A Radial Engined Fighter for the Australians to build (and maybe the Chinese and Indians)

[Wild_Bill_Kelso]

Are you sure about that? I have the manual for the P-40F/L from Dec 1942 and it states take off power at 54.3" Hg / + 12 lb, and "War Emergency" at 61" Hg

Screen shot:

View attachment 664808

One thing obviously wrong in this chart is that it shows 1300 horsepower for 54.3" Hg (+12 lbs), and the same 1300 hp at 61" Hg (+15 lbs)

I think both of those numbers are wrong, 54.3" Hg should be closer to 1400 hp I think, and 61" should be close to 1600 hp. Anyone know how to calculate that exactly for a Merlin XX? What is the RAF equivalent HP for Merlin XX at +12 and +15 boost respectively?

 

[tomo pauk]

One thing obviously wrong in this chart is that it shows 1300 horsepower for 54.3" Hg (+12 lbs), and the same 1300 hp at 61" Hg (+15 lbs)

I think both of those numbers are wrong, 54.3" Hg should be closer to 1400 hp I think, and 61" should be close to 1600 hp. Anyone know how to calculate that exactly for a Merlin XX? What is the RAF equivalent HP for Merlin XX at +12 and +15 boost respectively?

I'd agree that the table is wrong there.
At +15 psi, low gear, 3000 rpm,the Merlin 20 series will be making more than 1500 HP at 4600 ft. On +14psi, it is ~1450 HP at 4600 ft at 4600 ft, and ~1470 HP at ~6500 ft.
In high gear, at 12000 ft, power is to be some 1400 HP.
RAF was mostly using +14 psi for the Merlin 20 series, not +15 (and +12 earlier, and +18 on later marque)?
chart1
chart2

 

[SaparotRob]

Of course. That table is obviously wrong.

 

[Shortround6]

So how far can you push an R-1830?

About as far as this 71 year old man can push it one handed while wearing roller skates with the engine sitting on the ground.

I only seen any official clearance once for operating the R-1830 at higher than normal (book) settings and that may have been revoked. It was being permitted to over rev the engine for emergency carrier take-off.

Air cooled engines have several things working against them.
One, the air cooled engines were known as severe duty engines in the fuel industry. I may the adjective wrong but I hope you get the idea. Liquid cooled engines were considered mild or medium duty. The Air cooled engines were operating closer to their thermal limits to begin with and there may have been hot spots in the cylinders with some spots hotter than the liquid cooled engines had. Air cooled engines seldom operated at the pressures that liquid cooled engines did.

the air cooled engines didn't have the cooling fluid and radiator to act as a heat sink so when they were asked to make more power they overheated very rapidly.

An R-1830 in order to make 1200hp was already operating at 9lbs of boost. and there they stayed until 1943-44 ?
A few 1350hp engines running at 2800rpm were produced but they had a modified auxiliary section, a modified supercharger and used trickle down knowledge from the cylinder fins and cooling muffs from the later R-2800 engines. Some of these were used on the Convair P4Y2 which shows the time scale.

I have read personal accounts of some pilots doing exactly this. Some got away with it, some didn't. I have also read many accounts of blown engines from those early days.

It was noted that the Allison didn't always break on the flight that they were over boosted on. A fair number broke on the next flight or the one after without being over boosted on those flights.

Allison responded by strengthening components of the engines and agreeing to compromise boost levels.

This took several years, Allison was reworking 277 or so of the early engines in 1940 to get them up to specs. There was a miscommunication (?) between the army and the Allison about the 1040hp vs 1090 hp rating. The next major up grade came around Dec of 1941 with hundreds of -39 engines already built. They knew the change in the reduction gears was a positive thing but the change in the crankshaft and crankcase was the 2nd one since the summer of 1940.
Until they got out in the field for a number of months it would have been hard to justify upgrading them.

Better fuel also became available which made higher boost more tenable.

