b18c iat sensor

It’s good that you are thinking like that, but wrong. The throttle body and IM have coolant passages routed through them, so combine that with heat transfer from the head…temps can rise 15-20 degrees BETWEEN the throttle plate and the actual intake valve. Even with phenolic gaskets on the IM, and non-conductive hardware to isolate heat transfer the temp difference is still there. The IM itself is only cooled via air when the car is moving.

The point is, your ECU (under closed loop) reads the IAT signal and adjusts fueling as needed based on incoming temperature as it relates to oxygen density. Moving the IAT out further will tell the ECU a falsely LOW temperature, which equals MORE fuel delivery than is needed. Since you can’t have an IAT too close to the combustion chamber (where the signal would be most accurate, in theory) Honda placed it 1/2 way down the IM runners…or sometimes on the plenum. You WANT that sensor to be reading as close as possible to the actual temp of the air getting into the cylinder, not what it was a step or two previous to it in the intake tract.