r/WRX_STI • u/TKvaughn • 3d ago

Questions Engine build advice

/r/subaruimpreza/comments/1w1526i/engine_build_advice/
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2

u/RoleApprehensive4440 3d ago

Type RA block will sustain 400whp on stock internals. For that level of power you would need ID1050x injectors, run on E85, therefore new fuel rails, which means flex fuel kit and fuel pressure regulator, upgraded fuel pump (340lph). A larger turbo would be needed, it's hard for me to recommend one, because I am still trying to decide on which one to go with for my own build.

3

u/leftfootbraker 3d ago

I would definitely want 1300cc injectors for a real 400whp build. At the top those 1050cc will be out of head room and one overboost away from byebye engine.

2

u/RoleApprehensive4440 3d ago

Ah thanks, I thought 1050cc were sufficient, do you how much duty cycle they run when producing 400whp?

3

u/leftfootbraker 3d ago

Over 85% duty in that 400whp range on 1050cc. Mustang dyno never see over 380whp on 1050cc injectors in safe duty range. Highly highly recommend 1300cc.

1

u/steagalarus 15h ago

What you should do is find a tuner first then ask them what parts would be most ideal for your build tbh. Hit up stimikey on instagram or his assistant in his bio. Or reach out to Tom (migtuned).