Engine power increase via fuel injection: looking for some good info

[razor1uk]

I'm sure in the manuals section under engines or other aircraft systems, that there are pdf's about the servo-mechanical fuel injection system, certainly with regards the Jumo 211, if not the DB.

Both used a roughly similar fuel pressurisation/metering pump controller from Bosch, which used a mutlpie blended multi cam radiused control rod to proportion controls as desvised - fuel metering, ignition retard/advance, shifting the rod to input from barometric capsule (altitude fueling adjustment), and possibly IIRC supercharger oil pressure (clutch) control and part of the auto prop adjustment...

I think the one of the main differences of the 211 601/605 fuel control systems, was apart from the individual engine requirements of metering, fuel pressurisation ratios and timing etc, was that the Jumo's used Junkers injectors, wheres DB's the Bosch injectors.

The injector design I believe was akin to some todays electronic relay/sevo operated designs with partially shielded single (sparying) point/port injectors using much developed multi-cut/radiused like a racing valve and valve seat - to create a suitably atomised spray dropets. The sheilding of the valve was like the design of a racing surface e,lectrode spark plug - the injector poppet valve opening only inside and behind the specifically angled smaller spray port/orifice.

But this is all going on memory, mostyl gleened from this sites wealth of info... please correct as per actual

 

[rinkol]

There are some block diagrams in books such as Amazon.com: Flugmotoren und Strahltriebwerke (9783763761289): Kurt Grasmann Kyrill vo Helmut Schubert: Books

The German fuel injection systems were extremely sophisticated for the time. They had sensors for air temperature and presssure and produced a precisely metered amount of fuel for each power stroke.

 

[GregP]

I am familiar with mechanical fuel injection systems, but was simply not familiar with the DB system since I never worked on one. I HAVE worked on Allisons and Merlins.

One thing direct fuel injection WOULD do is to deliver the correct ixture to all cylinders ... IF you have an airflow sensor. If not, you get rch or lean depending on airflow, but it WOULD be better than an injection carburetor on average. Plus, it was immune to negative g-force. Not sure of the oil system was or if inverted flying was time-limited to some seconds, typically 15 - 25 on systems with inverted fuel but not oil systems.

 

[Denniss]

Permission to fly inverted depends on the engine oil system, at least te Jumo 211F was not designed for this although the manual permits acrobatic maneuvers even if they require short-time inverted flying.

 

[Shortround6]

The Junkers system was direct injection into each cylinder. The injector was screwed into the cylinder much like a spark plug. The injector pump plungers had a fixed stroke. The injector plunger head has an oblique groove that connects to a spill port and return line. By rotating the plunger more ( or less) fuel is returned instead of sent to the cylinder. All of the plungers are controlled at the same time by rack gears turning the injector plungers as a group. According to the drawings there doesn't appear to be any individual adjustment, either on the ground or in the air. The racks are moved by other gears connected to the throttle, a rich/weak control?, and a "capsule"( air pressure sensor) in the intake manifold.
The DB 601 system is described as being controlled by induction manifold pressure sensitive diaphragm, altitude pressure sensitive capsule stack, and induction temperature sensitive capsule.

 

[davparlr]

Permission to fly inverted depends on the engine oil system, at least te Jumo 211F was not designed for this although the manual permits acrobatic maneuvers even if they require short-time inverted flying.

And fuel system. Typically, negative g flying is quite limited in frequency and length, being almost instantaneous. It is very uncomfortable and the body cannot endure it for long.

 

[cherry blossom]

Sorry to resurrect an old thread but I find myself puzzled by two separate arguments.

Firstly:

1870PS = C3-injection used by Fw 190F/G JaBos and only permitted for low alts in the first supercharger gear. In mid 1944 all Fw 190 were available with erhöhte Notleistung without alt restriction, also available in the second supercharger gear. Power was increased to ~2000PS.
The fuel evaporation was use to cool the air prior to charging, somewhat similar to Water-Methanol injection.

and secondly:

...snip...

...
- elimination of backfiring problems..

