That's another problem. This
article from 1936 states that octane rating depends on the measurement method. Two methods exist in the US, which more or less give a difference of 5, ie what is rated 87 under one method is rater 92 under the other. The Bristish octane rating is yet another method, but I haven't found comparisons with the US method.
British 100 octane fuel could use up to (but not exceed) 20% aromatic compounds.
Aromatics give the fuel a better knock rating when running rich and are the major reason for ratings like 100/130 fuel.
American 100 octane fuel could contain
no more than 2% aromatic compounds.
Aromatic compounds did not get along with natural rubber very well and US fuel lines, gaskets, seals etc tended to start leaking. This is before self sealing fuel tanks showed up.
The British had noted the better rich mixture response of aromatic fuels when using 87 octane fuels. Some of this depends on which oil fields you are sourcing your oil from and how much trouble you take to refine it. The British wanted the better rich mixture response (more boost before knocking or detonation) even though they couldn't measure it in the 1930s or even 1940. When the Performance Number scale was developed and old stocks of 1939-40 fuel were tested in Britain the British 100 octane fuel of the BoB was found to be about 100/115-120 depending on the batch. There are a number of different aromatics and exact blends do give different results.
The US 100 Octane fuel showed no real increase in rich response. It was pretty much 100/100 although depending on exact batch it could be 100/98-104. Yes, running rich could actually decrease the knock rating of the fuel under test on occasion.
This was a lot more important than the difference between 87 and 92, although that is a lot more than most people realize because the the octane rating scale is not linier.
The difference between 87 and 92 is about 14% rounded up.
If you tried to use US 100 Octane fuel in a Merlin at 12lbs of boost you might very well blow the engine up. There was a lot of back forth between the British and the Americans during 1941 and 1942 about fuel standards to get the joint 100/130 specification/s but that is after the time in question. But what you could do with 100/117 fuel and what you could do with 100/100 when in combat is rather obvious.
However the often told fable about the US 'saving' the British with quick shipments of "US" 100 octane fuel is a myth. The British may have been sourcing Fuel from US refineries but it was not US spec fuel.
On the subject of the constant speed props and take-Off.
You don't have the constant speed prop you are screwed.
With the two pitch prop they took off at around 2700rpm (?) and shifted to Coarse pitch at about 2,000ft and 170mph. Engine RPM dropped from 2850rpm to 2080rpm.
If you tried to fly much faster than 170mph at low level you would over speed the engine.
You
might have had to use reduced throttle for take-off. You might have over spun the propeller on runway and lost thrust until the plane got to take-off speed.
The DH props were good for about 20-22.5 degrees of pitch change. The Rotol's had 35 degrees of travel. Maybe they didn't use all of it?
But the DH props, until they got converted, were pretty bad. After they got converted things were a lot better but there were still limits?
If you want full speed (max coarse) you are limited to how much fine pitch you have. Over revving or using max boost may give the sound of power but actually slow you down trying to take-off. The Prop can only transmit so much power at low speed, it is slipping at a poor angle.
A bit like tires on a slippery surface. Too much power at slow speed just makes the tires spin.
