Water injection in Daimler Benz engines on Messerschmitt aircraft

Some explanations on the supercharging and the injection of water or peroxides of Daimler Benz on the planes of the 2nd World War.

Keywords: engine, aircraft, Luftwaffe, overeating, limits, ceiling, injection water, octane, compression rate, improve, Merlin

The Daimler-Benz DB engine 605

In this section:
1) Introduction

2) A quick technical basic principles of DB 605:
- the basic concept and its performance
- the overfeed system

3) Chart performance and comments on the derived types: DB605A-, AM, AS, ASM, ASC, D, D-2, DB and DC.

4) Comparison with the Merlin engine two-stage compressor, direct rival DB 605


The Daimler-Benz DB 605 engine was an improvement of the famous DB 601 and served on the same aircraft as the latter: the Messerschmitt BF 109 and BF 110. The 605 version was used from 1942, it gave more power to airplanes, allowing to climb to a higher altitude and with an increased load capacity. Like the Me 109, the DB 605 proved indispensable throughout the war. It was gradually improved in order to remain competitive and, fortunately for the Luftwaffe, it had good development potential, although its reliability suffered a bit. War always required more power and better performance at altitude. The DB 605 was able to meet these constraints by using a fuel with a higher octane power, resulting in better compression ratios, more power during acceleration, better overfeeding and injecting a non-explosive mixture of water-methanol or peroxides. Thus, the final defeat of the Luftwaffe in 1944 can not be blamed on a failure of the engine.
Unfortunately (from the Germans' point of view), the most efficient versions were put into service in 1944 on too "large" aircraft when gasoline was already lacking, and especially piloted by inexperienced beginners. They were completely crushed by the Allied forces.

The basic technical principles of DB 605

The 12 degree V-60 upside down, pressure cooling - bore: 154mm, stroke: 160mm, total displacement: 35.7 liters - compression ratio: 7.5 / 7.3 (87 octane), 8.5 / 8.3 (96 index) b - length: 2303mm, height: 1050mm, width: 762-845mm - dry weight: 730-745 kg, assembled weight: 764-815 kg - 4 valves per cylinder, 1 overhanging camshaft - direct injection - mechanical compressor with variable speed (single stage) with a hydraulic clutch which adapted to barometric pressures linked to altitude (the DB 605L had a 2 stage compressor) - Engine speed: max 2800, uphill: 2600, maximum cruise: 2300 - performance: 1435-2000 hp (altitude 0) - altitude evaluated in climbing conditions: 5.8 - 8 km (except again the DB 605L) - several versions were equipped for system use MW-50 or 1-GM

The system of on-feed ..

Compared to engines with turbo compressor or two-storey and two-speeds of the Allied forces, developed by Daimler-Benz DB 605-a-floor is outstanding.

For comparison, the two-stage Merlin engines rose at an altitude of at 5.8 7.9 km. In 1944 altitude battles, the performance of the DB 605 rivaled those of Merlins series 60 and 70, Spitfire and Mustang.

While conventional mechanical on-feeders consisted of one or two compressors controlled by a transmission in two floor, Daimler-Benz used an ingenious hydraulic clutch adapted to barometric pressure changes which adjusted the speed of the compressor and consequently the engine supply the needs of the current altitude.

The conventional method induces a relative loss of efficiency as long as the aircraft has not reached its cruising altitude because the compressor uses energy for supercharging. A graphical representation of the efficiency of this type of engine according to the altitude of the aircraft would show a "sawtooth" line: the efficiency in first gear would increase with altitude to the ideal altitude for that speed, then the output would drop until the second gear engages and the output increases again to the ideal altitude. The Daimler-Benz system is more flexible. The graphical representation will show a smooth curve.

Chart performance and comments.

Click to enlarge

Source: Mercedes-Benz AG, Archives, Stuttgart, Germany. * = The DB 605D did not enter service before the spring of 1944 with the Me 109G-10.


Subcategories Me 109 were delivered with the following engines:
-Me 109g-up G1 4: 605-DB 1A
-Me 109G-5 / 6 G-DB-605A 1, AM, AS, ASM (ASB, ASC?)
-Me 109G-8: 605-DB 1A AM
-Me 109G-14: 605-DB 1A, AM, AS, ASM (ASB, ASC?)
-Me 109G-10: DB 605D, (D-2?) DB, DC
-Me 109K-4: DB 605dc, ASC

As the table shows, the different subcategories gave very variable results. Thus, the performance of the Me-109G 6 varied enormously since this model was equipped with many engines installed upon availability of the moment. The DB-605A 1 was still used at the end of the war.

About the MW-50

MW-50 (water / methanol 50/50) was injected through the air intake and served as an anti-detonator, allowing more thrust below the ideal altitude. Evaporation of the water also cooled the feed air, increasing the weight of the feed.

