GM-1 was always loaded as a liquid into the aircraft, but the method changed. Before mid ´41, they used high pressure to get a liquid. The serial installation consisted of 2 bottles, each with 7 liter. The problem was icing in the manifold channel, and it took some knowledge to overcome that problem. But the main problem was the vulnerability when hit. A single shell that penetrated the bottles (though they were made of steel and had 2 walls) made them explode like a grenade. So they changed later to liquid N2O that was cooled down but it wasn´t under pressure (-87,5°C is the boiling temperature). This method had also a better effectivity.
The reasons for GM-1 are: Higher portian of oxygen compared to air, use of disintegration heat (cooling effect), increasing pressure due evaporation in front of the cylinder and better combustion effectivity.
A Ju86R , with 150gramm/sec. GM-1, reached over 14500m (15000 INA). A Ju88 T (reconaissance aircraft) was equipped with BMW 801 D radial engines. While combat power dropped normally without GM-1 from 1600ps to 880Ps in 10000m, GM-1 brought it back to 1430PS (150g/s). Speed increase was 150km/h, from 500km/h to 650km/h. When the pilot (Kneymeyer) came back from the first combat sortie, he reported: "the Spitfires made hopeless pull-ups at my vapor trails"
Test with fighter aircraft were also done. A 109E with DB601Q engine was used first (report 2574, 15.8.41). The performance increase was:
In 9km altitude:
effectivity: 3,6 PS*s/g
cooling effect: -40°C (difference)
manifold pressure: +0.08 ata (difference)
in 13km altitude:
effectivity: 3,9 PS*s/g
cooling effect: -70°C (difference)
manifold pressure: +0.09 ata (difference)
This means, with 100g/s GM-1 what was used later in the 109 and 190, you could reach a performance increase in 13km altitude of 390PS.
Just for comparison the data for GM-1 that was stored under pressure:
effectivity: 2,9 PS*s/g
cooling effect: -18°C (difference)
manifold pressure: +0.07 ata (difference)
So the liquid GM-1 had much better effectivity and was much less vulnerable to hits compared to GM-1 stored under pressure. Disadvantage was the sensitivity for humidity what could cause icing of the charger, valves and "nozzles"(?). Furhtermore it took quite long until the engine reacted to GM-1, especially in long piping systems (up to 1min), because the liquid GM-1 evaporated in the warm piping system at the beginning until the pipes were cooled down, too. Only when the pipes were cooled down enough the liquid GM-1 reached the engine. I don´t know how long it took later in the serial fighter installations.
niklas
