[s-cars] Fans on the dyno

[Mark Strangways]

Well I suppose I will never find out as the fan come off with a sawzall.
And since I don't have an electric in there right now, there is no draw what so ever I guess I have the best of both worlds.
This begs the question... where did 40 HP come from, and... can I do it again.

The other variable might have been going from winter tires to summer rubber ?

Mark
  ----- Original Message ----- 
  From: QSHIPQ at aol.com 
  To: StrangConst at rogers.com ; petergolledge at gmail.com ; Djdawson2 at aol.com ; fastscirocco_2000 at yahoo.com ; s-car-list at audifans.com 
  Sent: Saturday, May 12, 2007 10:02 AM
  Subject: Re: Fans on the dyno


  Safety first!  I've stopped a lot of fans with gloves Mark, and the S car one is the easiest (you should see the blade on the landcruiser!).  I don't advocate it, just indicating that 40hp wouldn't allow me to stop that fan with a 2x4.

  Usually a mechanical fan is more efficient at higher engine rpm (electrics advantage is that it's not tied to engine rpm), and not so efficient at lower rpm, since fixed pitch blades have an "optimal" rpm.  Higher fan rpm does mean higher load, on both the mechanical and the electric (again see Spa specs).  This is a function of the work output of drawing air thru the radiator (or in the case of my supercharged landcruser at Steamboat, a function of drawing the blades thru the radiator core... doh!).

  That said, I think if you compare full load of the mechanical fan in the S car with a equivalent electric fan, the alt at 100% will draw more power.  If that wasn't the case, then the mechanical pulley for the fan in the S car should be on the front of the ribbed belt, not looped to the back.

  Again, I got a beer says taking the mechanical fan off the pulley of an S car, won't yield any measureable gain on the dyno, because I doubt it draws 1 hp fully locked up.

  My .02

  Scott Justusson
  Electric fans a plenty 
  1 landcruiser mechanical fan modded with the aid of rocket scientist Dave Lawson

  In a message dated 5/12/2007 7:41:01 A.M. Central Standard Time, StrangConst at rogers.com writes:
    I will not argue with your math, not one bit.
    But I would not be trying to stop my , or anyone else's seized VC fan. Not with a glozed hand, not with a block of wood.
    I don't remember what other changes where made between run's but it wasn't significant.
    I think I just removed the fan and adjusted the water injection.

    Maybe my only comments to your deductions is that a mechanical fan's power requirements are a function of it's RPM. Higher RPM = higher load ? No ?

    Just how many HP does it take to turn the alternator shaft when the load on it is 95% ?

    Mark






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