All a turbo is, is a driven fan made to do work. It's about expanding and creating more of an INTAKE charge. A windmill is the same principle. It just does different work. It is a driven fan used to do work, same as a turbo. A turbo just happens to compress the intake charge, being driven off the outgoing exhaust gasses. There are certainly more exhaust gasses because of the added intake charge, but those gasses do not escape until they exit the tail pipe, so in theory, the turbo could be plumed at the tail pipe exit. As long as it has exhaust gasses to drive it, it will do its job. As to whether or not being close to the head makes a difference.....Certainly it would. Because hot gas molecules are bigger than cold ones. That means the hot gasses must flow faster to get through the exhaust since their molecules are expanded. That creates more boost. Since you are cramming more intake charge in, surely more exhaust has to come out. That's beneficial to a turbo since it is powered off of the exhaust. It's not the heat that drives the turbo fan. It's the FLOW. The added heat at the exhaust outlet makes the turbo much more efficient by high spool speeds due to the increased flow from the high heat. Much in the same manor a steam engine operates on the expanding steam from boiling water. A turbo away from the heat will still create boost, but much more poorly than one close to the combustion.
Not sure Bill wanted a turbo discussion. We should try to get it back on track.