A superior German fighter

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Wiking85,

Purely as a query, what would fuel injection have to do with superior climb? Might have a short effect in a bunt dive ay first, but in a climb, the carburetor has no disadvantage. The superior skill of the Luftwaffe pilots in the BOB didn't seem to prevent them from losing it, even with "superior" aircraft, so I'm not sure where that came from. If they had better planes and better pilots, what was the cause for the loss? In my mind, the issues were leadership, target selection, and short-duration fighters coupled with no real plan for prosecuting or finishing the battle. By leadership, I don't mean leadership at the unit level, which was good, I mean leadership at the highest levels of the battle plan.
 
Perfectly correct Greg. FI had no affect on climbing and had a negative affect on supercharger effiency, due to the lack of charge cooling.

It was also more complex, harder to make, maintain and more costly.

In the pre electronic fuel injection days there was no real gain and, especially with turbo/super charged engines several downsides.
The correct way, used in Merlin 100 series engines, to do fuel injection was at the supercharger inlet.

There is an article in the Flight Glabal archives rolls-royce merlin | 1941 | 0562 | Flight Archive

That compares a Merlin X (first 2 speed Merlin, without Hooker's improvements) and a Jumo 211D. Came to the conclusion that it wasn't worth it.
 
Marcel said:
I read a book about Bader in which describes clearly that the Bf109F was definitely not superior to the Mk.V. The FW190A on the other hand clearly was.
Click to expand...

The 109F and the Mk V were very close in overall performance, as were the Spit 1 and 109E. One had some advantages over the other and vice versa, anyone that claims otherwise I think are kidding themselves.
 

Then you can please explain to me why both, the Jumo 210G (fuel injection) compare to the Jumo 210 D and the DB 601A (fuel injection) compare the DB 600, had both more power output (horsepower) and both fuel injection engines a better high altitude performance through a better supercharger effency and both fuel injection engines create more boost. How is this possible?
 
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Marcel said:
I read a book about Bader in which describes clearly that the Bf109F was definitely not superior to the Mk.V. The FW190A on the other hand clearly was.
Click to expand...

That would depend on the type. The 601N powered F-1/2 was slightly faster, especially since the Mark V. had serious production quality issues and was not faster in practice than the Mark I or II; the 601N on the other hand some development troubles and may or may have not developed full power in service.

The F-4 is a different class altogether, even the initial 1.3 ata rating is much better than Mark V, the 1942 version with 1.42 ata could do about 670 kph, that's much faster than the Mark V and about as fast as the 109G or Mark IX.
 

Which Mk V's factories/production runs had "serious production quality issues"?

If you're referring to some Mk Vs underperforming (typically by 15-20 mph) in RAF tests, I suggest you look at the age and condition of the tested aircraft before blaming production quality.
 

The DB-601 had a different supercharger.

They were later engines, boost went up over time (moderately for German engines, plus different valve timing and revs limits) in the endless struggle for more power.

The Jumo 211D had fuel injection (as per the article, it has pictures of it all disassembled).

The RLM apparently mandated fuel injection to be used, yet another of its (many) daft decisions.

Re the Jumo: "A major upgrade was started in 1940 in order to better compete with the 601, following in its footsteps with a pressurized cooling system. The resulting 211E proved to be able to run at much higher power settings without overheating, so it was quickly followed by the 211F which included a strengthened crankshaft and a more efficient supercharger. Running at 2,600 RPM the 211F delivered 1,340 PS and the 211J (a 211F with intercooler) delivered 1,420 PS. Further improvements to this basic line led to the 1,450 PS 211N and 1,500 PS 211P in 1943, they were equivalent to the 211F/J but with slight boost increases and running at up to 2,700 rpm. Continued development of the 211 line evolved into the 213." Wikipedia (not fact checked)by myself).

Interesting the almost universal use of fuel injection these days in cars, but people forget why that was. Pollution controls basically. Mandatory limits made the price difference shrink (yes you could trick up a carby to do it but it became as expensive as fuel injection). Computer controlled electronic injection, as it was introduced, made significant differences in performance and fuel economy. Even more so as turbo charged engines have become more the norm.

Amazing how that 27ltr Merlin managed to develop as much (or often more) power as its 33, 36, 42, etc litre German opponents. And with a carby too ... someone knew what they were doing....
 

Your numbers are wrong, but you have also made a good point.

The Spit V went through increasing boost levels which matched, or exceeded, the 109 at the various times.

But quality is a serious issue that the Germans and the US markedly exceeded the British in just about every area of production.
By and large the Britsh were the worst (excepting Rolls Royce), the Germans next and the US was (overall) the best in aircraft.

The German's weakness was far too complex designs, which despite their better quality meant they were more expensive and time consuming to build. The Tiger tank being the prime example.
The US, when it got its act together (which took some time), built good designs with good quality (except tanks of course).

You look at a Spit vs a Mustang or a 109, the better build quality is obvious (against the Spit that is).

What that meant in operational issues was important, now the allowable limit of a Spit was 3% (and everyone was tested). That meant that the average (official) top speed of 404mph for a LF MK IX (Merlin 66) could vary between 392mph and 416mph. Naturally, experienced pilots (and especially the higher ranked) got the good ones.

Maintenance was the other issue, out of the factory a plane could do Xmph, after a few months of combat it got slower and slower. Panels being opened and closed, dents, engine aging and so on.
You have your brand new P-51B that makes 440 mph (+- something), after 6 months of operations you would struggle to make 420 (or less).

Naturally, again, the top people got the best maintenance.

Translated: if you were down the pecking order you flew in a heap of rubbish, crap to begin with got even worse over time.

German Expertin, got the best, British and US experienced people and higher commanders (unless they were technically unskilled and unpopular and the rest of the squadron conspired to give them something poor) got the best.

If you were a newbie and unpopular .....
 



True, but then again these estimated or projected figures are confused anyway - the weight quoted without 1000 kg bomb is 6,620 lbs, but this is light because there is a weights table for the "improved Fw 197C" earlier in the book which shows the following:

equipped weight = 5,658 kg (minus bomb racks) = 5618 kg:

to this must be added Crew = 200 kg; fuel= 960 kg; oil= 70 kg; ammunition= 306 kg so additional load without bomb = 1,536 kg =

Gross Weight without bomb = 7,154 kg or 534 kg heavier than the 6,620 kg quoted for maximum climb speed of 18 m/sec = 3,453 ft/min. (3,453 ft/min is not really that spectacular anyway)



It can thus be taken that the rate of climb at a realistic weight, with crew, fuel, ammo, is somewhat slower than 18 m/sec. Plus there is no indication of the weights for the maximum speed quoted - chances are it is also measured at a minimal weight of 6,620 kg, or without some 530 kg of fuel and/or ammunition.


So? My comments still stand -an Fw 187 with Dampfheißkühlung would have introduced yet another DB601 variant into an already stretched supply chain; I doubt if this would have been acceptable to the RLM which was trying to limit the engine variants being used. Nor is there any indication as to whether or not the system would have been worthwhile under combat conditions.

Also note the commentary above the first table:
The He 219 was selected over the Fw 187, at least for the nightfighter role. Why was this? No official reason has yet been discovered.
Click to expand...

For one thing the Fw 187 had a very narrow fuselage; chances are it would not have been able to carry the typical radar equipment able to be carried by the He 219 or Bf 110 or Ju 88 without a large amount of modification. As it is the weight table shows that radio equipment - minus radar, Naxos etc - to be fitted weighed 141 kg: FuG 220 SN2 alone weighed 70 kg and any antenna would have also added to weight and drag.


Do these loaded weights include essential items like armour, fuel, ammunition - note, for example, that no armour had been fitted to any of the Fw 187 prototypes. Once again we have the weights and specifications of prototypes, not operational aircraft.
 
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You've answered your own question - it was because of improved supercharger efficiency that engine performance increased, no doubt because new superchargers were developed hand in hand with fuel injection to compensate for the power losses due to the reduced thermal efficiency of early mechanical fuel injection systems. Why add new superchargers to engines which were already considered to be obsolescent?
 

Without knowing more details it is hard to say what was causing what.

