# P-40 Performance - Allison versus Merlin



## HoHun (Jul 19, 2008)

Hi everyone,

Here some graphs on the performance of the Allison- versus the Merlin-engined Curtiss P-40 fighters.

That the P-40F was not as good as one might have expected has two main reasons: It was using an early Packard-built V-1650-1 that was similar to the two-speed, single-stage 20-series Rolls-Royce Merlin and not as powerful as the later V-1650 engines fitted to the Mustang that were based on the 60-series Merlins. Additionally, the P-40F was 160 kg heavier than the P-40E, and an amazing 750 kg heavier than the P-40B, which of course had considerable impact on its performance.

(The Allison-vs-Merlin issue was raised in this thread:

http://www.ww2aircraft.net/forum/aviation/p-38-merlin-engines-any-such-animal-13759.html

However, since that was a P-38 thread I decided to start a new one for the P-40 here.)

Regards,

Henning (HoHun)

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## claidemore (Jul 19, 2008)

Turn rates are in degrees per second?


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## HoHun (Jul 19, 2008)

Hi Claidemore,

>Turn rates are in degrees per second?

Oops - yes, they are!

Regards,

Henning (HoHun)


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## kool kitty89 (Jul 21, 2008)

How about adding in the P-40M?
(I think the P-40N is less comparable as there were many other changes to that model and many changes in that model its-self) And the P-40K is roughly the same as the P-40E (at normal loaded weight) except it has more power below 5,000 ft due to increased boost limit to 60" HG. (1,570 hp at ~3,000 ft)

The P-40M was basicly the P-40K with the V-1710-81 (as P-51A and P-40N) instead of the -73. The -81 having much better altitude performance due to the 9.6:1 blower (opposed to the 8.8:1 of the -36 and -73), as has been discussed before. This also had the disadvantage of lower max boost rating (than the -73) and lower max power available below ~5,100 ft.

So:

*P-40M*

Gross weight: 8,400 lbs

powered by one V-1710-81 with 1,200 hp takeoff, 
1,125 hp at 17,500 ft millitary rating, and 
1,480 hp at 10,400 ft at 57" Hg WEP rating. (1,360 hp at SL -although using 57" WEP at SL was not recomented-) These are with ram in high speed level flight.

Without ram (for climb) mil was at ~14,600 ft and
WEP at ~7,500 ft. (crit alt effectively drops by ~2,900 ft)

There's a graph for the P-51A-1 with power curves (climb and level flight) on WWII Aircraft Performance too:


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## HoHun (Jul 21, 2008)

Hi Koolkitty,

>(I think the P-40N is less comparable as there were many other changes to that model and many changes in that model its-self) 

Hm, I believe the P-40N-1 at 7800 lbs, 57" Hg is quite comparable and have included it in the comparison 

Note that the graphs for the P-40N decay a bit quicker with altitude than those of the other types. I suspect that is because the underlying engine graph is more accurate than those for the earlier models - during the war, a better understanding of high-altitude power developed. (And the engine graphs up high were calculated anyway.)

It was Sir Stanely Hooker who came up with an improved method of calculating high-altitude power, but unfortunately an important part of it consists of running the supercharger on a test stand to measure its performance parameters in isolation, so it's difficult to try it at home 

Regards,

Henning (HoHun)

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## Kwiatek (Dec 21, 2008)

What suorce of these data did you use? Could you show it. Im interesting expecially about speed pefromance at sea level of P-40. I cant find any data.


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## HoHun (Dec 21, 2008)

Hi Kwiatek,

>What suorce of these data did you use? Could you show it. Im interesting expecially about speed pefromance at sea level of P-40. I cant find any data.

The data was kindly provided by my friend Peril, who is the real P-40 expert here. You can find the data I had (and more) on Peril's site:

Perils P40 Archive Data

As always, the data can be somewhat self-contradicting due to differences in equipment states, sub-standard engine performance and the like. A good part of my analysis consisted of making sense of these differences and find out what "standard" performance actually means.

Have fun with the data! 

