Clutch Fan vs. Electrical

[digger]

Converting mechanical energy to electric then back to mechanical is not efficient and alternators have losses, there is no free lunch. Wish I owned a dyno to do all the test.

Anyways there is a carcraft may 2000 article that tested more fans and bassed on that info I set my underdrive to limit my losses of my plastic(EVIL) mech fan to about 11-13hp at my max rpm.

I like engine masters they r decent at confirming stuff.

An electric fan will consumer stuff all power compared to mechanical , simply because they cant move anywhere near as much air as a mechanical fan . You can get electric fans upto 700w or so that I've seen and factoring alternator efficiency it's still not much. The issue always is does it cool good enough for the worst conditions.

[Circlotron]

As part of my job, some years ago I had to measure the effect of various airflows in removing heat from a finned aluminium heatsink as used in some kinds of electronic stuff. Going from zero to just a slight waft of air made a huge difference. Slight to moderate made a further but less substantial improvement. Moderate to gale force made almost no improvement, maybe 15% or so. That being the case, an electric radiator fan would do more of a job than it's tiny power output might indicate. The much greater airflow from a good mechanical fan would be better at cooling, but not as much as the increased airflow might seem to indicate.

[fzsk4p]

Circlotron you got me !! Pleading the 5th and blaming AutoCorrect on that one.

Here again, we spend lots of time running at low speeds 1-2000 rpm. An occasional bounce off the rev limiter on an as needed basis. This environment is what I am calling the "hard to cool" time. The clutch fan works well and unlike the Spal that I was running keeps the engine cool.

Granted the Spal wasn't mounted or shrouded as well as it could of been the failure of 3 Spal temp sensors pushed me to the clutch fan.

Fast forward to today and my setup now includes an OBD2 management system (was OBD1) that has had the cal tweaked to include controlling electric fans.

Breaking this down.
The current clutch fan works well in keeping the engine cool. Problem is blowback when the conditions are such that the windage or actual depth of the environment doesn't play nice with the fan. Then according to the links it DOES eat a bit of power. Maybe more than I thought it would. Need to study this more and apply the findings to my application. The EM test and the Flex a Lite report seem quite different in some respects.

Who doesn't want more power or mileage ? Don't always idle around the rocks and mud. Typical pavement driving with a mix of surface streets and freeway. Maybe there is a way to have a reduction in parasitic drag and deal with the blowback.

[carmakerevive]

I would think that on a setup with well sealed ducting, that the HP loss would be somewhat reduced by the "venturi" effect of the air driving the fan?

But i guess that would be more effective at a constant rate of speed, without the accel/decel loads that the engine goes through having to power the fan up and down.

Personally Id prefer the electric fan on a temp switch over a clutch fan.

[cjperformance]

Well not a dyno number but on the strip running WITH a Ford 351 cleveland factory fan clutch 1:1 drive with crank and using a blade set from ~76 model 460 which are slightly larger in diameter and inside a properly fitting shroud (kept it at correct temp at all road speeds or idle in all weather)then removing the clutch and fan and running with NO fan on a cool 18-20*C afternoon made NO difference at all to 1/4 et in a proven consistent setup. Never tried the same car with elec fans so cant comment on any loss there but there would have not been a gain running elec fans over no fan at all !
Thats just one example.
Ive been thru it so many times and for many years now only use elec fans if there simply is no room for a good mech/clutch set up or if the customer just wont see sense! For a streeter a clutch fan is by far the best, fixed fan probably the most reliable, elec fan looks great in a magazine! Haha

[fzsk4p]

^^^This guys makes a lot of sense ya know^^^

The OEM cooling system has to deal with the heat of the desert and the cold of the artic. Customers are not happy if the vehicle is in the shop. Add the all the government regulations for emissions and mileage it becomes a challenge. Throw the finance guys in and engineering has a headache.

Suspect the system on my vehicle while perhaps not being the best or most efficient simply works. Plus the tooling is paid for. From the manufactures standpoint its a win.

In fact its good enough to cool a stroker running more cam, compression and gearing with nothing more than a HF WP. Which it probably didn't need but I HAD to do something to the otherwise stock cooling system.

As with most every hot-rodder we like to see if we can "improve" on what we are working on. Even if its a perceived improvement. Sometimes our operating conditions are so far removed from factory we are forced to engineer a system.

I need to look hard at this electric fan "improvement" and really decide if its going to be a benefit.
With the help of Speed Talk I now have some good data to work with.

Thanks guys, by all means if anyone has anything to add feel free to do so.

[aquartlow]

I went from using a 7 blade clutch fan/fan clutch assembly on my Ranchero's 472", to a '98 Ford Windstar dual electric cooling fan assembly, the biggest surprise I found was just how much faster the engine "spooled-up" once the heavy/bulky mechanical fan assembly was removed and replaced by the electric fans. I have noticed better idle/idle in traffic temp control, better mpg's and a bit of a boost in my A/C system's performance. Hope this helps.

[cjperformance]

I went from using a 7 blade clutch fan/fan clutch assembly on my Ranchero's 472", to a '98 Ford Windstar dual electric cooling fan assembly, the biggest surprise I found was just how much faster the engine "spooled-up" once the heavy/bulky mechanical fan assembly was removed and replaced by the electric fans. I have noticed better idle/idle in traffic temp control, better mpg's and a bit of a boost in my A/C system's performance. Hope this helps.

