R-2600 powered fighter?

Shortround6 said:

Not much of world beater. The Mustang was about a ton heavier than a 1941 109. Powered by the same engine it would have been in trouble. Good aerodynamics only gets you so far. A power to weight ratio 33% worse than your opponent is a big handicap.

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How is that? The P-51A had 1,150hp Allison and made 390mph, IIRC at 18,000ft. With a DB601 she would still not have the vertical mobility of a 109 but she´d be the best US-made fighter by a large margin. And if the Me109F can make 418mph@21,000ft, the heavier but laminar flow wing Mustang would hardly be slower.

Markus said:

How is that? The P-51A had 1,150hp Allison and made 390mph, IIRC at 18,000ft. With a DB601 she would still not have the vertical mobility of a 109 but she´d be the best US-made fighter by a large margin. And if the Me109F can make 418mph@21,000ft, the heavier but laminar flow wing Mustang would hardly be slower.

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Straight line speed is not the sole factor in which fighter was better. I am not a real fan of the 109 but hauling around 33% more weight is going to need some very, very good aerodynamics to overcome.

Which DB 601 are we talking about?
There are several candidates.

Which Allison powered mustang are we talking about?
Again there are several versions. For this comparison although different in time it might be best to use the numbers from the later version Allison which, although rated at 1200hp for take off did offer 1125HP at 15,500 ft if I recall correctly.

Compared to the DB601N of 1175PS at 4900meters it should be fairly close (only 4-5% behind) in power unless you are referring to the 601E?

Claiming a plane would be the best US fighter in 1941 is one thing, claiming that such a plane is a "world beater" is another.

Shortround6 said:

Which DB 601 are we talking about?

Claiming a plane would be the best US fighter in 1941 is one thing, claiming that such a plane is a "world beater" is another.

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The DB601E, 1,320hp at 16,000ft vs. the V-1710-81 with 1125hp at 14,600. And the 601E ran on 87 octane fuel. An "american" DB601 would get the good stuff with 100 octane and thus also generate more hp. Taking all that into consideration, such a Mustang might be a P-51 C/D equivalent.

Markus said:

The DB601E, 1,320hp at 16,000ft vs. the V-1710-81 with 1125hp at 14,600. And the 601E ran on 87 octane fuel. An "american" DB601 would get the good stuff with 100 octane and thus also generate more hp. Taking all that into consideration, such a Mustang might be a P-51 C/D equivalent.

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The Allison -81 was 1125 at 15,500 I believe.

There may be a question as to just how much you can "Boost" a 601, as much due to structural strength as much as to detonation limits.

Higher octane fuels only boost power at lower levels for an EXISTING engine where the supercharger can provide more boost. Once you are above full throttle height the supercharger cannot provide any more air or boost and higher manifold pressures are not available. Without higher manifold boost all the octane rating or performance number changes won't do a thing for power output. When British fighters got 100 octane fuel in BoB it did nothing for their performance over 17,000ft. While they were cleared to use 12lb of boost the supercharger could only deliver 6lb of boost at that altitude. Performance did increase the lower the planes flew as the boost went up to the 12lb limit at which point performance was limited by either cooling problems or structural limits of the engine.

For a power graph of the 601 E see:
Daimler-Benz

Note that at 7000 meters it is down to about 1000hp. While this is much better than an Allison would show it is nowhere near what the Merlins in a P-51B/C/D have available is it?

Or for a German source see:

Beim-Zeugmeister: Seite 13 - Kennlinien DB 601 E

Please note the downward slope to the left of the charts from about 2000meters to sea level. Many engine charts will show this decrease in low level power. It comes from flow losses in throttling the engine back and higher induction temperatures. The engines have to be throttled back because they will not stand full throttle operation at the low altitudes. The engine will make more power than the engine can withstand.