That would be a major benefit. Engine like the Merlin used backfire screens over the inlet ports - which would definitely cause a pressure drop.

My problem is that I don't understand why it is not necessary to add backfire screens if you are injecting fuel into the supercharger.

 

[Aozora]

OK, Wuzak. Can you describe the system?

What sort of fuel controller did they have?No problem compressing the AIR ... but how was the fuel atomized and injected into individual cylinders?

Just curious, not trying to argue since I have never worked on a DB series inverted V-12. I assume fuel pressure and tube diameter determined the fuel flow along with the orifice / nozzle into the cylinder. It MUST have been adjustable or they could not have used multiple fuel grades.

From Flight 1942:

From a DB 605 A B Motoren-Handbuch:

Entire Flight Article:
View attachment Daimler-Benz DB601N Described 1942.pdf

 

[wiking85]

Aozora, could you post the entire DB605 manual in PDF form please? I've been looking for one for a while.

 

[Aozora]

Aozora, could you post the entire DB605 manual in PDF form please? I've been looking for one for a while.

It is a big file and it will have to be split into several sections; I don't have a lot of spare time to do so for at least the next week or so: an alternative is that you can buy it from where I bought mine: Daimler Benz Daimler Benz DB 605

 

[Koopernic]

This link is worth reading. It discusses the radical cam shaft tuning made possible by direct fuel injection.
Daimler-Benz

hint scroll down to the bottom of the page past the data sheets.


Note Daimler Benz 'tuned' the intake ports (variable induction).

Here are some photographs of the quite different variable displacement fuel injection pump for the BMW801.
BMW 801 Fuel Injection Pump - Part 3

 

[wiking85]

It is a big file and it will have to be split into several sections; I don't have a lot of spare time to do so for at least the next week or so: an alternative is that you can buy it from where I bought mine: Daimler Benz Daimler Benz DB 605

Thanks.

 

[Koopernic]

I recall reading that the Germans adopted fuel injection after BMW reported a 6% improvement in fuel economy by fitting fuel injection to a BMW VI engine (try searching on the web).

The WWII era literature differs as to the benefits of fuel injection. Heron criticised it on the grounds that it did not provide as much charge cooling as could be obtained with a carburettor (he noted that US tests of captured DB engines showed no increase in achievable boost/power when the engines were adjusted to run rich). This may have been why the arrangement of spraying additional fuel into the supercharger of the BMW 801 engine was used. On the other hand, direct fuel injection had some important benefits:

- reduction or elimination of problems with uneven air/fuel ratios (a major issue with early R-3350s - supposedly early versions of this engine that used fuel injection may have had reduced power, but had better reliability);
- elimination of the need for a carburetor choke (and the accompanying presure drop);
- elimination of backfiring problems.

The Soviets adopted the German technology on their later engines - presumably they found it worthwhile.

Modern automotive experience seems to favor direct fuel injection ("solid fuel injection" seems to be the current term).

I'm still not on top of all of these issues but it's noteworthy that in 1944 two separate boost systems were introduced on Fw 190A8 and F equipped with the 801D2 engine.

In one type of system the manifold pressure was simply raised about 10% at sea level from 1.42 atmospheres to 1.57 (in fact that boost was usually 1.68 as the engine quickly changed to second gear with the ratios then employed). I don't know if rich mixture was employed to prevent preignition to exploit the C3 fuels relatively high rich mixture response, I seems likely it was. This system continued to use the direct in cylinder injectors to add the fuel. The power increase came from the increased amount of air/fuel compressed into the cylinders due to the higher pressure. Exactly why this was possible would be likely a result of strengthened components in the engine, better fuels, better spark plugs, better lubricants. I'm not sure what the enablers were but it wasn't allowed in 1942 but was in 1944 (having been demonstrated in mid 1943)

The second system, which was initially seen only on ground attack variants of the Fw 190 instead added the fuel into the eye of the supercharger, thereby cooling the mixture, contracting it in volume, thereby inducing more air/fuel mix into the engine and also reducing supercharger work.

A similar system was added to the Jumo 213A of the Fw 190D-9 thereby increasing power from 1750 to 1900 metric horsepower, interestingly this system used the 87 octane grade B4 fuel.

In effect the Germans added a throttle body type injection carburetor for use only during WEP.

I imagine when engaged the fuel that was injected via the injectors was reduced to some low value, equal to engine idle, which the fuel flow was transferred and increased to injectors into the eye of the supercharger.

This sounds complicated but the key of any fuel injection system whether throttle body, plenum or direct injection is an mass air flow sensor since the basic requirement is to add 14 parts air to one part fuel by weight. Once this sensor is in existence it can be used to modulate the cam of any kind of pump whether it be a swashplate for central throttle body type or direct injection.

One way of doing this is to have a venturi in the intake to create a pressure difference and then used a pressure sensor (eg an aneroid capsule or a spring loaded piston) whose deflection is proportional to the air flow which is then used to operate a small hydraulic servo.

Famously the latter Merlin eliminated a venturi entirely to avoid the losses it might cause and calculated the air mass flow out of a combination of engine RPM, exhaust back pressure (essentially ambient), throttle valve position and temperature. It is possible the German engines used a similar concept as I have never seen an airflow sensor for these systems. I would have been foolish not to copy this elegant system which would be readily adaptable.

Allied engineers then were, to an extent, right in avoiding direct injection. Nevertheless the Germans still benefited. Direct injection allows a more radical profiling of intake/exhaust valve overlap for more complete scavenging without fear of sweeping out perfectly usable fuel. It allows slightly more fresh air to be drawn in and gets rid of end gasses that can cause pre-ignition. When using rich mixture injection to obtain WEP this possible extra loss of fuel in the scavenge compared to allied engines was probably considered tolerable. These engines seem to have had very good high speed cruise characteristics and fuel efficiency so there was a benefit. Also the Germans, like the Soviets, wanted to avoid the problems of strictly controlling the vaporization characteristics of their fuels. I imagine starting an engine in a Russian winter may not have been to easy either.

One other factor is that British and American companies controlled all of the good carburetor patents which provided an incentive to the Germans to avoid Royalty patents and to exploit their high speed diesel injection technology.

Ultimately the German direct injection engines headed in the direction of water injection to obtain charge precooling. Water injection was added to the BMW 801TS around Dec 44/Jan 45 and the Jumo 213A of the Fw 190D9 perhaps a month earlier as a field modification. The motivation was at least partially that this was more fuel efficient. Every liter was scrupulously accounted for.

The attraction of rich mixture injection was that it didn't require the inconvenience of a water tank and its C of G issues and additional plumbing and seems to have been less aggressive on the engine. It took a while to solve the C of G issues an MW50 tank created. The idea in German aircraft seem to have been to add a 115L (25 gallon) multipurpose tank in the Fw 190 and Me 109 that could be used for MW50, extra fuel or GM-1 as required though in reality few if any were plumbed so as to allow this multi purpose mission.

The ADI water tank in the P-47 was only a tiny 15 gallons and couldn't have lasted long.

The DB605 received MW-50 in April 1944 (in Me 109 squadron missions) in the form of the DB605AM and DB605ASM used on Me 109G6AM and Me 109G6ASM. They never used rich mixture injection.

I do not know if water injection was used in parallel or instead of supercharger fuel injection it seems they could complement each other.

German engines seem to have been held back by lubrication issues.

Having looked around it seems to me that non of the German fuel injected engines bothered with an airflow sensor. The pumps and injectors was linked to crankshaft speed mechanically. Air pressure and temperature would estimate air density while throttle valve position would provide air flow.

