P-40 top fighter?

[Shortround6]

This -93 engine would have been an earlier version of the V-1710-121 that actually went into the P-40Q. This -93 engine would make 1180HP at 21500' and 1325HP for takeoff. For comparison the single stage engines used in the P-39N, P-40N and P-51A would produce about 950HP at 20000'.

Point is that the P-39, P-40 and P-51 would have all benefited greatly from the two stage Allison, and it was in series production from April/May 1943. To put that into perspective, the first combat mission for the P-47 was April 30, 1943 and the P-38 only reached combat four month's earlier.

A couple of points,

1. the is a big difference between going into production, being in large scale production and going into action

as of the end of April 1943 you had a total builds of

P-38s................2345
P-47s................1330
P-40s................7161
Mustangs........1463

the last includes the British Mustang Is and the A-36 production. take special note of the P-47 production total and it's it's first combat mission.
Any aircraft using the "improved" Allison is months away from combat.

2. If the -93 was in production it was in small scale production. It didn't pass it's model test until Nov 27th of 1943 and any P-63s flying with the early production engines were flying under restrictions. most of the summer and fall of 1943 were spent developing the parts needed to allow the engine to stand up to WEP power settings.
P-63s with the -93 engine didn't start leaving the Bell Factory until Oct of 1943 so any talk of production aircraft using this engine in the late spring or early summer of 1943 is highly suspect without a major shift in the real timeline.

BTW the Merlin used in the P-40L was rated at 1120hp at 18,500ft with it's single stage supercharger and was about 100lbs lighter than the 2 stage Allison. The -1 Merlin was also good for just under 1500hp at around 5,000ft and just over 1400hp at around 12,000ft so any idea of using the -93 Allison or equivalent without water injection or WEP power ratings is not going to see much of a boost in power. The -93 engine being limited to about 60in of MAP and the -1 Merlin was limited to 61in of MAP in WEP ratings.
The Merlin that started going into the P-51B in May of 1943 was good for 1330hp at 23,300ft so I think we can all see how greatly the P-51 would have benefited from a 150hp cut at 22-23,000ft. The -3 Merlin was also good for 1380hp for take-off.
There were over 5000 Merlin powered Mustangs on order by the end of May 1943. Jerking around production schedules is unlikely to increase the number of good fighters in the spring of 1944.

 

[jetcal1]

What makes you say that?

View attachment 564104Buccaneer

Seriously though, it surprises me that the US Navy was left with those two designs as options, particularly after the SBD. Surely a better design could and should have been produced in its wake.

A couple of points,

1. the is a big difference between going into production, being in large scale production and going into action

as of the end of April 1943 you had a total builds of

P-38s................2345
P-47s................1330
P-40s................7161
Mustangs........1463

the last includes the British Mustang Is and the A-36 production. take special note of the P-47 production total and it's it's first combat mission.
Any aircraft using the "improved" Allison is months away from combat.

2. If the -93 was in production it was in small scale production. It didn't pass it's model test until Nov 27th of 1943 and any P-63s flying with the early production engines were flying under restrictions. most of the summer and fall of 1943 were spent developing the parts needed to allow the engine to stand up to WEP power settings.
P-63s with the -93 engine didn't start leaving the Bell Factory until Oct of 1943 so any talk of production aircraft using this engine in the late spring or early summer of 1943 is highly suspect without a major shift in the real timeline.

BTW the Merlin used in the P-40L was rated at 1120hp at 18,500ft with it's single stage supercharger and was about 100lbs lighter than the 2 stage Allison. The -1 Merlin was also good for just under 1500hp at around 5,000ft and just over 1400hp at around 12,000ft so any idea of using the -93 Allison or equivalent without water injection or WEP power ratings is not going to see much of a boost in power. The -93 engine being limited to about 60in of MAP and the -1 Merlin was limited to 61in of MAP in WEP ratings.
The Merlin that started going into the P-51B in May of 1943 was good for 1330hp at 23,300ft so I think we can all see how greatly the P-51 would have benefited from a 150hp cut at 22-23,000ft. The -3 Merlin was also good for 1380hp for take-off.
There were over 5000 Merlin powered Mustangs on order by the end of May 1943. Jerking around production schedules is unlikely to increase the number of good fighters in the spring of 1944.

