Four-engined Junkers 288? <delurk>!

[Shortround6]

What is the power of the two engines?

DB 605A had 1475PS for take-off and 1310PS for climb at sea level rising to just under 1400ps at just over 2000 meters and then falling to about 1250PS at 5700 meters. Max cruise is 1075 PS at 5500meters?

The DB 603 had 1750PS for take-off (at 1.4 ata, no special fuel, no MW 50) and 1580PS for climb at sea level (1.3 ata)with 1510PS at 5700 meters (?). Max cruise is 1400 PS at 5360-5400meters?

DB 603 has a max cruise higher than the "Höchtsleistung" rating of the DB 605A at about the same altitude. While the engine is lighter (and so is the cooling system and the propeller needed and the ....etc. etc) you are dealing with a 70-90,000lb bomber when fully loaded. Why the HE177B/HE277 gained 20,000lb loaded (and around 10,000lb empty) over the He 177 I don't know but using around 84% of the take-off power isn't going to give good results.

You might be able to make a rather more reliable bomber than the He 177 but it is going to have a bit less performance in one or more areas due to the higher drag. Perhaps only 3-5% ???

 

[wiking85]

What is the power of the two engines?

DB 605A had 1475PS for take-off and 1310PS for climb at sea level rising to just under 1400ps at just over 2000 meters and then falling to about 1250PS at 5700 meters. Max cruise is 1075 PS at 5500meters?

The DB 603 had 1750PS for take-off (at 1.4 ata, no special fuel, no MW 50) and 1580PS for climb at sea level (1.3 ata)with 1510PS at 5700 meters (?). Max cruise is 1400 PS at 5360-5400meters?

DB 603 has a max cruise higher than the "Höchtsleistung" rating of the DB 605A at about the same altitude. While the engine is lighter (and so is the cooling system and the propeller needed and the ....etc. etc) you are dealing with a 70-90,000lb bomber when fully loaded. Why the HE177B/HE277 gained 20,000lb loaded (and around 10,000lb empty) over the He 177 I don't know but using around 84% of the take-off power isn't going to give good results.

You might be able to make a rather more reliable bomber than the He 177 but it is going to have a bit less performance in one or more areas due to the higher drag. Perhaps only 3-5% ???

The 277 and 177B are different aircraft in that the 277 is wider with a bigger bomb bay and has more fuel capacity. The 177B will be about the same weight at the 177A, perhaps with some extra weight from the larger wings and extra nacelles, but less from smaller nacelles, lighter engines, and smaller props. So 2-3,000kg extra? IIRC about 3-4% extra drag. I get why the DB603 was used, but it was not available in numbers and was less reliable.

 

[Koopernic]

"We can also note that German V-12s will get better fuel mileage than Allied V-12s."

Any details on this? I would have thought the higher-octane fuel of the Allies on its own would have given the Allies lower specific fuel consumption.

Note that the DB605, in performance equivalent to a Merlin, was nearly the displacement of the Griffon.

However only thing that matters is the weight and frontal area and in terms of weight the DB605A, DB605D and DB605L (two stage) were exactly equal to the Merlin 66 with both equal to 745kg +/-1kg. The Daimler Benz engine in fact had lower frontal area. The Merlin (and Griffon) may, I suspect, even have had a requirement for larger radiators given the inter-coolers requirements. The DB60x series used the threaded cylinder sleeve as a kind of giant hollow nut which was screwed into the integral cylinder head block combo and secured to the crankcase by a large nut (technically a threaded ring). The Merlin (and Jumo and Allison) engines had 4 bolt holes surrounding each cylinder which was used to tighten on the block to the crankcase. The need for sufficient structural material and clearances around these holes and the more peaky stresses forced the Merlin to used smaller cylinders and conversely allowed larger ones on the DB. Perhaps DB then designed for lower pressures. There is more than one way to skin a cat as they say.

Likewise the Griffon (34L) is about the same weight as the DB603(44L). The RR engines relied on processing more air not through higher swept volumes but through supercharging and then inter-cooling to get rid of the heat that would cause preignition and thereby sacrificing some efficiency and power by low compression ratios, losses in supercharging compression, losses in the heat extracted in the inter-cooler which would have been partially compensated for by the lower frictional losses in the smaller engine.

Daimler Benz did start introducing inter-cooling on the larger DB603L and were expecting a spectacular 2800hp out of the DB603N.
A DB605 variant, the DB628 which had separate drives for the 1st stage variable pitch LP supercharger and 2nd stage HP supercharger (infinitely variable drive type) had inter-cooling AFAIKT from photos and a spectacular full throttle height of 38500ft.

 

[wuzak]

What is the frontal area of a DB 605 compared to an Allison or Merlin? Or Griffon?

The Merlin (most of) has a higher frontal area than the Allison due largely to the updraught carburettor. The 130 series Merlins had a lower frontal area than other Merlins because it used a downdraught carby.

The Griffon was 37l (36.7l actually). The two stage Griffon was about the same weight as the single stage DB 603. But more powerful, and nowhere near as long.

Similarly the single stage DB 605 was about the same weight as the two stage Merlin.

 

[Koopernic]

How about the DB605A of 1942 on the He177B? Despite being restricted in RPMs until 1943, it was about 200kg lighter as an engine than the DB603 the He177B was tested with in 1943.

