Engine dyno for EFI project

[robert dingli]

Dave writes,
> 
> Hello,
> 	Does anyone have any tips or plans on how to build an engine dyno? 
> Before I start my efi project I want to build a dyno so I can benchmark my
> results and debug the system in the shop.  

Dynos can be categorised according to the job that they have to do.
How much power will your engine produce at the flywheel?
Do you require the dyno to motor the engine?
Do you wish to do transient tests or even full drivecycle tests?

A water brake is one of the simplest and most rugged apparatus. (In fact,
I have a disassembled 450 HP H&F water brake (circa 1926) sitting under
a shelf that I want to get rid of one day.  It is still 12 years newer
than one of the units in our lab).

An eddy current load cell is also quite simple (especially air cooled
versions).  They basically comprise a truck retarder (usually a Telma)
with a controller and cooling system.  Our air cooled chassis dyno
will handle 350 bhp at the wheels and has been used to test prime movers
as well as many cars.

For more real world simulation applications, a motoring dyno may be required.
In out labs we use a couple of different configurations.  There is an
eddy current load and DC motor drive system.  My own work revolves around
a hydraulic dyno/motor.  The load cell is a hydraulic pump/motor.  Next
to this is a large 50HP DC motor with another hydraulic pump and a heat 
exchanger.  The system can switch from motoring to absorbing within milli-
seconds.  Often I have run out of fuel during fixed speed tests and not 
even noticed before checking the gauges.

There is also a large disk brake dyno that isn't currently used, so I assume
this system is possible.

For your application, have you considered a simple inertia dyno (as used
for motorcycle tuning).  They are basically a large flywheel.  Another 
option for single speed tests would be a large torque convertor + associated 
plumbing for cooling.

One word of warning.  Make sure your driveshaft is properly balanced and
shielded, and avoid speeds which excite their resonant frequencies.  You
will require a much larger than standard engine fylwheel and a flexible 
coupling in the driveline somewhere between engine and dyno to absorb 
torsional vibration.  I'm sorry to sound so grim, but a student was killed 
in Victoria earlier this year when a dyno driveshaft let go.

Robert Dingli
-- 
----------------------------------------------------------------------
             Robert Dingli           r.dingli at ee.mu.oz.au

Power and Control Systems                 Thermodynamics Research Lab
Electrical Engineering                    Mechanical Engineering
   (+613) 9344 7966                          (+613) 9344 6728
  University of Melbourne, Parkville, 3052, Victoria, AUSTRALIA
----------------------------------------------------------------------