And even with the constraints you mentioned, we still had the luxury of having a base capable of concurrently building new factories for new production while expanding production of existing items.

 

[jetcal1]

What makes you say that?

View attachment 564104Buccaneer

Seriously though, it surprises me that the US Navy was left with those two designs as options, particularly after the SBD. Surely a better design could and should have been produced in its wake.

Which gets me to wondering, in the 1938 competition who else was playing besides Brewster? I can't find anything that references proposals submitted by any other companies except Brewster.

 

[P-39 Expert]

A couple of points,

1. the is a big difference between going into production, being in large scale production and going into action

as of the end of April 1943 you had a total builds of

P-38s................2345
P-47s................1330
P-40s................7161
Mustangs........1463

the last includes the British Mustang Is and the A-36 production. take special note of the P-47 production total and it's it's first combat mission.
Any aircraft using the "improved" Allison is months away from combat.

2. If the -93 was in production it was in small scale production. It didn't pass it's model test until Nov 27th of 1943 and any P-63s flying with the early production engines were flying under restrictions. most of the summer and fall of 1943 were spent developing the parts needed to allow the engine to stand up to WEP power settings.
P-63s with the -93 engine didn't start leaving the Bell Factory until Oct of 1943 so any talk of production aircraft using this engine in the late spring or early summer of 1943 is highly suspect without a major shift in the real timeline.

BTW the Merlin used in the P-40L was rated at 1120hp at 18,500ft with it's single stage supercharger and was about 100lbs lighter than the 2 stage Allison. The -1 Merlin was also good for just under 1500hp at around 5,000ft and just over 1400hp at around 12,000ft so any idea of using the -93 Allison or equivalent without water injection or WEP power ratings is not going to see much of a boost in power. The -93 engine being limited to about 60in of MAP and the -1 Merlin was limited to 61in of MAP in WEP ratings.
The Merlin that started going into the P-51B in May of 1943 was good for 1330hp at 23,300ft so I think we can all see how greatly the P-51 would have benefited from a 150hp cut at 22-23,000ft. The -3 Merlin was also good for 1380hp for take-off.
There were over 5000 Merlin powered Mustangs on order by the end of May 1943. Jerking around production schedules is unlikely to increase the number of good fighters in the spring of 1944.

1. Like you said, over 7000 P-40s had been built by the time that -93 production started, it was already a mature design being produced in quantity. It took 90 days for a new production Allison model to make it into a production airframe. The -93 was no surprise as it had been in development for years, so if the AAF had wanted to use it in the P-40 the design work should have already been done so that -93 P-40s should have been in production from July '43 (April plus 3 months).

2. The -93 was in production in April '43 according to Dan Whitney's Allison book. It was not a new "engine", it was the same engine Allison was producing at that time with 8.1 internal supercharger gears used with a turbocharger in the P-38. The only new item was the auxiliary stage supercharger which was just an impeller in a diffuser with a hydraulic coupling run from a jackshaft from the starter dog. Most of the summer and fall of '43 were wasted because the P-63 airframe wasn't ready until October. I'm aware of all the testing done during that period but WEP was being used in turbocharged P-38Js in August '43 so plenty of WEP testing on the Allison had already been done. The big delay was waiting on the new airframe. I'm saying that the -93 or an equivalent F series engine should have been installed in the P-40 as soon as possible resulting in a high altitude P-40 by July '43. Same for the P-39.

And the Merlin made a little more power than the Allison at that point in time. I guess all that Allison production was wasted, we should have just produced the Merlin in it's various forms under license instead of producing the Allison at all.

 

[tomo pauk]

...
And the Merlin made a little more power than the Allison at that point in time.

A 2-stage Packard Merlin of 1943 (the -3) was producing better power than a 2-stage V-1710, especially at high altitudes. At 25000 ft, it was ~1275 vs. ~1000 HP.