I have heard this sort of thing so many time and in EVERY case where I have been able to get hold of and check the removed clutch , the clutch was faulty! And in most cases had done 100K miles plus sometimes over double that.

Out of interest in the 1/4 mile example I posted above , when the fan/clutch assemble was removed the idle speed did not change much at all, note this was in cool weather so the clutch was not fully engaged.
Whereas in just one example of another customers car running 545ci bbf with a VERY mild smooth cam and big intake vacuum that also runs dual electric fans on a thermo switch, when the fans cut in the alternator loads the engine to the tune of an ~150 rpm drop at idle.
Most OEM's now bring the fan/fans on in stages to reduce this affect AND have ISC valves which mask the rpm drop (unplug an ISC and see what I mean when the fans come full on).
3 main reasons OEM use elec fans in so many light/medium duty applications...
1- manufacturing cost(profit)
2- ease of vehicle assembly(profit)
3- the ability to shut fans off in warmup which aids emissions equipment to operate sooner (epa, emissions advertising/sales-profit!)

So many 4wd, commercial,heavy applications still run clutch type fans, what does this tell you, and with that some if these turbo diesel engines get amazing fuel mileage even turning one if those evil clutch fan assemblies!

[aquartlow]

My fan clutch was brand new, maybe you were assuming I had a worn out or faulty fan clutch, not sure. I just gave the results I have seen and/or realized when I installed my own electric cooling fans, never advised anyone to change so you can stay with your choice of clutch fan assembly if that is what is wanted. If using a decent PWM fan controller as opposed to a simple Bosch style relay employed controller, the idle drop and subsequent electrical spike will not exist. Another reason electrical cooling fans are now so prevalent, which was left off the list, is increased efficiency. A mechanical fan turns and is a parasitic drag on the engine at ANY/ALL times the engine is running, electrical cooling fans(if set up properly) only loads the engines through the alternator at low speed and/or A/C is in operation when there isn't enough airflow like when at increased vehicle speed. Not here to argue and I do see your points, but what I have encountered and will continue to see/reap the benefits of using electrical cooling fans over a mechanical fan. Both have advantages and disadvantages, the individual owner has to weigh those out to determine which is a better fit for his/her needs. Good luck on your choices.

[benno318]

I went from using a 7 blade clutch fan/fan clutch assembly on my Ranchero's 472", to a '98 Ford Windstar dual electric cooling fan assembly, the biggest surprise I found was just how much faster the engine "spooled-up" once the heavy/bulky mechanical fan assembly was removed and replaced by the electric fans. I have noticed better idle/idle in traffic temp control, better mpg's and a bit of a boost in my A/C system's performance. Hope this helps.

I have heard this sort of thing so many time and in EVERY case where I have been able to get hold of and check the removed clutch , the clutch was faulty! And in most cases had done 100K miles plus sometimes over double that.

Out of interest in the 1/4 mile example I posted above , when the fan/clutch assemble was removed the idle speed did not change much at all, note this was in cool weather so the clutch was not fully engaged.
Whereas in just one example of another customers car running 545ci bbf with a VERY mild smooth cam and big intake vacuum that also runs dual electric fans on a thermo switch, when the fans cut in the alternator loads the engine to the tune of an ~150 rpm drop at idle.
Most OEM's now bring the fan/fans on in stages to reduce this affect AND have ISC valves which mask the rpm drop (unplug an ISC and see what I mean when the fans come full on).
3 main reasons OEM use elec fans in so many light/medium duty applications...
1- manufacturing cost(profit)
2- ease of vehicle assembly(profit)
3- the ability to shut fans off in warmup which aids emissions equipment to operate sooner (epa, emissions advertising/sales-profit!)

So many 4wd, commercial,heavy applications still run clutch type fans, what does this tell you, and with that some if these turbo diesel engines get amazing fuel mileage even turning one if those evil clutch fan assemblies!

cant agree enough with craigs points.

the example i always give is to look at a van, one of the hardest body styles to cool - im unaware of any vans in australia where i live that run purely an electric fan - all have a clutch type fan, as most of these rely on the fan to pull air whether in slow traffic or driving down the highway.

factory clutch fans are what i also use and recommend - when they fit.

[fzsk4p]

Spot on in so many ways. That is to say I agree with what Craig and several others are saying.

My setup is only using FRESH OEM parts. In fact I have a spare clutch (NIB) in the event the current one fails. Not to mention another OEM fan asm.

Whereas I cannot argue some of the supplied data there are still variables particular to each application. Even the supplied data points this out. Say the EM loss compared to the FaL loss as an example.

In my particular application the primary objective is to cool the engine. Not reduce ET`s or lap times. I came into this curious just how much power the clutch fan absorbed and whether it might be worth the time and expense to change to an electric.

Being that my engine runs cool........while others with electric`s have had overheating problems during the same day and time..........I think I`ve answered my own question. Sure, a bit of power is being consumed with parasitic drag.....how much is a variable.......the fact is, the current system simply works. Add all the complexity and potential failure points of the electrics to the mix and the clutch is the way to go for my particular application.

Home run Speed Talk.

[rfoll]

I have an new electric fan for the race car that I have never installed. When at the track, there is very little run time to allow the battery to recharge fully, and at sunset the make you run your lights. Add the moron staging lane attendant who feels that one car at a time from each row is sufficient, and you have a recipe for hot starting issues. I have been using the same clutch fan since 2002, and the engine never gets over 180.