TwinTurbo.NET: Nissan 300ZX forum - My Arduino multigauge/logger/e-fan controller project (Part
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Subject My Arduino multigauge/logger/e-fan controller project (Part
     
Posted by black300zx on September 17, 2017 at 8:58 AM
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Message It's been a while since I updated on this project, but I've made some nice headway over the summer while still taking the time to actually enjoy my Z (rather than having it torn apart :) )

Background for those who missed part 1:

Part 1

In part 1, I had two of the analog inputs allocated to the lateral and longitudinal axes of a tri-axis accelerometer. After some time I realized that I'd much rather log ambient temperature and perhaps speed or RPM, so I removed the accelerometer and mounted up a 10k thermistor near the intake t-pipe to measure air temp into the radiator. This let me characterize the performance of the stock cooling system as a function of ambient temperature.

The chart below shows average and max observed coolant temps collected from about 40 hours a mixed driving (my commute is ~50% highway, 50% stop-and-go). You can clearly see the 170F OEM thermostat dictating operating temperature below ~70F ambient. Above that, the operating temperature more-or-less increases linearly with ambient temp, as expected.

With that done, I moved onto figuring out a way to log vehicle speed along with ambient temperature. Some google searching turned up a chip from Texas instruments that converts a variable frequency square wave into a variable voltage output. Looking through the example application in the datasheet, it looks like it was specifically designed for interfacing with vehicle speed sensors and/or wheel speed sensors.

La-Z-Link

I grabbed a couple from Digikey and whipped up a little circuit on proto-board and hooked it up to the VSS at the gauge cluster:

It worked well for logging speed (accurate within 1mph according to my GPS), but it caused some flaky operation of the odometer. I kept it hooked up for about a month before pulling it out. I'll have to do some refinement over the winter before putting it back in. Regardless, I generated some interesting data.

The charts below show about 25 hours worth of data, and surprisingly operating temps increased with speed. It seems like the extra airflow at speed isn't enough to offset the additional heat generated by higher RPM. Note: The decrease in temps shown in the 80-99mph range is more an artifact of the small sample size at those speeds.

In the next month or so I'll be knocking out the e-fan install and getting the oil pressure sensor hooked up. More to come then :)

     
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