Jumo inverted vee's vs. Daimler-Benz inverted vee's - Pros and Cons

[Mike Williams]

My best info is that the US books from Amazon customer orders are on US soil now.

Fwiw my experience in ordering the book:

11/14/20 - Book ordered from Amazon

12/14/20 - Message from Amazon : We're encountering a delay in shipping your order. We'll make every effort to get the delayed item to you as soon as possible. If you still want this item, please confirm below. We apologize for the delay. If we don't hear from you by Wednesday, January 13, 2021, we will cancel the item. Otherwise, we will send it to you when we have a delivery date and it's ready to ship.

I confirmed I still wanted the book and received the following message.

12/16/20 - We have an updated delivery estimate for your Amazon order. As soon as your items ship, we'll send you an email confirmation. To view the status of your order or make changes, please go to Your Orders. New estimated delivery date: Saturday, January 2, 2021

I'm fine with that if the book arrives then, give or take.

On a related matter, I recently ordered Jagdfliegerverbände der Dt. Luftwaffe 1934-1945, Bd. 13/V from Ch. Schmidt bookstore München, Germany but they only did Paypal. I really dislike Paypal, so had to cancel the order. Bummer...

 

[tomo pauk]

From what I can gather, the 'altitude powers':

- 1939: Jumo 211A did 930 PS at 5.2 km for 5 minutes, 2200 rpm; DB 601A (version with 4 km rated altitude) did 900 PS at 5 km, 2400 rpm, but for 30 min (for comparison sake, Merlin III did ~1035 PS (1020 HP) at 5 km (16400 ft), 5 min rating)

- 1940: Jumo 211B/D/H was good for 920 PS at 5 km, 2300 rpm, 30 min rating; DB 601A (version with 4.5 km rated altitude) did 960 PS at 5 km at 2400 rpm also for 30 min; 1 min rating for 211B/D/H (not sure if it was ever allowed for use on bombers) was supposed to be 980 PS at 6 km at 2400 rpm; no 5 min rating for those Jumos; DB 601A was allowed for 2600 rpm operation in late 1940, that will improve altitude power; DB 601N was supposed to do ~1160 PS at 5 km, sources differ on duration (1 min, 3 min?), 2400 rpm 30 min power at 5 km of some 1030-1040 PS (V-1710-33 was supposed to do ~1000 PS at 5 km, 5 min rating; Merlin XX is the best)

- mid 1941: Jumo 211F, 1080 PS at 5.2 km, 2400 rpm, 30 min (1 min 'theoretical' rating of ~1190 PS at 5 km, 2600 rpm); DB 601E was good for 1180 PS at 5 km, the 5 min rating is not yet allowed (Merlin 45 and XX make ~1100 PS at ~5.4 km on max climb setting, or ~1200 PS at max rpm and 5 min, V-1710-39 is way behind the new Merlins, and starts lagging behind the German V12s)

 

[tomo pauk]

State of:
-1942: Jumo 211J (intercoled version of 211F) ~1150 PS at 5.5 km, 30 min rating, 2400 rpm, the DB 601E a bit less there, but it was allowed for 2700 rpm operation that gave ~1220 PS at 5.5 km for 5 minutes. DB 605A 30 min rating was ~1260 PS at 5.5 km, 2600 rpm (5 min rating at 2800 rpm was banned due to major reliability issues); second half of 1942 also sees Merlin 61 with excellent hi-alt performance, and late 1942 is the time the V-1710 finally gotten the faster turning impeller to narrowly beat the altitude power of the pre-war Merlin III...
- 1943: Jumo 211N - 2500 rpm gave 1170 PS at 5.2 km, 30 min rating; 211P (intercooled 211N) 30 min rating was 1280 PS at 4.6 km (works to around 1150 PS at 5.5 km); DB 605A is still at old values until October of 1943 finally saw the 2800 rpm operation being allowed
- late 1943: Jumo 211R, that to my knowledge never saw service (Jumo 213 production start interferred - corrections are welcomed), faster spinning impeller* than the earlier models at least by judging by a somewhat lower take-off power, 1130 PS at 7.2 km (!!) 30 min power; DB 605A 30 min rating 1020 PS for at that altitude

Jumo 211 engines used 1 min take off power (higher rpm, a bit higher boost than for 30 min next-best setting).
My guess is that lack of 5 min power setting, looking by manuals for engines (past the 211A), were more a reflection of the engine use that were mostly bombers, rather than something to do with suitability of engine for such a bit more aggresive power setting. The perceived weakness in power of 211 vs. 601 was probably just that - a perceived weakness, especially between the start of the war and mid-1942.

