mechanical fan vs electric?? with proof?

James10952001 said:

Who said it would?

I only suggested that the mechanical fan in a Volvo likely doesn't pull anywhere near 14HP, it's tiny compared to the mechanical fan in a lot of V6 and V8 domestic cars, and the energy required to spin the electric fan is not free. I have no data to compare but I doubt the difference is huge.

The noise thing has made me consider switching to an electric fan though. The mechanical fan really roars after sitting at a light in warm weather.

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No one said it was free, you just wanted to hear your own voice.

turbotankshane said:

That and I can't leave well enough alone

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THIS.

James10952001 said:

Don't forget that the alternator is only about 50% efficient, and that's before you factor in mechanical losses which are actually quite high for a V-belt.

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This paper really drives home how inefficient alternators are: http://www.delcoremy.com/documents/high-efficiency-white-paper.aspx

Key take-away: design cvt to run the alternator @ 2500rpm at all times.

M.H. Yount said:

30A @ 12V = .48HP. Say you're getting closer to 14V at the fan -- .56HP. You have some inefficiency in the fan motor and the alternator/belt drive --- but even in the worst case it doesn't take more than a HP or two even with larger electric fans. And, of course, that's only when they're running at full tilt. With variable speed controllers, you're often not even pulling that much when they're running --- I have a 'speed gauge' on mine and it rarely runs at more than 1/3 speed with the A/C off.

Moral of the story -- the switch to electric pretty much eliminates all of the parasitic losses associated with the mechanical fan. Losses from rotating the weight and aero losses that increase significantly with engine speed/air moved. There's a reason that most engines have had electric cooling fans for quite some time. VW broke the ground when they turned the engine sideways in the Rabbit/Golf back in 74/5. Eventually, even the longitudinal folk followed.

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I wasn't arguing that an electric fan wasn't more efficient, just simply wanted to see a dyno comparison.

Understood td - point is, with a bit of math, you can see that the load from the electric fan is relatively insignificant. With mech, you've got aero load when clutch is engaged (they never completely frewheel) and you've got the rotational load of spinning the clutch/fan assembly that's a function of how much it weighs. Perhaps linuxman will get us some numbers on the Volvo-specific unit.

If the T-static clutch actually works sometimes you really need that ~4hp worth of airflow unless you make the radiator or alternator sufficiently large to keep the car cool. That's all I measured anyway with the A/C on on the chassis dyno on an ~85 degree day with some pulls at the very very most. 84 245TIC. Obviously baseline readings aren't going to be as precise as a fresh engine on an engine dyno in a white-glove clean room...


I never really noticed excessive noise from a new tropical clutch. When the fluid gets old and over-sheared they become very much on off and rob power/cool ineffectively as well as taking forever to unlock or lock up...hence the excessive noise with revs.

Otherwise, it's been fine.

On a turbo-intercooled DD A/C car there is a lot of potential for heat soak. It's not so terrible to always have a little bit of air blowing to prevent that and a method of cooling that's less reactive than the e-fan often is, especially one that is only "on" or "off"
If you've got a relatively stock turbo car, just replacing a tired or stock fan clutch with a tropical instead of buying a sufficiently large custom radiator and alt to effectively use an electric fan is often effective and inexpensive.

With the 245T, mostly the clutch fan only made noise at startup for a sec or taking off from idle briefly with a near new tropical and 3-row in the heat in traffic with the A/C blowing freezing cold. Climbing long grades towing the E-fan never really worked all that well. It was less expensive to buy a $70 clutch (at the time) brand new in decent quality, burn a little gas (difficult to even measure) rather than buy a new engine or reduce the lifespan of everything under the hood drastically. Or reinvent what was already a pretty well packaged turbo-IC-radiator setup with a custom plumbing/radiator/alternator setup of some sort...
Fuel econ unloaded depended more on weather/road conditions and cruising speed. But on the interstate driving a reasonable speed unloaded where every little parasitic drag point can cost an MPG or two, 29-30mpg was possible in the turbo car with the clutched cooling fan, so how horrific can it really be?

mikep said:

I read a similar test a long time ago.
7hp was for an unlocked clutch fan. Way higher loss when that bi-metal spring heats up and locks the hub.