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Limited by over-supply system, the MW-induced 50 as maximum yield began to decline in 1.5 - 2 km below the ideal altitude, becoming inactive above this altitude (compare eg DB 605A -1 and AM).

Maximum usage time: 5 10 in minutes.

Constraints: shortened flight endurance and spark plug life, additional weight of MW-50 tank and lines. Most of the 109/1944 Me 45 subcategories were equipped for MW-50 use.

About GM-1.

Another way to increase the performance was the GM-1 (Göring Mischung 1).

It consisted in injecting nitrogen dioxide (nitro) in the on-feeder above the ideal engine altitude.

Nitrogen oxide served as an oxygen “carrier” to increase efficiency at high altitudes (the use of pure oxygen being too volatile).

The effect was phenomenal, instantly increasing the power of 25 - 30%.

GM-1 was used by the flight of groups specialized in high altitudes from 1941. Volume and excess weight were the main constraints of this system and the additional over-feeding was generally seen as more efficient.

Comparison with Merlin 2-floors.

We do not present here scorecards Merlin engines because we lack precise data (our sources ( "Allied aircraft piston machines" Graham White and "Jane's fighting aircraft of world war II")

Considering the Merlin's age of design and the few upgrades it received, this two-stage engine was a superb machine. Compared to German engines, the Merlin was lighter thanks to the relatively abundant use of light alloys.

When comparing the returns, we must bear in mind that the Allies were well supplied with high octane gasolines indices (100 / 130 / 150). The Germans had to settle with 87 indices 92 or 96, the highest indices species are extremely rare.

Merlin 60 series were commissioned at the end of the summer 1942, in perhaps around the same time that the DB-605A 1. The performance of Merlin 60 high altitude were higher than those of DB-605A 1. This superiority lasted until 1944 when subcategories AS and D went into service. These equalized and exceeded the performance of high altitude Merlin (Rolls-Royce and Packard), with the exception perhaps of Mark 70. But when the GM-1 went into action, the advantage was definitely DB 605.

The 605 DB had good performance at low altitude, especially at sea level (see paragraph on over-supply systems). From this point of view, the DB-605A 1 was superior to Mark 61, 63, 66 and 68 Merlins. The superiority of the last DB 605 at low and medium altitudes was very clear when they used the MW50: Methanol / Water 50 (versions AM, ASM or high octane and GM1 (DB versions, ASB) or high octane and GM1 and 50-MW (DC versions, ASC).

Appreciation of a partnership: 605 DB mounted 109G Me and K

The arrival of Me 109 G coincided at nearly with the position of turning to the Germans: the Allied offensive in Africa and Stalingrad. The Luftwaffe was facing a vast numerical superiority, aircraft and enemy pilots were becoming more powerful and soon came the Götterdämmerung in defense of the territory of the Reich, which deprived the Luftwaffe of its men, equipment and fuel.

If there is a symbolism in this, we will not move forward. But much has been written on hatred carried to G (Gustav) - a bit of blisters everywhere destroying aerodynamics and appearance of this aircraft, it was heavy and difficult to maneuver, a step backwards compared to the sub- class F. However, many of the biggest "Experten" killed a majority of enemies Gustav.

The Me 109G was, like previous models, a very good interceptor during combat. It was equipped with characteristics for low-speed flight, a high ceiling and light equipment to ensure a very good, even phenomenal ascent, rapid acceleration in level flight and the ability to make sustained maneuvers. . The normal armament, although relatively light, was extremely precise due to the central position of all the guns.

In short, it was a good fighter and classic.

The increased weight of course with the introduction of more powerful, heavier engines, which required strengthening of the structure and the old easy handling suffers a little.

Although comparable to the new Allied planes in terms of speed, climb and altitude ceiling, it was during the battles of 1943-1945 (against the day bombers and their escorts) that the imperfections in the design of these interceptors dating from the mid-30s.

Equipped like a bombarder with two 2 mm cannons under the wings, the Me-Gustav became difficult to use. This along with the fact that the high altitude performance was much better than that of the FW 20, the Gustav initially gained the upper hand over the Allied escorts. These air battles took place at high altitude and high speed, and at these speeds the control of the Gustav was very difficult (due to the force feedback on the controls: the sensitivity and effectiveness of the controls were almost zero as well as the directional stability. )

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With the loss of his Maneouverability the Gustav became a mediocre interceptor and being a lightweight fighter, the Gustav could not concurencer new American hunters.

Original version :

The Daimler-Benz DB 605

List of happy.
1) Introduction
2) A short note on the basic technical aspects of the DB 605
-Basic layout and performance
-the supercharging system.
3) Focusing on the single-engine applications of this engine, performance charts and commented-ries on the sub-type Following are presented:
-DB 605A-1, AM, AS, ASM, ASB, ASC, D, D-2, DB and DC.
4) Comparison with the two-stage Merlin engines - the direct rival of the DB 605. 5) Appraisal of a partnership: the DB 605 powered Me 109G and K.


