Cervan, if the turbo (either primary or secondary) is of the proper size and geometry, it extracts far more HP from the exhaust-heat than the pumping-work it adds to the piston-engine.
FI, thank you!! Yes, that was the point that got it all started.
You claimed that having the turbo doing zero pumping-work at cruise-power (20hp as I recall) was more efficient.
I pointed out that even at partial-output like 20hp, the piston-engine would run more efficiently if the turbo (using wasted heat-energy) was set up to do the work of overcoming intake-resistance; rather than using the pistons (whose work comes from burning additonal fuel).
JT, I think you summed it up well....
turbos need heat.....and obviously, turbos need a 'fan'...