* or perhaps a bigger impeller??

 

[Koopernic]

State of:
-1942: Jumo 211J (intercoled version of 211F) ~1150 PS at 5.5 km, 30 min rating, 2400 rpm, the DB 601E a bit less there, but it was allowed for 2700 rpm operation that gave ~1220 PS at 5.5 km for 5 minutes. DB 605A 30 min rating was ~1260 PS at 5.5 km, 2600 rpm (5 min rating at 2800 rpm was banned due to major reliability issues); second half of 1942 also sees Merlin 61 with excellent hi-alt performance, and late 1942 is the time the V-1710 finally gotten the faster turning impeller to narrowly beat the altitude power of the pre-war Merlin III...
- 1943: Jumo 211N - 2500 rpm gave 1170 PS at 5.2 km, 30 min rating; 211P (intercooled 211N) 30 min rating was 1280 PS at 4.6 km (works to around 1150 PS at 5.5 km); DB 605A is still at old values until October of 1943 finally saw the 2800 rpm operation being allowed
- late 1943: Jumo 211R, that to my knowledge never saw service (Jumo 213 production start interferred - corrections are welcomed), faster spinning impeller* than the earlier models at least by judging by a somewhat lower take-off power, 1130 PS at 7.2 km (!!) 30 min power; DB 605A 30 min rating 1020 PS for at that altitude

Jumo 211 engines used 1 min take off power (higher rpm, a bit higher boost than for 30 min next-best setting).
My guess is that lack of 5 min power setting, looking by manuals for engines (past the 211A), were more a reflection of the engine use that were mostly bombers, rather than something to do with suitability of engine for such a bit more aggresive power setting. The perceived weakness in power of 211 vs. 601 was probably just that - a perceived weakness, especially between the start of the war and mid-1942.

* or perhaps a bigger impeller??

Do you know what the features of the Jumo 211R were? My readings of the Ta 154 "moskito" show that repeated analysis of the aircrafts performance showed that it could not deal with the Dehaviland Mosquito unless it were equiped with Jumo 213 engines instead of Jumo 211N.

 

[tomo pauk]

Do you know what the features of the Jumo 211R were? My readings of the Ta 154 "moskito" show that repeated analysis of the aircrafts performance showed that it could not deal with the Dehaviland Mosquito unless it were equiped with Jumo 213 engines instead of Jumo 211N.

My guess is that main difference was in supercharger section - either it used a faster-spinning impeller, or it used a bigger S/C (from Jumo 213?). Not sure whether intercooler was used.
Against the Mosquito and bar the RAF pilot being unlucky, the Ta-154 with 211N will not cut it once the 'antlers' and flame dampers are installed - the Jumo 211 line was behind the curve past 1942. Germans needed the equivalent of the 211R aboard the night fighters by late 1942 in order not just to stand better chances against Mosquito bombers, but also against the Beaufighter and Mosquito intruders/night fighters. All while giving them real opportunity to make multiple passes on the bomber streams. (I've discounted the Fw 190 in night-fighter trim here)
But then again, a Ta-154 with 211N might've gave better return than other NFs of similar power but of bigger size & weight?
Against the Mosquitos outfitted with 2-stage Merlins, only jet-powered NF could endanger those.

 

[Deleted member 68059]

Do you know what the features of the Jumo 211R were? My readings of the Ta 154 "moskito" show that repeated analysis of the aircrafts performance showed that it could not deal with the Dehaviland Mosquito unless it were equiped with Jumo 213 engines instead of Jumo 211N.

No chance with 211, would have needed 213`s. Even the basic Merlin-XX beats a very decent 211 at altitude. All you can say is that a 154 with 211 N`s would have
been decent at sea level.

 

[GregP]

Postage to Europe from the U.S.A. is prohibitive. Not sure why, but the postage to, for instance, Ireland, is more than the cost of the things we send for Christmas.

