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These two excerpts come from the book Nest of Eagles: Messerschmitt Production and Flight-testing at Regensburg 1936-1945, by P. Schmoll. I would definitely recommend it to those interested in German aviation.
A further modification to increase the performance of the bf 109 was the installation of MW-50 (a 50/50 volume ratio of methanol/water injection) in the aircraft, with which a short-duration engine emergency power could be achieved and which was built in gradual stages into the Bf 109 G. Peter Duttmann, a pilot with II./JG 52, still possesses at the time of writing a datasheet for the DB 605 D, which with the MW-50 injection, could produce 2,200 hp. He related to the author "With the auxiliary MW-50 installation in my Bf 109 G-10 in which I flew till the end of the war, I was able to save myself in all of the prickliest situations, of which there were several in April 1945. When no methanol was at hand, we used distilled water which functioned just as well, except that we were no able to fly high, otherwise the whole installation froze. In the sorties we flew short before the end of the war in low-level flight in the Cham area and east of Regensburg, we often met US fighters, and although they were superior to us in numerical terms, we were able to get away from them. The fastest Bf 109 I ever flew in, I handed I handed over to the Americans on 8 May 1945 in Neubiberg"
Arno Fischer of I./JG 53 recalled of the MW-50: "At the beginning of 1945 we received the Bf 109 G-10 with MW-50. In my first sortie with the Bf 109 G-10 on 27 January 1945, I was in an air battle with 20 Yak 9s – four German fighters versus 20 Russians. For almost 20 minutes, we fought a turbulent air battle over StuhlweiBenburg in which much shooting took place, but nothing was hit by either opponent. During the course of this engagement, I used my MW-50 for brief periods many times. The engine turned at higher revs and made such a noise that it made me believe it would explode at any moment. In fact, it transpired that by longer use of emergency power, the base of the pistons burned through. I used the ME-50 most unwillingly since, as I said, the engine was being taxed to its limits and made a peculiar sound which did not sound very reassuring. In dangerous air combat situations, however, you had a short-duration power increase available to you abd could raise your speed near the ground to a good 600 km/h (373mph)".
Nest of Eagles: Messerschmitt Production and Flight-testing at Regensburg 1936-1945, de P. Schmoll, Classic Publications (2010).
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5) 2200ps out of the DB605D would require 2,3 ata boost. On theory possible,especially if special alloys were available, but even the1,98 ata use is doubtful. A 109 with such boost would have a decent power to weight ratio
3) It s interesting the comment that they could get away from us fighters at low level as late as April 1945. As far as i know ,the us fighters with their 150 octane fuel should have a massive speed advantage.
5) 2200ps out of the DB605D would require 2,3 ata boost. On theory possible,especially if special alloys were available, but even the1,98 ata use is doubtful. A 109 with such boost would have a decent power to weight ratio
Another thing that might've increased the power down low for the DB engines is switch from variable-speed S/C to the, say, 3-speed S/C - cancels losses due to slippage in the hydraulic coupling. For the Fw 190 installation - make a turbo DB engine with properly streamlined installation, or make a turbo-compound installation. Granted, historically, the latest is a bit beyond the ww2 time line.
I thought that feature provided the DB with a better power curve.And reducing the CR would further decrease the range of action. I would think an annular radiator(possibly with an inter cooler too), like the Fw 190D. It would provide better aerodynamic configuration for the 109 , plus better cooling efficiency. Thus perhaps the engine could be pushed harder. But without proper alloys to withstand the additional loads no fuel advances, or improved radiator, could have an effect. I wonder if would be possible with the technology of the era to use changing valve timing or 5 valves per cylinder in order to improve the specific output of the engine
The variable-speed drive was certainly better than 1-speed drive, and everyone uses 87 oct fuel and no ADI. However, no-one used 1-speed drive on their major military engines that late in the war except Soviets and British on some low-alt engines, and better fuel and ADI is videly used. Against a 2-speed drive, both choices have advantages - the variable-speed drive will make better power between the two power 'peaks', but a 2-speed drive will make much better power at low level (since there is no losses at hydraulic coupling), exactly where the engine was capable to develop the best power. See, for example 1-stage Griffon and BMW 801D vs. DB 603A.
The 3-speed drive can smooth the power curve further, and it can provide even better power down low vs. a 2-speed drive, let alone vs. variable speed.
I've also sugested the use of swirl throttle instead of the butterfly throttle, as it was done on the Jumo 213 engines. Nice thing about that throttle is that it does not increase the IHP (=BHP + losses) nor engine temperature and stress, while increasing BHP (= power available for the prop). That is avilable, admitedly, just under the rated altitude(s).
The BF 109G got a oil cooler some time in 1944 historically. As for the new raditor layout - perhaps in front of the wings like the Mosquito - will not be so tricky for the CoG like the annular layout? I'd certaily try to go with fuselage-connected engine cowl rather than with engine-connected cowl, in order to shave some drag.