The Fuel injection eliminates mixture distribution problems that just about ALL carburetor engines suffered from ( cylinders did not all get the same amount of fuel and air and even the same fuel/air ratio).
It allows a slightly higher compression to be used ( engine is not limited to the weakest cylinder like a carburetor engine) but I don't know if the injected Jumo 210 models and the DB 601 took advantage of that.
It allows for better fuel economy as (once again) all cylinders are getting the same amount of fuel and some are not running "rich" in order to ensure that the leanest cylinder is getting enough fuel.

None of these have anything to do with supercharger efficiency and some of the early German superchargers used some pretty terrible impeller designs. DO we know if some of the engines in question also changed impellers or other supercharger parts?
Did they use exactly the same gear ratios on the same superchargers?
Perhaps the improved fuel distribution allowed for a higher gear ratio to be used?

Still has little to do with supercharger efficiency even if a higher boost is used.

Most early superchargers (1939 or earlier), no matter how bad, could deliver more boost than the engines could use with 87 octane fuel. But boost is not really efficiency.

There is simply too much going on (or too many unkowns) to say that the fuel injection affected supercharge performance. Yes the injected engines made more power than the carburetor engines.
 
Sorry Aozora, in my eyes your statement is nonsense. In 1979 I bought a new car a brand-new Golf GTI with K-tronic fuel injection and 110 hp. The motor was basically the same as in the standard Golf
with carburettor and 75 hp. I would say this is an improvement and as a unit a new engine.
cimmex
 
Theoretically the advantage of carburetor was that the fuel injected into the carburetor cooled down and thus compressed the air, easing the engine's workload driving the supercharger. How much that gain amounted is the real question - German studies of water injection showed about 4% gain from injecting water alone (without increasing boost), which would amount to about 40-50 HP. That's not much and I would place a bet that the gain from using a carbburator is even less, especially in practical conditions, since carburetor also needs a lot of gimmicks installed to function safely - ice guards and so on, which decrease efficiency. In addition, that gain in power is probably further diminished/cancelled by the fact that fuel consumption is increased further (and as SR6 noted, DFI allows for higher compression, increasing fuel effiency even more), thus more fuel/weight needs to be carried by the airplane. Throttle response if probably worse, and there's always a danger of backfire as opposed to DFI engines.

The Flight article is interesting, but IMHO its more of a PR article from RR. Beggars cant be choosers, RR had no D.F.I. technology available, hell they even had problems making carburetors working properly... neither did they have any working engine in the 30 liter class - though they were developing the Griffon. It wasn't really a choice for them but a necessity, and make their arguments sound a very cheap. RR was an extremely conservative company and not very open to innovation. Still, they did one hell of a job with the Merlin, a conventional engine in all aspects, despite its limits with displacement. Given the constraints with a war going on and no time to develop a new 30-litre class engine (a path everyone choose in the end, but took steps sooner than RR), and no time to adop DFI, they did the right thing and sticking to what was already working was justifiable on the grounds of practicability, but not on engineering grounds. They made the best out of what was available, despite the handicaps of smaller displacement and having to do with carburetors. But that doesn't mean IMHO that their arguments against D.F.I. were valid at all (and apparently even at the time major figures in engine development strongly disagreed with them).
 
I would attribute the success of the Merlin to the following:

- development of efficient superchargers, particularly the two stage supercharger with intercooling;
- the use of wet cylinder liners;
- better fuel and materials;
- intensive development.

Fuel injection did provide significant advantages, aside from being suitable for operation under zero or negative g conditions, it provided more uniform fuel distribution and avoided problems with backfires. The later versions of the R-3350 received fuel injection to address the former issue.
 
Carbs not only cool the inlet charge, they had superior emulsification of the fuel into the inlet charge, they are also density/pressure sensitive, as altitude increases the air density obviously drops and a carb "self compensates" as the fuel pickup is directly relative to the volume, density and pressure of the air flowing through it! old mechanical injection had to have a compensating device which is only as good as its mechanical map allows!

Also throttle response is better with a carb, it took years and high tech electronics to get fuel injection to surpass carbs in this regard, the fuel injection used in the 40's was extremely crude, only in neg G did it have a clearcut advantage over a carb!
 