 

[Shortround6]

1. Like you said, over 7000 P-40s had been built by the time that -93 production started, it was already a mature design being produced in quantity. It took 90 days for a new production Allison model to make it into a production airframe. The -93 was no surprise as it had been in development for years, so if the AAF had wanted to use it in the P-40 the design work should have already been done so that -93 P-40s should have been in production from July '43 (April plus 3 months).

2. The -93 was in production in April '43 according to Dan Whitney's Allison book. It was not a new "engine", it was the same engine Allison was producing at that time with 8.1 internal supercharger gears used with a turbocharger in the P-38. The only new item was the auxiliary stage supercharger which was just an impeller in a diffuser with a hydraulic coupling run from a jackshaft from the starter dog. Most of the summer and fall of '43 were wasted because the P-63 airframe wasn't ready until October. I'm aware of all the testing done during that period but WEP was being used in turbocharged P-38Js in August '43 so plenty of WEP testing on the Allison had already been done. The big delay was waiting on the new airframe. I'm saying that the -93 or an equivalent F series engine should have been installed in the P-40 as soon as possible resulting in a high altitude P-40 by July '43. Same for the P-39.

And the Merlin made a little more power than the Allison at that point in time. I guess all that Allison production was wasted, we should have just produced the Merlin in it's various forms under license instead of producing the Allison at all.

mass producing engines that had not passed their model tests is a recipe for disaster. small scale production is something else.

You are also ignoring two rather major differences between using the same basic engine in a P-38 and in the P-63 or P-40 whatever.
The P-38 used an intercooler, perhaps a not very good one in the P-38H but it was there to lower the intake mixture temperature which means
1. the same pressure air is actually heavier and can make more power,
2, the engine is further away from the detonation limit.
3. the engine has less thermal stress, and needs less cooling. If you raise the intake temperature 50 degrees the peak cylinder temperature goes up 50 degrees if you burn the same amount of fuel and the exhaust temperature goes up 50 degrees.

the turbo in the P-38 gave "free" horsepower. Or relatively free. the exhaust powered the turbo giving the higher WEP pressures and all (or almost all) of the higher pressure and power could go to the propeller.

On a mechanical drive supercharger the engine has to make in the cylinders the power needed to drive the extra stage, which can be several hundred horsepower, which means the pressures and temperatures inside the mechanically supercharged engine are higher than the pressures and temperatures inside the turbo charged engine (even if the turbo engine had no intercooler).
So no, you can't take the engine out of a P-38H and rip the turbo off, bolt the aux stage on the rear end and fly thing the thing off into the wild blue yonder using the same manifold pressure settings as the P-38 used. Not without a lot testing and appropriately sized radiators and oil coolers. And you may have to settle for lower power to the propeller than the P-38 installation gave.

 

[P-39 Expert]

Absolutely you can take a P-38 engine, rip the turbo off, install the mechanical second stage and go on from there. Allison power sections (aft of the reduction gear and before any turbo or mechanical auxiliary stage) were all the same. Any advance or improvement made to the power section was applied to all the contemporary Allison engines. They could have remote reduction gears for the E models (P-39, P-63) or standard reduction gears for the F models (P-38, P-40, P-51), or they could have different gears for the internal supercharger (8.1 for two stage engines, 8.8 or 9.6 for altitude rated models), and they could have different carbs (PD for two barrel for single stage engines and PT for three barrel for two stage engines). All these items were interchangeable, but the power section was the same. As improvements were made to the power section they were included on all their engines.

And you don't need WEP. The whole purpose of the second stage was to improve performance at altitude. WEP only works below the critical altitude. The single stage Allison engined fighters had excellent performance at low altitude already. They needed high altitude performance which the auxiliary stage would give them. Without WEP you don't need an intercooler and you don't need all that April-October testing to perfect WEP (while awaiting completion of the P-63 airframe). And since the intercooler has been eliminated the carb can be moved up from the auxiliary stage to it's normal position on the engine stage supercharger adding another 2000'-3000' critical altitude.