 

[tomo pauk]

...
In one type of system the manifold pressure was simply raised about 10% at sea level from 1.42 atmospheres to 1.57 (in fact that boost was usually 1.68 as the engine quickly changed to second gear with the ratios then employed). I don't know if rich mixture was employed to prevent preignition to exploit the C3 fuels relatively high rich mixture response, I seems likely it was. This system continued to use the direct in cylinder injectors to add the fuel. The power increase came from the increased amount of air/fuel compressed into the cylinders due to the higher pressure. Exactly why this was possible would be likely a result of strengthened components in the engine, better fuels, better spark plugs, better lubricants. I'm not sure what the enablers were but it wasn't allowed in 1942 but was in 1944 (having been demonstrated in mid 1943)

BMW just managed to sort out the 801D by October 1942 to run reliably at 1.42 ata and 2700 RPM. The increased compression ratio (7.22:1) vs. the 801C (6.5:1) was not overly conductive to high boost, though it gave better altitude performance on same RPM.

A similar system was added to the Jumo 213A of the Fw 190D-9 thereby increasing power from 1750 to 1900 metric horsepower, interestingly this system used the 87 octane grade B4 fuel.

Interesting - I knew that two sub-versions of the 213-A were around. Any good on-line source that covers those obscure details?

Allied engineers then were, to an extent, right in avoiding direct injection. Nevertheless the Germans still benefited. Direct injection allows a more radical profiling of intake/exhaust valve overlap for more complete scavenging without fear of sweeping out perfectly usable fuel. It allows slightly more fresh air to be drawn in and gets rid of end gasses that can cause pre-ignition. When using rich mixture injection to obtain WEP this possible extra loss of fuel in the scavenge compared to allied engines was probably considered tolerable. These engines seem to have had very good high speed cruise characteristics and fuel efficiency so there was a benefit. Also the Germans, like the Soviets, wanted to avoid the problems of strictly controlling the vaporization characteristics of their fuels. I imagine starting an engine in a Russian winter may not have been to easy either.

Direct-injected engines, like the ones produced by Germany, were having better specific fuel consumption than comparable 'carburated' engines. Injection also avoided the state when some cylinders need to be run a with a bit more fuel, so other cylinders can have an enough rich mixture.

One other factor is that British and American companies controlled all of the good carburetor patents which provided an incentive to the Germans to avoid Royalty patents and to exploit their high speed diesel injection technology.

Interesting, to say at least.

Ultimately the German direct injection engines headed in the direction of water injection to obtain charge precooling. Water injection was added to the BMW 801TS around Dec 44/Jan 45 and the Jumo 213A of the Fw 190D9 perhaps a month earlier as a field modification. The motivation was at least partially that this was more fuel efficient. Every liter was scrupulously accounted for.

I'd like again to point out that there is about zero evidence that BMW-801 was ever using MW-50. I'd bow to a superior (= well backed up) information, of course.

The ADI water tank in the P-47 was only a tiny 15 gallons and couldn't have lasted long.

Prior the P-47D-25 (also known as bubble top) it was indeed 15 gals of water/alcohol mix, from D-25 it was increased to 30 gals.

The DB605 received MW-50 in April 1944 (in Me 109 squadron missions) in the form of the DB605AM and DB605ASM used on Me 109G6AM and Me 109G6ASM. They never used rich mixture injection.

Not needed with MW-50 anyway?

I do not know if water injection was used in parallel or instead of supercharger fuel injection it seems they could complement each other.

DB-605 never had a fuel injection into the supercharger, it was a direct (= in cylinders) injection. MW-50 mixture was injected in the S/C, IIRC.

German engines seem to have been held back by lubrication issues.

Oil foaming in the DB-605A, due to too tight installation and not enough of oil cooling, at least on the Bf-109?

 

[Koopernic]

BMW just managed to sort

Oil foaming in the DB-605A, due to too tight installation and not enough of oil cooling, at least on the Bf-109?

It was related to the oil pump and a very high system oil pressure. At high altitudes the oil would foam. An oil de-aerator was fitted as a solution when the problem was finally identified. One change between the DB601 and DB605 was the replacement of roller bearings with journal bearings and this probably drove the introduction of a higher oil pressure and this bug.

BMW801 lubrication problem was cased by an unauthorized lubrication specification change, postulated by some as one of the most effective acts of espionage ever (if it was espionage rather than bungling).