Yes and no. British fuel in the summer of 1940 was 100/115-120 while American fuel was 100/100. You could over boost an Allison engine using British fuel with better chance of success than using American fuel. I have no idea what the US was using where in Dec 1941. Like what the Canal zone had or what the Philippines had or whatever. By the Spring/summer of 1942 the British and Americans were both using 100/130 fuel, the British had gone to the 100/130 before the Americans but exact dates in 1941 are hard to come by. Now since the Mustang Is in British service didn't go operational until May of 1942 it doesn't make much difference.
A lot of people had over boosted the Tomahawks, in part because they had no boost control/limiter on the throttle. but since the -33 engine had the older crankshaft/s and crankcases you weren't getting good data on the -39 engine and later -39 engines

At 56" or 57" Hg a P-39D or P-40E basically becomes a 1,500 hp fighter below 10,000 ft.

Not really. see below

The K model P-40 was making almost 1600 hp down low. This to me really helps explain why these aircraft kind of had a split Jeckyll / Hide reputation, IMO.

The -39 engine in the E and the -73 engine in the K operated exactly the same except the the -73 was allowed to use a bit higher boost down low.
Yes it could use 60in at 2500ft (no ram so add a few thousand feet) HOWEVER it was back down to 1490hp at 4300ft just like the -39 engine and both engines were tapering off (in a straight line) to the 1150hp level at 11,700-12,000ft. Like without RAM the engine/s will be making about 1310hp at 8,000ft.

RAM decreases as the aircraft speed decreases. In other words if you are doing a hard climb or exiting a hard turn and your air speed is down around 200mph your power available is several thousand feet lower than it would be when flying straight and level at max speed or near max speed.

This was part of gain with the 9.60 gears, they may have lost some of the impressive horsepower figures down low (but since the air at those low altitudes sucks up power anyway it may not be so bad) but the -81 engine could give the P-40 pilot an extra 100hp 1,500ft higher than the -73 engine. and could keep giving that extra power as the altitude climbed.

 

[Shortround6]

I think both of those numbers are wrong, 54.3" Hg should be closer to 1400 hp I think

If the engine was being operated at wide open throttle you might be closer to being correct.
But the engine was being operated at part throttle which screws up the pressure to power ratio, much like putting the kink in the water hose.
Merlin III was good for 1030hp at 6lbs at 16,250ft.
But since they had to close the throttle to keep from blowing the engine up with 87 octane fuel they only got 880 hp at sea level at 3000rpm at 6lbs of boost.

The pressure to power ratio only works when the throttle is wide open, otherwise you are trying to figure in pumping losses, temperature changes and charge density changes

 

[MiTasol]

sometimes the manuals don't even agree between pages of the same manual (early version of cut and paste for manuals?)

Or simple human error of the technical writer and editor missing one or more parts of the manual where the fuel quantity was written - especially if the technical writer and editor was the same person.

 

[Wild_Bill_Kelso]

About as far as this 71 year old man can push it one handed while wearing roller skates with the engine sitting on the ground.

I only seen any official clearance once for operating the R-1830 at higher than normal (book) settings and that may have been revoked. It was being permitted to over rev the engine for emergency carrier take-off.

Air cooled engines have several things working against them.
One, the air cooled engines were known as severe duty engines in the fuel industry. I may the adjective wrong but I hope you get the idea. Liquid cooled engines were considered mild or medium duty. The Air cooled engines were operating closer to their thermal limits to begin with and there may have been hot spots in the cylinders with some spots hotter than the liquid cooled engines had. Air cooled engines seldom operated at the pressures that liquid cooled engines did.

the air cooled engines didn't have the cooling fluid and radiator to act as a heat sink so when they were asked to make more power they overheated very rapidly.

An R-1830 in order to make 1200hp was already operating at 9lbs of boost. and there they stayed until 1943-44 ?
A few 1350hp engines running at 2800rpm were produced but they had a modified auxiliary section, a modified supercharger and used trickle down knowledge from the cylinder fins and cooling muffs from the later R-2800 engines. Some of these were used on the Convair P4Y2 which shows the time scale.

