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Old 01-19-2019, 08:53 PM   #11
grafspee
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for me MW50 works as it should be working. MW50 is only for anti knock protection if supercharger hit its limit it wont help anymore if you have acces to high octane fuel like allied planes had there was no need of using mw50 systems becouse germans with 87 octane fule were strugling to keep up with allied engines powers and hight alt preformance since merlin used 2 stage supercharger with intercooling and that was very effiecient solution.
Yeap at high speeds you can get some boost from ram air intake designe too. i think almost all planes from WW2 had that kind of intakes
If we assume the Germany and allied countries like USA UK had similar technologies engine of bf109 running ata 1.8 ATA at 2800rpm with adition of MW50 which providin aditional internal cooling for engine, compared to v-1650-7 from p-51 wich runs 61inch/3000rpm which is something around 2.0ATA at higher rpm i would say that engine from bf109 can run much longer then p-51 engine.
Whats bothering me in bf109 is low speed efficiency of radiators you can fly at stall speed and still bf109 manages to cool engine down while p-51 or spitfire are blowing gasket imidietly, wonder is this some inaccuracy or the cooling system in bf109 was so good

Last edited by grafspee; 01-19-2019 at 09:18 PM.
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Old 01-22-2019, 01:13 PM   #12
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for me MW50 works as it should be working. MW50 is only for anti knock protection if supercharger hit its limit it wont help anymore if you have acces to high octane fuel like allied planes had there was no need of using mw50 systems becouse germans with 87 octane fule were strugling to keep up with allied engines powers and hight alt preformance since merlin used 2 stage supercharger with intercooling and that was very effiecient solution.
Nonsense, the charge cooling effect persists even above rated altitude. As long as the supercharger tap can provide higher than ambient pressure to the tank, the MW system will increase power output. With high octane fuel such as allies or germans in form of C3 had (145 grade fuel in the allied rating scheme) you will be able to run your engine with even higher boosts. If you understand the effect of MW50 charge cooling as it was injected into the supercharger you may be able to recognize why a heavy intercooler makes no sense at all in this configuration and just how similiar the effect is.

The germans used lean ratings to describe their fuels and the allied used rich ratings. The B fuels were made from natural hydrocarbons (eg from Ploesti) and were complete crap by the end of the war. While the C fuels were made by coal hydration (eg in Leuna) and were completely synthetic with controlled aromatic additives that made for very high octane ratings and constant quality fuel production. The eastern front was supplied mainly with B4 fuel while the western front was mainly supplied with C3 fuel. Considering logistics and demand that made a lot of sense.

Eg DB605 in DC config with C3 fuel at 2.0 ata or the P&W R2800 with water injection. Same engines just higher octane fuel + MW50 = further increased boost ratings.


PS: It makes absolutely no sense to compare boost ratings without looking at least at engine compression as well, it tells you nothing.
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Old 01-22-2019, 05:58 PM   #13
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Nonsense, the charge cooling effect persists even above rated altitude. As long as the supercharger tap can provide higher than ambient pressure to the tank, the MW system will increase power output. With high octane fuel such as allies or germans in form of C3 had (145 grade fuel in the allied rating scheme) you will be able to run your engine with even higher boosts. If you understand the effect of MW50 charge cooling as it was injected into the supercharger you may be able to recognize why a heavy intercooler makes no sense at all in this configuration and just how similiar the effect is.

The germans used lean ratings to describe their fuels and the allied used rich ratings. The B fuels were made from natural hydrocarbons (eg from Ploesti) and were complete crap by the end of the war. While the C fuels were made by coal hydration (eg in Leuna) and were completely synthetic with controlled aromatic additives that made for very high octane ratings and constant quality fuel production. The eastern front was supplied mainly with B4 fuel while the western front was mainly supplied with C3 fuel. Considering logistics and demand that made a lot of sense.

Eg DB605 in DC config with C3 fuel at 2.0 ata or the P&W R2800 with water injection. Same engines just higher octane fuel + MW50 = further increased boost ratings.



