it would be very interesting to know more about how to install the Q4 on a normal 156.
I know I am already slightly off the topic of this thread and though 2,5 V6 to 3,0 V6 seems simple, converting a TS to V6 would be much larger project and you can do it for fun, but you will loose a lot of money.
As I already translated the second part about the Q4 conversion and some people might find it interesting I will post it here, sorry for being of the topic.
So I had the 3,0 V6 from 164 including the gearbox which had the terminal for RWD that was just blanked. If I didnít have this, I would forget the idea. After 1 year of search I found a crashed crosswagon on a scrapeyard. I disassembled the crosswagon according to the ePER and I took all the parts and bits related to Q4. I cut out some of them including their holders and brackets. Than I brought everything to my garage and started with the rebuild. I had to make a new adaptor between the gearbox and Q4 shaft, this is milled from aluminum. The transmission shaft was shortened exactly by the length of this adaptor. In the rush after taking bad measurements I made the driveshaft tunnel too high, at the end it wasnít necessaryÖ. Everybody makes mistakes. I had to modify the car frame behind the gearbox to fit the parts and I welded the crosswagon brackets there, the same at the rear. The complete rear axle including rear differential and torsen is in the crosswagon located in separate sub-frame. During cutting the crosswagon I dint know it had a different brace (here I donít understand what the guy talks about so cant translate it exactly ) so I hade to make one by myself and I welded the crosswagonís sub-frame to it. I changed the upper wishbones for those from original car as crosswagon has higher ride height and the car looked as kicked from the back. (Again I donít understand what wishbones he means)
So the main components are in place and now to the control of the Torsen. It was necessary to insert into the power steering a part that gives information about the steering angle of the front wheels according the power steering pressure. Then I placed the torsen ECU and started wiring it. Unfortunately I was working with a quite chaotic system, one wire here, one thereÖ.later it showed up that it could be wired in a different way. As I donít have VDC, I soldered resistors on the ends of some loose wires so that ECU doesnít show faults. I didnít modify brakes at all; the ABS is original, ASR is disconnected (this made it a lot easier). And now the best part. Torsen has torque distribution in a straight line 80/20 front/rear but I wanted it opposite way. I made a very simple electrical circuit with primitive logic that swapped the sensor reading from the Torsen pressure sensor and the torque distribution is swapped. In corners the distribution is 40/60 front/rear. After test drive I made some fine tuning via regulation valves.
The rebuild actually wasnít so much work to do, I think that the Italian guys planned this since beginning but the system wasnít introduced. Driving Ė wise I am very happy, I can feel when each axle takes the power in difference to permanent 4x4 where you steer with gas pedal, here it doesnít work. In winter on ice its fun to slide with the door forwards. On dry you can feel understeer when entering the corner, than it bites into the road and grips and progressively passes to slight oversteer at corner exit when the rear pushes the car on the next straight. It grips like on rails in the corners, but after you pass the limit and the car starts sliding it is not so well controllable, opposite lock has undesired effects; the point is not to cross the limit. I was on the limit few times on the track, cornering is similar like in tilted corners, it grips, pulls, than pushes.