View attachment 264655

He 177A5 prototypes with 4 engines (BMW 801) were in fact flown in 1942. AFAIKT the only issues were that the 4 engines really required a larger tail area or contra rotation. Now the He 177A1 and 177A3 actually had 2 x DB606 and since these were paired engines it really means they had 4 x DB601E. Had the engines been mounted separately they could by 1942 have had a choice of 4 x DB605A, 4 x Jumo 211J, 4 x BMW 801 even 4 x DB603 all significantly more powerful than 4 x DB601E. Any drag increase is greatly over compensated for by the more powerful engines, any increase in fuel consumption is compensated for by the higher maximum takeoff weight enabled by the greater power. By late 43 or early 44 they can add in the Jumo 213A as an option or the enlarged supercharger variant the DB605AS or start using limited form of the MW50 boost systems for enhanced takeoff power eg 1.55 ata rating.

As it turns out the He 177A5 series was introduced in 1943 with a new, larger re-engineered wing. The first 200 or so still received only the 2 x DB606 (4 x DB601E) that had been used in the He 177A1 while the latter production batch received 2 x DB610 (4 x DB605A) the reason being the Luftwaffe didn't have the Stomach to introduce another new engine type too early. The next development was supposed to be the He 177A7 which had yet again an enlarged new wing with larger coupled engines again 2 x DB613 (4 x DB603 engines) however the new wing (3rd new wing) had been designed to handle either 2 large engines or 4 smaller separate engines in the manner of the Airbus A330/A340 and by this time the Luftwaffe was sick of the coupled engines. When configured with 4 separate engines a He 177A7 was known as a He 277B7.

You'll note the RLM (maybe not the Luftwaffe fault) persisted with the coupled engines to the point that it looks insane from our perspective, even re-engineering the wing totally several times, that effort could have been used to distribute the engines separately and introduce the 4 engined variant after the He 177A3 in 1943.

In regards to the Fw 191C (4 engined version) as far as I can tell Bomber B was supposed to enter production in late 1941 or early 1942 and if a backup plan in case of failure of the Jumo 222/DB604/BMW 802 to meet development schedule had of been in place production Bomber B could have been in production in 1942 using 4 separate engines. The difference is that the Bomber B was significantly smaller than Bomber A (He 177) and would have had speeds of around 380-440 mph. The internal bomb load of 4 tons (as opposed to 6-8 tons for He 177) however was still big, Bomber B was classified a heavy bomber. That is the kind of performance the Luftwaffe needed in the face of its numerical inferiority.

When He 177 started flying around the Atlantic and Mediterranean in 1943 with glide bombs (see Martin Bollingers book on the guided weapons) their great range and speed meant they often turned up the next day on missions thousands of miles away, becoming a threat over a large area. Had they been available in large numbers as reliable 4 engines aircraft they would have forced the allies to deploy more defensive resources while being very efficient from the Luftwaffe's point of view. The Bomber B also had this capability only they could have blunted the effectiveness of allied fighter superiority.

Note the suggestion of DB628 (a DB605 variant) use on the Fw 191C, this engine produced around 1100hp at 38500ft and this suggests penetration speeds of well over 400mph at well over 40000ft with service ceilings of 45000ft or more.

Junkers I think actually did rather well with the Jumo 222 since a new engine took at least 6 years to get into production, developing full power, reliable and in service. Doing it in 4 years was never going to work. Compare CW R-3350 (1937 first run) and Napier Sabre which started earlier.

By the end of the war the Jumo 222E/F with two stage supercharger on B4+MW50 was producing 2800hp and likewise the single stage Jumo 222A-3/B-3. The engine was scheduled for production but the bar had been raised yet again to 3000hp.

 

[tomo pauk]

...
The Packard Merlin V-1650-9 with 150PN fuel plus ADI (water ethanol injection) could manage about 2200-2300hp but I would imagine the DB605 could manage this as well i given the fuel, there was supposedly a German 140PN fuel being developed and DB605 was benching 2.3 ata. (I have no proof only other posters claims) and of course there was a DB605L with two stage supercharger, for which only 1.75 ata rating data is usually provided, which no doubt could have generated the pressures required. The sloweness of getting two stage supechargers in service is probably explained by the Germans developing highly sophisticated types such as the DB605 based DB628 that proved to hard to put into production with the available airframes.

We might compare the number of designs under development in the Daimler-Benz, with number of designs in other companies. The plethora of the types simply deluted the scarce resources. It is interesting that Germans (at least DLV) were perfectly aware of advantages of two-stage supercharging even before the ww2 broke out, yet they did not have anything such to install in the airframes before 1945. Even the Soviets were test flying the 2-stage versions of the M-105 in early ww2.
The DB-628 was a 2-stage engine, we do not know for certain that it would've been such an issue to install it in the Fw-190, for example.

Despite that, the evolution of the Jumo 211 shows a different possibility. This engine was closer to the configuration of the Merlin, Griffon, Allison in using a lower compression ratio and higher boost and perhaps beat even the Merlin 61 into service with an inter-cooler in 1942 when the Jumo 211J came into service on Ju 88A4

The Jumo 211F J were indeed using the lower compression ration (6.5:1, a bit lower than V-1710), yet the allowed boost was still only 1.40 ata, even for the 5 minute take-off power setting. It cannot beat the Merlin 61 at any altitude, the power for the inter-cooled sub type (211J) was 1180 PS at 4800 m (1164 HP at 15750 ft), on 2400 rpm and 1.20 ata (30 min rating). Maybe as a result of the Jumo 211 being the 'bomber engine', the engine was never rated for 'Notleistung' (5 min rating, 2600 rpm and 1.40 ata). The power was comparable with Merlin 20 series, apart for the Merlin's advantage for being also rated for 5 min power (circa 1400 HP at 12000 ft); also 1100+ HP at 17000 ft for 'max climbing power' at moderate boost and RPM - +9lbs and 2850.
No second stage equals low power at higher altitudes, irrespective to the country boundaries.

