RPM Signal Issues

Race Capture Pro hardware installation- power, wiring, physical installation, etc. See the dedicated forum for Sensor related topics

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Alex W
Posts: 41
Joined: Tue Apr 16, 2013 5:57 pm
Location: Bozeman, MT

RPM Signal Issues

Post by Alex W »

I'm trying to get an RPM signal from my v6 swapped MR2 into my RCP MKI, and so-far having little luck. Motor is from a 2012 Rav4, ECU is 2007 Rav4. I am attempting to use the "TACH" output from the ECU, which in the stock configuration goes to pin 9 of the OBD2 connector (just like the BMW setup). I am also using this output to drive my stock tachometer, via a frequency converter (tachometer was previously modified to work with a 12v signal). I also have a multi-meter that will read RPM, and it has no trouble picking up the RPM of of this source. Only thing I have not done is scope it, but given that it is the output from the ECU, it ought to be clean...

The RCP however shows mostly zero, with the occasional blip to 10,000,000. Logging at 10 hz, it will be six to eight 0's, then one or two entries of 10,000,000, then two to three 0's, then 10,000,000 again, pretty randomly. I have tried slow/medium/fast in the config to no effect. I have tried various pulse-per-rev values as well, although I don't think that should matter at this point, as the issue isn't with scaling but with picking up the signal at all. RCP is as mentioned a MKI, running the latest 2.8.7 firmware. I have tried two different input locations on the RCP, just in case it was a hardware issue on one of them.

One thing I have thought of trying to using the output from my frequency converter (this: http://www.bakerelectronix.com/products_tsd/ ), instead of the raw signal from the ECU. That should definitely be a 12v square wave (that's what it is advertised to output). Just would need to set my pulse-per-rev differently. Any other thoughts, before I go digging in my wiring harness to try that signal instead?

Alex W
Posts: 41
Joined: Tue Apr 16, 2013 5:57 pm
Location: Bozeman, MT

Post by Alex W »

I went ahead and tried hooking it up to use the output from the frequency converter, and it is working perfectly.

So I guess we learn two things here... One, there is something about the TACH output on a Toyota ECU that the RCP (MKI at any rate) cannot read. Two, the Baker Electronics frequency converter makes a suitable signal conditioner for this application.

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