I started this thread, because its a problem that some of us may have/or will run into later on.
The core engine management is SpeedPro. It does not have anything to control the Vtec function. So, you must hook up an RPM switch, with pills. I have a 4000 rpm pill in there right now.


This worked as designed until I hooked my Tach up, to the same signal wire, which is the RPM output on the MSD 6AL ignition box.

Hook the tach up, and the RPM switch wont switch over to Vtec until 5-6500rpm later. It varries. Unhook, it goes back to normal(Im assuming, since there is no tach there, but 4k rpm is fairly low, and you can tell when youre revving higher than that). Im using 1 spade connector from the MSD, to 1 other spade connector, with both signal wires crimped into the terminal.

Could there be too much draw from the Tachometer for the RPM switch to "see" the signal? Could it be altering the voltage so that the RPM switch "thinks" to shift later?
I would hook the Vtec switch up BEFORE the MSD box(on the ECU output), but if hooking all these accesories into eachother prove to alter signals, I dont want to risk un-timed timing...

 

Try using larger wire
If that does not fix it than you may have a bad tach
Try another tach

 

Ill try the simpler of the two first. Im using the supplied wire, thats meant to just power the tach, so Ill step it up a notch! Results at lunch time...

Anymore suggestions are welcome...