Just put the damn thing into the P-40 (and P-39) in April, test them for the three months it took to get a new model engine into a production aircraft, pass the test and have vastly improved planes quickly and cheaply. But of course at that point you don't really need P-38s or P-47s, and the AAF was committed to those planes at the expense of the P-39 and P-40. A terrible waste in my opinion.

 

[P-39 Expert]

A 2-stage Packard Merlin of 1943 (the -3) was producing better power than a 2-stage V-1710, especially at high altitudes. At 25000 ft, it was ~1275 vs. ~1000 HP.

True, depending on the model.

Always wondered why the Packard Merlins were rated lower than the Rolls Merlins.

The XX made by Rolls had a critical altitude in high gear of 21000' while the Packard V-1650-1 critical altitude was only 15600', same impeller diameter, supercharger gear ratio and same impeller tip speed? Boost was 16# for Rolls and 12# for the Packard.

The two stage Rolls Merlin 61 made 1370hp at 24000' while the two stage Packard V-1650-3 made 1330hp at 23000' with a slightly higher SC ratio (8.03 vs 8.095).

Seems like they would have been identical.

 

[Dan Fahey]

Regarding the P-40Q, the Allison two stage mechanical engine went into series production in April/May 1943 as the V-1710-93, an E model engine with remote reduction gear for the P-63.

Given Allison's modular design the same new auxiliary supercharger could have been fitted to an F series engine for the P-40 and P-51. Given the relatively clean installation in the P-40Q it appears that the big objection to the new engine being 16" longer than a standard Allison was somehow overcome. Probably could have been fitted to the P-51 also.

This -93 engine would have been an earlier version of the V-1710-121 that actually went into the P-40Q. This -93 engine would make 1180HP at 21500' and 1325HP for takeoff. For comparison the single stage engines used in the P-39N, P-40N and P-51A would produce about 950HP at 20000'.

Point is that the P-39, P-40 and P-51 would have all benefited greatly from the two stage Allison, and it was in series production from April/May 1943. To put that into perspective, the first combat mission for the P-47 was April 30, 1943 and the P-38 only reached combat four month's earlier.

Great Point and same as my point in earlier posts.
The British would have liked this upgrade for the P51-A.
Especially for the missions they were planning.
Do not think any P51-A's survived as they were all used up by the Brits.

 

[tomo pauk]

True, depending on the model.

Always wondered why the Packard Merlins were rated lower than the Rolls Merlins.

The XX made by Rolls had a critical altitude in high gear of 21000' while the Packard V-1650-1 critical altitude was only 15600', same impeller diameter, supercharger gear ratio and same impeller tip speed? Boost was 16# for Rolls and 12# for the Packard.

The two stage Rolls Merlin 61 made 1370hp at 24000' while the two stage Packard V-1650-3 made 1330hp at 23000' with a slightly higher SC ratio (8.03 vs 8.095).

Seems like they would have been identical.

For all intents and purposes, the Merlin XX and V-1650-1 were equal. Mentioning the rated altitue without the boost or power does not say the whole story, and not all countries will say the same rated altitude for the same engine. It took a while for the Mk.XX to be allowed for +16psi boost.
Long story short - we're looking at ~1150 HP at 18500 ft (no ram), while British were more eager to further over-boost either of the engines than it will be the case with AAF. See this chart. Being the 2-piece block engines, the US-made Merlin 224 and 225 were rated for same boost as the later Merlin 20 series.

 

[P-39 Expert]

For all intents and purposes, the Merlin XX and V-1650-1 were equal. Mentioning the rated altitue without the boost or power does not say the whole story, and not all countries will say the same rated altitude for the same engine. It took a while for the Mk.XX to be allowed for +16psi boost.
Long story short - we're looking at ~1150 HP at 18500 ft (no ram), while British were more eager to further over-boost either of the engines than it will be the case with AAF. See this chart. Being the 2-piece block engines, the US-made Merlin 224 and 225 were rated for same boost as the later Merlin 20 series.

So, what is the difference in those two charts? The 224/225 were rated higher, how so if they are the same?

