-----Original Message-----
From: Shaun.Hendricks@bergenbrunswig.com
[SMTP:Shaun.Hendricks@bergenbrunswig.com]
Sent: Tuesday, August 11, 1998 8:00 PM
To: dakota-truck@buffnet.net
Subject: DML: Pulley Ponderings
Hi all:
Just mulling this "Underdrive Pulley" issue over again, and put
with other
things being tossed around the list, I'm unsure if you'd really get
any real
gains of power with them. Follow me a second here:
People are running "Straight Water" in their cooling systems for
maximum
cooling of the engine, yet if you "underdrive" (aka, turn more slowly)
the
water pump, you'll be offsetting any possible gains (by running less
water
thru the system) 100% water may have given you and perhaps making
overheating
a possibility.
With the 180 thermostat, my temp is about tree millimeters past the
cold end of the operating temp. And at anything but idle (maybe not
even at idle) the water pump isn't a "sealed" pump - otherwise , at
wot, you would have 200 psi (I'm talking from impeller speed - not
pressure). Point is that the pump just "swirls" incoming water that
isn't caught immediately by the impeller and that water swirls around
and waits its turn to get caught and pushed through. Bottom line is
that I don't think a lower rpm would hurt one bit as long as it wasn't
too radical. Any kind of quick spinning (something you can't follow
with your eye) and the wp pulley is just fine.
These pulley's turn an alternator so slowly that it borders on not
being
able to charge the battery.
Radical race pulleys - different animal than what we're talking
about.
If this is true, then why turn the alternator at
all and just run your races with the alternator totally out of the
loop?
(combine that with the A/C out of the loop and you have 2 devices
less
running) (install a second battery if the power drain is too much for
1 batt
etc. etc.)
Excellent idea if you're serious about your et's.
Another thing, why 5 pulleys? Unless you need to specifically
lower each
devices RPM's by different rates (a true fine tuning of rpm speed
would
require this) you could just reduce the diameter of the crankshaft
pulley and
it would slow the entire belt down, and the motor could more easilly
turn the
belt over.
The point is to slow everything down by a good margin, but just slow
the alternator down a bit - or perhaps none at all. As for 5 pulleys,
the first thing is looks - all of the pulleys the same is sharp! Also
I forget the term, but there is a term for weight that has to be
moved. It is much more important than weight that doesn't. Example -
take a truck weighing 3800 pounds (mine) and remove 50 lbs - drop
about .05 seconds. Take the same weight off of the wheels (12.5 lbs
apiece, let's say) and you might drop about .07 seconds. These
guestimations aren't scientific, but they are not far off from actual
figures (I was a Hot Rod magazine addict for about five years). FYI -
a big deal about the "Magnum" motors was that the pistons were 100
grams lighter - less than four ounces. It matters.
Without seeing some concrete numbers on how much HP this gives back
to the
motor, this all seems like "snake oil" to me. Every thing that gains
by
adjusting the size of the pulley seems to lose something somewhere
else. On
the list of things that manufacturers tend to "over build" or "do
ineffieciently", I would think these pulleys would be down at the
bottom of
the list. The equipment needs to operate at certain rpms and a
trained monkey
could figure out the ratios to meet those speeds. Just some
"bah-humbug"
pessimism on this topic.
Point is that they look great, removes a little bit of the most
important type of mass (moving) and the horsepower is free - i.e. it
doesn't affect dependability if done properly.
Tate
Shaun
Tustin, CA
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