Lotsa boost with medium intercooler and WI
 

I'm putting in a built engine this summer and hope to hit 400+ hp with my GT3071 and water injection. Please, no "yah right" comments; the engine is sitting in my garage at this momment. Right now, I have the BEGI "type 3" intercooler which is (according to the BEGI website) rated for 300 hp.

Since I plan to run pretty high boost (20+ psi) at the top of the turbo's efficiency range, do I need to get a larger intercooler or will WI plus the medium size intercooler I currently have do the job well enough together? I would prefer to use the smallest intercooler I can get away with for the best response and efficiency. It would also be nice to not have to buy a new intercooler and redo my piping.

Considering that im making 300 or so whp with out any intercooler what so ever yeah i think you will be fine if you do it correctly.

Do the water injection right and the cooling will be more than adequate. I have a similar set-up using a BEGI MSM IC and aquamist WI and have very good (low) intake temps on boost (running 50/50 water/meth).

Let's be honest, here: You have a 3071. Looking to IC core size for response is like buying a pump-action 12-gauge and then complaining about the kick-back.

I plan to do the same thing, though. Mount a small intercooler out of the way to free up airflow to the radiator, and use water injection to keep intake temps down.

OK great, thanks. This is good news :)

Honestly if you have a bullet proof set-up you dont even need an intercooler, its just more un-needed pressure drop. I say keep the set-up you have and dont bother with a larger intercooler, its not going to benefit you in anyway