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I don't agree with some of your points. Engineers always strive to do more with less while trying to preserve an acceptable longevity. Turbos always make more power with less weight and sometimes with less cost. They came into their own with aircraft. Less weight applies here. Airplanes also benefitted due to the fact they operate at reduced atmospheric pressures snd oxegen content. Before Detroit Diesel came out with their V-designs, they turboed the 6-71. After they came out with the V designs they turboed some of the new designs. The turbos doubled their product line overnight. It has never been about efficiency. Pounds of fuel per horsepower hour didn't change that much. Sure the turboes extract power from the exhaust but they also add loads in pumping losses. You may point to reduced exhaust noise as evidence of power scavenging, but in reality, the reduction is caused by averageing the wave pulses through the turbine. They are self muffling and produce back pressure in the manifold. Turbo technolgy and application is very complex. Sometimes it cannot even be engineered. The applications have to be fitted and tested using different a/r ratios. A random turbo off the shelf or another application may benefit the engine, but it is a longshot. When all is said and done, most turbos are tuned for a narrow load, RPM, and horsepower range. This is why we see wastegates on many of them. It extends their power band by sacrificing max power.
Max power is a valid engineering consideration for farm tractors and over-the-road trucks as the loads are constanly changing. It may feel good to do a little shade-tree engineering, but I doubt if any of us has the experience, equipment, money, or smarts to do a good job on turbo selection.
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