Why is that? The actuator, V465, controls the wastegate and the manifold pressure is monitored by G31. Surely then the ECU will adjust the wastegate until the desired pressure is reached and that can be done independently of the exact turbo characteristics. What's more some early cars had a shim added between the watstegate actuator and the turbo body but AFAIK no recalibration had to be done!
The actuator is electronic on this engine, it doesn't have a vacuum operated waste gate. There are two mechanical variables on a VNT turbo; the vane angles and the spool speed, both of which are subject to tolerances that cause them to behave differently from one turbo/actuator combo to another. These then have to work in an environment of yet more variables, such as pressure, flow and temperature. The actuator has to be calibrated to the turbo so the ECU can accurately work out what the variables are to obtain the desired output. This is especially true when the turbo is running dynamically, for example if you put your foot down the vanes are moved to
guide the air onto the turbine to bring it up to speed as quickly as possible. But if this is done excessively due to say, your engine running at high rpm which requires more flow, then you can overspeed and damage your turbo.
The TPI for the shim recall included a software update to recalibrate the new actuator position to maintain correct actuator to turbo calibration.
Here's some further info which I posted on a previous thread:
I've just experienced the EPC fault on our 2011 1.2 TSI
Ibiza. Having done a fair bit of research there are two fault conditions you can get with the Mahle rotary electronic actuator (REA), most commonly a P334B mechanical malfunction which shows itself when driving and particularly lifting off after heavy acceleration. The second is a P334A electrical malfunction which shows itself on startup, so I'd be willing to bet you had the former.
As I understand it, the mechanical error is given when the REA finds fault with the turbo, i.e. sticking VNT due to carbon build up. This error was also very prominent with pre 2012 cars as they had a design flaw due to VW not doing their tolerance stacks properly. This was fixed under a TPI by fitting a 2mm shim to move the actuator (a metal disc that can be seen sandwiched between the actuator and the turbo mounting bracket) and a software update. With the OPs car being a 2012, it shouldn't have had this latter issue and I imagine will have been fitted with the updated parts.
The electrical error is given when the REA finds fault with itself when there is a discrepency between the ECU's output to the motor and what it receives as an input from the position sensor inside the REA. This is the
problem I've had on ours and is detailed in the "1.2 TSI P334A" thread which unfortunately no one's replied to, but then it is a much rarer fault as I've come to discover. Fortunately I've found a solution using just a tiny bit of glue, a spray of lube and some electrical contact solution which I'll detail in that thread once I get chance with some pics too.
SEAT's default move on either of these errors will be to replace the turbo + REA as a unit (circa £800-£1000 just for parts) as each REA is calibrated to it's corresponding turbo during manufacture. Good news if you're still under warranty as you'll get some shiney new bits that may even be freer of the gremlins which plagued the earlier versions. Not so good if you're not in warranty, especially as you can't replace just an actuator due to the calibration issue.