Hi Gripen,
>In the case of the AM-35/AM-38 we can see the from the curves that the swirl throttle certainly have a more effect than constant air flow mass at sea level.
Actually, it seems like both of the Russian engines were regulated to a constant boost pressure. However, I admit that in the case of the AM-38, the drop of air flow mass at sea level was only very slight (2%). The AM-35A actually had a higher air flow mass at sea level than at full pressure altitude, so it doesn't seem to make much of a difference indeed.
>Anyway, the swirl throttle increased the efficiency of the engine by reducing supercharge driving power and temperature rise in the charger while the constant airflow mass system was just a different way to adjust MAP.
Yes, but with modern-day experience, we shouldn't be suprised that improved engine software gives better engine power ;-) However, I previously thought that the new way of adjusting MAP was responsible for all of the power gain the Jumo 213 experienced, now it seems like it can only claim part of it.
Regards,
Henning (HoHun)