i am new to this whole vtec thing as i have just finished up putting my Z6 in my EF hatch yesterday all by myself... my question is what makes the vtec solenoid engage... a buddy of mine told me that there are two wires... one from a 12v source and one ground... he also told me that the ground is what is used to turn the vtec on and off... i looked at my motor today and there are 3 wires... a lone black wire on one plug and i believe a black/blue wire and a black/yellow wire on the other... which one is which and how do they control the vtec solenoid? thanks a lot for the info
-Josh

 

bump

 

a) shorten your sig

b) vtec is operated by the ecu. you will need to run a VTEC ecu and run the wires from the proper pins to the vtec solenoid. the single wire plug is the solenoid itself, whiel the green two wire plug is the oil pressure switch that acts as a safeguard to not engage vtec if the pressur eis too low

 

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

 

late night bump

 

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.

 

that was great! thanks a lot... so when i hear of all these guys using a manual switch to activate it then i assume thats not a good idea considering it will cause you to run lean? if this is true then wouldnt buying aftermarket cams and putting them make youre car run lean also? i always thought that the ecu senses how much air is going into the combustion chamber and throws in the right amount of fuel to the best of its ability... but if that was right then i dont think that you could run lean with a manual vtec controller or a switch? can someone clear this up for me? thanks
-Josh

 

Using a switch to activate vtec a stupid idea.
Running aftermarket cams in your vehicle would require you to tune your vehicle for those cams etc.

The stock ecu does not sence extra amounts of air from aftermarket modifications etc.

 

when vtec turns over you have to have the fuel to use with the extra air. simply put. thats why a vafc is better than an activated switch i think...i dunno for sure. most people do the rpm switch on a d15 for the extra compression.

 

hondas dont use air flow sensors they use air pressure sensors, and there is not much if any presure differance when the cam lobes are bigger than the stock ecu is programmed for, becuase the valves are open longer or open more, the air moves in more easily, without too much change in pressure. so the ecu does not "know" that there is more air getting in there. someone correct me if im wrong, this is just a guess.