Over the years we have seen many posts concerning blown engines on this forum. Causes are usually holed pistons, cylinders splitting at the top in that crack between cylinders (a problem Ford has acknowledged and redesigned the 2022 Escape motor for), and the base of the cylinders separating from the crankcase. In almost all cases a larger turbo was in use. For this poster the only thing limiting his engine from approaching 400 WHP is the fuel system and that is not a good method for limiting the power, because it's only a small hiccup away from a lean combustion event. Just one tiny little bit of junk in the ejector can result in a piston with a gaping hole in it. It's one reason why he should have a Meth system in place because they can provide a bit of protection from a lean combustion event.
As for my advice about limiting engine speed, it's real simple. If you enjoy getting a new engine every 15 to 20K miles go ahead and rev the snot out if it. If you want an engine to last for 10 or 15 YEARS, then limit the engine speed to that put in place by Ford.
Seriously the OP now has two choices. One is to go to an engine with forged pistons, premium connecting rods, and a carefully inspected and balanced crankshaft so he can increase the capacity of the fuel system and take full advantage of that Big Turbo. Or step down to one of the hybrid turbos capable of producing 280-300 WHP with the stock fuel system in balance with the output. Personally I would go with the smaller turbo, once you break that 400 HP threshold it really gets expensive. By the time you strengthen the Fiesta to work well with 400+ HP you'll have spent enough to purchase a used Focus RS Rally car in operating condition.
As for my advice about limiting engine speed, it's real simple. If you enjoy getting a new engine every 15 to 20K miles go ahead and rev the snot out if it. If you want an engine to last for 10 or 15 YEARS, then limit the engine speed to that put in place by Ford.
Seriously the OP now has two choices. One is to go to an engine with forged pistons, premium connecting rods, and a carefully inspected and balanced crankshaft so he can increase the capacity of the fuel system and take full advantage of that Big Turbo. Or step down to one of the hybrid turbos capable of producing 280-300 WHP with the stock fuel system in balance with the output. Personally I would go with the smaller turbo, once you break that 400 HP threshold it really gets expensive. By the time you strengthen the Fiesta to work well with 400+ HP you'll have spent enough to purchase a used Focus RS Rally car in operating condition.