I supposed the reverse postage from there to here was just as bad and Callum just confirmed that. Interesting that it was ecominical in the 1960's to send things back and forth when there were a lot of ships going back and forth, but it is now way too expensive when it is mostly airplanes.

 

[Deleted member 68059]

Postage to Europe from the U.S.A. is prohibitive. Not sure why, but the postage to, for instance, Ireland, is more than the cost of the things we send for Christmas.

I supposed the reverse postage from there to here was just as bad and Callum just confirmed that. Interesting that it was ecominical in the 1960's to send things back and forth when there were a lot of ships going back and forth, but it is now way too expensive when it is mostly airplanes.

Postage costs have become absolutely insane over the last few years. Inline with the "efficiency" we were all promised after privatisation... stuff like post, gas and electricity do not lend themselves to market forces... for very, very obvious reasons (i.e. virtually impossible to form a competitor). To send my book anywhere outside the UK costs about 80% of the cover price of the book, unless you pick "economy" which is anything up to 3months transit time (i.e. surface-only). Its total madness.

 

[GregP]

Well Calum, my Amazon copy is somewhere "in transit." After reading your post, it ws easier to get it from Amazon ... though it won't be autopgraphed, it still has your name on it.

 

[BiffF15]

Well Calum, my Amazon copy is somewhere "in transit." After reading your post, it ws easier to get it from Amazon ... though it won't be autopgraphed, it still has your name on it.

Ditto here as well except went through Abe Books.

Cheers,
Biff

 

[Ivan1GFP]

If any of you still have friends in the service, packages from US bases are basically US Postage rates for servicemen.

 

[xylstra]

Jumo vs DB:
standard supercharger with different speeds vs variable coupling
3 valves per cylinder vs 4
more automatic engine controls on the DB

Barometric control of the Föttinger hydraulic coupling sounds good in theory but is woefully inefficient and results in an already thirsty engine becoming more so, i.e. less range plus they suffered from overheating issues of the fluid.

 

[xylstra]

I am sure I read somewhere that the DB engines had a more efficient pressurised cooling system whereas the Jumo was atmospheric pressure.

The DB engines as installed in the Bf 109 employed a dual-coolant circuit - more reliable in the event of battle damage.

 

[xylstra]

There are a lot of myths regarding the superiority of the DB engines over Jumo but in reality are not true.
-All the German engines BMW801, DB60x series and Jumo implemented integrated 'kommandogeraet' controls that provided tightly integrated single throttle automatic control of engine power, RPM, propeller pitch, boost and mixture control. These were so advanced they even prevented engine over speed in a dive.
-The DB engines tended to use higher compression ratios, variable speed superchargers. The higher compression ratios with the DB resulted in superior specific fuel consumption figures per shaft horsepower however the Jumo engines tended to operate at lower compression ratios but higher boost levels (at least DB603 versus Jumo 213) this resulted in higher jet thrust that probably made the Jumo 213 the better engine for the same shaft horsepower. The Jumo 213 had better 'ehp' equivalent horse power. The Early DB601/605 engines had access to higher octane fuels due to their association with the Me 109 figher.

DB technology was
-No head bolts, used the cyclinder liner as a giant threaded bolt. This allowed a much larger swept volume, hence DB engines didnt need as much pressure to create power and so had good altitude performance.
-Variable length inlet manifolds ensured end gases were scanvenged and prevented preignition and allowed more mixture.
-infinitely variable speed supercharger.

Jumo technology was
Higher Compression, more jet thrust
Higher RPM
Variable inlet guide vanes for supercharger (copied from Russian engines) to control inlet flow effficiently.
Multispeed superchargers.
Succeeded with intercoolers earlier
Ran well on B4 fuel.

Can you supply documentary evidence that the KommadoGerat system was extended to the DB and Jumo? I was only ever aware that this was exclusive to the BMW 801, only. (And cost a fortune to develop!).

 

[xylstra]

Hmmm well I did spend 6 years putting it all in a book to clear up these points.... was rather hoping someone might have read it by now !

1) The Jumos until the 213 dont have an actual "kommandogerat" (my definition of that is ONE single "box" which does everything in ONE unit), prior to the 213
they`re like the DB, in that they have a couple of distributed systems which broadly achieve the same thing as the "kommandogerat", but its not
all stuck into one unit. So the 211 for example has separate boost control and fuel control boxes. They can be described as "single-lever" for the most part,
but this is not achieved by a single-master control box (the kommandogerat).

