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DKoor
05-25-2007, 04:47 AM
Well... I haven't checked but is there actually any difference between 109's regarding RPM at which you are allowed to engage methanol mixture?

Generally, I engage it below 2000RPM.
But I have never checked if there's a difference between 109's regarding highest RPM allowed when engaging the MW50.

We all know the drill..... it'll last for ~26 mins, it's actually engaged only if we go above 100% throttle, and shouldn't be used more than 5 mins in piece. When fluid is expended MW50 system must be switched off to prevent engine damage.

DKoor
05-25-2007, 04:47 AM
Well... I haven't checked but is there actually any difference between 109's regarding RPM at which you are allowed to engage methanol mixture?

Generally, I engage it below 2000RPM.
But I have never checked if there's a difference between 109's regarding highest RPM allowed when engaging the MW50.

We all know the drill..... it'll last for ~26 mins, it's actually engaged only if we go above 100% throttle, and shouldn't be used more than 5 mins in piece. When fluid is expended MW50 system must be switched off to prevent engine damage.

Kurfurst__
05-25-2007, 04:51 AM
I don't thinks so. Historically, MW 50 was only in effect above the 100% regime, as you've noted. 100% was 2600 rpm historically on all 109s using MW-50, ie. the ones built with various forms of the DB 605 engines.

The MW50 switch was rather like an 'arming' switch, which enabled the boost to be (automatically) in effect when the throttle was past 100%, rather than directly enabling it.

I guess IRL the actual function of the MW - 50 switch was rather to save wear on new engines in their run-in period, ie. not to kill them with huge powers unleashed immidiately.

Ratsack
05-25-2007, 05:19 AM
Wasn't its use also expressly forbidden during takeoff? If so, the switch may also have been for ensuring eager pilots didn't do something they weren't meant to.

cheers,
Ratsack

Kurfurst__
05-25-2007, 05:32 AM
I haven't seen any evidence of that, but most likely MW 50 was not used for take off - it would have have been completely unneccessary.

BF 109E series had a special 1-min Take off power regime explictely meant for take off for heavy loads (Abflugleistung).

Pollack2006
05-25-2007, 05:44 AM
What triggered the MW50 to engage? Was it the throttle lever being pushed beyond a certain point or something else?

Kurfurst__
05-25-2007, 05:59 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pollack2006:
What triggered the MW50 to engage? Was it the throttle lever being pushed beyond a certain point or something else? </div></BLOCKQUOTE>

AFAIK if the MW50 system was enabled, pushing the throttle past the 100% (1.3ata (605A)or 1.45ata (605D), 30-min rating) position would start injecting MW-50 and open the MAP's butterfly limiter (narrower) so as to allow for increased manifold pressures, 1.7ata (605A) or 1.75/1.8/1.98ata (605D engines).

Simply to put, it replaced the former 'normal', 'dry' 110% WEP or 'Start und Notleistung' (Takeoff and Emergency Power) when MW50 was enabled. It this latter case it was referred to as 'Sondernotleistung' - Special Emergency Power. It was also allowed to use maximum power for longer periods in this 'wet' case, up to 10 minutes at a time.

Pollack2006
05-25-2007, 06:15 AM
Thnx for the info..... http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Abbuzze
05-25-2007, 06:20 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Pollack2006:
What triggered the MW50 to engage? Was it the throttle lever being pushed beyond a certain point or something else? </div></BLOCKQUOTE>

AFAIK if the MW50 system was enabled, pushing the throttle past the 100% (1.3ata (605A)or 1.45ata (605D), 30-min rating) position would start injecting MW-50 and open the MAP's butterfly limiter (narrower) so as to allow for increased manifold pressures, 1.7ata (605A) or 1.75/1.8/1.98ata (605D engines).

Simply to put, it replaced the former 'normal', 'dry' 110% WEP or 'Start und Notleistung' (Takeoff and Emergency Power) when MW50 was enabled. It this latter case it was referred to as 'Sondernotleistung' - Special Emergency Power. It was also allowed to use maximum power for longer periods in this 'wet' case, up to 10 minutes at a time. </div></BLOCKQUOTE>

I think you are right, there where tests with a DB605DC with incresed ata 1,8 and 1,98 without MW50
From your homepage http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif
http://kurfurst.allaboutwarfare.com/Performance_tests/1...Start_noMW_steig.jpg (http://kurfurst.allaboutwarfare.com/Performance_tests/109K_PBLeistungen/files/5026-29_DCStart_noMW_steig.jpg)

But these tests were not very succsessfull, a usuall engine at more than "100%" Power would destroy it in very short time.

I read that 109 pilots used MW50 to improve "internal cooling" by lowering the combustion temerature. This was done over FTH/VDH. So the plane could run longer at max. throttle.

