fan / alternator hp losses ??? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> General Rodding Tech
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 04-19-2010, 06:44 PM
Registered User
 
Last photo:
Join Date: Apr 2010
Location: B.C. Canada
Posts: 56
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
fan / alternator hp losses ???

Interesting test, seems like a lot of hp losses for a conventional fan. Check it out

http://www.carnut.com/ramblin/dyno.html
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 04-19-2010, 09:26 PM
ericnova72's Avatar
More for Less Racer
 
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 47
Posts: 7,664
Wiki Edits: 0

Thanks: 10
Thanked 148 Times in 136 Posts
Doesn't surprise me in the least, the fan is the biggest hp draw of all the accessories. What cracks me up is the guys who won't run an alternator on their "race car" because the say it eats too much power . 1.28 hp on the test you linked, and I have seen the same result in other tests.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 04-20-2010, 09:39 AM
1ownerT's Avatar
Home School Valedictorian
 
Last wiki edit: Health and safety in the shop or garage Last photo:
Join Date: Dec 2004
Location: Iowa
Age: 52
Posts: 1,645
Wiki Edits: 4

Thanks: 0
Thanked 3 Times in 3 Posts
Really interesting.
Thanks for the link!
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 04-21-2010, 03:32 AM
Registered User
 
Last photo:
Join Date: Dec 2007
Location: Toronto, Ontario, Canada
Posts: 67
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Good stuff.

They mentioned "design flaws and safety issues" with the flexfan. I can imagine that it's to do with the constant flexing and the fatigue it might cause, but does anyone have more details/experiences/horror stories?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 04-21-2010, 06:22 AM
Member
 
Last photo:
Join Date: Nov 2004
Location: Lakeland FL
Age: 65
Posts: 4,110
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
my $.02:
VERY likely he has the decimal point in the wrong place for HP....

consider this ex:
746 watts = 1HP
typical oem 2k cfm plus 18" plastic blades electric fan operates with 14V x 20A =280 watts
280W/746W=.37HP to move 2k+ cfms of air...
(it does take "some" more power to spin a steel fan versus a plastic fan due to the steel mass/weight but it is typically/roughly .25HP depending on the fan and the pulley ratio)

AND his test has next to nothing to do with how a fan clutch actually does work in the real world...

random pick explaination:

http://bbs.zuwharrie.com/content?topic=12721.0;wap2

LOL,,,if the motor coolant temp is hot enough to actually lock up the fan clutch at 1600 or 4500 rpms,,,you won't be worrying about HP drain...

he didn't say what the pulley ratio was or rad core config but if you move the decimal point over one place those could be (????) legit numbers...
(yeah,,,,, a direct drive/no clutch BB 18" steel fan would/could pull about 4HP at 4500rpm's "but" there would also be a MAJOR hurricane's worth of air thru the rad and engine compartment to cool the motor!!!!)

Last edited by red65mustang; 04-21-2010 at 07:00 AM.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 04-21-2010, 06:56 AM
Registered User
 
Join Date: Aug 2007
Location: Sterling Heights, Michigan
Posts: 242
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
You make many good points, but in the real world most fans are setting in the engine compartment just spinning thrashing air about. The builders won't build or have know idea how to build a good fan shroud. Also they do not want the bulk uglyness of a shroud with the bling/chrome pieces.
The good electrics have built in shrouds that provide a plentum so air will be drawn across the full face of the radiator.
Also seen many ten inch fans slapped on the radiator face with zip ties trying to cool a smallblock!
Any way you look at it a 40 Hp loss is too much to throw away or just write off as operating expense.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 04-21-2010, 08:41 AM
Member
 
Last photo:
Join Date: Nov 2004
Location: Lakeland FL
Age: 65
Posts: 4,110
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
jag,
you missed my point?

doesn't matter what the fan blades power source is (steam/electric/hydraulic/whatever),,,there is NO way it takes 40HP to turn a 7 blades 18" fan at 4500 rpms with only air resistance putting a load on the motor...

LOL,,,the car makers do dumb things but no way would they have used motor driven fans with/without clutches for all those years if 40HP was needed (right at the typical oem cam HP peak rpms)....

if it was a particular pitch 7 blades 18" boat propellor test IN WATER then 40HP needed could make sense...

basically,,,just common sense is enough to tell you his fan HP numbers results have to be bogus by a mile...

and are proven wrong by many other tests articles...
Reply With Quote Quick reply to this message

Recent General Rodding Tech posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
New fan with adjustable temp control help redride Electrical 3 05-30-2009 10:22 AM
building a fan shroud - need help 32Tudor Hotrodding Basics 30 07-03-2008 09:01 PM
Electric cooling fan Z-Money Pit Engine 1 08-29-2006 08:27 PM
Need advice on a good electric fan set up. Streetmaster Engine 13 01-07-2006 02:37 PM
? about an electric fan for PU. Streetmaster Engine 8 08-20-2005 10:14 PM


All times are GMT -6. The time now is 11:03 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.