Did Japanese aircraft, especially fighters, use the equivalent of War Emergency Power (WEP) in combat?
Hello Windswords,
The answer gets a little complicated here and kind of depends on the particular engine. Some engines were a lot more tolerant of "overboosting" than others were. The Nakajima Sakae and its Army equivalents was apparently very tolerant.
The Japanese had a fairly low octane rating for their standard fuel: 91 to 92 octane. They compensated on some engines by using Water-Methanol injection for anything above cruise power settings, so use of Anti Detonant does not necessarily mean "War Emergency Power" for Japanese engines.
As an example here are some settings for the early Nakajima Homare / Ha-45 engine:
1850 HP @ 2900 RPM +400 mmHg Boost Sea Level Take-Off
1680 HP @ 2900 RPM +250 mmHg Boost 2300m Rated Power – Low Blower
1500 HP @ 2900 RPM +250 mmHg Boost 6500m Rated Power – High Blower
1520 HP @ 2700 RPM +200 mmHg Boost 2300m Maximum Cruise – Low Blower
1370 HP @ 2700 RPM +200 mmHg Boost 6300m Maximum Cruise – High Blower
1300 HP @ 2600 RPM +100 mmHg Boost 3000m Economy Cruise – Low Blower
1180 HP @ 2600 RPM +100 mmHg Boost 6900m Economy Cruise – High Blower
A couple things are worth noting here:
Anti detonant injection started at +180 mm boost which is below even the maximum cruise rating.
There is no listing for Emergency power other than for Take-Off.
An evaluation of a later series of engine suggested that sea level Take-Off boost pressures could be maintained up to 17,600 feet, so the higher boost pressures certainly were available even if they were not listed in the manual.
- Ivan.