Thanks!!!

Before I got my Graham scanner, I was building my own instrumentation for my Prius. These techniques are universal and work on any hybrid vehicle so I would like to share them. Some of our Japanese friends have followed a similar path with the NHW20 models, building their own instrumentation. Finally, good friend Hobbit of the Prius_Technical_Stuff YahooGroup has done similar work.

What we all did is start with the electrical schematics from the maintenance manuals. Without the schematics, many interesting signals will be terribly hard to hunt down. Then comes the easy part, measuring them.

Hobbit uses small jumpers to critical signals that he routes to the passenger seat oscilloscope or breadboards. Typically he records the data manually and is done. Our Japanese friends, do one better with instrumentation connected to uprocessors. This leads to some of the 'super scanner' devices. My approach is to use the stereo audio channels of a laptop to record the data for later analysis:


What you see is a miniature audio jack connected to some ethernet cable that goes to a pair of magnetic line coils. Earlier testing verified that 50 turns would generate a 1 V. peak-to-peak signal, exactly the right level for 'line input' to the laptop microphone jack. The pipe clamp, carriage bolt and wing nut are used to clamp around one of the MG power leads with the carriage bolt going through the magnetic pickup coil. With two pickup coils, one goes around an MG1 lead and the other around an MG2 lead. This allows recording the power going into or out of MG1 and MG2 as an audio recording:

http://hiwaay.net/~bzwilson/prius/magnetic.html

This gives you a way to see the current signals and begin to understand vehicle operation. The same technique can be used to monitor fuel injector timing and other AC signals. For DC voltages, you'll need a 'chopper' circuit and suitable voltage divider networks.

Once you have data, you can look at timing relationships and even calibrate the signal using a 120 W. light bulb and a single wire through the pipe hanger. Fairly simple programs can convert the audio data into spreadsheet compatible format. But the biggest gain is seeing what is happening:

http://hiwaay.net/~bzwilson/prius/motor.html

My last suggestion is to install an ethernet cable between the engine and the cabin to bring interesting signals inside. My approach is to find the 'fresh air' vent, remove the cabin air filter and drop the cable down, out the cabin filter holder:

Then I drilled a small whole in the filter frame, threaded the cable and voila, I have ethernet cabling between the cabin and engine compartment:


http://hiwaay.net/~bzwilson/prius/pri_tt.html

Obviously these techniques need to be adapted to your specific vehicle but the nice thing is:

1. Independent of OBD scanners
2. "Real-time" data versus lags found in OBD data
3. Subtle effects not visible in 'just a number'

The bad thing is you'll need some skills and resources:

1. laptop with audio input jack and 'open source' (free) audio software
2. understanding of basic electronics
3. self-calibration of test circuits
4. software if planning to convert to excel analysis format

Does this help?

Bob Wilson

Operation Iraqi Oil Freedom:

Automatic, stock, project car.

My other 1500 cc car:

Automatic, stock, backup car.
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