Fixing Code 66 T

[Jiranz]

Just playing around with an old 96 gt twin turbo...

 

1) Low on power compared to a single turbo so investigated why. Found how to make the primary turbo to self regulate at 17psi quite easily. It now delivers useful high speed cruisng power at lower rpm and reduces the vod but car still lacks the desired ooomph on acceleration when downchanged into higher rpm.

 

2) Abandoned the concept as in 1) above. Different approach... Put a T connecter in the vacuum line to the intercooler bov - air bypass valve and use it to feed the secondary turbo actuator positive pressure port (blanked off the regular feed to the solenoid box). This produces excellent exponential? acceleration at higher rpm from about 3psi as the secondary turbo slowly climbs to follow the capability of the primary turbo. It will run all day quite happily configured like this but there is a specific road/user/pedal setting which causes Code 66T to occur. I know how to prevent it but not why it happens. Not often, just sometimes with gentle pedal movement. (The car is stock standard apart from the pressure feed switch - no other mods apart from forcing the secondary turbo to operate sooner).

 

3) I tried removing both feeds from the differential pressure sensor so it would think all things were equal but it didn't like that instantly. Obviously it needs an imbalance which changes. How do I fool this sensor enough to keep it doing its thing? Do I do it electronically by dropping its max return voltage by a percentage factor or could I bleed off some pressure on one side or another so it gives lesser readings?

 

4) If the above 2) & 3) is not solvable, could I divert the secondary Intake control valve to the inlet manifold and let vacuum control it? (also the secondary turbo bov - supercharged pressure relief valve) That would do the same job that the diff sensor does and effectively make it redundant. So In this case how do I fool the ecm to not recognize the presence of the differential sensor?

 

Summary - I was not comfortable with 1) above and much prefer the concept of 2)+ because the manifold pressure remains low for the same gains in power and other things mechanical will break first. But I need to confuse the ecm enough to prevent the (occasional) Code 66.

 

Apart from the inevitable screams of fear and concern as in "you can't do that" for multiple good and valid reasons, has anyone actually thought it through and can see an answer on disabling Code 66 generation against the above background?