Real HP loss numbers

[Roger Heflin]

On Fri, 12 Mar 1999, Dan Llewellyn2 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
> 
I have heard of people engine dynoing, and then dynoing the engine in
a car (manual tranny) and coming up with 12% for a manual.  I don't
remember who did the work.   The big places to lose the heat are
tranny (I don't know how much heat a tranny can dissapate), rear end
(again I don't know how much), rear brakes and axle (friction), again
no estimate on waste.  75 hp is 55kw so something is dissapating alot
of energy, but since we know the radiator is able to dump alot more
than 55kw (My engine is rater a 370rwhp, so about 275kw, so the engine
is dumping close to 2x that much energy or about 500kw into the
radiator/exhaust flow), so the tranny doing around 55 kw or so does
not seem that far off.  I guess someone needs to put a temp monitor on
the tranny and see how much heat is being dumped in it, at least on
the heat up you could get some idea how much heat it took to heat it
how fast.

				Roger