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I'm not so sure it was unlocked in the video...if it's of a design similar to the Aisin in the Volvo, if you just slap it on there and run it from cold/stationary, it is almost completely locked until the pump is allowed a minute or two to pump all the fluid out.
I'd imagine/guess that they feed that engine warm coolant/keep it warmed up in advance to prevent damaging it and monitor it closely on "life support" if you will, radiator is dry, clutch probably is all solid locked up and isn't given a minute or two idling to unlock I'd guess.

The volvo (Aisin) plastic clutched fan if it's unlocked I can literally hold the blade still with a flimsy stick/roll of newspaper and rev the engine immediately after it unlocks from totally cold. So, unlocked and clutch working it's drawing what, .25hp or something silly? It takes a second to even spin up a little from idle if held still. If the pump and T-stat works the Aisin clutch can achieve near free-wheel basically. I literally don't hear it whatever after startup until the sun comes out and it is 70-75+F out sometime in the very late spring here except some hills towing.

Just because all of you are declaring your standard issue 200K mile clutch fans "junk" doesn't really mean they are/were when they were younger. Maybe they need $10 worth of silicon fluid at the hobby shop or a lower mile tropical hub or new one at the worst. Maybe a new blade if the blade got damaged/out of balance or whacked against the shroud with broken engine mounts.
I still have 10 fingers and toes...

I had an IPD electric fan and it was super noisy and hammered on the electrical system when it was on which was a good bit once the turbo and cat got hot.

a decent E fan, even with alternator losses isn't coming anywhere near 7HP, even if it was always on (which it isn't.) However, the amp draw of some of the junkyard e fans can be much higher than you think, so it might in those cases.

I've got a Flex-A-Lite 114 puller on my car, and it is rated for a draw of 9.5 amps. At 14V, that translates to 113 watts... which is .15HP. And remember, the mech fan on these things is on the belt driven water pump, not the pulley, so all the belt losses are on your mechanical fan and amplifying its power draw too.

I just mounted it straight to the radiator and ditched the shroud, used the temp sensor from a later 740 and a headlight relay from a '90s Accord to wire it up. Total cost was something like $120, I could have done it a lot cheaper with a junkyard fan, but I think it is worth it for the peace of mind and lower power draw. It's been on there a good 4 years now. It keeps it cooler than the stock setup. I've been caught in traffic well over 100. The fan rarely runs, in traffic, it will go on for maybe a minute before it yanks the temp back down and shuts off. It never runs while moving. It stays cooler moving too, I think the lack of shroud helps there. I've got one of the Nissens 3 core brass units.

The power gain isn't hugely noticeable... a little more pull at higher RPMs in the first two gears is about all you notice, but it is much, much quieter. And doing some work on the engine is easier. I'd definitely do it again.

Not arguing at all, and I see the points in favor of a clutch fan. I still have one on my truck, and on everything I have ever towed with.

The points in favor of an electric fan have been stated by others, but I will reiterate the most important one: This is performance, and when we are talking 110-180hp engines, it makes a difference. 1/2 hp loss versus 7-15hp is noticeable, and can be measured. HAS been measured.

Some of dude's comments seem off.

1) The amount of space he said that you needed between the blade tips and the shroud may be considered cool for the auto industry, but it's too much to counter drag resulting from tip vortices in the higher RPM's.

2) Considering the fan (as attached to the front of the motor) is acting as a puller (pulling air through the radiator) you want all of that fan blade inside the shroud. Instead, you're creating a region of instability at the outlet that is greater than it would otherwise be.

But whatever.....

I'm throwing the wagon on a dyno today. Want to get a baseline run before I add the turbo to it. You guys want to pitch in $30 for an extra run, I'll be more than happy to unbolt my clutch fan for a second run.

^lol, $30 for 4 10mm nuts and a couple 8/10mm shroud bolts.

I gotcha covered for free when this 240 settles down and runs right. we can do loaded tests, unloaded tests, coastdown tests to determine total driveline differences... and since it's mine, it's free. I may even retrieve my old lh tuning stuff and see what can be beaten out of an otherwise stock car..

linuxman51 said:

^lol, $30 for 4 10mm nuts and a couple 8/10mm shroud bolts.

I gotcha covered for free when this 240 settles down and runs right. we can do loaded tests, unloaded tests, coastdown tests to determine total driveline differences... and since it's mine, it's free. I may even retrieve my old lh tuning stuff and see what can be beaten out of an otherwise stock car..

