VTEC amendment
Posted: Thu Jul 22, 2010 9:56 am
Thnx to novak to point it out, I should explain a bit more about connecting the VTEC when performing mini-me.
When no power is supplied to the VTEC solenoid the valve is closed, no oil is passed through the VTEC drums inside the rocker arms and no VTEC is engaged. Meaning the rockers are running on its lower non-VTEC lobes.
Now by connecting the VTS pin from the ECU to the 1-wire connector the ECU can send power to the VTEC solenoid. So to engage VTEC around 4 to 6k rpm depending on your configuration. This is required to have VTEC work. What it does is sent oil to the for mentioned drums, interlocking all rockerarms (so the lost motion arms are locked) and forces the rockers to move with the higher VTEC lobe.
There is a secondary thing going on. On some VTEC solenoids there is a oil pressure sensor as well. This will have a 2-wire connector, green. Those two wires are VTM (or VTPS) on the ECU and a ground signal originating from SG2 if you want to do it properly.
Now there are 4 options:
1: Your solenoid has the pressure switch, the ECU expects a pressure switch. Normal for most OBD1 cars, just connect as above.
2: Your solenoid has no pressure switch, the ECU does not expect it. Normal for most OBD2 cars, no connections possible or needed.
3: Hybrid setup: your solenoid has de pressure switch, but the ECU does not expect it. No connections possible, leave the pressure switch unconnected.
4: Hybrid setup which is very common: your solenoid has no pressure switch, but the ECU expects it! Happens when you have D16Y8 head combined with P28 ECU as in my setup. In this case we can't connect the pressure switch since it is not there. To fool the ECU you connect a split from the properly connected VTS signal towards the VTM (or VTPS) on the ECU. This setup only once triggered an error code in my case, but is 99.9% failsafe. Right after engagement the ECU puts 12V on VTS. then it starts measuring for the oil pressure signal... hey what do you know, it sees 12V! So it is ok it thinks. There is a nicer solution: which is switching of the VTEC pressure switch error code in the ECU which most ECU software is able to do.
