Hey guys got a b16 turbo with 270whp 9psi, stock sleeve, forged bottom end, stock head. Everytime i make back to back pulls freeway or rural area it overheats rite away. I found this forum https://honda-tech.com/forums/showthread.php?t=2889523&styleid=18
tryed replacing or checkin all the parts listed but still havin this problem. I have a mishimoto half sized radiator, flex a lite fan. I programmed the fan to come on earlier at 180, and made it so the check engine light for overheating doesnt come on till 230. Also have a mishimoto thermostat open at 175, and two 10AN fitting venting thr front of the valve covrr. Also changed fan relay and coolant temp sens, i even put motul racing radiator fluid with watter wetter everything seems to be working but i cant get the car to stay coooooool. Can someone help me before i blow a headgasket. Btw i cant get the car to cool down by driving i have to turn it off. I live in the bay area so its not super hot or humid, usually like 65-75 on an average day

 

Stupid question but have you bled the coolant?

 

Here's a good star to solving your problem.

I'm assuming you don't have ac and thus no condenser core.

air takes the path of least resistance.. so with nothing in the place of the condenser the air will go through that opening rather than through the radiator.

you need to make some sort of block off plate to force the air through the radiator. this can be a sheet of aluminum or carbon fiber sized and cut to properly fill the gap.... or you can use the stock Honda block off for the non ac cars (same part number 92-00) I'll try and find the OEM part number

also fill any gaps between the radiator and upper/lower core support and surrounding vehicle structure using silicone or rubber weather stripping. this will further help force air through the radiator, eliminating any potential spots for air to bypass the radiator