It was noted that the Allison didn't always break on the flight that they were over boosted on. A fair number broke on the next flight or the one after without being over boosted on those flights.

Yes agreed. I think it became standard practice when they came down leaking oil and a fresh scorch mark on the side of the fuselage, and maybe a broken wire on the boost control, to change all the spark plugs and check the rings etc. Mechanics weren't happy to see a plane landing like that, even if they were glad to see it landing.

This took several years, Allison was reworking 277 or so of the early engines in 1940 to get them up to specs. There was a miscommunication (?) between the army and the Allison about the 1040hp vs 1090 hp rating. The next major up grade came around Dec of 1941 with hundreds of -39 engines already built. They knew the change in the reduction gears was a positive thing but the change in the crankshaft and crankcase was the 2nd one since the summer of 1940.
Until they got out in the field for a number of months it would have been hard to justify upgrading them.

My understanding is that all of those improvements were implemented by the end of 1942.. of course there were probably some of the older engines still around. Some were sent back for overhaul, from what i gather.

Yes and no. British fuel in the summer of 1940 was 100/115-120 while American fuel was 100/100. You could over boost an Allison engine using British fuel with better chance of success than using American fuel. I have no idea what the US was using where in Dec 1941. Like what the Canal zone had or what the Philippines had or whatever. By the Spring/summer of 1942 the British and Americans were both using 100/130 fuel, the British had gone to the 100/130 before the Americans but exact dates in 1941 are hard to come by. Now since the Mustang Is in British service didn't go operational until May of 1942 it doesn't make much difference.

In the US literature they mention 98 or 96 fuel and 100 fuel. The latter was authorized for higher boost settings. Gasoline doesn't last too long in the field so presumably they were on the better stuff fairly soon after it started being produced.

A lot of people had over boosted the Tomahawks, in part because they had no boost control/limiter on the throttle. but since the -33 engine had the older crankshaft/s and crankcases you weren't getting good data on the -39 engine and later -39 engines

I'm sure you are right, but I've never seen hard data on overboosting the -33s on the Tomahawks. The Tomahawks, especially the P-40B types, were closer to their optimal weight, especially if they flew for about half an hour before combat, so the need to increase the standard boost settings may not have been as pressing.

Not really. see below

The -39 engine in the E and the -73 engine in the K operated exactly the same except the the -73 was allowed to use a bit higher boost down low.
Yes it could use 60in at 2500ft (no ram so add a few thousand feet) HOWEVER it was back down to 1490hp at 4300ft just like the -39 engine and both engines were tapering off (in a straight line) to the 1150hp level at 11,700-12,000ft. Like without RAM the engine/s will be making about 1310hp at 8,000ft.

1310 hp is still quite a bit better than the 1050 or 1150 hp they are usually quoted as having in hundreds of books, which is also incidentally what you get with a V-1710-39 at 42" Hg - 1150 hp. Which is the military power rating.

I used to think that the higher boost settings were only available at near sea-level but that is clearly not the case.

The 60" may not have been available above 4 or 5,000 feet but from the flight tests it's clear that they were boosting to 57" Hg up to about 9,000 feet and still at 50" well above 12,000 ft. Obviously depending on atmospheric conditions, temperature, fuel, and other factors.

RAM decreases as the aircraft speed decreases. In other words if you are doing a hard climb or exiting a hard turn and your air speed is down around 200mph your power available is several thousand feet lower than it would be when flying straight and level at max speed or near max speed.

This may be why so many maneuvers commonly used by P-40 pilots relied on nose-down turns (like low-yo-yo) dives and zoom climbs, split S and so on. But it's also clear based on what both German and Allied pilots said, they had no trouble out turning German and Italian fighters (except the biplanes).