It might even have made a better fighter engine in 1942 given the power of 1420hp on only B4 fuel (1500hp for the Jumo 211P on only B4 though it was not produced in numbers). It's curious to imagine this inter-cooled engine receiving two stage supercharger given the inter-cooler and two speed gearbox is already present and perhaps C3 fuel.

Against the DB-601E and 605A (even de-rated), the chances are slim. It 1st need to be tested and rated for 2600 rpm beyond tale-off regime. It (maybe?) need to be modified for the prop gun, so the Bf-109 can use it. It is a wider engine than DB-60?. With two stage S/C, now that would be an engine.

Something went wrong between 1942 to 1944 with German fighter engine performance particularly the DB, some item of technology was missing.

Too many products went nowhere, while consuming resources and time.

(Tomo, thanks for the data, one day I mean to overlay DB and RR power v altitude on dated charts. The bolt-less integral head design seems authentically DB technology, remeber Rolls Royce messed up the head design of the Merlin originally. I know that Hispano Suiza used a similar idea on the HS-12 series and this technology ended up in Soviet production in the form of the Mikulin engines but the HS-12 series was way down on DB601 performance, it was this rather than airframe issues that nobbled the Morane-Saulnier M.S.406 though the Dewoitine D.520 had hideous handling with a viscous completely unannounced stall)

The Hispano 12 was too light, compared with DB or Jumo, with 2 valves per cylinder. So the allowable RPM and boost were low, and that means power is lacking. The Soviets bulked up the Klimov versions several times, so the M-105 turned 2600 rpm vs. 2400 of the French 12Y. That improved power at all altitudes. Soviets also installed 2-speed S/C drive, that gave 'altitude flexibility' to the power. Further weight increase allowed greater boost, 1st with VK-105PF, then with 105PF2 versions. The VK-106, 107 and 108 were to be further bulked up, with 4 valve head and up to 3200 rpm (!). The weight cost was to be above 200 kg against the M-105.

The Jumo 222, at least going by the article about it in the 'Flugmotoren und strahltriebwerke' was a huge resource hog, that was not helped with RLM upping the bar every now and then. It was also not helped by numerous relocations of test and perceived production facilities. Despite passing of bench tests, the flight tests were many times interrupted by malfunctions of numerous main components. Corrosion, vibrations, crankshaft troubles, S/C malfunctions - the 222 have had it all.

 

[wuzak]

It is interesting that Germans (at least DLV) were perfectly aware of advantages of two-stage supercharging even before the ww2 broke out, yet they did not have anything such to install in the airframes before 1945.

Daimler-Benz built the Mercedes-Benz W154 in 1938. It had a 3l V-12 with twin Rootes type superchargers - these were two parallel, single stage superchargers. For 1939 the engine was redesigned as the M163 with twin stage supercharging.

 

[Koopernic]

The idea that the Germans are dissipating their resources in a plethora of R+D programs while the allies are highly focused doesn't bear scrutiny.

Rolls Royce piston engines in development between 1940 to 1945
Rolls-Royce Merlin single stage, two stage and turbo
Rolls-Royce Griffon
Rolls-Royce Eagle (1944)
Rolls-Royce Exe
Rolls-Royce Peregrine
Rolls-Royce Crecy
Rolls-Royce Vulture
Rolls-Royce Pennine

Some of these engines are highly unconventional, bordering on crazy with sleeve valves or two stroke cycles requiring technology that didn't exist or seemingly provoked by competition from Napier. Only a few were cancelled, such as the Peregrine.

Less is known about Bristol R+D effort except that the Centaurus did not see service until after the war (unless one counts the oversize Wellington-the Warwick) and did nothing that the PW R-2800 or CW R-3350 could not do better and earlier. The British and US duplicated effort in many areas for reasons of national pride, post war strategy or to develop some unique aspect of technology.

Napier expended a great deal of effort on the Nomad turbocompund diesel that went nowhere.

This is the sample of the US effort.
Pratt Whitney X-1800
Pratt Whitney XH-3130
Wright R-2160 Tornado
Wright R-3350
Chrysler IV-2220
PW R-4360 (did not see combat service in WW2)
Turbo compound Allison V-1710
Lycoming XR-7755 edited in.

Only the R-3350 and R-4360 became a useful engine and then barely.

While fascinating engines they represented huge R+D programs that failed to produce useful engines in time while their economic viability was dubious as well.

As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150

Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead.

The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.

The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.

Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.

Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.

 

[wiking85]

The Jumo 222 started development in 1937 and wasn't ready until 1943 then only with unacceptable amounts of heat resistant metals Germany didn't have. That's 7 years of development to get to production ready status and it never entered production even after being declared 'ready'.

 

[wuzak]

The idea that the Germans are dissipating their resources in a plethora of R+D programs while the allies are highly focused doesn't bear scrutiny.

Rolls Royce piston engines in development between 1940 to 1945
Rolls-Royce Merlin single stage, two stage and turbo no turbo as far as I am aware
Rolls-Royce Griffon development suspended briefly 1940
Rolls-Royce Eagle (1944) development started in 1943/4
Rolls-Royce Exe development suspended 1940, cancelled 1941
Rolls-Royce Peregrine development suspended 1940, cancelled 1941
Rolls-Royce Crecy Rolls-Royce wanted to cancel the Crecy, but were not allowed to by the MAP. Development proceeded slowly due to lack of resources put into the project.
Rolls-Royce Vulture cancelled 1941
Rolls-Royce Pennine development started in 1943/4, intended for post war transport industry

Basically the main part of the war Rolls-Royce concentrated on the Merlin and Griffon, and moreso on the Merlin.