 

[tomo pauk]

So, what is the difference in those two charts? The 224/225 were rated higher, how so if they are the same?

1st chart is for power vs. altitude without ram effect.
2nd chart is power vs. altitude with ram effect for aircraft flying at 400 mph.

 

[swampyankee]

Which gets me to wondering, in the 1938 competition who else was playing besides Brewster? I can't find anything that references proposals submitted by any other companies except Brewster.

Grumman and Seversky. The former submitted a biplane, which was redesigned as the F4F-2 and the latter a variant or derivative of the P-35

 

[P-39 Expert]

1st chart is for power vs. altitude without ram effect.
2nd chart is power vs. altitude with ram effect for aircraft flying at 400 mph.

Most all the Allison power charts are without ram, right?

Thanks.

 

[tomo pauk]

Most all the Allison power charts are without ram, right?

Thanks.

IIRC - all of them are without ram effect.
I've shown the chart with ram for the Merlins to point out that Merlin 20 series made in UK and it's siblings made in USA were as comparable as it gets.

 

[GregP]

Reference post 24, the P-51H and P-47N were good airplanes and both were faster than the P-40Q amd had better range. But, that's about all they had on it. The P-40Q would have been a better dogfighter then either of the others and very probably could outclimb at least the P-47N. Given the war situation at the time, I probably would have made the P-515H / P-47N choice, but the pilots would NOT have been disappointed in the P-40Q if they had to go fight in it. It basically was what the P-40 SHOULD have been all along, but never was.

 

[Shortround6]

It basically was what the P-40 SHOULD have been all along, but never was

This may have been more to do with engine availability than anything in the airframe. The bubble canopy could have been introduced sooner and armament selection of 6 guns was always a bit questionable given the power available.

However the -93 engine from the P-63 does show that "just" sticking a two-stage supercharger on the Allison was not the answer to many people's hopes.
You need a good two stage supercharger and not a fair to poor one.
The supercharger set up on the -93 engine could not maintain 54in of MAP at 22,500ft in a prototype P-63 using 398mph of ram (power was 1165hp) and could not maintain 54in of MAP at over 20,000ft when climbing. The -3 Merlin in the P-51B could hold 60.5 in of MAP to 29,800ft (1275hp) but did have bit more help from RAM. (20-40mph worth out of 400mph)
Please note Merlin -1 engine (or British XX series) could hold 48in to 20,400ft in a P-40F(British trial at Boscombe down Aug 1942)using about 350mph of RAM (1120hp?)
The Allison that about 4% bigger in displacement need a two stage supercharger to pick up 2,000ft of altitude??
Something was not right with the Allison two-stage supercharger if it can barely beat a single stage supercharger.

Not all superchargers were created equal.

 

[PAT303]

The P 40 was like the Hurricane II and Spitfire MkV, not the best, not the worst, but available.

 

[Shortround6]

Absolutely you can take a P-38 engine, rip the turbo off, install the mechanical second stage and go on from there. Allison power sections (aft of the reduction gear and before any turbo or mechanical auxiliary stage) were all the same. Any advance or improvement made to the power section was applied to all the contemporary Allison engines. They could have remote reduction gears for the E models (P-39, P-63) or standard reduction gears for the F models (P-38, P-40, P-51), or they could have different gears for the internal supercharger (8.1 for two stage engines, 8.8 or 9.6 for altitude rated models), and they could have different carbs (PD for two barrel for single stage engines and PT for three barrel for two stage engines). All these items were interchangeable, but the power section was the same. As improvements were made to the power section they were included on all their engines.

And you don't need WEP. The whole purpose of the second stage was to improve performance at altitude. WEP only works below the critical altitude. The single stage Allison engined fighters had excellent performance at low altitude already. They needed high altitude performance which the auxiliary stage would give them. Without WEP you don't need an intercooler and you don't need all that April-October testing to perfect WEP (while awaiting completion of the P-63 airframe). And since the intercooler has been eliminated the carb can be moved up from the auxiliary stage to it's normal position on the engine stage supercharger adding another 2000'-3000' critical altitude.

