Real HP loss numbers

[Roger Heflin]

On Fri, 12 Mar 1999, Clive Apps   Techno-Logicals   416 510 0020 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.
> 
> 
> just estimate how much torque it takes to compress a valve spring
> multiply x 1/2 revs x # springs X length of valve travel x
> x losses in the vlave gear and add in the amount that it takes to
> move the valve train components around
> 15% sounds reasonable
> on 300 HP that would meav that another 52 HP was being eaten by the engine
> to move the valves
> 
> Clive 
> 

For the 15% number everyone has generally ment the amount of hp lost
after the flywheel.  The wheel dynos hp nubmer vs.  the engine only
dyno numbers.  So that claim is rear wheel hp * 1.15 (manual tranny)
is roughly equal to the engine hp at the flywheel.   The valves are
the same and already accounted for in both cases.


			Roger