Some of these engines are highly unconventional, bordering on crazy with sleeve valves or two stroke cycles requiring technology that didn't exist or seemingly provoked by competition from Napier. Only a few were cancelled, such as the Peregrine.

The Crecy was based on designs from Ricardo. It was unconventional, but it was a promising research project.

Rolls-Royce's first sleeve valve engines were modified Kestrels (modified by Ricardo). These were the RR/D (Diesel) and RR/P (petrol). The Exe was designed and built in the '30s, but never had any serious amount of resources directed to it. The Pennine was an enlarged version, started late in the war.

The Vulture was an X engine. Not exactly crazy, or unique.

The Eagle was, indeed, a response to Napier's Sabre. But it, too, was a late war design.

Less is known about Bristol R+D effort except that the Centaurus did not see service until after the war (unless one counts the oversize Wellington-the Warwick) and did nothing that the PW R-2800 or CW R-3350 could not do better and earlier. The British and US duplicated effort in many areas for reasons of national pride, post war strategy or to develop some unique aspect of technology.

The reason why the Centaurus did not see service untillate in WW2 is that practically all the resources at the disposal of Bristol went to sorting and improving the Hercules.

Napier expended a great deal of effort on the Nomad turbocompund diesel that went nowhere.

Most of that effort was post WW2.

This is the sample of the US effort.
Pratt Whitney X-1800
Pratt Whitney XH-3130
Wright R-2160 Tornado
Wright R-3350
Chrysler IV-2220
PW R-4360 (did not see combat service in WW2)
Turbo compound Allison V-1710

These are projects from several different companies. And the US war economy was far more capable of supporting them than the German one was.

Only the R-3350 and R-4360 became a useful engine and then barely.

You will get arguments on the usefulness of these engines. The R-3350 did make a significant contribution - in the B-29.

As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150

As I understand it, B4 was better than the pre-war British 87 octane, and more akin to the 100 ocatne being used at the start of the war.

Of course the option for the Merlin would have been, as the Germans did, to use ADI to compensate for lack of octane.

Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead.

Interesting that you say that most of German engine projects were derivatives of exiting engines, but then call out the variants on the Merlin (single stage, two speed and two stage). All of Allison's WW2 piston engine projects were based on the V-1710. Even the turbo-compound was additional components bolted up to the back of a standard 2 stage V-1710.

There were some German projects that went nowhere. The DB604, for example. An X-24, like the Vulture.
The DB609, a V-16. You could say this was based on the DB603 (it was, using the same bore and stroke dimensions) - but you could say the R-3350 was based on the R-2600 and the R-4360 was based on the R-2800.
BMW 802
BMW 803
Junkers 223 (IIRC a Diesel)

And a myriad of gas turbine projects.

As for being too small, the DB605 was of Griffon capacity, give or take a litre.

The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.

I guess it would be the same situation as for the Allies - production trumps development.

The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.

The Bf 109 was too small. But it could have been used for a new development, or for a Fw 190 version.

Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.

I think you will find that the modifications were anything but minor.

Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.

I think that the DB 604 had, possibly, more potential. But it was cancelled after less work had been done it than the Jumo 222.

 

[Koopernic]

The Jumo 222 started development in 1937 and wasn't ready until 1943 then only with unacceptable amounts of heat resistant metals Germany didn't have. That's 7 years of development to get to production ready status and it never entered production even after being declared 'ready'.

While the Jumo 222 development program started in 1937 the Wright R-3350 actually ran in 1937 and it still had problems in 1943 and then at only 2000/2200hp.

Jumo 222 did enter low rate production, approximately 289 were produced and Ju 288 did fly on it as did Fw 191. First run of the Jumo 222 was 1939. First run of the Sabre was 1938. First run of the R-3350 1937.

By demanding 2500hp on only 87 octane fuel rather than accepting 2000hp or even less, too much demand was placed on the engine too early. The engine was back on the production program in 1944.

The reason it didn't enter production was probably that its only customer was the Ju 288 and it wasn't powerful enough. Perhaps they might have tried it in de-rated form on the Do 217 or He 219 in 1942. If de-rated to 1900hp it still provides more power than a BMW801 or DB603 while having the same or better power to weight ratio.

One issue halting production was a lack of tin for the bearings.

 

[Koopernic]

"As I understand it, B4 was better than the pre-war British 87 octane, and more akin to the 100 ocatne being used at the start of the war."

No, B4 was 87 octane as was British 87 octane. Both fuels, if tested, would slightly exceed their nominal 87 octane rating. RON is RON.
The reason is that the acceptance tests always added a safety margin.

There were slight differences in the test engine procedures. The Germans were more rigorous in their test by preheating the fuel to 150C rather than just using ambiant which leads to a slightly more conservative result however the Germans tested at 600RPM while the British at 800RPM which also leads to a more conservative result. In effect the tests are the same to within a point.

The result is that German B4 started out at 87 octane was often tested at 89 octane using the British methods but then RAF 87 octane was also slightly higher than the nominal 87 octane rating.