Hmm, thinking about this makes me wonder a bit. If you fly high enough, and the charger is just reaching the boost for what we call 100% the time till overheat should be longer even if the throttle is in 110% position. Hmm maybe one of the countless shortcomings of CEM.. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif

DKoor
05-25-2007, 06:48 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Abbuzze:
I read that 109 pilots used MW50 to improve "internal cooling" by lowering the combustion temerature. This was done over FTH/VDH. So the plane could run longer at max. throttle. </div></BLOCKQUOTE>This is the interesting part IMO.
In game I can't say that I noticed some gain in this regard by using MW50.
On the contrary, 109 in my experience with MW50 cools harder than without MW50.
Also it is impossible to run it in climb without almost insta-overheat, after the first overheat message appears (after engine rad reaches certain temp).

So these facts confront each other in a way. http://forums.ubi.com/groupee_common/emoticons/icon_confused.gif

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Abbuzze:
shortcomings of CEM.. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif </div></BLOCKQUOTE>In the light of the discussion above, I agree.

DKoor
05-25-2007, 06:53 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kurfurst__:
I haven't seen any evidence of that, but most likely MW 50 was not used for take off - it would have have been completely unneccessary. </div></BLOCKQUOTE>And I would agree on that. Thing is.... why waste methanol? http://forums.ubi.com/groupee_common/emoticons/icon_biggrin.gif Why increase rad temperature with MW50? (Although it shouldn't be so, if we take my post above in account)

There is no need for all that.... after all MW50 is emergency power, that should only be manually engaged when there is a combat about.

But MW50 is the most special boost in game..... I can engage all other at will but this one... I actually engage as soon as I spot E/A. Because sometimes I simply cannot afford to lower the RPM in combat.

Kurfurst__
05-25-2007, 07:00 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Abbuzze:
I think you are right, there where tests with a DB605DC with incresed ata 1,8 and 1,98 without MW50
From your homepage http://forums.ubi.com/groupee_common/emoticons/icon_wink.gif
http://kurfurst.allaboutwarfare.com/Performance_tests/1...Start_noMW_steig.jpg (http://kurfurst.allaboutwarfare.com/Performance_tests/109K_PBLeistungen/files/5026-29_DCStart_noMW_steig.jpg)

But these tests were not very succsessfull, a usuall engine at more than "100%" Power would destroy it in very short time. </div></BLOCKQUOTE>

It's a question of fuel's octane rating vs. compression ratio and manifold pressure. Better quality fuel could resist more without pre-ignition and pinging. Take note DB engines had very high compression ratio compared to others, which is one one the reason of their good fuel effiency and high altitude performance.

Ie. with the 87-octane B-4 fuel the 605D engine would tolerate up to 1.5ata (~1550PS) w/o use of MW-50, and with MW50 1.8ata manifold pressure.

With use of the C-3 fuel, which was roughly (ca grage 96/143) equal to Allied 150 grade fuel, the engine would tolerate (ie. no pinging) 1.8ata (ie. the same with B-4 + MW50) manifold pressure, and 1.98ata

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I read that 109 pilots used MW50 to improve "internal cooling" by lowering the combustion temerature. This was done over FTH/VDH. So the plane could run longer at max. throttle. </div></BLOCKQUOTE>

What MW-50 in fact was doing was cooling the charge as it heated up in the supercharger (this reduced effiency and power) - pretty much the same thing as having an intercooler. The added effects were delicate workings inside the engine, AFAIK fuel particles gather around water particles, forming a big bubble with water in the middle, and this improves internal effiency. Water injection is still used in modern jets.. also, the methanol content of the MW-50 itself has very high knocking resistance, like very high octane fuel - it's a fuel on it's own right.

Cut the long story short, MW-50 not only allows for higher outputs via enabling higher manifold pressures (which would be limited by the performance of the supercharger), but when injected in itself without any other change it comes with around 4% power increase at the same manifold pressure.

You can see this break on the speed and climb curves you noted where MW-50 is being switched off.

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Hmm, thinking about this makes me wonder a bit. If you fly high enough, and the charger is just reaching the boost for what we call 100% the time till overheat should be longer even if the throttle is in 110% position. Hmm maybe one of the countless shortcomings of CEM.. http://forums.ubi.com/groupee_common/emoticons/icon_frown.gif </div></BLOCKQUOTE>

Probably, even though CEM keeps track of Manifold pressure. Keep in mind though the rpms are constant at 110%, they don't fall with altitude.

OTOH, many German curves imply that above rated altitude, the maximum WEP 2800 rpm can be used instead 30-min 2600 rpm, so I guess above rated altitude using maximum rpm was quite ok without much limitation.