This was part of gain with the 9.60 gears, they may have lost some of the impressive horsepower figures down low (but since the air at those low altitudes sucks up power anyway it may not be so bad) but the -81 engine could give the P-40 pilot an extra 100hp 1,500ft higher than the -73 engine. and could keep giving that extra power as the altitude climbed.

yes they could maintain pretty high power up to about 16 -17,000 ft compared to around 12-13,000 for the earlier types with the 8.8-1 superchargers.

 

[Shortround6]

1310 hp is still quite a bit better than the 1050 or 1150 hp they are usually quoted as having in hundreds of books, which is also incidentally what you get with a V-1710-39 at 42" Hg - 1150 hp. Which is the military power rating.

I used to think that the higher boost settings were only available at near sea-level but that is clearly not the case.

The 60" may not have been available above 4 or 5,000 feet but from the flight tests it's clear that they were boosting to 57" Hg up to about 9,000 feet and still at 50" well above 12,000 ft. Obviously depending on atmospheric conditions, temperature, fuel, and other factors.

We seem to be confusing the different Allisons.
The "military Power rating" of 1150hp at 11,700ft or 12,000ft depending on backfire screens and whatnot, was at wide open throttle. There was no more boost to be had.
There was no 50" well above 12,000ft in an engine with 8.80 gears. Not unless you are winding the engine well above 3000rpm. And you better have played with the prop governor or blade pitch adjustments to do that. RAM is not going to give you over 5.6 in of manifold pressure at 12,000ft or above.


I have said it before, you can draw a line on a graph and plot all the points on one straight line on the graph. 1150hp at 11,700ft becomes 1090hp at 13,200ft continuing on the line you get 1040hp at 14,300ft and the chart goes up to 25,000ft. going the other way the engine will make about 1360hp at 6500ft at 50 inches (no ram ) and continue down 61 in at sea level.
I repeat, this is at ZERO ram. The supercharger can flow less by being throttled back. It cannot flow more air unless RAM provides more air going into the intake.
RAM is not fixed. It has two variables, one is the airspeed of the airplane. The faster the plane the higher the pressure in the duct before the carb.

BUT, the supercharger is operating at a fixed ratio, it can only compress the air a certain amount/ratio at a certain RPM.
If the air is 29.92in at sea level and the Allison airplane with 8.80 gears is stationary it may only make 61in or 2.039 times the air pressure going in. IF you are going fast enough you can get 34.44in in the intake and that will give you 70in after the supercharger.

However at 11,000ft the air pressure is 19.79in and the supercharger can only give you 40.35in without some aid from RAM. Yes you fly faster than you do at sea level but trying to get 4.52 inches ram is going to be harder. The air is roughly 2/3 rds the pressure it was a sea level. While the air is 66.14% the pressure it was at sea level the air is still 71.54% the density it was it was sea level so it do come out slightly ahead in power/fuel burn.
You are not going to see a higher boost from Ram at higher altitudes because the supercharger is working on the fixed ratio.

yes they could maintain pretty high power up to about 16 -17,000 ft compared to around 12-13,000 for the earlier types with the 8.8-1 superchargers.

Somebody has been using the rose tinted glasses.
The "High power" was 1125-1150hp.
The P-40N-1 was good for 1480hp at 10550ft with the 57in of MAP.
Nominal altitude was 9,500ft...................however when climbing the 1480hp level was only maintained to 8,000ft before the 57in pressure could not be maintained.

The Nominal power rating of 1125hp at 15,500ft was maintained to 17,300ft

The rose colored glasses come in with the fact that out of well over 2000 P-40Ns built only about 400 (at best) were the N-1 version and many of them were modified in the field which slowed them down and they weren't getting quite the RAM effect.

A P-40N-5 recorded a max speed of only 350mph instead of 371mph and could only hold the 1125hp setting at 16,400ft (44.5in) in high speed flight and when climbing it could only hold the 44.5in setting (1110hp) at 14,000ft.

Depending on Ram for hi power is a bit dicey as I have said before as many people want to take the power rating for high speed and forget about what happens when trying to climb or accelerate out of a speed robbing maneuver.

 

[Wild_Bill_Kelso]

We seem to be confusing the different Allisons.
The "military Power rating" of 1150hp at 11,700ft or 12,000ft depending on backfire screens and whatnot, was at wide open throttle. There was no more boost to be had.
There was no 50" well above 12,000ft in an engine with 8.80 gears. Not unless you are winding the engine well above 3000rpm. And you better have played with the prop governor or blade pitch adjustments to do that. RAM is not going to give you over 5.6 in of manifold pressure at 12,000ft or above.


I have said it before, you can draw a line on a graph and plot all the points on one straight line on the graph. 1150hp at 11,700ft becomes 1090hp at 13,200ft continuing on the line you get 1040hp at 14,300ft and the chart goes up to 25,000ft. going the other way the engine will make about 1360hp at 6500ft at 50 inches (no ram ) and continue down 61 in at sea level.
I repeat, this is at ZERO ram. The supercharger can flow less by being throttled back. It cannot flow more air unless RAM provides more air going into the intake.
RAM is not fixed. It has two variables, one is the airspeed of the airplane. The faster the plane the higher the pressure in the duct before the carb.

I'm going by this chart which I posted previously, from an Australian test with IIRC a Kittyhawk Ia so a -39 or maybe up-engined to a -73. This shows WEP of 57" right up to 9200', (and it certainly looks like more is available right up to that point) then slowly tapering off and it appears to still be 50" Hg at 13,000 ft. Military power (probably 42") is available right up to 17,000 ft.

Somebody has been using the rose tinted glasses.
The "High power" was 1125-1150hp.
The P-40N-1 was good for 1480hp at 10550ft with the 57in of MAP.

Which is plenty of power

Nominal altitude was 9,500ft...................however when climbing the 1480hp level was only maintained to 8,000ft before the 57in pressure could not be maintained.

WEP never lasts as long (as high) when climbing... so what? I understand how Ram works.

The Nominal power rating of 1125hp at 15,500ft was maintained to 17,300ft

The rose colored glasses come in with the fact that out of well over 2000 P-40Ns built only about 400 (at best) were the N-1 version and many of them were modified in the field which slowed them down and they weren't getting quite the RAM effect.

The N-1 wasn't the only 'light variant', but much more importantly, most, though not all, of the weight saving measures were either permanent (aluminum radiator, lighter wheels) or could be easily replicated in the field (removing a pair of guns and the oil cooler armor). When they were flying missions over the Himalayas, or any other time they felt they needed more power from an N, they did these lightening measures in the field, just as they did with various other P-40 types in similar circumstances (like with P-40Es when defending Darwin).

A P-40N-5 recorded a max speed of only 350mph instead of 371mph and could only hold the 1125hp setting at 16,400ft (44.5in) in high speed flight and when climbing it could only hold the 44.5in setting (1110hp) at 14,000ft.

In combat though, you don't climb at 200 mph. You use your E, swoop and dive and zoom climb. What they typically did with P-40s in the CBI and Pacific was fight until it went south, then dive away, extend, zoom and come back into the fight from a better position. The slow steady climb typically happens before engaging.

Depending on Ram for hi power is a bit dicey as I have said before as many people want to take the power rating for high speed and forget about what happens when trying to climb or accelerate out of a speed robbing maneuver.

I don't think they were necessarily depending on Ram for high power, though this is in part how the zoom climb works. My point is that if they were fighting at say, 15,000 or 20,000 feet, and got into trouble, in what, 30 seconds? they could be down at 10,000 or less, and they are back in quite good shape. In these discussions you sometimes make it out as if they had to be at Sea Level to get any power. That was clearly not the case. 57" Hg was available from 9200' on down, according to the test I linked, and quite a bit more as you went further down. 50" was still available at 13,000 feet.

To me this makes it, as I said, basically a low-medium altitude fighter, with at or close to 1,500 horsepower up to about 10,000 feet. Closer to 1,300 hp for a few thousand feet above that.