Regards,

Henning (HoHun)


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## Kwiatek (Dec 21, 2008)

Thx i check these site and its very helpfull! I wonder from which test, data you got speed numbers for P-40 E? I cant find such fast speed at the deck in any charts?

BTW i also tried to find any reliable data for maximum speed expecially at the deck about Bf 109 E famliy - expecially BF 109 E-3, E-4 and E-7. I know Kurfust site about 109 but still i need more info about these. I really want to know how fast was Bf 109 E-4 during BoB time .


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## HoHun (Dec 21, 2008)

Hi Kwiatek,

>I wonder from which test, data you got speed numbers for P-40 E? I cant find such fast speed at the deck in any charts?

Note that the P-40E speed in my chart is for the engine boosted to 56" Hg - early on, it seems to have been limited to 44.5" Hg or 45.5" Hg depending on the type of boost control used, which would obviously result in lower speeds.

I'm not quite sure any more what the original data source for the P-40E was, but from comparison to the P-40N I concluded that the P-40E had the same coefficient of drag as the P-40N and calculated the P-40E speeds from there.

>BTW i also tried to find any reliable data for maximum speed expecially at the deck about Bf 109 E famliy - expecially BF 109 E-3, E-4 and E-7. I know Kurfust site about 109 but still i need more info about these. I really want to know how fast was Bf 109 E-4 during BoB time .

The Me 109E is tricky because it had five different engines types (and the prototype had yet another). The DB601A-1 and the DB601Aa were both used on the Emil, and at some time before the Battle of Britain, the supercharger on the DB601A engine was replaced by another one that gave 500 m higher full throttle heights, so after the change both of the above engines had different characteristics. Additionally, the DB601N was used during the battle of Britain by one Gruppe of JG 26.

(A Me 109E captured during the Battle of France was equipped with the "old" supercharger, but other aircraft that came down on British soil during the Battle of Britain had the "new" supercharger. I don't know the proportions of each type in service during the Battle of Britain.)

Here is a site created by my friend Mike Williams that has a good discussion of the topic:

Spitfire Mk I versus Me 109 E

You have to be aware that the Messerschmitt speed graph he gives are for climb and combat power (though are not explicitely designated as such in the original graph, this is evident from the implicit conventions of German performance diagrams). The power setting corresponding to the Spitfire's +12 lbs/sqin would be take-off and emergency power.

As his article was written when the full complexity of the engine question was not yet clear to us, the article is somewhat outdated, but still a good start. As mentioned at the very bottom of the article, at that time it was believed that the DB601Aa was an export engine only, but since then a Luftwaffe Emil has been retrieved from a Russian lake with a DB601Aa engine, and Olivier Lefebvre who's quoted in that footnote has done some additional research, indicating that a certain proportion of the DB601A production was of the Aa variant and that these engines went into Luftwaffe service aircraft.

As the DB601Aa seems to have been a DB601A-1 with raised boost level and thus improved power output, this would actually affect your question for top speed at sea level, too. The supercharger type on the other hand would only influence speed at altitude.

Regards,

Henning (HoHun)

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## Marshall_Stack (Dec 22, 2008)

Does anyone know anything about the engine for the XP-40Q? All I have read is that it had a two-stage supercharger and a higher rated Allison. Was this the same arrangement as the P-63?


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## Kwiatek (Dec 22, 2008)

HoHun said:


> Hi Kwiatek,
> 
> >I wonder from which test, data you got speed numbers for P-40 E? I cant find such fast speed at the deck in any charts?
> 
> ...



Thx Henning for replay

I made some reserch about Bf 109 E perfomance but its hard to find really how fast was E model at the deck. At the Kurfurst site about 109 i find that according to some test speed at sea level was from 467-500 km/h:

109 E-1 manual : ( with DB 601 Aa - 1175 hp)
sea level - 500 km/h
5 km - 570 km/h
7,5km - 550 km/h

Kurfrst - Baubeschreibung fr das Flugzeugmuster Messerschmitt Me 109 mit DB 601.

109 V15 prototype: near the same as above

http://www.kurfurst.org/Performance_tests/109E_V15a/files/109v15a_blatt6.jpg

Swiss test:
sea level - 465 km/h-472 km/h
5km - 565 km/h

Kurfrst - Swiss level speed results for Bf 109E-3, WNr. 2404, J-347 with Escher-Wyss and original VDM propellers.

