Thanks guys, glad you like it.
Adrian, thanks for the tips on the Turnigy watt meter. I will be sure to check the calibration of the sensors before I take any of the readings too seriously.
Acuteaero, Yes the load cell stuff comes from the cheap source on ebay (search for 'load cell kit' ). It uses parts from the 25lb kit.
The microprocessor, and usb link of the kit are not useable for this job, because the firmware wont output any readings unless the load on the cell is absolutely constant (which it never will be on an operating dyno).
The front end of the kit uses an Avia HX711 chip which is a combined instumentation amp and autonomous 24 bit ADC. You can find a summary data sheet for it on the internet:http://www.aviaic.com/UpLoadFile/hx711_brief_en.pdf
If you look at the kit pcb, you can find two tracks carrying clock and serial data going from this chip (pin 11 +12) to the processor.
You will need to connect your own microprocessor to these clock and data lines to capture the 24bit data which is transmitted 11 times a second.
You will then need to write your own filtering and scaling/calibration functions.
PS I like your approach of using a car alternator as the generator and varying the field current to change the load, -very neat