch fan. According to all the literature I have read from Hayden and others the fan is designed so the silicon is spun away from the contact area at fan RPM's of 4,400 - 4,600 and the fan free wheels after that. While the HO and RA engines had under driven fans, most engines had an 8" pulley on the bottom and 6.5" on the top for an overdrive ratio of 125%. Working backwards, the fan clutch should free wheel at engine speeds over 3,600 RPM (OK, actually free wheels allowing the fan to only spin at 4,600 RPM). Power loss should be the same for 4,600 on up to redline - where other fans continue to draw more horsepower as the RPM is increased.

[Formulafr]

hello,

well, i don't have all your experience, but i run electric single fan since 2 years and with a true no hp engine like mine i really feel the difference between electric and OE (7 blades 19" and new HD fan cluth, A/C car but no more blower). the engine seems to rev up a little faster.

the problem that makes me thinking about electric was that one day after a long high speed, i shut of the car and smell burning rubber. i check twice and didn't see nothing untill i put fingers on my fan rope, it was like glue. the rope was 6 months old and with a good tension. i guess that the fan was slowing the engine at high rpm.

what cost power, cost fuel. i get my best mpg when pull off the mecanic fan for the electric one. remember that fan is only needed when you're driving at low mph. once you drive around 40-50mph, the natural air flux is enough to cool the engine, even on hot day. fans don't spread air like if you were at 100mph!

[Joel Koontz]

I have run an electric (Mark IIIV) fan for seveal years. I noticed that the engine seemed slightly more responsive when I took the mechanical fan off and installed it.

It is on a thermostat and seldom runs, unless I am stopped at a traffic light or something. I have no idea how much, but this HAS to be saving fuel and using less power than turning a mechanical fan all the time. Pleanty of cooling capacity, NEVER goes over 195 degrees. I could run it even cooler, with a lower thermostat setting if I wanted to, but I assume this would just take more power/fuel.

The mechanical fan, belt etc. has to be (or act as) reciprocating weight and take power to run, and especially to accelerate.

I don't race, but if I did, I would try to have a fully charged battery and turn the electric fan OFF before starting the run.

I would think that running with NO FAN (assuming the car is not overheating) has to make if faster.

If you disagree, please explain why?

[lust4speed]

Thermal fans only engage when the bi-metallic coil gets hot enough to engage the fan clutch, otherwise you only have the parasitic draw of the fan belt. Electric fans are only 80% efficient at best, and running the alternator to power the electric fan wastes that 20%. So an electric fan is less efficient on a daily driver. Electric fans are such a draw that I do shut off my electric fan on the drag car when pulling up to stage -- might not make that big of difference, but I feel better. When I pull to the return road I switch the fan back on and the alternator loads down -- all I did was trade a little less drag for a few seconds (OK, many seconds in my case) to be paid back on the return road. On the street providing the same cooling, the electric fan has to pull more energy due to its inherent inefficiency. That 45 amp load of the Mark VIII on high speed is quite a load.

[Schoust]

So in a nut shell what would be the best overall fan for street and strip?

[Joel Koontz]

Thermal fans only***FULLY***engage when the bi-metallic coil gets hot enough to engage the fan clutch.

I have never seen a thermal fan setting still when a motor is running so there is SOME drag being created by the fan. How much I don't know, perhaps 5 or 10 percent, but it is taking place the entire time the engine is running.

Under normal conditions my fan runs less than 5% of the time my car is running.

Without knowing the actual #s, I can't prove it, but I feel confident that it is more efficient than running a mechanical thermal fan.

If I was going for max fuel economy(instead of detonation resistance) I would set it up like most late model cars and it would run less than one percent of the time.

I have a C5 Vette and my brother has a 2002 TA WS6. On both of these cars, during normal driving(w/o AC) the fan NEVER runs unless the car sits still for a VERY long time, like 10 or 15 minutes. I used to have a 95 Z-28 and it was the same way. I remember several months after I first got it, I thought the fan might not work because I NEVER heard it run. I eventually got curious enough that I just let it set at idle until the fan finally kicked on. Could have taken a nap while waiting for the fan to kick on.