The 1941 Spitfires and 109s gained a good part of their high altitude performance from their power to weight ratios.
As for being a world beater in 1941 you not only need straight line speed but climb and here the old Spitfire MK V might be a competitor. A draggy airframe but with it's Merlin 45 offering up to 1230 hp at 18,000ft or a Merlin 46 offering 1190hp at 23,000ft. it might be able to show a DB engined Mustang a thing or two at 25,000-30,000ft.

Shortround6 said:

Not much of world beater. The Mustang was about a ton heavier than a 1941 109. Powered by the same engine it would have been in trouble.

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No. No contemporary P-51 could outclimb 109. Does that mean that the P-51D was inferior to Bf109G-6 ?
Having a superior level and diving speed gives you the chance to enter and exit combat at will.
German pilots did not have this luxury in 1944.
Even that was not the most important thing I had in mind. It was the range, the sheer fuel capacity. The capability to combat 750 miles from your base.
As this this offtopic i don't comment this further.

Your obsession with the "forged steel crankcase" is a bit funny. As I have said, this is is a "what-if" scenario, not "what was". In market economy , the production will be adjusted to the demand pretty quickly. Mind you, this is not with the war time constraints, but in US peacetime in 1940-1941. If you claim that the Wright would not have to been able to meet the increased demand, I would like to see some proof.

Timppa said:

No. No contemporary P-51 could outclimb 109. Does that mean that the P-51D was inferior to Bf109G-6 ?

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Which engine are you using for the 109G-6?
If it is the standard 605A it only proves the point. The Mustang's Merlin had several hundred more HP than the 109G-6 at the higher altitudes and still couldn't climb as well. Putting the same engine in the much heavier Mustang would make things worse.

Timppa said:

Having a superior level and diving speed gives you the chance to enter and exit combat at will.
German pilots did not have this luxury in 1944.

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Having a superior dive speed helps with fighter survival and chasing down escaping planes but it doesn't really do much for bomber escort or repeat firing passes on bomber interception. A world beating fighter should be making the other fellow dive away.

Timppa said:

Even that was not the most important thing I had in mind. It was the range, the sheer fuel capacity. The capability to combat 750 miles from your base.

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That DB 601 must have been a wonderful engine. Allison powered Mustangs didn't use drop tanks for quite a while and didn't have rear fuselage tanks. Their range was usually given as around 1100-1200miles at most economical cruise and without combat allowance. Better than many other 1941 fighters but not the numbers you are giving out.

Timppa said:

Your obsession with the "forged steel crankcase" is a bit funny. As I have said, this is is a "what-if" scenario, not "what was". In market economy , the production will be adjusted to the demand pretty quickly. Mind you, this is not with the war time constraints, but in US peacetime in 1940-1941. If you claim that the Wright would not have to been able to meet the increased demand, I would like to see some proof.

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You seem to have a funny idea of the US "peacetime" economy or industrial situation in 1940-41. Especially in relation to aircraft and aircraft engine production. President Roosevelt had announced a goal of a 50,000 plane air force in 1940. This was in addition to French and British orders. P&W had quadrupled their floor space from 1938 to 1940 and were still adding on to the Main plant, buying and building new plants in Connecticut and licencing manufacture of engines to other companies. Ford broke Ground on a new factory just for R-2800s in sept of 1940 that was the size of the P&W Main Plant. Packard, Allison and Wright all constructed new factories during this time.
The new Wright facility in Cincinnati was the largest aircraft engine plant in the world (or at least the west) when it opened. It delivered 6 engines in June of 1941, followed by 12 in July, 22 in August, 17 in Sept, 45 in October and then began to hit it's stride with 135 in November and 206 in December. In 1944 this plant with further additions to the structure would average over 2,000 engines a month.
Measured in HP delivered and not engines, the American Aircraft engine industry more than tripled it's output from the beginning of 1940 until the end of 1940 and then tripled it again from the end of 1940 till the end of 1941. And roughly tripled it again in 1942. A 27 fold increase in 3 years.
Skilled labor was in short supply ( the airframe makers were under going a similar expansion), Allison records show employees going from over 500 in June of 1939 to nearly 10,000 by December of 1941. Machine tools were allocated by a government priority program. I have no figures for Wright but Allison was short 200 machine tools in Sept of 1941 even though it had an A-1-C priority rating. Allison was listed behind 525 other contractors on the priority list. Because of the tooling shortage Allison was failing to meet production schedules and the Air Corp had to ration engines to the airframe manufacturers.
Maybe Wright was in a better position, I don't know but to claim that a "market economy" would have solved a shortages of engines for proposed new projects in 1940-41 doesn't hold up well in light of what was really going on in the US at the time.
There may be a reason that some of those Buffaloes and export P-36s got overhauled Airliner engines instead of new engines.
The Wright Patterson plant's output of R-2600's went up 12 times from 1939 to 1940 and over 3.7 times from 1940 to 1941. I think they were expanding production about as fast as they could in addition to farming out production of smaller engines to other companies.

