Originally Posted by N1_STYLEz
hows that? lol yeah i guess i never really thought about how large it was... anyways... i am running a p28 ecu and everything is working fine... i just wanted to know what each of the wires do to activate vtec... is the single wire a ground that is controlled by the ecu to activate the solenoid itself or is it a 12v source? i know how vtec works i just want to know what the ecu does to activate it... thanks
-Josh
In layman's terms:
The ecu has a vtec engagement point set on it....
When the vehicle meets the default vtec speed requirements & coolant temp requirements, then the ecu will then look for vtec oil pressure using the 2 wire oil pressure switch on the vtec solenoid (JDM solenoids do not use vtec pressure switch).
Once the ecu gets all of the required items (vtec oil pressure, vtec speed, coolant temp etc). Then at the rpm at which vtec is set to engage at, the ecu will activate the vtec solenoid via a 12v single wire connector. The ecu will then switch it's ignition & timing maps to something called "high cam" maps .
The name "high cam" comes from the fact that the vtec lobe is bigger then the non-vtec lobe.
Using a vafc or a piggy back which activates vtec on its own eliminates the ecu from seeing high cam maps or vtec activation. This is part of the reason why piggy back units are not the greatest.
I hope that was enough info for you.
