Originally posted by pasoleati
At this stage I can only say that the minimum oil pressure at 2600 rpm for the 605 is 2.6 kg/sq.cm, while Jumo 211F/J´s figure at the same rpm is 5.5 atü.
Why do you think is it a problem that the minimum oil pressure that the DB could sustain is lower value than the Jumo?
And the 605 does also have pressurized cooling system, Kurfürst[/B]
Yes most ww2 fighter coolant systems had, however the Merlin went extreme on pressurized system, making it more vulnerable to coolant leaks than others.
And K, your fuel consumption claim is pretty far off the mark. Will provide details later. [/B]
I am most positive it`s not. Compare the DB with the Merlin at a similiar power output, and you will see that it consumes 30-50% more fuel to get the same output.
Ie. you can compare the the Merlin 66 at +25lbs boost, it developed ca. 1940-2000 HP this way, with a fuel consumption of 197 imp. gallons per hour, or 895 lit/h.
At +18, the engine developed 1680 HP at SL, at 150 gallons/h... 681 lit/h.
The contemporary DB 605D, operating at 1.98ata and developing 2000PS (ca 1970 HP) had a fuel consumption of 650 lit/hour, 37.5% more efficient than the Merlin. The 605AM developed 1800 PS at 1.7ata, at 560 liter per hour consumption.
"No replacement for displacement" - running on such extreme boost as the Merlin did to compansate for it probably lead to very bad thermal effiency and such huge consumption. Just look at the range of 109s/Spits.
Starting from 2.1 km the oil supply to the coupling itself increased until at 5.7 km all oil was supplied to the coupling. Basically it means that at low altitude considerable power was wasted on driving the impeller when the variably coupling could have allowed full throttle operation, if properly executed.That would require another variable speed for the 1st gear, making the whole system extremely complex and prone to mishaps. It didn`t worth it. At SL the DB 605A-1 developed 1475 PS, at 2.1km 1550 PS. The difference is from the loss of fixed 1st speed, and it`s only 75 PS, even less on later models, 30-40 PS or so. On the 601s, 10-20 PS maybe....
Why bother to complicate things, when the possible gain is a minimum amount of power at very narrow - and of little practical combat use - altitude range.
Well, I don't know even if the supercharger gear of the DBs was a good design; large parts of the advantages of the hydraulic coupling were wasted due speed controll system and oil cooling was a problem. 
Try to be honest for once, you know that the coupling`s heating problems were solved with the 601 family already. Besides, if it wasn`t any good, was there any better system (Jumos would be strong candidates, though)?
The Merlin looses like what, up to 200-250!!! HP
between MS and FS gear, because it`s just a orthodox fixed gear supercharger system that just throws power out of the window on a whole 11 000 ft altitude range... certainly Daimler Benz would be mad to go on that road, when it had a system that could save 95% of this loss..
In addition throttle system and intake manifolds were not so good (the throttle system was redesigned for the last models but probably none reached service). Intake manifolds were not so good? Because? The DB 60x series intake manifold was used on tenthousends of planes and even the FW 190D and TA 152 used practically the same design.
The system relied on the same principle as the Mustang`s radiator scoop, ie. pushing the intake away from the fuselage to minimize surface turbulance and drag. It was also very good being very close to the s/c itself, just 30 cm or so route for the air to make inside, internal losses were minimized. Far better than on the Merlin, when the air was sucked in on the chin, creating turbulance on the whole fuselage already, and loosing much effiency as it had to be lead through all under the engine in a 2m+ long ducting to the supercharger.
