Bf 109 F series

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Mr Aozora
The fact that Mr Kurfust has been banned from this forum cancels his great knowledge? His great research?
You claim that the author of the article K4vs XIV has done very good work at his site and for free. So has Mr Kurfust at his own site. And never was accused for inaccurancies.
You ask good evidence. Go read Mr Kurfust s response to the article K4 vs XIV . ITS FULL OF EVIDENCE. Evidences and arguments that have never been answered by the other side.WHY? (eg Is it fair to take datas of gondolas equiped K4 to compare them to XIV s ?)
You know , the problem with the site in question, is not that is "accused by partisans" like me, a worthless amateur. The problem is that serious reserchers of german aviation have proved it of questionable reliability , at least as far as german aircrafts are concerned

And somethimg ...irrelevant...
I asked my motorbike enginneer , with vast experience in engine tunings . I asked car enginneers. I asked race engineers. I asked greek air forces mechanics
Is it possible to increase an piston engine s output 30% by SIMPLY provide higher octane fuel? They ALL laughed . Not me. The proffetionals
 

Mr Oldsceptic
I may have been rude and should have avoided this. But the analysis that you ask has been made by Mr Kurfust with evidences
In my opinion it is clear that there are more than human mistakes at that text. I find clear manipulation of evidences, and biased judgement from the author. Especially , if you consider that the author is very experienced , some mistakes are unexplained
 
Is it possible to increase an piston engine s output 30% by SIMPLY provide higher octane fuel? They ALL laughed . Not me. The proffetionals
Click to expand...

You can if you are super or turbo charging the engine. Because it will allow higher boost without pre-detonation. Naturally the engine has to mechanically and thermally capable of it.

So, looking at the Rolls Royce chart 87 octane (all values are British ones of the time and not entirely directly comparable to German ones) was limited to about 9lb boost. 100 octane could go to 20lb, 25lb with water injection. 150 octane about 35lb.

Putting it in very simple terms (and not allowing at all for power used for the supercharger, etc), the 27 ltr Merlin was equivalent to a 43ltr non-supercharged one at 9lb boost. 60 ltr at 18lb boost and a whopping 73ltr one at 25lbs boost. Of course diminishing returns set in. So instead of a theoretical 2,700 bhp engine at 25lbs boost it was only 2,050bhp for the Merlin 66 (and about 2,150 for the more efficient RM17SM).

The RM17SM engine got even higher, with about 2,300bhp at 30lb boost and a whopping 2,600bhp at 35lb boost.
 
Jim, I never said I agree with all of Mike's analyses. So I do my own and come to my own conclusions. The data is all there provided by him for anyone to do that, which is what I mean by intellectual honesty.

I have never seen any sign, in any way, of 'manipulation' etc as some have claimed. Anything but in fact.

Analysis and interpretation is not an exact science, Mike is perfectly free (as is everyone else) to come to his conclusions based on the evidence.

But I'd much rather see someone do a comparable analysis (and as well written, Mike is a good writer) that comes to other conclusions than just name calling.
I'm happy to read it, and of course come to my own personal conclusions .... which can be different from anyone else's of course.

But I think the key thing is some respect and politeness when you are intellectually disagreeing with someone, especially with someone who has gone to great lengths and a heck of a lot of hard work to provide us all with so much good data.

There is no absolute right or wrong here, only 'rightish' and 'wrongish' sort of stuff with a lot of wriggle room between those limits, heck even today it is hard to compare modern plane's performance right across their whole flight envelope to determine what is overall 'better' or 'worse'. Have a look at the recent stoush between Boeing and Airbus over various claims for the 747F and the 380.......
 
If they all laughed then you asked the wrong question.

IF you run an engine on 87 octane fuel and set it up correctly and then switch to 100 octane and do NOTHING to the engine you will get a ZERO PERCENT increase in power. ALL these men are quite correct.

HOWEVER, 100 octane fuel allows you to change either the compression ratio or, on a supercharged engine, the amount of boost used. Or some combination of both.

But that is NOT SIMPLY providing higher octane fuel. To change compression ratio usually requires new pistons. To change boost requires a new supercharger or new supercharger gears or at the least changing the supercharger boost controls.