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Haha, not paying me for my time, it's for the shop. They charges $30 a pull. I'm only going to make one pull to see where my car stands. I think I can pull the fan for free if someone cares enough to see what difference it makes and wanted to pay for a second pull.

We don't all have dyno's available to use at our will

BDKR said:

Some of dude's comments seem off.

1) The amount of space he said that you needed between the blade tips and the shroud may be considered cool for the auto industry, but it's too much to counter drag resulting from tip vortices in the higher RPM's.

2) Considering the fan (as attached to the front of the motor) is acting as a puller (pulling air through the radiator) you want all of that fan blade inside the shroud. Instead, you're creating a region of instability at the outlet that is greater than it would otherwise be.

But whatever.....

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+1
the fan shroud should act as ductwork with the fan having both an inlet(pre scroll) and outlet (discharge from fan) static pressure. sealing gaps in the inlet side(ie between ic and radiator) will net you more effective delta t due to all draw being forced through the cores. Discharge ductwork(backside of shroud) should be short and unrestricted. I like using the stock volvo clutch fan shrouds on efans for that reason. CFM and FPM should be more than enough w a properly sized electric fan.

linuxman51 said:

^lol, $30 for 4 10mm nuts and a couple 8/10mm shroud bolts.

I gotcha covered for free when this 240 settles down and runs right. we can do loaded tests, unloaded tests, coastdown tests to determine total driveline differences... and since it's mine, it's free. I may even retrieve my old lh tuning stuff and see what can be beaten out of an otherwise stock car..

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In for results

the results will surprise you (it wasn't actually the 242, that car is turbo, and has an e-fan amoung 1000 other non stock things)

uploading info..

aight. so here's the setup:


They don't come a whole lot more stock than this, the only "mods" it has are.. no cat (wasn't me), and the egr system is ****ed up so I blocked it off at the intake. Even the hot air intake was still hooked up until I needed to move it for the dyno's optical pickup.

I was troubleshooting some other stuff initially (and fixing things as they came up). Very first pull was 77 whp, running very poorly. After running some stuff through, I ended up replacing the oxygen sensor (still not 100% sure that it's acting completely right, but I think there's other stuff going on right now) with one off the parts 244, things cleaned up a little. Fixed a trans leak, did a couple runs to let the ecu sort itself out, played with cruise control (Works... sort of, think it's got a leak still somewhere), and tried to get as much of the year-old 82 octane out. Then I added 5 gallons of fresh 93, and it was a different car entirely.
So, that's where this story begins:



First pull on the graph (run 7) was after letting it idle for a few minutes (where it finally leaned out into the 12's at idle, suspect knock enrichment is to fault for some of that), everything was up to temp already. the mechanical fan never fully engaged before, during or after the pull

Second pull was minus the shroud and mechanical fan. I will say this about the mechanical fan on the car.. either it's leaked out and garbage, or conditions in the room didn't warrant it engaging. The car never indicated any kind of overly warm running condition, so, it could go either way. I would guess the unloaded weight of the unit to be a couple of pounds. The car *sounds* like it rev's easier without the fan on. Car was off (obviously) for the removal of the fan, would estimate 10 minutes or so. other fans in the shop were blowing around the car.

Third pull was minus the mech fan, and with the top of the airbox open and filter pushed out of the way (i.e. simulating some sorta high-flow intake or whatever). More intake noise, sounded throatier, aaannnddd... that was about it.

Statistically, I'd say all were a wash. The biggest (and least of a surprise) change I got out of the car was getting better gas in it.


From a performance perspective, in the summer with the a/c on, I'd wager the E-fan helps a noticeable amount esp off of idle vs an engaged mechanical fan. Once you get going, it's likely to disengage and not be a big problem. It does take up a lot of space, however, and I have not noticed any substantial problems with the swap. YMMV.

going forward, I'm going to play with the LH/ezk setup on the car and see if I can get it to do better (and ignore the o2 sensor for the time being), esp up top even though the ol M cam is past dead up 'air

I'm guessing it's an auto?

I have seen Volvo 's own dyno sheet with solid and clutch fan. Engine was B21E or A. 1-2 hp difference.

That's awesome Kenny, great data, thanks. Those M-cam torque curves look so much better then they feel..