The Germans also did a number of analyses of the octane rating of captured allied fuels, using their own "Oppauer Verfahren" or Oppau Process.
I haven't translated a full description of the process itself, but it basically used a small motor with three small fuel containers. Warmed up the motor on the motor's standard fuel, then tested response against a known standard fuel to set a benchmark, then switched over to the fuel to be tested, which was then compared to the standard.
The result was a continuous octane-rating curve against the full range of air-fuel mixtures.
They also tested 150-octane fuel against C3 knock limits to determine the relative performance of both fuels under supercharging. They didn't have large enough samples to undertake this test against other captured fuels.
Interestingly, they identified 150-octane as an American fuel, as they recovered it from P51-Ds. This gives the lie to some internet grognards who insist 2 TAF was the only unit to use 150.
Note the B4 is there for comparison and originally appears on a separate document which compares it to standard C3.
Here's the knock limits curve.
The Germans believed the 150 fuel would run at 2.7 ata, which corresponds quite accurately to + 25lbs boost.
Interestingly, one of their concerns was the high octane content at lean mixtures, which they believed would aid the US escorts in long-range missions. Will dig out the orginal quote later - being yelled at to shut the computer off now.
Edit - For the sake of keeping the thread on-topic, there's the myth that C3 was as good as 150-octane. It clearly wasn't, according to the Germans' own tests. There's also the myth, in some quarters as noted, that only 2 TAF used 150. That's also incorrect, again according to the Germans' own reports.
I haven't translated a full description of the process itself, but it basically used a small motor with three small fuel containers. Warmed up the motor on the motor's standard fuel, then tested response against a known standard fuel to set a benchmark, then switched over to the fuel to be tested, which was then compared to the standard.
The result was a continuous octane-rating curve against the full range of air-fuel mixtures.
They also tested 150-octane fuel against C3 knock limits to determine the relative performance of both fuels under supercharging. They didn't have large enough samples to undertake this test against other captured fuels.
Interestingly, they identified 150-octane as an American fuel, as they recovered it from P51-Ds. This gives the lie to some internet grognards who insist 2 TAF was the only unit to use 150.
Note the B4 is there for comparison and originally appears on a separate document which compares it to standard C3.
Here's the knock limits curve.
The Germans believed the 150 fuel would run at 2.7 ata, which corresponds quite accurately to + 25lbs boost.
Interestingly, one of their concerns was the high octane content at lean mixtures, which they believed would aid the US escorts in long-range missions. Will dig out the orginal quote later - being yelled at to shut the computer off now.
Edit - For the sake of keeping the thread on-topic, there's the myth that C3 was as good as 150-octane. It clearly wasn't, according to the Germans' own tests. There's also the myth, in some quarters as noted, that only 2 TAF used 150. That's also incorrect, again according to the Germans' own reports.
Last edited:
