Jumo 211 valve question: 4 valve cylinder version?

[wiking85]

I know that the Jumo 213 had a version in development that would have changed the 3 valves on the cylinders to 4 for more volumetric efficiency. Supposedly that was to boost the base HP from 1750 to 1900. Was this ever attempted on the Jumo 211? If not, any idea why not? If they had tried what could they have gotten out of it in terms of fuel efficiency and horse power? Is 100 or 150hp boost too much?

https://en.wikipedia.org/wiki/Junkers_Jumo_211

Components
Valvetrain: Overhead camshaft, 3 valves per cylinder

https://de.wikipedia.org/wiki/Junkers_Jumo_213

Valve control : each cylinder bank an overhead camshaft ( OHC ), three valves per cylinder (two Einlass-/ein exhaust valve).

https://de.wikipedia.org/wiki/Junkers_Jumo_213

Jumo 213 J / T / S
Projects with 4 valves (J), project with exhaust gas turbocharger (T), project for low pressure full heights (S)

https://en.wikipedia.org/wiki/Junkers_Jumo_213

A more major upgrade was projected as the 213J, which replaced the earlier model's three valves with a new four-valve-per-cylinder design for increased volumetric efficiency.

 

[rinkol]

I know that the Jumo 213 had a version in development that would have changed the 3 valves on the cylinders to 4 for more volumetric efficiency. Supposedly that was to boost the base HP from 1750 to 1900. Was this ever attempted on the Jumo 211? If not, any idea why not? If they had tried what could they have gotten out of it in terms of fuel efficiency and horse power? Is 100 or 150hp boost too much?

I suspect that the gain from going to 4 valves with the Jumo 211 would not have justified the disruption to production. There would have been a much more worthwhile gain with the faster running Jumo 213 and it would seem to be a good question as to why the Jumo 213 did not go to a 4 valve cylinder from the start. It may be that they were hoping to get the Jumo 213 into production with minimal delays and wanted to avoid fundamental changes, though, as we know, there were significant delays anyways.

 

[wiking85]

I suspect that the gain from going to 4 valves with the Jumo 211 would not have justified the disruption to production. There would have been a much more worthwhile gain with the faster running Jumo 213 and it would seem to be a good question as to why the Jumo 213 did not go to a 4 valve cylinder from the start. It may be that they were hoping to get the Jumo 213 into production with minimal delays and wanted to avoid fundamental changes, though, as we know, there were significant delays anyways.

It just seems like a huge gain in HP for the 213J, which was 2240hp on B4 fuel and 3700 rpm, vs. the 213A at 3200rpm and 1750hp. I know the gains were from the increased RPM, which I assume resulted from the more efficient exhaust set up, but why couldn't something like that appear with the Jumo 211F or the later improvements? A 22% increase resulted, so if something like that were possible for the Jumo 211F that would add about 300hp, which would leave it nearly at 1650hp, assuming the later intercooler improvements aren't added.

Its also mystifying to me why Jumo didn't have it for the 211 because the DB601 had it from the earlier DB600, which was getting greater performance out of less displacement than the Jumo 211B.

 

[tomo pauk]

Part of performance gain was due to increased displacement, from 35 to 37,4L, via increase in the bore from 150 to 155mm. Another parts of the gain might be due of use of 2-stage supercharger, inter-cooler, and, if this web page is to be believed, the use of C3 fuel.

When the 211 and 601 were turning the same RPM, their power was in the ballpark?

 

[wiking85]

Thanks Tomo, that's an extremely helpful link.

 

[Piper106]

Part of performance gain was due to increased displacement, from 35 to 37,4L, via increase in the bore from 150 to 155mm.

This is the first I have heard that the Jumo 213J had its bore increased to 155mm. I had always thought that all versions of the Jumo 211 and 213 had a bore of 150mm and a stroke of 165 mm. Question. Was it just the 213J that had the enlarged bore, or were all of the later "Luftwaffe 1946" versions of the 213 going to switch to the larger cylinder size??

 

[wiking85]

This is the first I have heard that the Jumo 213J had its bore increased to 155mm. I had always thought that all versions of the Jumo 211 and 213 had a bore of 150mm and a stroke of 165 mm. Question. Was it just the 213J that had the enlarged bore, or were all of the later "Luftwaffe 1946" versions of the 213 going to switch to the larger cylinder size??

According to the link only the J series had the increase; all others were 150mm.

 

[Denniss]

A bore increase sounds strange as it may have required further changes to the engine block causing even more delays.

 

[wiking85]

A bore increase sounds strange as it may have required further changes to the engine block causing even more delays.

It seems like they were trying to accumulate upgrades and incorporate them all at once to boost performance to make for the lack of a +2000hp engine. Which of course is why it never entered production.

 

[rinkol]

You can be sure that there would have been numerous mechanical changes to accommodate the increased rpm.

There is another case where an engine was redesigned to have an increased number of valves - the Klimov M-107 went to 4 valves per cylinder, an increase from the previous M-105. It took a long time for this engine to reach production and even then, it was not without issues.