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

[bdefen]

Mainly curious. I've seen here some references to certain Luftwaffe aircraft having to "settle" for the Jumo engines when DB engines were all spoken for. I know there were production limitations, but what other factors made the Jumo engines "second best"?

 

[Denniss]

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

 

[tomo pauk]

Nominally, at least, DB 601 engines seem to offer the same level of power vs altitude by about 1 year earlier than it was for the Jumo 211. When Jumo 211 offered similar or better power, that was the take-off power limited to 1 minute. By mid-war, 211 seems not to have the 5 min limit anymore, but then the 5 min limit was often 'banned' for the DB 601s and 605A. Per German Wikipedia, engines (Jumo 211s) were culprit for 3 of 12 crashes of the Ta 154 prototypes (6 were due to the landing gear, for comparison).
Early Jumo 211 superchargers (before F version) are criticized by NACA when tested. DB seem to improved it's S/C by about once a year.

Note that there was a far bigger difference between Merlin and V-1710, as employed in 1-engined fighters, than it was between the 601 and 211.

 

[bdefen]

Thanks for the information. Hopefully, there will be a few more.

 

[fastmongrel]

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

 

[Admiral Beez]

Mainly curious. I've seen here some references to certain Luftwaffe aircraft having to "settle" for the Jumo engines when DB engines were all spoken for. I know there were production limitations, but what other factors made the Jumo engines "second best"?

Considering the Jumo replaced the BMW 801 in the Fw 190, does that make the DB third best?

 

[Denniss]

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.

 

[Shortround6]

Mainly curious. I've seen here some references to certain Luftwaffe aircraft having to "settle" for the Jumo engines when DB engines were all spoken for. I know there were production limitations, but what other factors made the Jumo engines "second best"?

Make sure they are comparing to like to like. Some German planes had to "settle" for the Jumo 210 engine (19.7 liters) when they wanted the DB 601 engine (33.9 liters).
The Jumo 211 (34.97 LITERS) was a completely different engine than the 210. The Big Jumo used the same bore as the DB 601 but about 5mm more stroke and might have been a bit more limited in RPM in certain models? Early Jumo superchargers were pretty poor specimens but they got better fairly quickly.

Jumo vs DB:
standard supercharger with different speeds vs variable coupling
3 valves per cylinder vs 4

Not sure the valves really had much to do with it. Porting in the heads, boost pressure/supercharger and other things could make as much or more difference. American radials seem to do OK with two valves?

 

[Koopernic]

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.

 

[tomo pauk]

I'd say that D Deleted member 68059 can help us here

 

[Deleted member 68059]

I'd say that D Deleted member 68059 can help us here

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!

 

[fastmongrel]

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!

I am waiting for Father Christmas to bring my copy.

 

[rochie]

I am waiting for Father Christmas to bring my copy.

i'm trying to decide if i'm intelligent enough to understand it before i buy mine !

 

[Koopernic]

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!

Well there is this article in enginehistory.org
Daimler-Benz

Which shows that from the DB601E onwards a radical valve overlap was introduced that lead to low speed problems.

The solution was a secondary induction system, which activated at low rpm and which looks longer path to me.

This is what I received from Amazon. I missed it due to spam and only checked now. Preorders have never worked for me.

"Hello,

We're contacting you about order #250-2788350-5525440 for the following item(s):

Secret Horsepower Race, The: Western Fighter Engine Development

We're unable to fulfill your order for the item(s) listed above because they are no longer available from the supplier. As a result, we've had to cancel them from your order and your original payment method won't be charged for them.

We're sorry for any inconvenience or disappointment this may have caused."

 

[BiffF15]

Well there is this article in enginehistory.org
Daimler-Benz

Which shows that from the DB601E onwards a radical valve overlap was introduced that lead to low speed problems.

The solution was a secondary induction system, which activated at low rpm and which looks longer path to me.

This is what I received from Amazon. I missed it due to spam and only checked now. Preorders have never worked for me.

"Hello,

We're contacting you about order #250-2788350-5525440 for the following item(s):

Secret Horsepower Race, The: Western Fighter Engine Development

We're unable to fulfill your order for the item(s) listed above because they are no longer available from the supplier. As a result, we've had to cancel them from your order and your original payment method won't be charged for them.

We're sorry for any inconvenience or disappointment this may have caused."

I got the same thing from Books A Million.

 

[fastmongrel]

i'm trying to decide if i'm intelligent enough to understand it before i buy mine !

I had a sneak peek before it was stashed away and there were lots of pictures to look at

 

[fastmongrel]

I got the same thing from Books A Million.

The Morton's website has the option to post to the USA. I don't know the cost as it needs an address to calculate postage at the check out.
8504 - THE SECRET HORSEPOWER RACE - WESTERN FRONT FIGHTER ENGINE DEVELOPMENT | Mortons Books

The website is a bit crap so you might have to persist when navigating it

 

[Deleted member 68059]

Well there is this article in enginehistory.org
Daimler-Benz

Which shows that from the DB601E onwards a radical valve overlap was introduced that lead to low speed problems.

"

Yes it has a low-revs air bypass system to allow the engine to idle stably with the very high overlap, but I wouldn't really call that "variable length",
it doesn't work by increasing or decreasing any lengths, it is a secondary set of pipes which routes the inlet air into a different position, to help
stop nearby cylinders from influencing each-other. Extracts from RAE report on which the AEHS article is based below, I suspect we`re just
using different terms and have got confused.

 

[rochie]

I had a sneak peek before it was stashed away and there were lots of pictures to look at

ah !
i might be ok then

 

[Deleted member 68059]

Well there is this article in enginehistory.org
This is what I received from Amazon. I missed it due to spam and only checked now. Preorders have never worked for me.

"Hello,

We're contacting you about order #250-2788350-5525440 for the following item(s):

Secret Horsepower Race, The: Western Fighter Engine Development

We're unable to fulfill your order for the item(s) listed above because they are no longer available from the supplier. As a result, we've had to cancel them from your order and your original payment method won't be charged for them.

We're sorry for any inconvenience or disappointment this may have caused."

Yep the trouble is the supply chain length, we have them printed abroad, they then get sent to the publisher in the UK by boat in a huge crate, then, the UK publisher sends out individual orders all over the world direct to the customers.

Anyone who ordered from a secondary chain like Amazon etc, doesnt get those books, because Amazon decides that they dont like me getting cover price, and discounts it by about 30%, so my Publisher cant very well sell people books at two prices at once, so to get that deal, Amazon have to order in bulk. So we send them maybe 500 books in a crate, which has to go by surface vessel for cheapness, those take about 6 weeks to cross the Atlantic, and then have to travel all the way from the port to the Amazon warehouses in the USA etc, THEN they get broken down into individual books and sent to US customers. So, if you ordered from Amazon, you get a nice discount, but, you also get about 2 extra supply chain steps, which ends up being at least 2months.

Add to that the fact that everything is just working really slowly right now, and it adds to much time that the automated systems eventually decide that its never going to arrive and cancel peoples orders.

Its unbelievably frustrating and I am powerless to do anything. My best info is that the US books from Amazon customer orders are on US soil now.

I cant even make a secondary income by posting them to people myself, because I tried it and sent one to a guy in Poland, it cost me more than the entire cover price of the book to send ! - So that was the end of that idea...