CAI insulation idea

Originally posted by highlander
Ok Im sorry, but I cant understand that. What makes the air hot is the heat from the air? ... coating the inside is the same as coating the outside, and it would be a major PITA to coat the inside smoothly... the air sucks cold air from the wheel well (away from the engine) and is hot by the time it reaches the manifold... conclusion: air heats up while it is in the tube... question: what heats it up? underhood temperatures from the engine... therefore if we can isolate the intake from the heat of the engine, it will be colder... unless of course the ambient air temp is higher than the under-hood temp

Does anybody know the air velocity of the intake at some fixed RPM, or better yet a chart showing it across the rev band?

Here's a very simple lesson in the dynamics of what is going on:

The air your car sucks in is composed of molecules from various gases as well as things like water vapor or droplets, dust, etc. When gases flow through tubes 2 things happen. One is that the molecules of the gas strike one another, this reaction produces thermal energy. The other is that the gases interact with the sidewalls of the tube and generate heat via friction with that surface (resistance). The faster the air flows the more thermal energy is created.

We can draw upon some electrical knowledge for those who have some. There are two benefits to a smooth intake system. The first benefit that most people think of is volatility of the airflow. The smoother the bore the less impedance (or resistance if you prefer) to the airflow. Lower resistance means higher flow current for the same potential (pressure or vacuum in this case). So by decreasing the flow resistance you either increase the flow current or decrease the pressure drop.....or you help them both a little. The lesser thought of benefit is that by decreasing the flow resistance you also decrease the heat buildup from the flow. A very smooth surface provides less surface area for friction and also provides a less volatile fluid flow meaning fewer molecular collisions for the same air velocity.

Now, completely thermally insulate your intake from your engine bay (difficult to do) and you will find that the intake will still heat up, I'm not exactly sure how much but I can assure you it's noticeable and measurable. You may not notice it if you've wrapped the intake in an insulator for the same reason that a wet hand doesn't freeze to the outside of your freezer when opening the door. By putting a thermal protector on your intake you may notice that it's cooler to the touch and think "wow, this product really worked." But the air is INSIDE the intake, you've gotta feel the internal temperature to know if your air is cooler....

We used to have someone very familiar with fluid dynamics on here who could elaborate much more on this, but I can't recall who it was or if he's still around.

b