The Daimler-Benz DB 605 engine was an up-bore faster running development of the famed DB 601 and served the same main aircraft types as its predecessor: the Messerschmitt bf 109 and bf 110. Introduced in 1942 it presented the fighters with more basic power , better altitude performance - and higher weight. As the Me 109 remained a mainstay throughout the war - so did the DB 605. It was progressively developed to stay competitive, and luckily for the Luftwaffe it had good develop-ment potential, although reliability suffered somewhat. The war demanded ever more power and - in the west - still better altitude performance, and that challenge was met by the DB 605 through the use of higher grade fuel, higher compression ratios, higher boost pressures, better supercharging, and injection of anti- detonant water-methanol and oxygen carrier nitrous-oxide. As it turned out, the final demise of the Luftwaffe fighter force in 1944 can hardly be blamed on this the primary fighter engine of the Luftwaffe. Sadly from a Luftwaffe point of view, when the fine high-power, high-altitude versions came into service during 1944 they were put to use in an overstretched airframe piloted by inexperienced rookies, who starved of fuel were completely overwhelmed by superior allied forces.

Basic technical aspects of the DB 605.

(This description and the following performance tables will be using metric measurements.) - 60 degrees inverted V-12, pressure-cooled - bore: 154 mm, stroke: 160 mm, total volume: 35,7 liters - compression ratio: 7.5 / 7.3 (87 octane), 8.5 / 8.3 (96 octane) - length: 2303 mm, height: 1050 mm, width: 762-845 mm - dry weight: 730 - 745 kg, built-in weight: 764 - 815 kg - 4 valves per cylinder, 1 overhung camshaft - direct fuel injection - single-stage variable speed mechanical compressor driven via a barometricly controlled hydraulic clutch (the DB 605L had a two-stage compressor) - rpm: max. 2800, climb: 2600, max. cruise: 2300 - performance: 1435 - 2000 hp at sea level - rated altitude in climbing condition: 5.8 - 8 km (again excluding DB 605L). - several versions ecquipped to use MW-50 or GM-1

A note on the supercharging system.

Compared to the two-stage two-speed and turbo-charged engines of the western powers it is im-pressive what Daimler-Benz could achieve with the single-stage DB 605. By comparison the two-stage Merlin engines had a rated altitude ranging from approx. 5.8 km to 7.9 km. At the combat al-titudes of 1944 the performance of the DB 605 rivalled that of the high altitude Merlins 60 and 70 series of the Spitfire and the Mustang. While the conventionel mechanical superchargers consisted of one or two compressors driven via a two-speed gear, Daimler-Benz utilised an ingenious barometricly controlled hydraulic clutch which adjusted the compressor speed and thus the charging of the engine according to the needs at a given altitude. The conventional method results in a relative loss in efficiency below rated altitude, because the compressor uses energy to produce surplus charging. A graphic presentation of engine output relative to altitude would show a "saw-touth" line: the output in low gear rising with altitude until reaching the rated altitude, then output falls until the high gear kicks in, when the output again rises the rated altitude is reached. In comparison the Daimler-Benz system is more flexible. A graphic presentation would show a smooth shallow curve. A source of efficiency loss with this system being progressive heating of the oil as pressure in the clutch builds with altitude.

Performance charts with comments

Source: Mercedes-Benz AG, Archives, Stuttgart, Germany. * = The DB 605D didn't enter service until spring of 1944 with the advent of the Me 109G-10.


The Me 109 sub-type Were Delivered with The Following power trains:

Me 109G-1 4 through G-DB-605 1A

Me 109G-5 / 6 G-DB-605A 1, AM, AS, ASM (ASB, ASC?)

Me 109G-8: 605-DB 1A, AM, (others?)

Me 109G-14: 605-DB 1A, AM, AS, ASM (ASB, ASC?)

Me 109G-10: DB 605D, (D-2?), DB, DC

Me 109K-4: DB 605DC, ASC (others?).

As the table shows, the different sub-type gave very different performance, the performance of the THUS Me 109G-6 varied a lot as this model Was powered by a whole ranks of engines DEPENDING ON availoability. The DB-605 1A Was still installed to the very end of the war.

A note on MW-50.

MW-50 (water-methanol 50 / 50) Was injected into the air-intake and served as an anti-detonant ALLOWING Higher boost to be used below normal rated altitude. The evaporating water aussi cooling load the air THUS Increasing the weight of the load. Limited by the performance of the supercharger the MW-induced 50 max. Declining output Began 1.5-2 km. below normal rated altitude up to it est devenu impotent at and above the normal rated altitude (compare for example DB 605A-1 and AM). Max. continous use: 5-10 minutes. Penalties: drasticly shortens flight endurance and spark-plug life, added weight of MW-50 tank and piping. Most sub-type Me 109 from 1944 / 45 Were equiped to use MW-50.