The best ( or easiest) example is the Merlin. The Merlin III was good for 1030hp at 16,250ft at 6lbs boost with 87 octane fuel. 100 octane fuel is good for a potential 30% increase over 87 octane ( argue with Sam Heron, not me). When the British ran them on 100 octane ( actually 115-120 performance number) There was absolutely NO CHANGE in power ABOVE 16,250ft. The supercharger was maxed out and could supply no extra air above that altitude. Below that altitude the supercharger could supply extra air and the higher octane fuel allowed higher pressure without detonation. Max power was 1310hp at 9,000ft at 12 lbs boost. The increase from 6lbs boost to 12lbs boost is about a 28.5% increase in manifold pressure. A few other things are going on like different intake temperatures and pumping losses than can affect things by a few %.
Please note that further increases in power required new superchargers (Merlin XX and 45) different supercharger gears and finally the two stage supercharger. Also note that the British fuel changed twice AFTER the first 100 octane as used in the BoB.
G0 back and ask the professionals what happens when you increase the manifold pressure by 25-30%. It should increase the amount of fuel and air going though the engine in any given time period by 25-30%.

The performance number scale is much more linear than the octane rating scale. 87 octane is 68.5 on the Performance number scale. 100 octane is 100PN. Going from 100PN to 130PN should give another 30% ( if the supercharger can supply 30% more air the engine doesn't break/bend). Going from 130 to 150 should give about another 15%
 

No Mr jin this is just adding to your crap. The reason why no-one finds fault with Mr Kurfurst, and why Mr Williams hasn't bothered to answer is because Mr Kurfurst's response to anyone trying to debate his facts and figures is usually so unpleasant/nasty/full of distortions and half truths that ANY "discussion" isn't worth the trouble. You are indeed a "worthless amateur" that you can take Mr Kurfurst so seriously.

As it is you don't even have the decency to call Mr Williams a liar to his face, using your real name, via PM, so your opinion isn't worth a whole lot.
 
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Mr. Kurfürst's site is basing on primary german sources and documents, there is not much room to discredit him or his site about the Bf 109.
Or perhaps you want to claim that primary german sources are lies?
 
silence said:
What does this do to the rate of fuel consumption?
Click to expand...

According to the Spitfire II PNs fuel consumption was:

Maximum Cruising (weak mixture, 2,650 rpm) = 55.5 gall/hour at 13,000 ft

Maximum Cruising (Normal mixture, 2,650 rpm) 77.5 gall/hour at 13,000 ft

All-out level at 3,000 rpm = 98 Gall per hour at 14,500 ft


Modifications to Merlin II/III series to enable +12 lbs boost:



 
DonL said:
Mr. Kurfürst's site is basing on primary german sources and documents, there is not much room to discredit him or his site about the Bf 109.
Or perhaps you want to claim that primary german sources are lies?
Click to expand...

Mr Kurfurst has been banned from enough websites to have discredited himself and his site, except to his most dedicated fans. Enough said on the subject.
 
You will be confronted with his research and his site every time the issue is the Bf 109, simply there is no other site at the web, which provide more german primary sources and documents about this a/c.
This is simply a fact.
To discredit him, because of his behaviour (to your opinion) and also try to discredit his site, research and provided primary sources will not function!
You will be also chanllenged in the future with his provided primary sources about the Bf 109, if you deny this sources or discredit his site, you automaticly discredit primary german sources.
 
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Just to clarify, the boost rating is the max that a given engine will hit in flight: there might be no boost at a normal cruise, half boost at max cruise, and full boost at emergency power (just as a general "for example" statement)?
 
Yeah by 'boost' I mean full manifold pressure at full throttle. + 6.25 being the max you can hit with 87 octane, + 12 with 100 octane.
 
I see Kurfurst post the absoute highest numbers that can be found on his site as known fact, not the average numbers. I belong to another forum dedicated to WWII aviation, too, as well as this one. Most members over there know Kurfurst simply isn't a reliable souce for factual data on the Bf 109. I am not sure how the majority feels in here yet but won't argue about it much either way. People believe or don't.