PS: It makes absolutely no sense to compare boost ratings without looking at least at engine compression as well, it tells you nothing.
Yes allies used 100/130 first is for lean mixture second is for rich germas used 87 if i recall corectly.
I did write that way to focus on what primary job is for MW50. MW50 will cool charge in some extent providing extra power true but this gain is very very small
Basicly this thing looks like that
MW50 will provide a lot anti knock protection and little increase in charge density
INTERCOOLERS/AFTERCOOLERS will provide very little anti knock protection and big increase in charge density
Take note when you injecting MW50 in to intake of the engine you are taking away some volume from charge volume which is not involved in combustion but you gain a lot anti knock protection soe you can boost much higher overcoming this effect by far far.
that's why in p-47 both intercooler and mw50 injection were used.
Germans used MW50 to bypass low grade of their fuel allowing engines runs higher boost.
Boost it self is not made by any of those neither MW50 neither intercoolers do this
Boost comes from supercharging system or ram air system.
Supercharger will alwayes give you higher pressure at supercharger discharge hose then ambient.
Comparing compresion ration of the engine is problematic becouse i dont have any data on this.Compression ratio isnt some global thing which is the same everywhere germas could have difrent requirements for determining compresion ratios then british. So i cant compare it.
Higher boosted engines will have lower compression ratios you want to lower peak combustion pressure in you engine if you want boost your engine much more you need to lower its compreassion ratio so engine designed for high boost will have lower compresion ratio than engine with low boost.
But i will agree 100% with you to campare engines it is require a lot more data then boost ratings rpms.
On another hand take a look at DCS FW190 this one blowing engien after a couple of seconds of running MW50 at not much higher boost then bf109 something around 1.9ATA with low supercharger speed engaged
Take note the bf109 oil tem can go up to 130 celcius degree that is a lot more then p-51. Fw190 oil can go up to 130 if i remember good that must mean something

Yest 2.0ata bf109 my dream same as 75inch boost p-51

Last edited by grafspee; 01-22-2019 at 09:10 PM.
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Old 01-23-2019, 01:00 AM   #14
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Yes allies used 100/130 first is for lean mixture second is for rich germas used 87 if i recall corectly.
I did write that way to focus on what primary job is for MW50. MW50 will cool charge in some extent providing extra power true but this gain is very very small
Basicly this thing looks like that
MW50 will provide a lot anti knock protection and little increase in charge density
INTERCOOLERS/AFTERCOOLERS will provide very little anti knock protection and big increase in charge density
Take note when you injecting MW50 in to intake of the engine you are taking away some volume from charge volume which is not involved in combustion but you gain a lot anti knock protection soe you can boost much higher overcoming this effect by far far.
that's why in p-47 both intercooler and mw50 injection were used.
Germans used MW50 to bypass low grade of their fuel allowing engines runs higher boost.
Boost it self is not made by any of those neither MW50 neither intercoolers do this
Boost comes from supercharging system or ram air system.
Supercharger will alwayes give you higher pressure at supercharger discharge hose then ambient.
Comparing compresion ration of the engine is problematic becouse i dont have any data on this.Compression ratio isnt some global thing which is the same everywhere germas could have difrent requirements for determining compresion ratios then british. So i cant compare it.
Higher boosted engines will have lower compression ratios you want to lower peak combustion pressure in you engine if you want boost your engine much more you need to lower its compreassion ratio so engine designed for high boost will have lower compresion ratio than engine with low boost.
But i will agree 100% with you to campare engines it is require a lot more data then boost ratings rpms.
On another hand take a look at DCS FW190 this one blowing engien after a couple of seconds of running MW50 at not much higher boost then bf109 something around 1.9ATA with low supercharger speed engaged
Take note the bf109 oil tem can go up to 130 celcius degree that is a lot more then p-51. Fw190 oil can go up to 130 if i remember good that must mean something

Yest 2.0ata bf109 my dream same as 75inch boost p-51
MW50 does not have a primary job, it is injected into the supercharger for a reason and its effects are twofold. If charge cooling wasnt a major expected effect you could inject it into the carb (not in case of the DB since DI) or into the charge air duct or into the cylinders directly. But you dont. You inject it into the supercharger with all the detrimental effects due to droplet damage to the very high RPM supercharger. Why is that you ask?

