I'm preparing one 20VT engine to go on the back of my mid-engined 156's i'm using only for trackdays.
I need electronic and wires only for the engine to run fine, and minimum wires inside.
Question:
Is there a problem for the ECU and engine behavior if i don't attach speed readings from the gearbox - i'll use Alfa 156V6 box with 3.9 diff(or Kappa's GB with 3.5 diff) and both have different sensor for reading speed. And i don't need speed readings anyway, just revs.....
Did someone have any experience driving with speed sensor or speedo broken????

Should be fine, the car certainly drives OK with the speed sensor disconnected, you just get no speedometer reading.

The service manual says the speed sensor is also used for "better management of the engine idle adjustment and for the fuel cut-off (overrun) strategy".

It doesn't mention a specific recovery mode for when the sensor fails, as it does for most other sensors, so they apparently don't consider it a major issue.

Also thought that it will be OK, 3.0V6 166's engine had no problems with it.....