30-4900 adding speed MPH | AEM
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Last seen: 5 years 9 months ago
Joined: 10/09/2014 - 11:17
30-4900 adding speed MPH

I have the 30-4900 wideband gauge with boost, I really like this set up. I am using the recordings to adjust my system and its going great. I want to add MPH to the recordings and I see pin 9 is for optional engine spped input square wave. What does that mean? I am using an 1997 ish Ford explorer rear end that has a sensor that i believe outputs AC voltage. Can this be configured to read MPH? Is there an aftermarket cheap setup that I could buy and plug into pin 9 and record MPH? I dont want a whole data logger expensive set up. I love this gauge and the recording ability.

Last seen: 15 hours 27 min ago
Joined: 06/06/2014 - 09:31
Like the name implies, a

Like the name implies, a square wave looks like a square like this:

What the WBFS is looking for is a good, clean square wave tach signal.  I do not suggest attempting to input an AC sine wave into the WBFS as it could damage the gauge.  I can really only suggest that you use it as it was designed which is an engine speed input.  Please keep in mind that the inputted signal should look like the example above.  A lot of tachometer gauges get their signal from the negative terminal of the coil primary circuit which looks like this (ignore the letter references):


Notice that the coil primary does NOT provide a good square wave signal and in fact can damage the WBFS because the voltage can spike up to many hundreds of volts.  You can use something like the MSD GMR pickup to indirectly pickup off of the coil.