as to my "obsession with the "forged steel crankcase" " I figured the people promoting the R-2600 powered fighter would want to use the best version available at the time or the best version in prospect. While the Aluminium cased version is rated at only 100hp less for take off it is usually listed as 200rpm lower in max rpm. This lower rpm also affects the supercharger and the altitude performance. Of course you plan on a turbo to solve the last problem.
Except for a small batch (under 150) built at Patterson all the Steel crankcase engines came from Cincinnati. And the batch from Patterson weren't delivered until 1942.
So for the "what If" to work you need more rapid development of the R-2600. More rapid development of turbochargers and earlier development/production of the "C" series turbo. The "B" series turbo used in the P-38, P-43, B-17 and B-24 is too small to work properly on the R-2600 unless you want to restrict performance. Ground breaking of the Cincinnati Plant much sooner ( or a retooling of the Paterson plant) and/or re-prioritizing a host of strategic supplies and Programs.
And for what?
A plane that will barely out perform an Allison P-40 if you don't have a turbo. And if you do? The added weight and bulk of the turbo is really going to hurt this thing at low altitudes. You are going to wind up with something about the size of a P-47 only with 15-20% less power.

Shortround6 said:

That DB 601 must have been a wonderful engine. Allison powered Mustangs didn't use drop tanks for quite a while and didn't have rear fuselage tanks. Their range was usually given as around 1100-1200miles at most economical cruise and without combat allowance. Better than many other 1941 fighters but not the numbers you are giving out.

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Brewster put three(!) additional fuel tanks into the F2A-3, so we can take it for granted NAA could have installed one without much dealy and trouble.

Regarding the DB605´s power at high altitudes, how much was fuel related and how much due to the supercharger.

Markus said:

Brewster put three(!) additional fuel tanks into the F2A-3, so we can take it for granted NAA could have installed one without much dealy and trouble.

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There is the question of weight and center of gravity. Both the Mustang and the later Spitfires that used rear fuselage tanks had some rather severe flight restrictions when the rear tanks were full or even part full. This was AFTER their original engines were replaced by the 2 stage Merlin that weighed several hundred pounds more than the original engine and had bigger, heavier propellers fitted than the early versions without the tanks. wing roots are already taken with the existing tanks and landing gear. Putting fuel tanks in the bottom of the plane means something else has to move or making the plane thicker top to bottom. Kind of leaves the outer wings or wing leading edges as the only solution. Of course that reduces roll response, the extra weight of the self sealing tanks (even empty) reduces performance and the extra plumbing increases vulnerability.
Buffalo was a fat porker of an airplane ( with a Cyclone engine on the front it is kind of hard not to be) that had extra volume available near the center of gravity for 50% of the fuel increase/switch.

Markus said:

Regarding the DB605´s power at high altitudes, how much was fuel related and how much due to the supercharger.

