To all,
Remember we had this great dialogue a year or so ago? Dan Masters had some
actual "numbers" posted. Without a major rehash, the electric fan is a
great idea but not just for the bhp it liberates. The fan pulls (or pushes)
a rev-independent amount of air, thus it is as effective at idle (likely
more effective) for cooling. At high revs, the inertia drag of the fan does
rob some power as it "slows everything down" a bit.
More to the point, an engine driven fan does nothing for cooling above
about 30 mph. Proof lies in my "stock" GT6 racer, sans fan (got ruined in
the crash) not overheating an 60 deg. ambient temps, even as I putter around
town. Stoplights provoke an almost instantaneous rise in coolant temps.
As far as the alternator story goes, pick your story. Removing the
alternator completely saves weight and thus makes your car go faster.
However, the voltage drop in the system may (or does) affect coil output,
and thus spark. Weak spark, as we all know, costs bhp too. Why else do we
put nasty coils and electronic ignition systems on instead of points?"
Simply disconnecting the alternator just might, might, make a small
difference, but if one bhp is 730 watts (or something like that), a 60 amp
alternator will draw 1 bhp at full load. Big deal.
And lets also not forget about torque. This twisting force is what makes
your car move. Torque divided by time is bhp. Therefore, revving the motor
faster should produce more bhp. Lightening the flywheel reduces the torque
needed to overcome flywheel inertia, and this is likely much more relevant
than an engine fan or alternator. Carrying baggage (or passengers, or bondo
for that matter) increases torque needed for a given acceleration. Dragging
brakes or poorly adjusted wheel bearings will do likewise.
I have an old CCC magazine detailing a Lotus Elan engine builder that had a
reputation for "legal motors making illegal amounts of power". His theory
was simple and stands today....find a detail that makes an extra bhp.
Repeat as required. But first, take care of cheap and easy stuff. And
remember, speed costs money.
So, thumb your nose at the purists and get the electric fan (as much for
cooling efficiency as bhp gains). Leave alternators alone (and don't even
start on generators). Tune your car for power, not economy or emissions
(now I didn't actually SAY that guys, lest the EPA get on my case). Give it
more spark. Inflate your tires properly. Do an alignment. Adjust your
brakes and bearings. Carry little ballast. Reduce exhaust restrictions via
headers and/or free flow mufflers. Etc. Etc. Etc.
Dave T
PS: something I remember reading (concerning daytime running lights in
Canada) suggested that DRL's caused a decrease in fuel efficiency of 0.1% vs
American cars. That would be about 1/10 bhp (% figure) or 0.025 mpg on a TR
if translated back into real numbers. Now, if 2 55w lites (8.5 amps,
about) takes .1bhp....
D
-----Original Message-----
From: Shawn Loseke <SLoseke@vines.colostate.edu>
To: LBPB1@aol.com <LBPB1@aol.com>; triumphs@autox.team.net
<triumphs@autox.team.net>
Date: March 12, 1999 1:00 PM
Subject: Re: Power Upgrades
>
>All right, the fan is likely to free up some H.P. because your reducing
>mass that the motor has to turn. 12 H.P. is probably optimistic. But an
>on/ off switch for the alternator is a load of crap. Sorry to be blunt, but
>the only horses to be gained from eliminating the alternator is to remove
>the parasitic drag from the alternator belt. An on/off switch for the
>current it creates would have no beneficial effect what so ever.
> While were at it, seat of the pants acceleration tests are not a good
>indicator for performance enhancements either. It might feel different, but
>that doesn't mean it's faster. The only accurate way to judge whether a
>change is beneficial or detrimental is by dyno. If that's not available,
>try a stop watch.
>
>Rant mode now in retrograde
>-------------
>Original Text
>From: <LBPB1@aol.com>, on 3/12/1999 10:21 AM:
> Tom,
> I work with a friend on racing projects every now and then and he
>informed me that two ways to collect wasted HP were to one, remove the
>standard fan and replace with an electric one (about $60.00 at disount
>auto)
>and two, set the alternator up with an on-off switch. According to him both
>these things are worth about 12 hp each. Its almost like free power! Some
>people spend hundreds or thousands of bucks to get an extra 24 horses. He
>told
>me to test it by making an acceleration run with the fan and then remove it
>and try agian. He claims that the difference is very noticable. I have not
>tried it yet since my car is still on the shelf and in boxes :(
>
>PLB3
>
>0
>
>
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