Just put the damn thing into the P-40 (and P-39) in April, test them for the three months it took to get a new model engine into a production aircraft, pass the test and have vastly improved planes quickly and cheaply. But of course at that point you don't really need P-38s or P-47s, and the AAF was committed to those planes at the expense of the P-39 and P-40. A terrible waste in my opinion.

I believe you missed the point or I didn't explain it well enough. It doesn't matter how many different gear cases you bolt to the nose of the power section or how many different carbs or other bits and pieces you could bolt on the rear end.
what mattered was what was going on in the cylinders. See page 344 of Vees for Victory.

using 10,000lbs per air per hour as point for illustration that amount of air is good for 1672IHP (Indicated HP or HP developed in the cylinders) of which 147hp is used up in friction and driving pumps and accessories. leaving 1525hp but after we power the supercharger we get 1285hp to the prop (the supercharger used up 240hp) using 9.60 gears, if we use 6.44 gears we can get 1415hp, as the lower gear supercharger only needs 110hp to supply the 10,000lbs of air (it just won't do it at much altitude).
There is a chart showing the power needed by different supercharger gear ratios and different air flows on page 344.
using a set of 8.10 gears the supercharger would need about 175-180 hp leaving 1350hp for the prop. Now we have two choices for getting out 1350hp at high altitude, the turbo which might cause a bit of back pressure in the exhaust manifolds and cost a bit of power but is taking no power from the crankshaft to run OR we can bolt that auxiliary supercharger to the back end of the engine and go for it.
Unfortunately there is a chart on page 347 that shows the power required to drive the auxiliary supercharger using different gear ratios and airflows and the 6.85 gear ratio used in the -93 engine needs about 220hp hp to supply 10,000lbs of air. Our hypothetical engine is now down to 1140hp but needs radiators and oil coolers to deal with 1672hp worth of heat.

If you want more power you need more than 10,000lbs of air per hour and the power needed by the superchargers goes up. going to 11,000lbs of air should get you about 1840Ihp and the internal friction/pump loses should stay the same but the engine supercharger is going to need about 195hp and the auxiliary supercharger is going to need 245hp leaving you with 1252 for the prop but you need to cool that 1840hp and/or handle the stresses in the engine the extra power in the cylinders create.

as to the idea of not needing an intercooler if you are not using WEP. lets just say it isn't true.
A supercharger of 65% efficiency and supplying enough air to support 1200hp at sea level pressure (29.92in Hg) will heat the intake mixture on a standard day (59 degrees F) to just over 100 degrees F at 10,000ft, just over 150 degrees F at 20,000ft and just over 200 degrees F at 30,000ft. this is despite the intake air temperature dropping to 23-24 degrees at 10,000ft, -12.3 degrees F at 20,000ft and -47.99 degrees F at 30,000ft.
Please note that this is for 0 lbs of boost - 29.92 (30) in of MAP. If you want 42-44in of MAP the temperature gets a lot hotter.

The Army tried to get their turbo installations to supply sea level air pressure to the intake of the carb at no more than 100 degrees F. This was the goal of their early intercooler installations and the goal the XP-39 failed miserably to even get close to. Better fuel pushed back the detonation limits but hot intake charges are less dense (fewer pounds of air per 1000 cubic ft) and make less power and hotter intake charges add to the cooling problems.

a few reference numbers, if you are trying for 60 in MPA (15lbs boost) you need to compress the air

times 2 at sea level
times 2.41 at 5,000ft
times 2.91 at 10,000ft
times 3.55 at 15,000ft
times 4.36 at 20,000ft
times 4.85 at 22,500ft
times 5.40 at 25,000ft
times 6.75 at 30,000ft.

if you are trying for just 45in (7 1/2 lbs) things get a bit easier.

times 1.5 at sea level
times 1.80 at 5,000ft
times 2.18 at 10,000ft
times 2.66 at 15,000ft
times 3.27 at 20,000ft
times 3.63 at 22,500ft
times 4.05 at 25,000ft
times 5.06 at 30,000ft.

at the beginning of WW II nobody's single stage supercharger could compress air at a 3 to 1 ratio (at least in the field, laboratory was bit different).