Water and methanol injected into the charge air cause a big enthalpy delta due to vaporization. And no, you take away no volume at all, on the contrary you increase the oxygen supply when measured at same temp because the charge air is densified through cooling. Around a 100 HP increase can be expected due to MW charge cooling alone, keeping boost pressure constant. So thats 5,4% of total engine output at SL.

The charge temp rise of the Merlin 61 was 205°C at max F.S. revs and intercooler efficiency was ~35%. That is a delta of 72°C. So, rule of thumb ~13% engine output gain at FTH. That means MW charge cooling alone provides 42% of the benefit of a heavy intercooler. It is a bit of apples to oranges because we are comparing SL vs FTH and at low ambient temperature an intercooler gives better performance. Also a single stage blower will not heat up the air as drastically in the first place.

I just tried to explain that german "low grade" fuel was the same as allied fuel on the western front, because germans classified their fuel in lean rating and allies in rich! At the end of the war the german C3 fuel was pushing a 145/100 rating.

Whatever boost the 109, Dora and Mustang are running is not comparable because they run different compression ratios. The DB605 runs at 7.5:1 and the Jumo at 6.5:1 with B4 fuel. Both higher with C3 fuel. The Dora blowing its engines after a few seconds at 1.9 ata is a bug and not an engine design feature. With the lower compression ratio it can obviously sustain higher boost pressure than a DB605 engined 109.
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Old 01-23-2019, 05:24 PM   #15
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first mw50 injection systems in bf109 were just field kits so the easiest way was to inject mw50 in to supercharger inlet.
check this out
https://www.rbracing-rsr.com/downloads/NACA_H2O_2.pdf
https://ntrs.nasa.gov/archive/nasa/c...9930091835.pdf
this one is about char air cooling https://ntrs.nasa.gov/archive/nasa/c...9930093159.pdf
this raport is testing water/fuel ratios up to 2.0 and in bf109 there is no way that mw50 system injecting wather/methanol at this ratio it would require bigger mw50 tank then fuel tank
So you teling me that mw50 in bf109 isnt for knock protection ?? or what becouse a lots track a little
i though that allies got 100/130 fuel and it was better then 87 german counterpart. Fuel rated 100/130 is for both lean and rich i think and this is waht allies were using
but you must agree that this sudden jump in ATA form 1.45 to 1.8 is because the ECU is increasing supercharger impeler speed nothing more
finaly found this proper NACA raport
https://ntrs.nasa.gov/archive/nasa/c...9930093582.pdf
i noticed that in game when you engage mw50 at high alt in bf109 you can see that prop gage snaps forward it mean that engine want to speed up so there is some power increase at hight alt is it 100hp i dont know at high alt it maby less but it is definetly modeled in game
so mw50 engaged above critical alt it will increase power output of the engine due to cooling air charge introduced to engine so ECU must take it to account to introduce more fuel too actualy make it happen. but what power increase are we talking about ?? and what evaporation level are we talking about at high alt since inlet air tem will be very low
so thae power increase of increased density of charge air will be present through all altitude of plane but power gain because increased knock limit of fuel will fade away since supercharger wont be able to put ata above 1.45.
but i will hold up to that german fuel had less octane number then allied one but if this not true i dont see any reason to use mw50 in bf it could just run 1.8 ata without mw50. as i said earlier compresion of engine can be tested in difrent way givign difrent numbers so i will not take it as legit comparison
B4 and c3 fuel was captured and tested by allies dont know about db engines

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Old 01-23-2019, 10:16 PM   #16
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MW50 does not have a primary job, it is injected into the supercharger for a reason and its effects are twofold.
I dont believe you understand most of what I am saying... You commented some partly correct stuff in another thread where I explained in high detail how MW50 actually works. I am pretty sure I know how it works. Of course it acts as antidetonant, but charge cooling is the second major desired effect! I have been saying that the whole time.

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first mw50 injection systems in bf109 were just field kits so the easiest way was to inject mw50 in to supercharger inlet.
Why is it easier for a "field kit" to inject into the supercharger than through the cylinder injection nozzles which are there anyway in a DI engine?