His data don't agree with the surviving operating examples (E and G) of the type while the P-51B/D, Spitfires, Sea Furies, P-47's, P-40's, etc., meet book values from when they were produced. In fact, we fly (at the museum) more than 30 WWII types and they ALL meet book specs when pushed. We have a Bf 109E ready for restoration, so I'm sure than in a couple of years, we'll see if a second Bf 109E also meets book spec like the one originally restored at Chino now flyingas the Russel Bf 109E. We already KNOW the Paul Allen Bf 109E meets book specs. They didn;t try top speed but it makes book rate of climb, book cruise, and book takeoff distane from grass. Of course, it might depend on whether or not the owner elects to have an authentic prop made in Germany, which he well might. That would be nice to see.

Were German factory books wrong or is Kurfurst a bit optomistic?

The US and British tests of the type mostly DO nearly agree with one another and the surviving operating examples of the type (E and G), while there are few tests that were run at lower boost when the proper boost levels weren't known.

Wish we had an operating F model with the proper fit out flying. I'm sure it would be welcome anywhere at an airshow, whether or not they had authentic props or not.

Sorry to hear about the recent forced landing. Hope it is repaired to flight status again amd not turned into a static unit.
 
GregP said:
Were German factory books wrong or is Kurfurst a bit optomistic?
Click to expand...

Not necessarily wrong, but different calculations used. For example, over at wwiiaircraftperformance there is this explanation in a British P47 trial:

'Since the P-47C has not been through the hands of the Performance Testing Flight of the Aeroplane and Armament Experimental Establishment, some careful check flights were made at this Unit to obtain an approximate idea of its performance. ... In an independent trial the U.S.A.A.F. obtained slightly higher figures, possibly owing to the ... different methods of reduction. At this Unit the British Performance Reduction Methods for Modern Aircraft (A. &A.E.E./Res/170) were used.'

I've seen things like this come up a few times when looking in on aircraft performance. Not every establishment used the exact same math when calculating aircraft performance.
 
Kuffie/MW site: Both are known for their more or less existing bias towards their favorite a/c. As always with data posted on the net, take it with a grain of salt and cross-check it with other sources (if available).
 
Yeah, I know what you mean about the grain of salt, Denniss.

I am of the opinion that the Bf 109 was one of the finest fighters in existence when WWII started, right there with the Spifire and the Zero, and it maintained rough parity for the duration of the war in the ETO. That doesn't mean the Bf 109 could not have been improved and also doesn't mean the Spitfire could not have been improved as well. Both could have used some improvement but were VERY good on an as-is basis when compared with the state of the art everywhere else.

As for the performance claims, they are the subject of some scrutiny. I tend to take the reports from established flight test agencies rather than combat reports. Many combat fliers only flew ONE fighter and their opinions are next to useless when other planes are concerned. The opinions of people whose job to was to fly and evaluate fighters is much more reliable when coupled with performance data from such tests. German flight test were no less thorough than Brittsh (or US, Japanese or French test). I tend to suspect some Soviet tests since meeting the spec could mean somone's life or relative freedom.

The Bf 109 had major weaknesses that didn't come into play if the pilot had YOU in his sights. The short range affected the usefulness of it and the relatively light armament made for a tougher time for the Bf 109 pilots. But they learned to adjust and were able to set a high standard with it. I am relatively sure, though obviously not positive, that had they swapped their mouints for the British mounts and the numbers had been the same, with neither the Luftwaffe nor the RAF getting any more or less planes, that the outcome would have been the same. That is, the RAF fliers would adapt to the Bf 109 / Fw 190 and the German fliers would adapt to the Spitfire / Hurricane with about equal success as they achieved in the war. I could easily be wrong there, but it will be hard to prove, won't it?

That's relatively high praise for both planes and I personally rate them as nearly equal with the winner being determined by the pilot and the situation when they entered combat. Saying the Bf 109 was flawed to the point of being useless is to go against all the real and achieved evidence to the contrary. Saying the Spitfire was not as good as the Bf 109 does almost the same from the other direction.

Two greats if ever there were two. We need more Bf 109's flying ... off GRASS. Someone neeeds to make some new-build DB 601 / 605's ... and some props! Od course, some new Allied engine would be a welcome sight, too, but the German engines are just too scare.

Who here besides ME had heard a running Jumo 213?

I heard the former Doug Champlin Fw 109D start up once. It now rests in Seattle at the Museum of Flight, but sounded wonderful when started in the mid-1980's and probably still COULD. When it started, I was surprised that the prop only turned 3 - 4 blades before it kicked off just fine. Probably means they ran it earlier to be sure, but nontheless it was a neat sight and sound.
 
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