It's time for you guys to beat my speed record.
Rules: build a stock turboprop, set global drag multiplier to 0.1 (I'm comparing with 0.90 performance, my old speed record) and see if your aircraft can go faster than 173m/s (623 km/h). Make the airplane available for download with instructions so we can verify it, after July 6, the date this challenge ends.
Allowed mods:
V.O.I.D. (you need any kind of reliable engine speed readout or you'll not be able to build a high performance engine without it, period).
Some kind of automatic pilot, best go with Pilot Assistant. SAS will only give you frustration due to engine vibration.
Editor Extensions Redux (highly recommended).
Part Angle Display.
For examples how to build turboprop/turboshaft engines and vehicles, head over here.
Here's a picture of my airplane doing it.
Have fun and please post your entries, even if unsuccessful!