2) The DB doesnt have a "variable length inlet manifold".

3) The lack of head bolts on the DB does not permit greater swept volume, the limit to engine length and bore size/spacing is always the minimum
gap needed between the cylinders where they meet in the middle, not where the bolts are. The 211 is actually larger in capacity than the 601,
and nearly as large as the 605. I think you`ve got mixed up comparing the very early 210 with the 601.

4) The Jumo does have lower CR, and indeed the DB had higher CR to improve fuel economy and altitude performance, but,
due to other factors this still left the DB with at best equal and usually slightly worse fuel economy than the Jumo.

other points about pressure cooling and valves are correct, except for the assertion that it doesnt matter how many you have because
"american engines only had 2 and were ok". Indeed, and they would have been "even more ok" with 3 or 4.... however its a huge pain
with the valvegear on a radial to have more than 2, so most dont.


Broadly:

601A < Jumo211A (due to very poor "box" type supercharger of the jumo)
601E = Jumo211J (pretty comparable, 211J has much better supercharger)
605A > Jumo211J (605 has slight advantage in swept volume)
605A < Jumo213A (213 is a much later developed, more modern engine, so is naturally a bit better overall)

All Jumo`s had outstandingly good oil systems, which helped them avoid the worst of the bearing troubles which DB experienced.

There is a lot more to it, but in all seriousness if you`re interested in stuff like this you really do need my book!

Curiosity question Calum: in your extensive researches for your book did you manage to dig up any material on DB's intriguing Wankel Disc Rotary-Valve cylinder-head conversion for the '601? I vaguely recall it might have been dubbed the 'L' model.

 

[rinkol]

DB had pressurized cooling from the 601E on, Jumo from 211F/J. Both available in 1941 although i believe DB was rather mid 41 and Jumo late 41.

The Jumo engines had wet cylinder liners (i.e., the coolant directly contacted the cylinder liner). The DB engines had dry liners - the cylinder liner was screwed into the aluminum cylinder block and this was designed so that the cylinder liner was surrounded by aluminum. The wet liner arrangement was better for cooling. DB had thermal problems with the DB601E/F and DB605 - for some time both engines had to be derated. This was likely part of the motivation for the extreme valve overlap on these engines - forcing pure air through the exhaust valves during part of the intake cycle would have provided some extra cooling.

 

[Deleted member 68059]

Can you supply documentary evidence that the KommadoGerat system was extended to the DB and Jumo? I was only ever aware that this was exclusive to the BMW 801, only. (And cost a fortune to develop!).

DB never implemented a full kommandogerat system, but had it designed, Jumo had it on the 213. Kollmann ended the war as chief engineer at DB (as from about Sept 1944), and I`m publishing his memoirs next year through ASME (American Society of Mechanical Engineers).

 

[Deleted member 68059]

Curiosity question Calum: in your extensive researches for your book did you manage to dig up any material on DB's intriguing Wankel Disc Rotary-Valve cylinder-head conversion for the '601? I vaguely recall it might have been dubbed the 'L' model.

Yep, page 94 and 95 will start you off.

 

[Deleted member 68059]

Barometric control of the Fottinger hydraulic coupling sounds good in theory but is woefully inefficient and results in an already thirsty engine becoming more so, i.e. less range plus they suffered from overheating issues of the fluid.

Compared to a gear driven SC, it saves about 10% of engine power at take off actually.

 

[MiTasol]

Postage to Europe from the U.S.A. is prohibitive. Not sure why, but the postage to, for instance, Ireland, is more than the cost of the things we send for Christmas.

I supposed the reverse postage from there to here was just as bad and Callum just confirmed that. Interesting that it was ecominical in the 1960's to send things back and forth when there were a lot of ships going back and forth, but it is now way too expensive when it is mostly airplanes.

If you think postage from the US is bad try postage from Canada. For one 1942 Aviation magazine I bought two years ago I had a choice of one from the US that was not pristine and expensive or one from Canada that was pristine and $20 cheaper.
Cheapest mail from the US was USD$13.
Cheapest mail (surface mail) from Canada was C$75.
I got the US one and it was delivered in under 10 days.

I recently bought tools from a Canadian shop and their postage was good. When the goods arrived I found they were shipped from Washington state in the US.