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A complicated question.
Later 605s used the supercharger from the 603 and got better altitude performance. However trying to put a single stage supercharger against a two stage is always going to be difficult. At 27,000ft your engine is going to need the ambient air compressed from 4.26 times ( for an engine with 1.42 ATA) to 6 times (engine with 15lbs or 60in)to get sea level power. Getting to a pressure ratio of 4 or above was difficult for a single stage compressor even at the end of the war. For the same level of compression the 2 stage supercharger heated the air less than a single stage AND required less power from the engine to do it.
Germans had a vague hope of getting the performance they needed from a single stage super charger although the higher the boost above 1.42 the more that hope faded. Allies had no hope of using a single stage supercharger give the boost levels they needed.

Here is were the fuel comes in. The higher the level of boost the higher the intake air temperature and the the closer to detonation you get even with the same engine compression and boost pressure.
3 ways around this.
1. higher octane or performance number fuel. Were Germans limited by fuel?
2. Use inter or after coolers. Used by Allies on most two stage engines. was actually used on some planes powered by Jumo 211s.
3. Use ADI. used by both sides.

Given this mix and match solution, some aircraft used all three, it is a little hard to say that fuel alone hurt the Germans at high altitude.

IF, big IF, the Germans had KNOWN they could get large quantities of high performance number fuel a few years earlier than they did would they have designed their engines differently?
It can take 2 years or more to go from design to manufacture of a MAJOR MODIFICATION of an existing engine design.
Getting higher performance number fuel can boost the power of an existing engine, BUT, repeat BUT, only if the cooling system can handle it, only if the engine structure can stand the strain, and only at altitudes BELOW full throttle hight were the supercharger can supply more air.
To take full advantage of higher performance fuel the engine/supercharger combination has to be designed with it in mind to begin with.

Came to this discussion 7 years late but here is what I put together - concept side view.

The Mitsubishi Kasei in my mind was comparable to the Wright R-2600.

Using the Kasei for power, Mitsubishi was able to come up with the J2M Raiden. From what I have read the J2M appeared to be a effective short range interceptor.

Then there is the speculation of 'what if' when Kawanishi was reworking the Kasei powered N1K1 float plane into the land based N1K1-J they had stayed with the Kasei instead of switching to the Nakajima Homare. As I recall, later versions of the Kasei were nearly as powerful on paper as the Homare, and if I believe some of my other reading, the Kasei would have been more or less equal to the Homare in the field.

Some R-2600 history: R-2600 Case History

As an aside, the R-2600 had 14 cylinders, while the R-3350 had 18.

Piper106 said:

The Mitsubishi Kasei in my mind was comparable to the Wright R-2600.

Using the Kasei for power, Mitsubishi was able to come up with the J2M Raiden. From what I have read the J2M appeared to be a effective short range interceptor.

Then there is the speculation of 'what if' when Kawanishi was reworking the Kasei powered N1K1 float plane into the land based N1K1-J they had stayed with the Kasei instead of switching to the Nakajima Homare. As I recall, later versions of the Kasei were nearly as powerful on paper as the Homare, and if I believe some of my other reading, the Kasei would have been more or less equal to the Homare in the field.

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The Kasei was a far better altitude performer than the R-2600, due to a bigger S/C (impeller of 12.6 in vs. 11 in). The low altitude performance was also very good. The 'hi-alt R-2600', ie. it's 2-stage version, never flew operationally, nor did the turbo version.

Hi, first post. To me, this is an interesting topic. While the Hellcat was a great carrier-based fighter, what the US really needed was something substantially better than the Wildcat, sooner.

I think what happened was this. First, Grumman designed the basic airframe for the Hellcat. Looking to have something bigger and beefier than a Wildcat. Then Escort Carriers became a thing, then they found out how much faster and more agile the Zero was. I think with perfect foresight of when the war would start, the capabilities of the Zero, and the value of having a fighter that could fly off Escort Carriers, the Hellcat would have been made a bit smaller. They chose the size based on a R-2600 and what speed/climb rate they thought was adequate. Then got the wakeup call that it wasn't adequate and thus the re-engine. I don't really believe the high altitude/supercharger issues would have been much of a problem if they were a high priority.

