Stock clutch fan max RPM
07-03-2018, 02:14 PM
#21
Le Mans Master
I think that there is no question that an electric fan is more efficient at cooling the engine....There is no way every car on the road today would use a cycling on/off electric fan if there was not a HP/efficiency benefit versus a mechanical clutch fan. Every car I own that is 1994+ forward has an electric only fan. There is a great reason for this configuration.
For many of the reasons stated previously about mechanical clutch fans like on my 78, I have retained the OEM fan setup. PLUS, if you run a tranny cooler ,if your car is an automatic, which all autos should have in my opinion, a mechanical fan is great for pulling all through the cooler at all times. Pluses and minuses................
BTW-An electric fan setup correctly from the factory will not allow temp fluctuations on the gauge like on earlier cars with electric fans. My Daughter's 2001 Pontiac grand prix does show fairly wide temp swings on the gauge depending on whether the fan operates or not. However, all the more modern cars do NOT show any gauge fluctuations on the gauge since the fans operate immediately if the temp moves beyond a very narrow window........
For many of the reasons stated previously about mechanical clutch fans like on my 78, I have retained the OEM fan setup. PLUS, if you run a tranny cooler ,if your car is an automatic, which all autos should have in my opinion, a mechanical fan is great for pulling all through the cooler at all times. Pluses and minuses................
BTW-An electric fan setup correctly from the factory will not allow temp fluctuations on the gauge like on earlier cars with electric fans. My Daughter's 2001 Pontiac grand prix does show fairly wide temp swings on the gauge depending on whether the fan operates or not. However, all the more modern cars do NOT show any gauge fluctuations on the gauge since the fans operate immediately if the temp moves beyond a very narrow window........
Last edited by jb78L-82; 07-03-2018 at 02:19 PM.
07-03-2018, 02:32 PM
#22
Team Owner
Very interesting clip. I was impressed that they installed a radiator and shroud with the fans to make an realistic model for testing Results were similar to what I would expect, with the clutched fan coming out the 'winner' of the mechanical fan options.
It's no surprise that a mechanical fan without a shroud uses LESS power. But, it also does a very poor job of cooling, due to the much less air actually drawn thru the radiator.
It's no surprise that a mechanical fan without a shroud uses LESS power. But, it also does a very poor job of cooling, due to the much less air actually drawn thru the radiator.
07-03-2018, 04:41 PM
#23
Racer
I run a DZ302 fan (no part number) and clutch, 7 aluminum blades with curved tips, pointed drilled and balanced spider.
Lighter, quieter, and moves more air than the stock steel 5 blade.
Gm thought it could handle all the RPM's a 302 could muster.
Lighter, quieter, and moves more air than the stock steel 5 blade.
Gm thought it could handle all the RPM's a 302 could muster.
07-03-2018, 07:32 PM
#24
Race Director
Member Since: Apr 2007
Location: South Western Ontario
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Here is the one link. The other one is now dead.
http://www.carnut.com/ramblin/dyno.html
Note that the alternator test was installing it and loading it, so the HP loss included spinning the alternator which every engine in a street car is already doing.
There is decent proof of how much more loss a mechanical fan can have between this and what Fred posted.
http://www.carnut.com/ramblin/dyno.html
Note that the alternator test was installing it and loading it, so the HP loss included spinning the alternator which every engine in a street car is already doing.
There is decent proof of how much more loss a mechanical fan can have between this and what Fred posted.
07-04-2018, 03:17 PM
#25
Le Mans Master
We all have our "beliefs". Some beliefs are actually based on reality; others are just what we wish them to be. Whether a mechanical fan or the electric version will be most efficient for a specific vehicle is more a function of the selection of temperature settings (thermo trip-point or e-temp controller settings) and the actual "needs" of the cooling system. The actual energy used for either is not as much different as you think. The mechanical fan runs all the time (mostly in "slip" mode)...but it is always pulling cool air through the radiator, too. The e-fan runs only when controller calls for it, but it sees larger swings in temp and works harder....when it works.
Bottom line: If both systems keep a running engine managed to the same average temperature, the amount of cooling air going thru the radiator MUST be about the same. Thus, the work done by either must be very similar. To the engine, work is work, whether it is done by the alternator (via fan belt) or by the water pump shaft (via a different belt).
Bottom line: If both systems keep a running engine managed to the same average temperature, the amount of cooling air going thru the radiator MUST be about the same. Thus, the work done by either must be very similar. To the engine, work is work, whether it is done by the alternator (via fan belt) or by the water pump shaft (via a different belt).
Short version of the story, the car was making 445 rwhp on a SuperFlow chasis dyno, while running the oem 7 blade clutch fan and Hayden #2799 fan clutch (severe duty). After a series of pulls, I removed the fan while on the dyno, the car immediately went to 460 rwhp...so it gained 15 rwhp going through a T400, 3200 stall and heavy IRS parts.. That’s at least 20hp at the crank. Not to mention the engine was already heat soaked.
Weeks later, I now had an electric fan setup on it, CS144 alternator on the car and I was at the drag strip testing. The car was consistently 1.5 mph faster....and one pass was even 2 mph faster without the E fan running. Last run of that day. I forgot to turn the fan off after staging, I made the pass with the fan on, and it was still 1 mph faster then ever with the clutch fan on. 1 mph at 3660lbs is easily 15hp. Verified. Proof is in the pudding.
As for temp swings, during the summer, my temp is always 178-188*, fan comes on at 188 and off at 178. 10* temp swing is nothing. With the AC on, the fan running with the compressor cycles, the temp holds 185-188*, even on a 100* day. With a clutch fan I would be 215+
Thats the facts, that’s the reality.
The following 2 users liked this post by ajrothm:
jb78L-82 (07-04-2018),
lionelhutz (07-04-2018)
07-05-2018, 07:50 PM
#27
Le Mans Master
I have a Lincoln MKVIII fan, this car can idle for hours with the AC on and never get over 190*.... The fan will still cycle off with the compressor.....It stays MUCH cooler with the E fan then it did with the 7 blade clutch fan. If I run the fan in manual, I can cool it down in the 170*s on a 95* day.... which is good for hot weather racing. Normally it cycles with the temp switch or the compressor switch.
07-06-2018, 01:29 AM
#28
Team Owner
I ended up with twin Spal fans. something like a true 3200 cfm. I had to get a 105 amp alt. to run them because they take 30 amps if they are both running. In general I only have one on. I also have much brighter lights, no stereo, and a AGM battery
