In my youth changing an engine was easy, pull one out put another in, usually bigger. So my son has a 146 1.6 ts and I have a 2.0ts engine out of a 155. I know it will go in but what about the ECU, what possible problems will I be faced with.
Your thoughts gentlemen please.
You'll find that the 155 engine has additional sensors for oil level etc in the sump. You could swap the sumps or just leave the sensors in place unconnected.
An alloy top head is the same as a plastic top. You just need to use the plastic cover due to oil breather architecture.
You'll probably find that all the sensors are different including the cam phase sensor. Unfortunately, to swap that, you need to take the cam belt off and in the inlet cam pully. The rest of the sensors are relatively easy to replace with the engine out of the car.
The wiring to the coil packs is probably different too. Use the 1.6 set up.
I'm making a few assumptions regarding the 146's engine management type but I think your main problem will be the engine management. I'd be inclined to run the 2.0 on 1.6 management for the time being (just make sure you use a 1.6 MAF if they're different to the 2.0) then go looking for a plastic top 145 QV /146 Ti that's being broken. To make it work you'll need the engine management, code box and ignition keys or the key transponders as a minimum. - FYI, I'm running a 3.2 GTA engine on a standard management and a 2.5 MAF. I have an Innovate wideband lambda and AFM on it and the fueling is fine...
Additionally, I think the M2.10.3 (?) and M 2.10.4 (?) management in the 145 and 155's I had the maps for ALL the T/S spark engines programmed in. The diffence between .3 and .4 management was the .3 had an EGR valve....
Which brings me to my next point. The 155 engine may be a .3 varient with a slightly different exhaust manifold. If it is I think you'll be able to get away with junking the egr gubbins and using the manifold off the 146.
Finally, I found that chipping the 145/155 involved buying a replacement management chip from Squadra. If the 146 still requires the chip to be replaced you could just buy a 2.0 mapped chip off them, or alternatively look at getting it remapped through the OBD port if that option is availible.