 

[P-39 Expert]

I believe you missed the point or I didn't explain it well enough. It doesn't matter how many different gear cases you bolt to the nose of the power section or how many different carbs or other bits and pieces you could bolt on the rear end.
what mattered was what was going on in the cylinders. See page 344 of Vees for Victory.

using 10,000lbs per air per hour as point for illustration that amount of air is good for 1672IHP (Indicated HP or HP developed in the cylinders) of which 147hp is used up in friction and driving pumps and accessories. leaving 1525hp but after we power the supercharger we get 1285hp to the prop (the supercharger used up 240hp) using 9.60 gears, if we use 6.44 gears we can get 1415hp, as the lower gear supercharger only needs 110hp to supply the 10,000lbs of air (it just won't do it at much altitude).
There is a chart showing the power needed by different supercharger gear ratios and different air flows on page 344.
using a set of 8.10 gears the supercharger would need about 175-180 hp leaving 1350hp for the prop. Now we have two choices for getting out 1350hp at high altitude, the turbo which might cause a bit of back pressure in the exhaust manifolds and cost a bit of power but is taking no power from the crankshaft to run OR we can bolt that auxiliary supercharger to the back end of the engine and go for it.
Unfortunately there is a chart on page 347 that shows the power required to drive the auxiliary supercharger using different gear ratios and airflows and the 6.85 gear ratio used in the -93 engine needs about 220hp hp to supply 10,000lbs of air. Our hypothetical engine is now down to 1140hp but needs radiators and oil coolers to deal with 1672hp worth of heat.

If you want more power you need more than 10,000lbs of air per hour and the power needed by the superchargers goes up. going to 11,000lbs of air should get you about 1840Ihp and the internal friction/pump loses should stay the same but the engine supercharger is going to need about 195hp and the auxiliary supercharger is going to need 245hp leaving you with 1252 for the prop but you need to cool that 1840hp and/or handle the stresses in the engine the extra power in the cylinders create.

as to the idea of not needing an intercooler if you are not using WEP. lets just say it isn't true.
A supercharger of 65% efficiency and supplying enough air to support 1200hp at sea level pressure (29.92in Hg) will heat the intake mixture on a standard day (59 degrees F) to just over 100 degrees F at 10,000ft, just over 150 degrees F at 20,000ft and just over 200 degrees F at 30,000ft. this is despite the intake air temperature dropping to 23-24 degrees at 10,000ft, -12.3 degrees F at 20,000ft and -47.99 degrees F at 30,000ft.
Please note that this is for 0 lbs of boost - 29.92 (30) in of MAP. If you want 42-44in of MAP the temperature gets a lot hotter.

The Army tried to get their turbo installations to supply sea level air pressure to the intake of the carb at no more than 100 degrees F. This was the goal of their early intercooler installations and the goal the XP-39 failed miserably to even get close to. Better fuel pushed back the detonation limits but hot intake charges are less dense (fewer pounds of air per 1000 cubic ft) and make less power and hotter intake charges add to the cooling problems.

a few reference numbers, if you are trying for 60 in MPA (15lbs boost) you need to compress the air

times 2 at sea level
times 2.41 at 5,000ft
times 2.91 at 10,000ft
times 3.55 at 15,000ft
times 4.36 at 20,000ft
times 4.85 at 22,500ft
times 5.40 at 25,000ft
times 6.75 at 30,000ft.

if you are trying for just 45in (7 1/2 lbs) things get a bit easier.

times 1.5 at sea level
times 1.80 at 5,000ft
times 2.18 at 10,000ft
times 2.66 at 15,000ft
times 3.27 at 20,000ft
times 3.63 at 22,500ft
times 4.05 at 25,000ft
times 5.06 at 30,000ft.

at the beginning of WW II nobody's single stage supercharger could compress air at a 3 to 1 ratio (at least in the field, laboratory was bit different).

You are aware that those engines in the P-40Q did not have an intercooler, right? And none of the P-63 engines had intercoolers.