I own a 2015 base model lancer with the 4b11 and I want to turbo it so I’m going to get another 4b11 and put all my mods on it and when it’s done pull my stock engine and put the built one in my question is for when I go to get it tuned do I need a new ecu for the new 4b11 or will They be able to use the old one
My memory's a little hazy on this one (and Lancers were never really my area of expertise to begin with) but I'm fairly sure it will run with the N/A ECU but not run well.
You can flash an Evo X ROM onto the Lancer ECU and tune it for the appropriate boost levels but you're going to have numerous DTCs, one of which (P0365) will disable your MIVEC and that will cause rougher running, and a reduction in power and economy.
You can however get a second hand Evo X ECU and a dealer or anyone with a MUT-III machine can copy the VIN info and ecu-coding from your stock ecu to the donor. That'll get rid of the P0365 and MIVEC will function again. You'll still have the two DTCs referencing the boost solenoids that the Evo X has but you can either ignore them or fit the solenoids.