GScholz MW-50 and 109s and the a8

[Batz]

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.

MW-50 (water-methanol 50/50) was injected into the air-intake and served as an anti-detonant allowing higher boost to be used below normal rated altitude. The evaporating water also cooling the charge-air thus increasing the weight of the charge. Limited by the performance of the supercharger the MW-50 induced max. output began declining 1.5-2 km. below normal rated altitude until it became impotent at and above the normal rated altitude (compare for example DB 605A-1 and AM).

MW 50 was used  below rated altitude. The 190a8 normally flew above its rated altitude to engage bombers. At an altitude where mw 50 gave no benefit.

Another means of improving the performance was GM-1 (Göring Mischung 1). In short the system worked by injecting nitrous oxide into the [supercharger above normal rated altitude of the engine. The nitrous oxide serving as an oxygen carrier to improve the output at high altitude (pure oxygen proving too volatile). The effect was phenomenal, raising output 25-30 % instantly. GM-1 was used by dedicated high altitude formations from 1941 onwards. Excessive bulk and weight were major penalities though, and additional supercharging was generally seen to be more efficient.

The Me 109 sub-types were delivered with the following power trains:

Me 109G-1 through G-4: DB 605A-1

Me 109G-5/G-6: DB 605A-1, AM, AS, ASM, (ASB, ASC ?)

Me 109G-8: DB 605A-1, AM, (others ?)

Me 109G-14: DB 605A-1, AM, AS, ASM, (ASB, ASC ?)

Me 109G-10: DB 605D, (D-2 ?), DB, DC

Me 109K-4: DB 605DC, ASC (others ?).

The DB 605D didn't enter service until spring of 1944 with the advent of the Me 109G-10.

http://w1.1861.telia.com/~u186104874/db605.htm

[GScholz]

I give I give! What was so special about the chart hazed mentioned? (hazed?) Was it GM-1 or was it an unboosted 190A8, in which case the AH model is drastically inferior.

[Vermillion]

The Aces High Fw190A8 matches the Data curve from the Flight Manual for the standard (no GM-1) 4 gun 190A8.

Big Pics or I would put them in the thread directly.

Standard 190A8

http://www.vermin.net/fw190/190-1.jpg

190A8 w/GM1

http://www.vermin.net/fw190/190-2.jpg

190A8 with x2 30mm cannons in wings

http://www.vermin.net/fw190/190-3.jpg

[HoHun]

Hi Batz,

>MW 50 was used  below rated altitude. The 190a8 normally flew above its rated altitude to engage bombers. At an altitude where mw 50 gave no benefit.

Technically, "no benefit" isn't strictly true.

However, the benefit was a meagre few percent of power at high altitude due to the charge cooling effect achieved by the evaporation of the liquid alcohol-water mixture, compared to twenty or thirty percent at low altitude.

The Fw 190D with Jumo 213E used MW50 injection at high altitude to make up for the lack of an intercooler, so in some instances MW50 injection actually made tactical sense even at high altitude.

Regards,

Henning (HoHun)

[Batz]

Hiya HoHun,

Just to cear up something, am I correct in stating the a8 didnt use MW50?

From another thread I replied as such:

The 190as used a system called "Erhonte notleistung" . C3 fuel was used exactly like the Mw50 to cool down the mixture so that you can increase the pressure in the cylinders. The C3 system did not require any special installtion to work. IIRC the mw50 installation on the BMW801 was a real problem.

If I am not mistaken it could be used up to 5500m. It was usable for 10 minutes. It was tested on a A5 in August 43 was standard on the A8 by June 44.

No A series outside a few a4s used mw50.

Would this be correct?

[HoHun]

Hi Batz,

>Would this be correct?

It matches my current state of information :-)

Regards,

Henning (HoHun)

[GScholz]

Thanks for the info

[MANDOBLE]

Cant see it clearly in the chart, but 10.7 minutes? to 26248 feet at 1.58 ata is correct? And what climbing angle or speed?

[GScholz]

Yes, just noticed that too, and only 14.4 minutes to 26k on 1.32 ata.

[GScholz]

That chart for the "standard" A8 which we have in AH states time to alt 19,688 feet at 9.1 minutes on 1.32 ata / 2400 rpm, and 7.5 minutes on 1.42 ata / 2700 rpm.

I just did a test, and our A8 reaches 19,700 feet in 11.3 minutes on MIL power (1.32 ata?) / 2400 rpm, and 8.5 minutes on WEP (guess that is 1.42 ata?) / 2700 rpm. I also noticed that on WEP the climb rate was the same as on the chart initially, but started to drop off too quickly with alt compared to that chart. Using MIL/2400 rpm the climb rate was off by 500 fpm at and below 5000 feet (forgot to look at higher alts).

The 190A8 in my test had 100% fuel and 4x20mm loadout like the real 190A8 in the chart. I used default autospeed for climbing and that may not be the best angle/speed?

[Batz]

Are you using auto climb?

If so theres your problem. Auto climb doesnt set best climb through out your climb. I believe its sets best climb at SL.

This is another one of those traps that gets everyone panties bunched.

You would need to be at the same climb speed as that chart  through out to get the same results as that chart.

to get to 19688 in 9.1 min you need an average climbrate of 2164fpm.

[GScholz]

Ah I see. Do you mean the speed range listed below (to the right of) the climb rate range?

EDIT: And that would be IAS i presume?