Supercharging on the 109's

[SageFIN]

The climb and and speed curves on all the 109's except the 109F show two clear points where the otherwise linear curves "bend" or so.

Well, some information I have sought up states that the DB605 engines had a variable speed compressor that adapted to the altitude. Thus the engines power output varied smoothly between the altitudes. So I gather that the climb and speed curves should also be more smooth than they currently are?

A good website that has this information can be found at http://w1.1861.telia.com/~u186104874/db605.htm.

A quote from that page:
"While the conventionel mechanical superchargers consisted of one or two compressors driven via a two-speed gear, Daimler-Benz utilised an ingenious barometricly controlled hydraulic clutch which adjusted the compressor speed and thus the charging of the engine according to the needs at a given altitude.

The conventional method results in a relative loss in efficiency below rated altitude, because the compressor uses energy to produce surplus charging. A graphic presentation of engine output relative to altitude would show a "saw-touth" line: the output in low gear rising with altitude until reaching the rated altitude, then output falls until the high gear kicks in, when the output again rises the rated altitude is reached.

In comparison the Daimler-Benz system is more flexible. A graphic presentation would show a smooth shallow curve. A source of efficiency loss with this system being progressive heating of the oil as pressure in the clutch builds with altitude."

Any comments? I don't know exactly if implementing this system would benefit or hinder the DB605 equipped planes. I would like to see this done anyway (if this whole issue is correct).

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SageFIN

"The wolves are gathering, the stars are shifting...
come, join us in the hunt!"
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[Nath-BDP]

I have a comment...

German engines own.

[juzz]

It would make bugger-all difference to the planes performance in the game, just that the climb/speed charts would look pretty...

[Jigster]

Bah the B-17, P-38, and P-47 all work the same way.

Willy just figured a way to trick a super charger into thinking it was a turbo charger.

- Jig

[Nath-BDP]

Messershimitt designed DB engines? hmm

[SageFIN]

Well the climb curve for P-47D sure is smooth and curvy. Why not so for the other planes then? And I do think that if the graphical representation of a planes power output is more rounded than jagged, it would result in a small but perhaps decisive (in some situations) advantage in speed or climb.

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SageFIN

"The wolves are gathering, the stars are shifting...
come, join us in the hunt!"
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[juzz]

Must be another part of the conspiracy...

[SageFIN]

Umm. So I came off sounding like an advocate for the universal allied conspiracy theory? I said "other planes" not "axis planes".

I merely wish that if this is an aspect that has not yet been modelled that it would be so. Jigster mentioned that at least the P-38 and B-17 worked the same way. HTC doesn't yet have a curve up for the B-17 but the P-38 and P-47 climb and speed look rather similar.

Sooo... if the DB605 worked in the same way then how come the speed and climb curves for the 109's are quite jagged? And what about Rolls-Royce Merlin? Did it have the same system? I have absolutely no idea. If it had, then shouldn't those curves be more rounded too.

I'm sort of stumbling in the dark here and would appreciate some light. Not from a flamethrower though.

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SageFIN

"The wolves are gathering, the stars are shifting...
come, join us in the hunt!"
---

[Karnak]

SageFIN,
You came off sounding like part of the universal non-German plane conspiracy theorists.

The non-Allied plane conspiracy was a sham that was revealed when the Japanese turned out to have a good kite.  The pro-German guys had been using the Japanese and Italians as armor to defend from alligations that they only cared about German aircraft.  As soon as another Axis plane, the N1K2, was shown to be VERY good, they attacked it too (others did as well).

 

HTC hasn't shown much inclination to redo those diagrams.  If the Bf109 doesn't perform correctly in the game, that is something that should be posted, with evidence.

Sisu
-Karnak

[This message has been edited by Karnak (edited 10-19-2000).]

[funked]

Sage, AFAIK the curves on the charts are based off of real performance data.  So regardless of what the supercharger was control was supposed to do, this is what the plane did.  Some of the shapes do seem a little odd though.  I will look into this.

Obviously above the rated altitude, boost and power will drop regardless of what the supercharger speed controller does.  Maybe the some of the fluctuations at lower altitudes are due to changes in the efficiency of the fluid coupling with respect to altitude?

The P-47 and P-38 curves are smooth because they had turbosuperchargers which could maintain full rated power to 30,000 feet and beyond.

Nath, German engines had some neat gadgets, but in terms of power output per cubic inch and pound of weight, and especially in high-altitude performance, they weren't quite up to par with US and UK designs.  They are still really nice works of engineering art though.  BMW and especially DB engines had some really clever design features.

[Nath-BDP]

Hmm... Jumo 213EB, funked? DB 605L?


Late war German engines were the best in the world.

[wells]

I think that's just so the pilot can set his manifold pressure and not have to worry about pushing the throttle up to maintain it as he gained altitude.  The P-51 had the same kinda thing.  It wouldn't affect the speed chart any.  Any jagged edges are caused by having at least 2 stages in the supercharger.  One had to let the manifold pressure drop before the second stage kicked in or else the engine would overboost.  There's also ram air effect.  Full boost was rarely used on takeoff as the boost would increase with speed.  The ram effect raises the critical height about 3000 ft in most cases and from 18k-21k in the DB605.

[Jigster]

 

Originally posted by Nath-BDP:
Hmm... Jumo 213EB, funked? DB 605L?


Late war German engines were the best in the world.

So...why was the Merlin mated with the 109 after the war?  

Scary to think of the equipment the Germans could of kept going if they would of designed it simpler. When it takes a team of engineers to build, and another team to try and repair it something ain't right.

Other then the claustraphobia, the US volunteers liked the late model 109's...heck they even got some kills vs the Royal Egyption Spitfires. How ironic is that?

Benz sure had one thing right...fuel injection. If it wasn't for that, the generation of diesel engines might of never come along. Wonder who the Catapillar guy was who stole it and licensed it in the US?  

[funked]

Nath if you count jets I agree.

But BMW 801 vs Pratt & Whitney R-2800?  No contest.  The 801 never broke 2000 hp in a production plane while the 2800 was good for... 2800 hp in three different aircraft.

The Jumo and late 213 and late DB 605 were good, but still barely had more power than the Packard-Merlin V-1650-9 in the P-51H, despite having much more displacement and being a bit heavier engine.

Like I said, per cubic inch and per pound of weight, the German engines were nothing special.

[This message has been edited by funked (edited 10-19-2000).]

[funked]

Agree on the injection Jig.  Last year I did a bunch of reading on the injection system in the BMW 801, found a bunch of pictures from a guy who was restoring one.  Then I was looking at mid-60's F-1 Ferrari engine, and... same dang system!    

[This message has been edited by funked (edited 10-19-2000).]