Real HP loss numbers

[Ord Millar]

There is also a lot of energy that is stored in the driveshaft, axles and
wheels.  A certain ammount of torque is taken for the angular acceleration
of these parts.  This shows up as "loss" when dyno testing the car (or any
other type of acceleration test).


-----Original Message-----
From: Frederic Breitwieser <frederic.breitwieser at xephic.dynip.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Date: Friday, March 12, 1999 3:26 PM
Subject: Re: Real HP loss numbers


>> 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)
>