Most of the German engines projects were derivatives in that the basic DB605/603 were used as the basis

Rolls-Royce Merlin XX Turbo-Supercharger Cutaway Drawing from Flightglobal

List of aircraft engines of Germany during World War II - Wikipedia, the free encyclopedia


Daimler-Benz DB 600 12-cylinder inverted-V
Daimler-Benz DB 601 improved DB 600 with fuel injection
Daimler-Benz DB 602 16-cylinder diesel powered the two Hindenburg class airships
Daimler-Benz DB 603 enlarged DB601 for use in bombers and fighter-bombers, little fighter use
Daimler-Benz DB 604 prototype 24-cylinder (X-24) engine, cancelled in September 1942
Daimler-Benz DB 605 improved and slightly enlarged DB601 for use in fighters
Daimler-Benz DB 606 composed of twinned DB 601 engines, a coupled "power system", derided as a "welded-together engine" by Goering in August 1942
Daimler-Benz DB 607 a four-stroke diesel version of DB 603 engine.
Daimler-Benz DB 609 16-cylinder version of DB 603 engine. this was still not an entirely new development.
Daimler-Benz DB 610 composed of twinned DB 605 engines, a coupled "power system", to replace the DB 606
Daimler-Benz DB 612
Daimler-Benz DB 613 two coupled "power system" DB603 engines as with the 606 and 610, experimental only
Daimler-Benz DB 614 development of the DB 603G, 2000 hp. Abandoned June 1942
Daimler-Benz DB 615 consisted of two coupled DB 614 engines. 4000hp. Abandoned in June 1942.
Daimler-Benz DB 616 a development of the DB 605. Abandoned in June 1942.
Daimler-Benz DB 617 a development of the DB 603 for long-range flight.
Daimler-Benz DB 618 two coupled DB 617 engines.
Daimler-Benz DB 619
Daimler-Benz DB 620
Daimler-Benz DB 621 DB 605 with a two-stage supercharger. 1620 hp. Abandoned in September 1942
Daimler-Benz DB 622 DB 603 with a two-stage mechanical supercharger and a turbosupercharger. 1970 hp. Abandoned in January 1943
Daimler-Benz DB 623 DB 603G with twin turbo-superchargers. 2265 hp. Abandoned January 1943
Daimler-Benz DB 624 DB 603 with both a two-stage mechanical supercharger and a turbosupercharger. 1900 hp. Abandoned in April 1943
Daimler-Benz DB 625 DB 605D with turbo supercharger. 1755 hp. Abandoned
Daimler-Benz DB 626 DB 603G with twin turbosuperchargers and induction cooler. 2125 hp. Abandoned November 1942
Daimler-Benz DB 627 603 with a two-stage supercharger and after-cooler. Development abandoned in March 1944
Daimler-Benz DB 628 DB 605, fitted with a two-stage supercharger. Abandoned in March 1944
Daimler-Benz DB 629
Daimler-Benz DB 630 36 cylinder Double W engine with a capacity of 89 litres and output in the 4,000 HP class (2,940 KW)
Daimler-Benz DB 631 DB 603G with a three-stage supercharger. 1900 hp. Abandoned
Daimler-Benz DB 632 DB 603N, with a drive for contra-rotating propellers two stage supercharger with intercooler, two mechanical speeds with infinetly variable drive.

The only engines which are truly new developments I have highlighted in blue text.

BMW 801 14-cylinder two-row radial, air-cooled — most-produced radial engine of the Third Reich
BMW 802 experimental, 18-cylinder two-row radial (same bore but longer stroke as 801) but abandoned.
BMW 803 experimental, 28-cylinder liquid-cooled four-row radial, originally Bramo/Siemens

For Junkers

Jumo 204 6-cylinder opposed liquid-cooled diesel;
Jumo 205 improved Jumo 204 of smaller size;
Jumo 207 improved 205 with a turbocharger;
Jumo 208 enlarged development of the 207;
Jumo 210 inverted V-12;

Jumo 211 inverted V-12, mostly for bomber use, most produced German aviation engine of World War II;
Jumo 212 Two Jumo 211 "coupled" (geared together), same design as DB 610;
Jumo 213 improved Jumo 211, inverted V-12;
Jumo 222 experimental 24-cylinder supercharged liquid-cooled "star" (six banks of four cylinders) aircraft engine; nearly 300 examples built
Jumo 223 "box" engine made of four 207s;
Jumo 224 "box" engine made of four 20's.

The ones I have highlighted in blue are essentially prewar engines.

Most of the projects by Argus and Klockner go back pre war and were not perused through the war.

 

[wuzak]

Rolls-Royce Merlin XX Turbo-Supercharger Cutaway Drawing from Flightglobal
View attachment 264736

Was there anything other than this drawing for Flight (ie not a RR drawing) to suggest that there was a turbo Merlin?

 

[GregP]

I don't think anyone says the Allies didn't develop new prototypes ... rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat.

The Allies DID develop prototypes, but also didn't pursue them to the point of neglecting the materiel needed to prosecute the war, and had more resources to spare since the prototypes usually consisted of very small teams that tried a few things and got back to work on the necessary engines.

 

[Koopernic]

I don't think anyone says the Allies didn't develop new prototypes ... rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat.

The Allies DID develop prototypes, but also didn't pursue them to the point of neglecting the materiel needed to prosecute the war, and had more resources to spare since the prototypes usually consisted of very small teams that tried a few things and got back to work on the necessary engines.

"rather they say the Germans developed many MORE prototypes with resources that were in shorter supply and were sorely needed on projects that could get into combat."

I just don't see that at all. The numbers to support that don't seem to be there.

