For piston engines the drag increment of the graphic may be used as a guide
If the exhaust configuration of the turbopropeller engine is reverse-flow (the exhaust nozzle is closest to the forward portion of the engine), the drag increments of the graphic may be used as guide.
If the exhaust configuration of the turbopropeller engine is flow-through (the exhaust exits the aft portion of the engine), the additional drag penalty caused by the exhaust may be negligible.
For jet engines mounted in nacelles the value should be set to zero.