I have a few questions regarding tuning and adjusting VTEC cross over point.

I have a general idea of how VTEC works. ECU send power to the VTEC solenoid. VTEC engages.
VTEC pressure switch gets grounded and send the signal back to the ECU showing that the VTEC
is correctly activated.

When using a VTEC controller or Piggyback ECU (E-manage, AEM F/IC, VAFC, etc) to control the
VTEC engagement point, obviously the VTEC will be engaged at a point different from the stock
VTEC engagement point, will that trigger off any kind of error code?

For instance, if the stock VTEC crossover point is at 4800rpm. I then adjust the VTEC to activate
earlier at 4000rpm. When this occurs, VTEC will be switched on at 4000rpm and VTEC pressure switch
will tell the ECU that the VTEC is on. However, the ECU will know the VTEC is on when it is not
supposed to. Will that trigger any kind of error code? (Or in the reversed case the VTEC is OFF
when it is supposed to be on.)

In terms of fuel and ignition. When the VTEC is switched on at the factory crossover point, the ECU
will supply more fuel and adjust ignition to allow the engine to produce the optimal power.
Is this action triggered by the engagement of the VTEC, or is it hard coded into the stock
ECU's fuel map? If let's say I adjusted the VTEC to be off all the time, will the ECU still adjust
fuel and ignition as if the VTEC is on?

For example, if the stock VTEC crossover point is at 4800rpm. I then adjust the VTEC to activate
later at 6000rpm. Will the ECU still start adjusting the fuel and ignition at 4800rpm as if the VTEC
was on?

 

well wouldn't a piggy back also fool the ecu into thinking it was correct?

 

I am currently working with the AEM F/IC and it doesn't have a connection to the VTEC pressure switch so I would guess it doesn't fool the ECU into thinking it's correct.