They, the Germans, developed exactly what they had to and suspended anything that was diverting resources from the here and now after around 1941. They did that to a fault in fact, sacrificing long term developments quite frequently.

The prolific designations that are noted by Daimler Benz are almost all turbo/supercharger variations of the DB601/605/603 series or variations of such as pairing via a gearbox or simple modifications such as adding contra rotating gearbox. Few of these went past theoretical investigation. One can argue that the DB605 was hardly even a new engine: being essentially a bored out DB601 with heavier parts. A lots of these simply needed suffix designations rather than a type number.

The three engines that the Germans did build to the point of running and close to mass production were the DB604 (X24), BMW 802 (18 cylinder radial) and Jumo 222 (24 cyclinder star) of which the DB604 and BMW802 were abandoned, perhaps foolishly since they may have been less promising in frontal area and weight but more reliable.

The Jumo 213 was a logical progression Jumo 210->Jumo 211 ->Jumo 213 to meet greater needs.
You can see the same progression in the Rolls Royce Family eg Kestral, Merlin, Griffon, Perigin, R-type.

It would have been irresponsible to have neglected development of such engines.

The DB engines were a family based around an inverted V12 using the same technology, merely scaled. They weren't really developments of each other but hatched in parallel. The bigger engine, the DB603 is almost as old as the DB600 but they were less a progression than a planed family of engines.

The BMW 801 ->802 was a logical progression. The BMW803 was abandoned and received minimal resources. The DB603/5/1 series seems more coherent that the Rolls Royce program which used radically different configurations (X,V and H blocks) with different valves (sleeve, poppet and 2 stroke) wherease the German variations were often to do with supercharging, gearboxes to pair engines.

We do have some odd balls, the big 4000hp Argus AS413 H24 based on Jumo 213 pistons,

And the two giant flying boat diesels
Kloeckner-Humboldt-Deutz:
DZ 710 16-cylinder horizontally opposed diesel
DZ 720 32-cylinder H-block version of the 710

There is nothing crazy about these programs. They were logical programs to provide power plants in the 1000, 2000 and 4000hp class. All were necessary.

The Reich, the German military needed 4000hp class engines and it needed high altitude engines.

They would be needed for the giant transports envisaged for global trade one way or another or the giant 500+mph piston fighters that were being conceived and might come in useful if there was an need to conduct an intercontinental bombing war between a successful third Reich and North America. Remember in 1939 the only country seriously developing such a weapon was the USA with its B-36 which was a fully funded program.

Had the Reich have won in Europe giant transports powered by low wear economical diesels might have been plying a global trade to Sth America, Asia, Africa and even a neutral America rather than R-4360 or R-3350.

It was obvious by 1943 that the turbojet was viable so these engines were abandoned. By flying efficiently in thin air where there is no parasitic drag even the thirsty turbojets of the day promised intercontinental range.

The variations in allied engines are also significant: you can find single stage, two stage, 1,2 and 3 speed superchargers. the R2800 came with single stage and two stage superchargers, some with independent drive, some with inter-cooling. It came also with turbos. V-1710 with turbocharged, two stage, turbocompound.

Ditto with R-4360. That's just the ones that were built, not just projects that were theoretical investigations.

 

[wuzak]

They, the Germans, developed exactly what they had to and suspended anything that was diverting resources from the here and now after around 1941. They did that to a fault in fact, sacrificing long term developments quite frequently.

They kept working on the Jumo 222 which, basically, was a lost cause.

You are only talking about piston engines. There were also a myriad of gas turbine projects - turbojets and turboprops. Even 3 aviation steam turbine projects - two cancelled early in the war, another started late in the war for the Me 264.

The prolific designations that are noted by Daimler Benz are almost all turbo/supercharger variations of the DB601/605/603 series or variations of such as pairing via a gearbox or simple modifications such as adding contra rotating gearbox. Few of these went past theoretical investigation. One can argue that the DB605 was hardly even a new engine: being essentially a bored out DB601 with heavier parts. A lots of these simply needed suffix designations rather than a type number.

This is quite true. Quite a few of them were built and tested, though.

The three engines that the Germans did build to the point of running and close to mass production were the DB604 (X24), BMW 802 (18 cylinder radial) and Jumo 222 (24 cyclinder star) of which the DB604 and BMW802 were abandoned, perhaps foolishly since they may have been less promising in frontal area and weight but more reliable.

I didn't think the BMW 802 was anywhere near production. Nor was the DB 604, frankly.

The DB 604 would have been about the same in frontal area than the Jumo 222, if not lower.

The Jumo 213 was a logical progression Jumo 210->Jumo 211 ->Jumo 213 to meet greater needs.
You can see the same progression in the Rolls Royce Family eg Kestral, Merlin, Griffon, Perigin, R-type.

It would have been irresponsible to have neglected development of such engines.

Your history of the Rolls-Royce product is a bit out of kilter.

The Kestrel was developed into the Goshawk (steam cooled) and the Peregrine (basically an all new update of the Kestrel).
The Kestrel was scaled to create the Buzzard. The Buzzard was developed into the racing R. Which was detuned to become the Griffon I, which did not enter production.

The Griffon that went into production was started later ~1938.

Note that the Buzzard, R, Griffon I and Goshawk were all developed and finished before the DB 600 had even ran.

The DB engines were a family based around an inverted V12 using the same technology, merely scaled. They weren't really developments of each other but hatched in parallel. The bigger engine, the DB603 is almost as old as the DB600 but they were less a progression than a planed family of engines.