Perhaps the most suitable to receive the R-2600 would be the Republic XP-44, it would have been a good intermediary between the P-43 Lancer and the P-47 Thundebolt.

The Problem is you can -and they did- fit a R-2800 to the P-44. The R-2600B was competitive with the R-2800B in terms of specific power but has 8% more frontal area. Net drag would probably come out as a small advantage for the R-2800 factoring in cooling drag.
The real kicker is the installed weight. The R-2600 should weigh ~400-600lbs less installed. For the optimistic weight ~8700lbs for the P-44 with R-2800 you get 4.7lb/4.35lb per HP A/B. The R-2600 gives you at best 4.76lb per HP at a weight of 8100lbs. For heavier aircraft this disadvantage gets worse. It's easy to see why the R-2600 was abandoned quickly post-war.

Jugman said:

The Problem is you can -and they did- fit a R-2800 to the P-44.

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That is very interesting. Care to provide some details of the R-2800-powered P-44?

The P-44 was to be powered by the 1850hp R-2800-7 with D-2 turbo and a four blade Curtiss electric propeller. Armament was to be 2 .50 cal in the nose and four .30 cal in the wing. Top speed was expected to be 402mph at 20,000ft.
Design gross weight 8700lbs
empty weight 6939lbs
normal fuel 162.5 US gal
overload fuel 98 us gal

The data comes from Bodie's book. I don't know if the P-44s ordered was always R-2800 powered or if it was amended some time shortly after contract signing. It's clear from the memorandum reports that this was the model actually being worked on. Furthermore, as far as I can tell the the R-2180 was already dead by the time the P-44 was ordered in September, 1939. It seems strange to me to order an aircraft off the drawing board with an engine that was essentially exclusive to it. The R-2180 suffered the same problem as the R-2600.

Jugman said:

The P-44 was to be powered by the 1850hp R-2800-7 with D-2 turbo and a four blade Curtiss electric propeller. Armament was to be 2 .50 cal in the nose and four .30 cal in the wing. Top speed was expected to be 402mph at 20,000ft.
Design gross weight 8700lbs
empty weight 6939lbs
normal fuel 162.5 US gal
overload fuel 98 us gal

The data comes from Bodie's book. I don't know if the P-44s ordered was always R-2800 powered or if it was amended some time shortly after contract signing. It's clear from the memorandum reports that this was the model actually being worked on.

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That you for the data.
However, since the P-44 never existed, it follows that it was never outfitted with any engine. Thus stating that

Jugman said:

The Problem is you can -and they did- fit a R-2800 to the P-44.

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is misleading; no offense.

tomo pauk said:

That you for the data.
However, since the P-44 never existed, it follows that it was never outfitted with any engine. Thus stating that



is misleading; no offense.

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huh? They had a converted P-43 fuselage and left wing as a mock-up with a R-2800 installed. Keep in mind they never ordered a prototype. The P-44 was to go straight into production when the design was finalized and fully approved by the AAC.

I began working as a line boy in 1953, when there were a lot of WWII vintage aircraft still sitting around USA airfields and flying. We quickly learned how to tell if radial engine aircraft had C-W or P&W engines by looking at the puddles of oil beneath the engines. Big puddles meant C-Ws. Common "knowledge" was the P&W engines were generally more reliable and longer lived. Whether this was true or not, I cannot confirm, but probably there is data somewhere that could be analyzed to find the real truth. There was also a little jibe about the DC-7: The DC-7B was a four engine plane with 3 bladed propellers and the DC-7C was a three engine plane with four bladed propellers. Also, there are comments that when jet transports became available, airlines got rid of C-W powered DC-7s before P&W powered DC-6s because of reliability and maintenance issues. Personally, if I had been a WWII fighter pilot, I would rather have flown an R-2800 powered fighter if I had a choice, of course in WWII, pilots couldn't choose.

ArtieBob