Use of J1850 VPW for RPM ( external trigger) ?

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Use of J1850 VPW for RPM ( external trigger) ?

Postby nurber » Tue Feb 02, 2016 4:51 pm

Hi Forum. Considering purchasing the Pico NVH kit, or at least the accelerometer from the kit. I have the Scantool
OBDLink SX scan tool connected to this vehicle ( '2004 Dodge Ram with Cummins Diesel ) and the refresh seems slow to act as an external trigger. Is this really a reliable source for engine speed on this system ? There is a CRANKSHAFT POSITION SENSOR that can be easily used, wouldn't this make for a better trigger ?

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Re: Use of J1850 VPW for RPM ( external trigger) ?

Postby Mark Dalton » Mon Feb 29, 2016 12:18 am

The Engine RPM is not used a "Trigger" in the NVH Kit. Have you looked at what the NVH Kit is and the software it uses? It sounds like you're expecting it to look like the normal Oscilloscope format, which it isn't. My understanding is that you could not use a raw RPM signal from a sensor when using the NVH Kit anyway. In the NVH Kit Engine RPM is used as a base frequency and from that the diagnostic software will then calculate the frequency of the driveline components, wheels and engine components etc. which it then correlates to the inputs from the accelerometer to tell you the source and amplitudes.
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