The DB 605 was not part of the original program. It was a later development of the DB 601.

The BMW 801 ->802 was a logical progression.

Yes. As was the R-2600 -> R-2800 and the R-2800 - R-4360.

Even the Centaurus was a logical follow on from the Hercules.

The BMW803 was abandoned and received minimal resources.

I can't speak to that. I thought that the BMW 803 was started during the war, rather than before it.

The DB603/5/1 series seems more coherent that the Rolls Royce program which used radically different configurations (X,V and H blocks) with different valves (sleeve, poppet and 2 stroke) wherease the German variations were often to do with supercharging, gearboxes to pair engines.

Rolls-Royce's war program consisted almost entirely of the Griffon and Merlin, with the Merlin taking up by far the greater amount of energy and resources.

The X engines - the Vulture was being developed at the same time as the DB 600. It was cancelled in 1941, after having developmen suspended during the BoB. The Exe was designed by Rowledge in the early to mid '30s. Only one was built, and development was stopped before the war. The Pennine, as I said before, was begun later in the war and was with the post war period in mind.

The H engine - there was but two. Only one was built. There was some though to making a H-Merlin, with 4 banks of Merlins. And the Eagle.

Sleeve valves - there was the Exe, Pennine, Eagle and Crecy. The Crecy was also two stroke. To repeat, the Exe was finished before the war, the Eagle and Pennine were late war and low priority and the Crecy was developed by only a handful of people, slowing its progress significantly.

You mention that the BMW 803 didn't take up many resources, but you don't concede the same for Rolls-Royce's projects.

We do have some odd balls, the big 4000hp Argus AS413 H24 based on Jumo 213 pistons,

It was actually based on Jumo 213 blocks and cranks, etc. Quite logical really.

And the two giant flying boat diesels
Kloeckner-Humboldt-Deutz:
DZ 710 16-cylinder horizontally opposed diesel
DZ 720 32-cylinder H-block version of the 710

I don't know anything about these.

There is nothing crazy about these programs. They were logical programs to provide power plants in the 1000, 2000 and 4000hp class. All were necessary.

There was nothing crazy about British and American programs in the main, either. There were the odd ones, like the Wright Tornado, but that isn't any worse than the BMW 803.

1000, 2000 and 4000hp class. All were necessary.

The Reich, the German military needed 4000hp class engines and it needed high altitude engines.

Did they really need a 4000hp engine?

There wasn't a 4000hp piston engine for the Allies, even post war. I suppose the R-4360 came closest.

The one that was under development, the R-7755, didn't proceed past prototypes.

The variations in allied engines are also significant: you can find single stage, two stage, 1,2 and 3 speed superchargers. the R2800 came with single stage and two stage superchargers, some with independent drive, some with inter-cooling. It came also with turbos. V-1710 with turbocharged, two stage, turbocompound.

Ditto with R-4360. That's just the ones that were built, not just projects that were theoretical investigations.

The difference here is that the American engines for use with turbos were separate engines connected to the turbo usually by the airframe manufacturer. The change between a non turbo and turbo Allison was the gear ratio in the supercharger drive. All the turbo and intercooler parts were external to the engine. Daimler-Benz, at least, were integrating the turbos in the engine itself - not just the QEC, but the engine.

 

[Gixxerman]

while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications

This puzzles me. Perhaps they did manage significantly over 2000hp on a test rig but as I understand it - and I'll be glad to be put right if I'm wrong - one of the LW's big problems is that they never did have engines available (in numbers) of a genuine 2000hp+ rating ( I don't mean ps or brief periods of MW or GM boost either).

 

[Shortround6]

How many projects a "country" can undertake depends on the number of design teams available and the size of those teams. Most, if not all, of the companies underestimated the problems of advancing along the development path. Development had been fairly easy from 1914 to the 1920s and with better fuel (1920s fuel was about 40-50PN) further increases didn't strain or outrun materials and engine design knowledge that much. But the further they went the harder increases got. Desires started to outrun capability of manufacturing and materials.

Germany was in a bad position because they competing against 3 world powers. They were vastly outnumbered by the allied engineers and engineering staff. It is not enough to have good idea men, you need large numbers of simple draftsmen and number crunchers to turn the "ideas" into reality. You also need foundry men and materials men and machine tool experts to turn the tens of thousands of drawings into actual hardware in large numbers.

The allies also had better fuel which meant older, smaller engines could be kept in the front lines with less development work than new engines would require (Not that more than a few allied companies didn't try to develop technological marvels that wound up going nowhere). Use the R-R development method, Flog it until it breaks-fix it-flog it again. This lessened the demand for new, larger engines. (the R-2800 was proposed as a 1650hp engine in 87 octane fuel). It meant that the Griffon could be delayed and the Vulture dropped with less loss. It meant that the Centaurus could also be put on the back burner. If the Hercules had topped out at 1300-1400hp with 87 octane fuel the Centaurus could have been pushed somewhat harder.
However air-cooled engines almost always had a harder time with high boost than liquid cooled engines. For fuel development air-cooled engines were usually referred to as severe duty engines and most liquid cooled engines were considered mild duty engines.

As far as P W engine development pre and early war goes, P W was working on the R-1830, R-2180 and R-2800 pretty much on their own. The X-1800 and XH-3130 were military development contracts but were started by Mead after a visit to England where it might have been over influenced?. The story (welcome correction) is that Hobbs told the military that he doubted that P W could get any sleeve valve liquid cooled engine into service in time to do any good during the war ( This was in 1940 and who knew how long the war would take?) and asked to be let out of the contracts to work on the R-2800 and R-4360 which used R-2800 cylinders.
This use of common cylinders or at least common sized cylinders was very common as it helped hold down development work. Using a constant sized cylinder eliminated some variables.