Pratt Whitney regarded their 'secret' as indium coating of the bearings, they seem to think that the Germans never worked out their advantage. As soon as you loose that micron thick oil film your engine is dead in minutes.

BMW801 was released for MW50 in December 44 and again Jan 45. Whether that was a release on paper or a real introduction. My understanding is that it was in use by the time of the Ardene Offensive. The tanks were certainly in place but seemingly being used as a supplementary fuel tank.

 

[tomo pauk]

I won't goo too much into espionage or sabotage re. 801D; one of the cures was the change in spark plugs' type, for example.

Focke Wulf charts and tables available at Williams' site always state the increse in fuel tankage for the A-8 and A-9 (vs. A-7), never the presence of MW-50 mixture. Again, I'm calling for someone capable to bring out the good data that would really prove the service use of the MW-50 on BMW-801.

 

[GregP]

Hi Cherry Blossom,

About the backfire screens ... if you have the correct mixture in the chamber, you don't get a backfire ever.

Backfires are a result of excessive fuel mixture and fuel injection would eliminate this condition ... assuming it is working.

I recall VERY clearly when I got a Kawasaki GPZ 1100 with fuel injection. It had no choke since only the correct mixture was injected. As a direct result, you couldn't tell when the engine was warm or cold without feeling the temperature with your hand. That made it mandatory to carefully warm up the engine before harsh acceleration or excessive wear would occur.

Altogether a great motorcycle and it convinced me tat fuel injection was the best option ever for mixture.

No more Amal carbs ... unless FI was not available for your selected sport, like Observed Trials. They ALL had carbs. The trick was to choose the right carb.

 

[Stuttgarter]

The air-fuel mixture is done by the Bosch injection pump completely.

Please see http://ww2aircraft.net/forum/engines/daimler-benz-601-amp-603-aircraft-engine-manuals-38202-post1226983.html#post1226983
Thank you Augsburg Eagle for die Lehrbildreihe DB 603 613.

Please read http://ww2aircraft.net/forum/engines/daimler-benz-601-amp-603-aircraft-engine-manuals-38202.html#post1048274
Thank you mikec1 for das Motorhandbuch DB 603 die Wartungsvorschrift DB 601.

The pump and the fuel injectors of the engine DB601 are similar to those of a Mercedes 6-cylinder engine M198 which was used for the 300SL built from 1954 to 1963.

If its pump needs to be overhauled that would cost you about 20.000 Euros but that corresponds to the 1M value of the car.

The pump measures rpm by centrifugal force, air temperature outside, coolant or oil temperature, air pressure outside and maybe even air pressure and air temperature inside of the manifold.

This is a simple 6 cylinder pump of that time:

It even uses a physical map (Raumnocken), today these maps are digital.

This is a Bosch PES 6 KL pump for a newer 280SL:

Search for Bosch PES MW or Bosch PES 6 KL or Bosch Stempelpumpe Fliehkraftregler.

PES 6 KL dismatled:

Centrifugal regulator for idle speed and speed limiting,
I could not locate that part in any of the DB601 injector pump pics:

I did not find any idle speed adjustment for the DB601.
How is it done ?
Regulating centrifugal wheights of the speed limiter:

Pmeumatic regulator:

Here is the regulator of an injection pump for the DB603:

This seems to be the injection map (Kurvenscheibe):

Since 1973 regulators are replaced with simpler but more accurate mass air flow meters (MAF) first used by Bosch in their K-Jetronic.

Hi Cherry Blossom,

About the backfire screens

 

[Stuttgarter]

You find the fuel injection pump in the lower middle with 12 fuel connectors.
It is upside down as everything:

The pump is located between the cylinder banks.
Here is to see that the fuel is injected into the combustion chamber.
The fuel pressure was lower than it is in injection systems of today.
Hence fuel could be injected only during intake stroke, not during compression stroke:

Spur gear device driver and upright shaft to the camshaft of DB601:

 

[Stuttgarter]

It is still a piece of high tech, die DB601 Einspritzanlage:

DB603 Einspritzanlage cut-open view: