Does any one know at what voltage will the stock ECU start retarding timing? Is it progressive? Twin-air

I read somewhere that only the first generation TA engines started with retarding the timing. Apparently FIAT switched around 2011 to a strategy that starts by reducing the boost pressure, since retarding the timing would increase exhaust gas temperature too much for the little turbo. I don't know if it's true, but it sounds plausible. Maybe it's no longer valid for the Euro 6 TA engines though, since these have an exhaust manifold that's integrated in the cylinder head and that reduces the exhaust gas temperature a lot.