Real HP loss numbers

[Clint Corbin]

At 12:52 PM 3/12/99 -0500, you wrote:
>I have wondered about this myself.  I have heard anywhere from 15%
>to 25% in drivetrain losses.  What I can't figure out is where the
>energy is going.  If you have a 300HP engine with 25% drivetrain
>loss, then you are losing 75HP somewhere.  Since it doesn't just
>disappear, something has to be soaking up 75HP of energy.  My
>guess is that the loss would be in the form of heat which would
>mean of lot of drivetrain parts would have to be getting really hot
>(assuming the 300HP load on the engine).  Since I have only seen
>my transmission get warm, it doesn't really make much sense unless
>I just haven't had the load on for a long enough period.
>
>I wonder sometimes if people don't estimate drivetrain losses on the
>high side because they don't want to admit that their engines aren't
>as powerful as they want them to be.
>
>Dan L

Here is a couple of things to think about.  One, friction is "usually" a 
function of velocity.  The faster you spin everything, the greater the 
friction.  If you are climbing a cliff and are actually delivering, say, 200hp
to the drive train instead of the normal 35hp your drive train friction
shouldn't increase much.  If you have an automatic, you will probably 
get a bit of an increase at the torque converter under this senario.  Two,
There are a LOT of things on your car that get hotter than hell going down the
road.  When I was a kid (5 or 6), my folks had a Dodge van.  On cold days
during long trips I had two places I liked to take a nap: right behind the 
engine cowl (directly over the transmission) and right over the rearend.
Why?  In both places the floor was nice and toasty warm!  Even when the
weather was in the teen's, there was enough energy dumped by the differential
to keep the floor nice and warm even with the ice cold air flowing under it!

Clint