i should have qualified my statement by including "while the car is moving."
back in the day i temporarily mounted a thermocouple array and a portable data scanner to measure temps under the hood. since then there have been several people who have reproduced the same data.
turbo versions are a little different because there is a considerable amount of infra-red coming off the turbo housing and i have dealt with that by using various shields and insulating turbo blankets. also, with a turbo and megasquirt the iat sensor is positioned after the intercooler. inducted air hits the cold side turbo snail where it picks off a percentage of the hot side's heat along with generated heat of compression, then it passes through the intercooler to help drop the charge air's temp before it is fed through the throttle body and intake manifold. still, the inducted air gets pre-heated by the throttle body and intake manifold unless you do more fancy stuff to reduce thermal transmission from the head and coolant.
with a typical n/a engine there's not much more than a degree or 2 difference from ambient.
once again, the throttle body and intake manifold both have engine coolant running through them which essentially raises the temperature of inducted air as it enters the engine so even if you extend the intake to induct outside air, it is still being heated as it enters the manifold.
giving a turbocharged engine a pass in this discussion and relating to a normally aspirated engine, i still maintain that the reduction of air velocity that comes from extending the inlet piping causes worse performance than using a short induction pipe and inducting air from the corner of the engine bay. a "ram air" type intake is virtually ineffective, a cold air system is virtually ineffective, but building a short runner, smooth walled, slightly larger diameter intake with a high flow filter works great. i have done a number of twincam engines this way with positive results.
i try not to get into discussions unless i have some personal experience on which i can base my comments. this is one area where i have more than a few years' experience on which i can base my assertions.