BTW

It was obvious by 1943 that the turbojet was viable so these engines were abandoned. By flying efficiently in thin air where there is no parasitic drag even the thirsty turbojets of the day promised intercontinental range.

Is not even close to being right, unless you consider that taking until the early to mid 1950s was sufficient promise. Unless you think that all the work done on Turbo-compound engines, turbo props and even late conventional piston engines was wasted. The low efficiency early turbo jets had no hope of intercontinental range without aerial refueling. While the British did use Comets on long routes they used stages, London to Johannesburg took five/six stages.

 

[tomo pauk]

Wuzak and SR6 covered most:

...
As far as your notations on the inferiority of the Jumo 211F/J you overlooked that the engine was operating on 87 octane rather than 100 and latter 100/130. The 6psig the early 87 octane Merlin operated at is essentially 1.4 ata. To get to 12psig (about 1.8 ata) the Merlin needed 100 octane and to get above that level, the 15psig (2.1 ata), 18psig (2.3ata) it needed 102/130 or 102/150 and 25psig it needed 104/150

Whether the fuel is 87 oct, 100 oct, or 150 oct, the Jumo 211J will not go above 1300-1400 PS above 4 km. Not even on 2600 rpm. The better fuel improves power 'under' the rated altitude, not above it. For improving the power above rated altitude, one needs a better supercharger installed (as for Merlin III to 45, for example; or installing a two stage S/C on various engines; or several DB engines with improved S/C, even before the big S/C from the DB-603 was installed), or turning an even greater RPM (DB-601 can serve as an example here).
The improvements for the Merlin power, with ever better fuel, were also noted at ever lower altitudes.

Most of the duplicated engines of the German programs are derivatives eg DB628 (DB605 based), DB627(DB603 based) and so not really duplications but programs adding sophisticated supercharging or turbo charging. The DB605 and hence DB628 was simply going to be too small, just like the Merlin was getting too small, by 1945 hence it would have made sense to focus on the larger 627 instead.

Who says that DB-628 is going to be to small? The DB-603 has issues as late as second half of 1943, we are to expect that a two stage variant of it will be devoid of those just because there is another stage installed? Merlin was good to propel fighters to 450 mph mark, and bombers to 420? mph, that is quite a feat for a 'too small' an engine.
Neither DB-628 nor 627 employed turbo chargers -the 624 did

The DB605D with enlarged supercharger first ran in 1942 so its surprising an enlarged supercharger took 2 years to enter service.
The 628 might have made sense on a 4 engined bomber if ready early enough but even if fitted to the Me 109 wouldn't the 109 require too many airframe modifications. These two stage supercharged engines had independent drives, variable pitch fans and variable speed drive on the second stage and were much more effective than more conventional two stage engines.

Where we can read the math that DB version of two stage supercharging used on 628 and 627 was much more effective than conventional two stage systems? That were at least three types in Allied inventory (in service use), so we don't know what one did you have in mind when making such a blanket statement.
I'm also at loss how of the sudden the Bf-109 is promoted from an un-suitable airframe for a 2-stage engine (DB-628 ), into a suitable one.

Abandoning most piston engine programs made sense after 1944. Only Jets now made sense, even for long range aircraft that were to target the US east coast, while the existing Jumo 213/DB603/BMW801 were more than capable of performing any remaining job; up to 2800hp, with minor modifications.

Please, do try to post some sources when stating such stuff.
BTW, the time to abandon many projects was once the BoB was not won by the LW.

Jumo 222 didn't seem to have any problems other engines didn't have. It was pushed into production after only 4 years development when 6 were needed by all other WW2 engines. The RLM or Luftwaffe might have accepted the engine into service in derated form but apparently that wasn't an option due to airframe weight growth.

Jumo 222 have had a full list of issues, not just one or two.

 

[Shortround6]

I would note that the BMW 801 must have been a rather amazing engine if it could have gone to 2800hp

with minor modifications

.

The R-2800 only required a completely new engine to make 2800hp, they saved the bore and stroke and, according to one story, the starter dog. New crankshaft, new connecting rods, new crankcase, new pistons, new wrist pins, new cylinder barrels, new cylinder heads and on and on and on. Just minor modifications right? Granted the older R-2800 gave them a good starting point ( one of the old engines hit 3500hp on a test stand for a moment or two) but service engines are a far cry from momentary test results or even racing engines.

While some sources say the DB603N was: "Power (max): 2800 PS (2762 hp, 2059 kW) at 3000 rpm at sea level" it was a prototype engine and it is not stated if that was a goal or actually achieved in tests or achieved for a long enough period of time to be usable in a service engine or what it might have done to service life. The increase in RPM from 2750 to 3000rpm results in a 19% increase in stress on the reciprocating parts, on the crankshaft and crankcase. This is in addition to the increased loads due to higher pressures in the cylinder due to higher boost.
Shorter engine life may be acceptable to the service user to get the desired performance ( and was accepted by the Russians on certain models engines) but tends to be ignored when comparing some German engines to allied engines. German engines may have suffered from material (alloy) shortages or even lubricating oil, I don't know.

Trying to say which was better gets difficult due to the fuel, material and perhaps oil questions. Different paths were chosen and once started on were very difficult to reverse ( and both sides built their share of clangers).