I have a knightsport FCD that was given to me by a friend. The only downside is that it is for an s5 and I own an s4. Now I could always go the route of trading or selling it for the correct series FCD, but I'm also aware the only difference is a matter of adding a 4th wire (12v) to jump each plug. Does anyone have a write up on this or know where to pull the 12v source from? It doesn't sound overly complicated but if it's too big of a headache I can go the route I previously stated.

 

They are calibrated differently. The s4 models had stock boost at 6psi and fuel cut around 8psi. The s5 models had stock boost around 8psi and fuel cut around 10. So the s4 FCD clamps voltage to the ecu at a lower boost level than an s5 one would...making your boost gauge and timing control all the more inaccurate.

 

Ah, I didn't even think about the calibration portion of the equation. I just assumed they were the same with the exception of the slight wiring difference. Thanks for the info!