We've discussed the STS as well as other turbos on here recently.
The theory is sound, while the application might be off some. The STS won some innovative design awards and offers some unique looks at where turbos can possible go. Header coatings' purpose is not to keep the exhaust gases hotter, that is just a product of what their real purpose is, which is the retain the heat in the exhaust system and not bleed it into the engine bay.
In theory, the exhaust gas idea is somewhat the reverse of the increasing the intake charge. Cooler gas is more dense and therefore can react with the turbine more effeciently as opposed to hotter less dense air.
Your other observations are somewhat on target though, but that, IMO, is a product of application and not of sound theory. For instance, turbos on diesel engines start creating boost as low as 1200 RPM. So you can obviously create boost at lower RPM with turbo as long as the properly handle the higher RPMs with a wastegate control or something. So, it is possible to have a smaller impeller on the STS type and spin the boost up much sooner to get the torque.
It really depends on what you are wanting to accomplish. I believe most H2 owners are really wanting higher torque numbers but there are situations that having a higher HP number at higher RPMs would be desired. Balancing these two needs is where everything is headed.
The turbo in this application might have spooling time but obviously a turbo can be designed to lessen or do away with it.
As far as the idea of a turn around time, that seemed logical but I don't know how noticeable the lag would be just because of the extra piping. If the turbo was a smaller one that spooled up sooner and created boost at lower RPMs, there would be a charge in the intake pipe to begin with. Now, go to WOT, and there would be some "time" lost between the sucking of the air and the increasing of the pressure all along the pipe. Since there is more volume of air that has to increase in PSI your idea of delay makes sense. The question would be how much of a delay.
But it's innovations like this that drives the technology to the point that we end up with the right setup. I don't see much improvement or innovation in the application of the screw supercharger and there is a certain efficiency that goes with the turbo systems that would be a plus.
I think it boils down to individual need and application. Personally, I have no desire for a system that starts creating boost anywhere above 2000 RPM. I would want boost to occur around 1500 RPM or so to increase the available torque.
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