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Originally Posted by MikeSTI
I agree but with a car like the STi which is sold to a limited market they could have gone a step further with the design to help hold better power on the after market aplications. Thats all  |
I think what Kevin was trying to touch on was that by the time the lack of forged pistons in the EJ257 are limiting your power generation, the design of the block itself is going to be limiting you as well.
Basically the cast pistons in the EJ257 are good for tons of power, and once they max out you're going to need to switch to the EJ22 motor (2.2L fully closed deck, forged internals) anyway. In fact, the 1st run of US STi had forged pistons, but Subaru decided they were unnecessary and saved some money by going to cast ones.
Remember, forged pistons allow a motor to handle higher cylinder pressures, but they will still break if the car knocks. Unlike the EVO motor, the EJ motor will start to knock at high boost pressures, even if you're giving it enough fuel, as it's a limitation of the block itself. Even if the pistons were forged from the factory, they wouldn't reduce knock unless they were lower compression pistons, whch would allow for more power (assuming a bigger turbo) but would reduce the low-end grunt that make the STi motor so fantastic.
Frankly, the FQ400 may make 400hp, but I'll bet a 350hp STi is more fun to drive in the real world, due to the low-end torque.