Tach to Pcm

[davepl]

If you're using a factory tach you'll need an adapter box. I don't know if the LS is "waste spark" but long story short there are TWO ignition impulses per firing event, so you get double the frequency.

If you have an aftermarket tach, just set it to 4 cylinder more, add the resistor, and you're done. For some reason now that I type that it sounds completely backwards, and you're really need a V16 setting, but I'll ignore my instincts as that's what the docs said.

If you can't set your tach to 4 cylinder, you need an adapter box. I got this one from Dakota Digital via Amazon:

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Works great, simple to connect. My factory tach works perfectly.

The purpose of the pull-up resistor is to change the +5v pcm tach signal to +12v

Can anyone explain that in a way that a software guy can understand it? I get Ohm's law and all of that, but how can adding a resistor increase the voltage?

[Liltroy]

Originally Posted by davepl

If you're using a factory tach you'll need an adapter box. I don't know if the LS is "waste spark" but long story short there are TWO ignition impulses per firing event, so you get double the frequency.

If you have an aftermarket tach, just set it to 4 cylinder more, add the resistor, and you're done. For some reason now that I type that it sounds completely backwards, and you're really need a V16 setting, but I'll ignore my instincts as that's what the docs said.

If you can't set your tach to 4 cylinder, you need an adapter box. I got this one from Dakota Digital via Amazon:

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Works great, simple to connect. My factory tach works perfectly.



Can anyone explain that in a way that a software guy can understand it? I get Ohm's law and all of that, but how can adding a resistor increase the voltage?

Please watch the video I posted. If you're doing a swap then theres no reason why you cant just change the signal in the pcm when you have your pcm flashed. Converter box is a completely unnecessary cost.

Also the resistor isnt there to increase voltage. As I explained in the video, youre pulling 12 volts from a switched 12v source and adding it to the tach signal, the resistor is there to DECREASE the voltage and to a safe level and prevent backfeeding and damaging the pcm I believe.