 

[Wild_Bill_Kelso]

Needless to say with the P-40F and L they had WEP available higher ....

 

[tomo pauk]

I'm going by this chart which I posted previously, from an Australian test with IIRC a Kittyhawk Ia so a -39 or maybe up-engined to a -73. This shows WEP of 57" right up to 9200', (and it certainly looks like more is available right up to that point) then slowly tapering off and it appears to still be 50" Hg at 13,000 ft. Military power (probably 42") is available right up to 17,000 ft.

That chart is with full ram effect, ie. the aircraft is at max speed (5 min worth for war emergency power applied). If the aircraft is climbing or cruising, the boost level (and with it the power) will be lower, much closer to the no-ram-effect power levels as posted at post #114 here.
Un-sporty thing with ram effect is that the enemy also benefits from it.

 

[Shortround6]

The chart you provided looks like what a V-1710-81 would provide.

the date of the test is March of 1944 which makes it a little bit suspect as to why they would be testing a -39 engine well over 1 1/2 years since the stopped making them.

What is even more suspect is that the serial number of the aircraft belongs to a P-40M (KIttyhawk III) which as built had a -81 engine.

The test weight of the plane is about 400lbs below that of a normal P-40M which means under 1/2 the internal fuel or they had lightened the aircraft by pulling a couple of guns and some ammo.
Test weight of aircraft has little to do with engine performance.

 

[Shortround6]

That chart is with full ram effect, ie. the aircraft is at max speed (5 min worth for war emergency power applied). If the aircraft is climbing or cruising, the boost level (and with it the power) will be lower, much closer to the no-ram-effect power levels as posted at post #114 here.
Un-sporty thing with ram effect is that the enemy also benefits from it.

That chart uses an engine with 9.60 supercharger gears.

 

[tomo pauk]

The chart you provided looks like what a V-1710-81 would provide.

the date of the test is March of 1944 which makes it a little bit suspect as to why they would be testing a -39 engine well over 1 1/2 years since the stopped making them.

What is even more suspect is that the serial number of the aircraft belongs to a P-40M (KIttyhawk III) which as built had a -81 engine.

The test weight of the plane is about 400lbs below that of a normal P-40M which means under 1/2 the internal fuel or they had lightened the aircraft by pulling a couple of guns and some ammo.
Test weight of aircraft has little to do with engine performance.

The chart for -81 is indeed applicable for the chart other member provided.

 

[Shortround6]

We can also compare it to http://www.wwiiaircraftperformance.org/P-40/A29-418-speed.jpg

Which is a P-40N-5 in Australian service.
It doesn't show WER but it does show both planes getting just about 40in of pressure at 19,000ft (or within a few hundred feet) at 3000rpm.
It also shows the engine making Military power (44"?) at 16,200ft in the P-40N vrs about 45" at a bit over 16,000ft on the P-40M after the WER had dropped off with altitude.
Not going to worry about slight difference due to accuracy of drawings, translating test numbers to the drawings and the differences in individual aircraft.

the P-40M seems like it would hold 50in up to about 13,000ft. giving it around 1300hp instead of 1125hp at that altitude?

 

[Wild_Bill_Kelso]

You are right, I found the source of this, I made a mistake I mistook it for another Australian test. That chart I posted is for a P-40N-1CU in Australian service. They also tested an N-5 they had a lot of engine trouble with.

http://www.wwiiaircraftperformance.org/P-40/P-40N-RAAF.pdf

Here is the full report. The climbing trials (at 150 mph) noted that they had WEP of 57" right up to 6800 feet, and still 50" at 10,000 ft, and were climbing at better than 3,000 fpm just short of 10,000 ft. (3.1 minute to get to that altitude).

They had overheating problems due to very high temperatures at the testing site. They also mentioned problems with the carburator.

FTH for level speed was 9200 ft. Both climbing and level flight was at 3,000 rpm.

