Excellent, we don't have many German-specific threads as we speak
That is a question that has been running around my head for a while, how much would the DB601E have improved with C3/96 octane fuel had it, and not the BMW 801 got it in 1942 once cleared for 1350PS?
I see the C3 as the crutch that allowed the 801 to live, what if it is used to help the 601E and prevent the premature introduction of the 605?
Not all BMW 801s were created equal. The 801C have had a 'slower' supercharger than the 801D, as well as lower max RPM in the second gear initially - meaning that altitude power will be much better for the 801D, even if it was running at a bit restricted settings initially. Not everything was great with 801D, either - perhaps increase of compreession ratio pushed thermal loads a bit too much (while adding a small bit of power), necessitating the introduction of new sperk plugs and other mods for the engine to operate as fully rated (2700 rpm, 1.42 ata). Net result was the 801C making 1380 PS at 4.6 km at 2550 rpm/1.30 ata, vs. 801D making 1440 PS at 5.7 km at 2700 rpm/1.42 ata. The fully rated DB 601E: 1320 PS at 4.8 km at 2700 rpm
Point I'm trying to make is that, as SR6 above noted, the DB 601E will not be able to beat the 801D in power, with both engines fully rated. It will consume far less fuel, though.
Engineers at DB were aware that 601E has it's limits, hence the 605A - as small modification of the 'power section' as possible, extra 100 rpm, while introducing a new supercharger, meaning the power of 1250 PS at 5.8 km at 2600 rpm (30 min rating), and 1350 PS at 5.7 km at 2800 rpm. The 601E will do ~1175 PS at 5.8 km at 2700 rpm (= fully rated engine,
5 min rating).
Any late war Allied fighter would've had far easier time with a Bf 109G that has DB 601E fueled with C3 than it had with the historic 109G.
One can wonder how much the reliability and allowed boost would've increased with decrease of the compression ratio on the DB and BMW engines, a path not taken.