This may be true for car engines, but evidently not so for aircraft engines. The following is from a British trial report of a DB engined 109:

Throttle. – The throttle arrangements were described by one pilot as " marvellously simple, there just being one lever with no gate or over-ride to worry about ". It may be mentioned here that, while the pilots were not greatly impressed with the Me.109 as an aircraft, the D.B.601 direct injection engine came in for very favourable comment. The response to throttle opening is particularly good, it is apparently impossible to choke the engine, and there is no tendency to splutter and stop when the aircraft is subjected to a negative g by suddenly pushing the stick forward.

Its seems logical that the basis of comparison (response, choking, neg g comment) were contemporary carb RR engines.
 
No way, no how, no when, a carb is better then direct port injection. Even in 1940. On a carb engine with a supercharger, that air/fuel mix will be hot, turbulent, the fuel will tend to separate from the air mix, and the fuel will be leaner in the cylinders further from the carb. One won't get those problems with direct port injection. 30 year drag racer talking here.

For fun, look up the specs for the MECHANICAL fuel injection specs for the 1957 Chevrolet 283 The 1964 327 Chevrolet. Crude, rude, but got much better horsepower economy then there carbureted counterparts.
 

That "extreme conservatism" is why R-R were world leaders in helping to devise and adopt new high-strength high-temperature alloys, such as Hiduminium for their engines and that's why they adopted two-stage two-speed superchargers and intercoolers. And, of course, that conservatism meant that they didn't bypass direct injection in favour of adopting the Bendix-Stromberg direct injection system as soon as was practicable, because it was a better system than both carburettors or direct injection into the cylinders. (The Bendix Stromberg system was described by Flight in 1941: )

Carburettor, Injection or?
Carburettor, Injection or?

and here

Bendix-Stromberg pressure injection
1941 | 2102 | Flight Archive
1941 | 2103 | Flight Archive
1941 | 2104 | Flight Archive

To claim that Rolls-Royce didn't go with direct injection because of their supposed "extreme conservatism" is the usual simplification and myth making of the ignorant, similar to the claims about what a horribly complex aircraft the Spitfire was to build. Luftwaffephile always like to describe the problems with fuel starvation
choking, neg g comment)
Click to expand...
during the Battle of Britain but don't seem to recognise that relatively small engineering changes eliminated the problem, which was then bypassed completely when the Bendix Stromberg direct injection carburettor was adopted.
 
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Britain didn't have the support infrastructure (read sub-contractors) to make direct fuel injection units in the numbers needed.

On the Merlin XX engine the intake charge was cooled by 25 degrees C by the evaporation of fuel in the supercharger. Other models may show slightly different numbers.

In the early years of car racing fuel injection (1940s and 50s) could give more power but it tended to be less flexible. Poorer response at part throttle or near idle, not a consideration for racers but helped prevent normal non racing cars from going to it.

How much time does an aircraft engine spend at full or near full throttle compared to cruising?

They were different and each did have pluses and minuses. I am not sure which was better OVERALL at the TIME. What cars use 30-60 years later has next to NO bearing as most cars are not supercharged, the systems, both carburetor and fuel injection are not the same, manufacturing base (ability/cost to make) is not the same, engine performance goals are not the same (what pollution control on a 1940s aircraft engine????)
 
How many times does a aircraft change its speed in a non-combat/normal flight? I'm sure throttle response wasn't that big of a deal.
That Rochester Fuel Injection on those 283s 327s were archaic as compared to say the DB605 DPI. No pollution control on those Chevys,
And part throttle response was there. NOT saying WW2 DPI systems were perfect, but certainly better the carbs. I don't know enough about
the Merlin Bendix-Stromberg unit other then it gives continuous injection of fuel into the entry of the supercharger. I don't think I ever read of an account of pilots complaining about a lack of 'get up and go' with the DB series engines.

The only 'Pro' I seen with carbs are its simplicity. I've never seen temp drops on 25^c on a roots or centrifical supercharger without intercoolers.
Even the BEST carbureted engines today the mix settings etc are tempermental, nevermind if you use it on a supercharger. And that's with todays
tech.

So how does a single carb solve for the lean out conditions on the outmost cylinders? Manifold design helps, varying the ignition timing per cylinder also helps. That's at the cost of the more inboard cylinders running way to rich. With DPI, problem solved.

Anyways great conversation
 
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