They get into all the detail about the weight and drag related details. They had 6 guns fitted with ammunition The aircraft from the chart was recorded as both 7900 lbs and 7802 lbs. It doesn't say anything about "full ram"

 

[Wild_Bill_Kelso]

Here is another Aussie test, with a P-40E at 8600 lbs, they were able to maintain "Military power" of 44" Hg to 12,300'. Unfortunately no WEP on this test.

http://www.wwiiaircraftperformance.org/P-40/P-40E_A29-129.pdf

Here is a Boscombe Down test with a P-40F at 8910 lb (6 guns) where they were able to maintain 48" to 14,700' in first gear and to 20,400' in second gear (level flight) and 11,000' / 17,000' (climbing)

http://www.wwiiaircraftperformance.org/P-40/FL220.pdf

 

[Shortround6]

http://www.wwiiaircraftperformance.org/P-40/P-40N-RAAF.pdf

This report is a bit confusing.

Maybe I am reading it wrong but it almost seems like somebody screwed up which airplane was in which part of the test.
They have the A29-412 as a P-40N but the US books show it as a P-40M.

Their description of the A29-418 as a P-40N-5 seems to line up with most descriptions of the P-40N-1.

Perhaps the US records/books are wrong but the N-5 in tests not only has the light weight parts (aluminum radiators and oil coolers and small wheels) but
has the had starter only
electric trim tab taken out
has all the vacuum instruments taken out.
much smaller radio outfit
wing bomb racks removed
Fuel tanks changed from metal with SS liners to non metallic tanks and front fuel tank taken out
Oil capacity reduced by about 30%?

Most accounts has that change of equipment as the N-1 and the N-5 having some of the stuff put back in, like blind flying instruments, the electric starter, a better radio outfit, going back to the 3 fuel tank set up (even if none metallic) and the normal oil supply.

The A29-412 doesn't seem to line up well with either the P-40M or the P-40N-5.
Could be a hybrid or somebody got a number wrong?
Anyway it has the forward fuel tank taken out (or not filled?) the lower oil capacity and was only carrying 1000 rounds of ammo for 6 guns. )166 round per gun?)

 

[Wild_Bill_Kelso]

That chart is with full ram effect, ie. the aircraft is at max speed (5 min worth for war emergency power applied). If the aircraft is climbing or cruising, the boost level (and with it the power) will be lower, much closer to the no-ram-effect power levels as posted at post #114 here.
Un-sporty thing with ram effect is that the enemy also benefits from it.

But in combat you won't be in a slow climb or cruise, or anyway not for long, right? Fighter pilots would build up energy by diving and zooming, extending at full power and so on.

So long as we compare like with like, it's fine to me. The point I'm making is that higher (not just WEP) power settings were not only available at Sea Level, and in fact for this aircraft were available almost to 10,000 feet, or considerably higher depending on the type.

 

[tomo pauk]

But in combat you won't be in a slow climb or cruise, or anyway not for long, right? Fighter pilots would build up energy by diving and zooming, extending at full power and so on.

So long as we compare like with like, it's fine to me. The point I'm making is that higher (not just WEP) power settings were not only available at Sea Level, and in fact for this aircraft were available almost to 10,000 feet, or considerably higher depending on the type.

Fighter pilots do build up energy if they have either altitude advantage, or speed advantage, or both. Diving does not catch the enemy above you. Against Luftwaffe, P-40E/K was often operating with Spitfires V providing top cover, since Spitfire V have had favorable power-to-weight ratio above 10000 ft, and was faster above 10000 ft. Aircraft with unfavorable power-to-weight ratio can't climb well, and can't accelerate well.

I've already agreed that P-40 with V-1710-33, -39 or -73 used the over-boost (= boost greater than 42 in Hg in case of these engines) well above S/L. We can call over-boosting whatever the name we want, AAF called it WER when the WER was established. Or, in the other words, WER meant 'boost greater than 42 in Hg' here.