Getting super accurate IAT readings with an ITB setup isn’t so easy without a cold air intake plenum. While a cold air box is ideal, to begin with, I’m running an open element air filter. Accordingly, I must accept that there will be some IAT error no matter where I mount the sensor.
Initially, I mounted my IAT to the shock tower on the exhaust side of the engine bay and some people questioned that decision. I figured it wouldn’t be that big of a deal since the exhaust manifold is getting a thermal insulating blanket from Track Dog Racing. And while the underhood temps are hot and will be hotter on the exhaust side even with the header blanket, turbulent air is circulating throughout the engine bay all the while the car is moving. This turbulence will also have an effect on IAT readings. Ideally, you want your IAT relatively stable, not swinging wildly from 90F to 165F depending every few seconds depending on which way the wind is blowing.
I like the look of the IAT mounted to air filter backing plate but that suffers from heat soak so is not an ideal place to put it, either. Unashamedly, I’ve been copying much of what Quinn did with his build. Here’s what he had to say back in 2012 about IAT sensor location. I’m not sure if he’s changed it since then.
Also, to contribute to the IAT sensor mounting part of this thread. I am using the factory NB one and I have it zip-tied dangling off of the hard line for the brake booster. I figured this is where the air will be the hottest next to the runner for cylinder #4. I’d highly recommend against tapping them into the runners of the ITB manifolds as some have done. Not only will that cause heat soaking (I don’t care if the GM sensor is open element), but two it disrupts the air flow velocity in the runner. When I was helping CND_Eunos diagnose some issues with his Jenvey ITB’s, his IAT sensor was heat soaking being tapped into the runner. LINK
FooSchnickens had a nice idea to get the IAT close to the air horns but I’m not running a shock tower brace.
Instead, I plan to run an upper engine torque damper type mount from the driver side shock tower to the front engine lift point.
Best case scenario the IAT is going to get an average approximate of the ambient air available in the engine bay in the vicinity of where the air is getting sucked into the engine. In my case, behind the passenger side headlamp somewhere between the intake runners is probably a good place for it. Ultimately, I decided to get a new pigtail harness and move the IAT closer to the air horns. The biggest drawback now is how close the coolant return pipe is to the air intake. That aluminum coolant return hard pipe gets as hot as the engine coolant itself, which means I need to insulate it to help lower intake air temperatures until I can manage a proper cold air box.