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A note on GM-1.

Another moyen de Improving the performance Was GM-1 (Göring Mischung 1). In short the system Worked by injecting nitrous oxide into the supercharger Above normal rated altitude of the engine. The nitrous oxide serving as an oxygen carrier to Improve the output at high altitude (pure oxygen prooving too volatile). The effect Was phenomenal, raising output 25-30% Instantly. GM-1 Was used by dedicated high altitude training from 1941 onwards. Excessive bulk and weight Were major penalities though, and additional supercharging Was Generally seen to be more efficient.

Comparison with two-stage Merlins.

I shall not present performance charts for the Merlin engines here, partly to limit the size of this page, and partly because I lack detailed data (my sources are: "Allied aircraft piston engines" by Graham White and "Jane's fighting aircraft of world war II ”).

Taking into account the age of the Merlin Design and Its relative small displacement this two-stage inter- and aftercooled engine Was a superb maschine. In comparison with the german engines Merlin Was the lighter due to the relative abundance of metals for making light alloys. When Comparing outputs one shoulds bear in mind aussi que la allies well Were Supplied with high grade fuels (100 / 130 / 150 octane). The germans Had to make do with 87, 92 or 96 octane, the higher grade fuels Being Especially scarce. ADI Was used by Both Sides in the later stges of the war.

The Merlin series 60 Were put into service in the late summer of 1942, around the time même que le-DB 605A 1 Went into service. The high altitude performance the Merlin series 60 Was superior to the DB-605A 1. This superiority Lasted into 1944 When the new AS and D sub-type Went into service. These late sub standard equaled or bested the high altitude performance of the Merlins (Rolls-Royce and Packard) Perhaps with the exception of the Mark 70. When GM-1 Was used the picture changed Thoroughly in favor of the DB 605.

The DB 605 basicly gave good low altitude performance, especially at sea level (read the discussion of the supercharging systems). In this regard the DB 605A-1 was superior to the Mark 61, 63, 66 and 68 Merlins. The superiority of the late mark DB 605's at low and medium altitude was very pronounced when using MW-50 (AM, ASM), high octane and high boost (DB, ASB), high octane high boost and MW-50 (DC, ASC ).

Appraisal of a partnership: the DB 605 powered 109G Me and K.

The advent of the Me 109G coincided, Roughly Speaking, with the irreversible shift in the fortunes of war for the germans: the allied offensive in Africa and Stalingrad. The Luftwaffe Confronted has vast numerical superiority and Increasing allied, enemy planes and pilots Were of increasingly better quality, and soon the cam Götterdämmerung home in defense of the Reich, the Luftwaffe qui bleeded of men, material and fuel.

Whether there is any symbolism in that, I shall leave unspoken. But a lot has been written about how the Gustav was loathed - blisters everywere destroyed the aerodynamics and looks of the plane, it was heavy and unresponsive, a retrostep compared to the F sub-type. Still many of the greatest Experten tallied the majority of their kills in the Gustav.

The Me 109G WAS, you Were The Earlier models, a very able fighter interceptor in vs. fighter combat. It was endowed with fine low-speed flight characteristics, a high ceiling, and It was lightly loaded THUS Ensuring a very good-even gold phenomenal climb, fast acceleration in level flight, and the Ability to perform sustained maneouvering. The normal armament ALTHOUGH Relatively light Was deadly accurate due to the central positioning of all guns. In short It was a classic dogfighter.

Weight of course escalated with the installment of stronger and Heavier engines, qui again necessitated structural Strengthening, and the ease of handling old to Suffered Some degree.

Although keeping up with the new allied fighters in terms of speed, climb and ceiling, it was in the fighting of 1943-45 against the US day bombers and their escorts, that the shortcomings of the mid-30's vintage interceptor were to show themselves. Equipped as a bomber destroyer with two underwing 20 mm cannons the Gustav became very unwieldy. As a result of this and the fact that the high altitude performance was much better than that of the Fw 190, the Gustav primarily took on the american and british escort fighters. These air battles took place at high altitude and very high speed, and at these speeds the control forces of the Gustav grew very heavy, the responsiveness and effectiveness of the control surfaces became very poor as did directional stability. Maneouverability was lost and the Gustav became a poor gun platform. Being a light interceptor the Gustav could not compete in dives with the new american fighters.

These Shortcomings shoulds not be overstressed though. The real horror of the air battles over Germany Was the downright impossible for tactical situation Where the overstretched Luftwaffe Had to face Overwhelming numbers of well trained, well equipped and aggressive allied force

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