WWII Inline engines: Daimler Benz vs Rolls Royce vs Allison vs Klimov vs Jumo

[Viking]

2064 G-6/AS and G-14/AS plus 3600 DB 605D G-10's and K-4's. That’s 5664 high altitude 109's out of some 17,000. One in three 109's.

[Viking]

Originally posted by Meyer
Viking, I suggest you to register there. You won't regret

Oh I think I would. I would have to give up any attempt at having a life!

[MiloMorai]

Here is a data sheet on the G-10 (K-4 would be simular)



Here is a data sheet on the G-6

[Viking]

Thanks again!

(What's with you Milo? The old Milo that I knew would more likely post a picture of a burning 109 wreck and profess the absolute dominance of the Spitfire! I think this new Milo scares me. )

[Angus]

Not as fast as a Mustang, - well, overlapping.
And nowhere near a Spitfire from the same era in ROC. Except very high up?
I have one good document of a 109G. tested in 1944 (ahh, Gripen), and it's rather in the same ballpark, some 6 mins+ to 20K.

Now there is one thing about the DB that I wanted to mention. Due to material problems etc.(war situation)  the legend goes that they were not up to what the design was about. So would that apply to top-notch measurements, or just the lifetime?
There are some documents about this I belive, but I got on the lead from Rall, who was not at all happy with his DB and his 109 when he had be jocking around with Allisons, Merlins and P&W's, P51, Spitty, P47 and the P38.

Anyway, there are always grayzones.

[Angus]

who had the sig "A good Spitfire is a burning Spitfire" by the way? Kuffie? Or was it Niklas???

[MiloMorai]

No Viking, it is only when Barbi put on his hobnailed boots and started doing the goosestep. Someone had to counter the utter bs spewed by Barbi.

Yes Angus it was Barbi.

Here is another little trivia about German aero engines written by a German,

I don't know for shure about the alloys the Allies used for their aircraft engines - but the Germans made excessive use of ELECTRON for their engine's light-alloy-castings - that is: an alloy with up to 60 percent Magnesium to 40 percent Aluminium - throughout the entire engine.

By doing so, you can reduce the wheight of a casting down to 2/3rds of that of a sheer aluminium-alloy. Bad point is, that Electron-alloys must be coated to become oil- and water-tight, as Electron-castings tend to be porous.

Secondly, Electron-castings corrode like Hell: Electron is hysterically sensitive to water, due to it's high Magnesium-contence. The applied coating had to fight that corrosion, too. But it could do so only to a certain extent. as even the finest cracks, fissures and, punctures in the laquer-coating would allow enough humidity, if not sheer coolant liquid sip into the Electron and initiate intermolecular corrosion hat, it would render that specific casting scrap before long.

If you should ever have asked yourself, why there are so few airworthy genuine german engines from WWII left in the World - there you have the answer for this question: They are all corroded down to unairworthiness (if such a word should exist at all in English) - if not (white) dust...

[gripen]

Originally posted by Viking
A 109G-6/AS(M) is still a G-6. And I sincerely doubt any DB 605 engine was produced without MW50 after June 1944, unless with GM1.

Most of the G-6/AS planes were without MW50 (at least those built/converted before June). And the production of the DB 605A (as well as standard G-6) continued until late 1944. There were large number of G-14s without MW50 as well.

[Knegel]

Originally posted by Nashwan
FTH for the V-1650-7 was far lower than that, as it was a low alt engine. FTH unrammed was under 20,000 ft.



A better comparison with the 605AS is the Merlin 70, the high altitude variant of the Merlin 60 series. That produced 1210 hp at 26,000 ft at reduced rpm and boost, ie at its 1 hour rating (2850 rpm, 12 lbs boost).

At 3000 rpm and increased boost, power would be higher at 26,000 ft.

(and btw, the DB 605AS produced 1200 PS, which is about 1180 HP)

Dont forget to add the exhaust thrust to the DB´s power, this is specialy important at high altitude and high speed.

Originally posted by Nashwan

No. The Merlin produces more power at what is basically a cruise setting than the DB does at maximum power. And peak power on the Merlin 70 is 1710 hp at 11,000 ft.

The DB605ASM had 1800PS at sea level, around 1850PS at 1500m(4900ft)  and still 1500PS in 6500m(21000ft) + the exhaust thrust and all this for up to 10min usage.  I guess it still had around 1700PS + exhaust thrust in 11000ft, while this is "only" a peak for the Merlin70, the DB has a rather constant powercurve.
Both designs had advantages and disadvantages, changing with different altitudes and speeds, but all over the result was rather similar i would say.
The used airframes of both engines got droven rather easy to their limitaions, what was pretty much in the highest class of propdriven planes with normal airfoils.


Hi Milo,

your 109G6 scan is actually rather a G14 scan.

The G6AS w/o MW50 must have been a bit faster at hight, due to less weight.

This planes wear MW50 and show the Vmax of the G14 and G14AS.

Greetings,

Knegel

[Nashwan]

Dont forget to add the exhaust thrust to the DB´s power, this is specialy important at high altitude and high speed.

Then I'd have to add the exhaust thrust for the Merlin, too. The Merlin figures I gave are unrammed, and exclude exhaust thrust.

[Knegel]

The supercharger of the two stage supercharger merlin afaik did use the exhaust thrust and didnt left much, while the DB supercharger did not.

Rammed power isnt exhaust thrust, rammed simply mean that the air inlet system use the presure of highspeed aiflow to load the engine in a better way, to increase the power. This work somewhat like a supercharger. The listed DB power is also unrammed.

Greetings,

Knegel

[Viking]

Umm... I don't think the Merlin's two-stage supercharger was exhaust driven. It was driven off the crankshaft, just like on the DB. You must be thinking of the turbo-supercharged Allison. However I do agree with your point on the DB’s smooth power curve vs. the Merlin’s max power being only a peak at a very narrow altitude band. That is an important point.

[Knegel]

Hi,

oh, i thought only the early single stage once was crankshaft droven, but probably your right.

Then of course the exhaust thrust could be there as well, depending to the exhaust.

The BMW801D for example never got the better exhaust, which did provide more power(80PS) but also more exhaust thrust(the late FW190A9´s got this feature).

Greetings,

Knegel

[gripen]

Originally posted by Viking
However I do agree with your point on the DB’s smooth power curve vs. the Merlin’s max power being only a peak at a very narrow altitude band. That is an important point.

The adjustment of the hydraulic coupling in DB engines was not particularly efficient because it was not based on MAP but altitude and some degree on RAM. The phenomena can be seen in the charts which gives the "ladedruck" and "gebläsedruck"; the engine runs more or less throttled up to the FTH. Basicly large part of the theoretical advantage was lost due to this. In the 603L and 605L the throttle system was improved to reduce this problem but these never reached service.

Even in the optimal case, the hydraulic coupling gives advantage only between the 1st and 2nd FTH, in all other areas direct mechanical connection is more efficient.

[Viking]

I think you exaggerate a bit, or don’t understand the workings of a supercharger. A conventional supercharger like the one on the Merlin produces a lot of overpressure at altitudes below the FTH of each stage. This overpressure is just dumped, but the engine must still use a significant amount of power to produce this overpressure. The DB design added a hydraulic converter (like on an automatic gear box) that reduced the amount of power delivered from the engine to the supercharger depending on the barometric pressure (altitude). This ensured that the supercharger produced enough pressure to feed the engine at WEP at any given altitude up to FTH, but reduced the waste of engine power used to produce unnecessary overpressure below FTH to a minimum. It could have been made even more efficient at lower throttle settings by factoring in throttle setting/manifold pressure, but to say that it was inefficient compared to a conventional supercharger is disingenuous at best.

At FTH a direct-drive supercharger is slightly more efficient since the hydraulic converter absorbs some power in the form of heat generation (again just like an automatic gear box), but at all other altitudes (below FTH) the DB supercharger is much more efficient.