Real HP loss numbers

[Frederic Breitwieser]

> 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

Typically heat. As you accelerate, even if you don't spin
your tires, the tires do in fact heat a little bit.  Drive
at 65 miles an hour for little while in 30 degree weather
and touch the tire surfaces - you can actually feel some
warmth on the tires.  Also, your automatic transmission has
many places for losses, and these losses generate heat also,
hence the requirement for tranny coolers and such under high
loads.  Also, your torque converter, when it locks, doesn't
quite lock at 100%.  Being a fluid based "clamp" so to
speak, there are losses in there as well.  Also, engine
bearing friction, rear seal friction, etc all add up.  Even
your rear heats the fluid slightly, as you have a mechanical
connection (ring and pinion) that as it rotates, generates
heat.  It makes heat because the teeth intertwine with each
other, and the pinion frictionally moves the ring gear
around.  Some vehicles, especially long-bed trucks, have a
split driveshaft going to the rear end, which at the joint
of the two shafts, have a giant sperical bearing of some
sort.  This heats up too :)

Heat!

> 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.

Could be.  The only way to really know for sure is to dyno
the engine and measure flywheel torque and estimate the HP
from there, then do the same at the rear wheels, and compare
the two mathematically, then you know what your drivetrain
losses are.

-- 
Frederic Breitwieser
Bridgeport, CT 06606

http://www.xephic.dynip.com
1993 Superchaged Lincoln Continental
1989 500cid Turbocharged HWMMV
1975 Dodge D200 Club Cab (soon to be twin turbo 440)
2000 Buick GTP (twin turbo V6)