Originally posted by 420agreenvilleSC
Not exactly sure why the brains at hahn wants you to use this rather than just tapping into your RPM signal at the ECU

Because they might know what they were doing when they built a "for the public" mod?

Originally posted by Ebster1085
I actually spoke to Bill Hahn today and he said that becuase the 420A runs off a distributor'less ignition, the tach signal that the ECU puts out is not with what the Portfuler module looks for. The tack adapter modifies the signal to be compatable with the Portfueler module.

The tach adaptor does more than just modify the stock signal, it intercepts it and provides the signal to not only the Porkfueler but also to the stock ECU emulating the stock tach wire signal and keeping the ECU from throwing a CEL.