trying to figure out the "ata" gauge

[Crumpp]

In addition, the German engine operates at 6.5 : 1 compression ratio against the 6.0: 1 of the Merlin. This difference in compression ratio should give the German engine an advantage of rather more than 3 per cent, in power output, and at the same time 3 per cent, lower fuel consumption.

http://www.flightglobal.com/pdfarchi...0-%200563.html