Where on earth was I talking about water fuel ratios? But since you brought it up, please show me the water/fuel ratio to charge temp graphs in that NACA doc, because I cant find it (and dont know what it could possibly tell me about inlet charge temp). MW50 consists of methanol and water btw.

How could a sudden charge pressure increase not be from the blower? Where else is it supposed to come from? But the temperature of this air is hugely important and that is independent of what pressure you inject it into the cylinders. Do you realize that in a highly supercharged engine ambient temperature and charge air temperature differ by a vast amount? Why do you think a intercooler gives you no benefit in natural aspirated engine? I tried to give you an example with the Merlin 61, but I am not sure you read that part.

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The charge temp rise of the Merlin 61 was 205°C at max F.S. revs..
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and what evaporation level are we talking about at high alt since inlet air tem will be very low
Let me explain to you the basics. If ambient temp is -50°C then after compression the charge air has a temperature 155°C. What levels of Methanol evaporation could possibly be expected by a temperature of 155°C with its (sea level) boiling point of 65°C? Or water?

Do you know how the fuel ratio is calculated by the ECU in 109?
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Old 01-23-2019, 11:47 PM   #17
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i am very aware of temp increase while compresing air.
It very depends on what pressure is in supercharger discharge house if it is around 1.8 ata and what water/methanol solution temperature is so at 155 celcius degree evaporation maby limited i think. but supercharge up high may increase temp more then at SL it will boost much more. Since we know that mw50 system is lifting knock limitation for DB605 engine that i can tell for sure that evaporation isnt completed 100% part of injected mw50 have to evaporate in combustion chamber to lift knock limitation of fuel used in engine
I m not sure if using cylinder nozzles would be easier than just single spray bar at supercharger intake.

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Old 01-24-2019, 12:55 AM   #18
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i am very aware of temp increase while compresing air.
It very depends on what pressure is in supercharger discharge house if it is around 1.8 ata and what water/methanol solution temperature is so at 155 celcius degree evaporation maby limited i think. but supercharge up high may increase temp more then at SL it will boost much more. Since we know that mw50 system is lifting knock limitation for DB605 engine that i can tell for sure that evaporation isnt completed 100% part of injected mw50 have to evaporate in combustion chamber to lift knock limitation of fuel used in engine
I m not sure if using cylinder nozzles would be easier than just single spray bar at supercharger intake.
True, at lower altitude the supercharger isnt heating up the charge air as much, but the ambient temperature also isnt -50°C. That means that the resulting charge air temps will still be more than enough to boil Methanol.

So you are saying that gaseous Methanol does not provide ADI effects because suddenly its octane rating changes, am I understanding that correctly? Why would you need 100% evaporation to cool the charge air?

A direct injection engine already has a bunch of cylinder nozzles for, well, direct injection. So why not put the Methanol into the fuel like in racing fuel? Instant higher octane rating, no detonation, done! Thats not easier than a bunch of piping and a MW tank and pressured gas tanks and a supercharger injection nozzle and an extra throttle mechanism and a seperate pump etc.?
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Old 01-24-2019, 05:54 PM   #19
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i think we can expect lower temp increase in bf109 at SL than in merlin 61
as far as i know merlin 61 is dual stage supercharger diven by crank shaft
at SL at 3000rpm supercharger system in merlin 61 is doing crazy staff like
1st stage of proces is lowering incoming pressure via throttle this rapidly decreasign inlet air temp may couse icing in some scenarios then air is entering 1st supercharger and 2nd supercharger boosting inlet pressure to max rated manifold pressure this kind of setup will bump air intake temp a lot more then bf109 supercharger setup. At hight alt dual stage supercharger will take ahead position.
But any way you are probably right methanol will likly vaporise in almost 100% so only water will work as ant knock and combustion chamber coolant
mixing methanol with fuel inst good idea because fuel systems are very sensitive to methanol
at least p-51 engine cant run fuel with methanol addition.
Another reason is that they wanted it as emergency system that can be engaged and disengaged at any time. And mixing methanl with fuel would require aditional tanks and aditional housing and fuel pumps too.
Difrent story is r-2800. this one is air cooled so combustion chamber is much hotter in this engine so without water injection engine could not run any near boost levels as in p-51.
but air cooled engines is whole difrent world

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