The usual advice is to keep charge pipes as short as possible. The reasoning is that a shorter path holds less air, so the turbo has less volume to fill before pressure reaches the engine. Shorter is treated as automatically better.
That reasoning is only partly right. Length is one factor among several, and chasing the shortest possible route can create bends, tight clearances and heat exposure that cost more than the length saved.
Charge pipes hold pressurised air, and all of it has to be filled before the engine sees full boost. A large-diameter pipe holds more volume per unit of length than a smaller one, so bore can matter as much as length. A long thin pipe and a short fat one may hold similar volume.
The pipe bore also sets flow speed. Too small a bore restricts flow and adds pressure drop; too large a bore slows the air and adds volume. There is a sensible range for a given flow, and the best routing works within it rather than minimising length alone.
Every bend adds resistance and disturbs the flow. A tight bend costs more pressure than a gentle one, and a series of bends adds up quickly. Two routes of the same length can have very different losses depending on how they turn.
A slightly longer path with sweeping bends can therefore flow better than a shorter path forced through tight turns. This is where the shortest route is often the wrong answer, because it hugs the engine bay and turns sharply to do so.
Pipes near hot parts pick up heat and pass it back into the charge air. That partly undoes the work the intercooler just did. A short pipe routed past the turbo and manifold can pick up more heat than a longer pipe routed clear of them.
Material and finish affect this. Metal conducts heat readily, so routing matters more with metal pipes than with insulated or composite ones. Keeping the path away from heat sources is often worth more than cutting a little length.
The charge path has a cold side and a hot side. The side before the intercooler carries hotter air, so heat pickup there is less critical. The side after it carries cooled air, so it should be kept away from heat and kept flowing smoothly.
This is why routing decisions should be made for each side separately rather than treating the whole path as one pipe. A car that improves its intake and charge path usually does so by looking at the two sides on their own terms.
On a real car, routing is constrained by the engine bay, the subframe, the steering and whatever else is already there. The ideal aerodynamic path often does not exist in the space available, so the practical task is to get as close as possible without making things worse.
That is where fabrication and the rest of the system meet. The routing has to work with the exhaust pipework, the intake and the intercooler in the same bay, which is why these parts are best planned together rather than one at a time.