France test:
sea level - ~480 km/h
5 km - 570 km/h ( radiator closed)

Kurfrst - CEMA : Performance trials with the captured Messerschmitt Bf 109E-3 WNr.1304

German test 109 E-3 - with MG FF and without

sea level - 467 km/h (dont know at which power)

Kurfrst - Meprotokoll vom 16.2.39, Geschwindigkeitsunterschied mit und ohne Flgelwaffen Bf 109 E3

It must be noted that these test was done with pre BoB 109 E which didnt have armour plate behind the pilot and armoured windscreen.

Its really hard to find how fast was Bf109 E-3 or E-4 from BOB time - with armour plate and armoured windsreen.

Also i have problem with climb rates.

At the site which you gave the link i found climb rate for Bf 109 E - ~2800 ft/min ( 14 m/s) also according to these:

http://www.wwiiaircraftperformance.org/me109/me109e-handbookcurve.jpg

Emil have 14,5 m/s initial climb rate and climb to 4 km in 4 min , 6 km in 7 min

If really Emil have 14,5 m/s initial climb rate so must climb to 4 km in 4,6 min not in 4 min so must be some error here.

In manual for E-1 there is climb times:
1 km - 1 min
2 km - 1,9 min
3 km - 3 min
4 km - 3,8 min
5 km - 4,9 min
6 km - 6,3 min

So E-1 must have initial climb rate ~ 16,7 m/s - 17 m/s - but there is no info about setting power - if it is 5 minut power or climb and combat power ( 30 min). If these climb times are for climb and combar power (30 min) so at 5 minut emergency power E-1 should climb even better ~ 18,7 m/s (1122 m/min) and climb time would be:

1 km - 53 sec
2 km - 1,8 min
3 km - 2,6 min
4 km - 3,5 min
5 km - 4,45 min

These would be climb times and rates equal for Bf 109 F model rather.

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## HoHun (Dec 22, 2008)

Hi Kwiatek,

You're quite right that the data is hard to consolidate and sometimes even contradictory in itself.

Here is an (somewhat older) analysis I prepared from the Me 109 handbook data for the DB601A-1 with the early supercharger (designated as "DB601A-1 4.0 km" for its full throttle height). If I'd do that analysis again, I'd probably arrive at slightly different figures due to some improved methods, but it should still be good enough to gave an idea of how to read the handbook graph.

(This is for the condition of the handbook Me 109E, which I presume is without armour glass windscreen.)

Regards,

Henning (HoHun)


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## kool kitty89 (Dec 22, 2008)

Interesting, those turn rates are fairly similar to the Spitfire Mk.I's, correct HoHun. (not to get too off topic, but this _has_ been the subject a continuing argument betwwen the Spitfires and 109's performance)


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## oldcrowcv63 (Sep 17, 2012)

Anyone have a time to climb chart for the P-40F? or know where I can find one? I have the tables but they only go to 25,000 ft. I'd like to know the ToC to 30,000 ft.


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## Greyman (Sep 17, 2012)

A&AEE test I have for a Kittyhawk II (V1650-1) at 8,910 lb and at 2,990 rpm indicates:

28,000 feet in 18.5 minutes
30,000 feet in 21.8 minutes
32,000 feet in 26.7 minutes
34,000 feet in 35.8 minutes

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## krieghund (Sep 17, 2012)

Marshall_Stack said:


> Does anyone know anything about the engine for the XP-40Q? All I have read is that it had a two-stage supercharger and a higher rated Allison. Was this the same arrangement as the P-63?


These engines were similar in ratings but of course the P-63 required the extended propeller shaft. The P-63 engines were of the 'E' series and the P-40Q was of the 'F' series.
Below is a chart of their respective performance and leading dimensions however the War Emergency powers are not given but I have provided them from "America's Hundred Thousand"

P-63 -93 = 1820HP at S.L.
-109 = 1750 HP at S.L.
-117 = 1820H.P. at S.L.

XP-40Q -121 = 1800 HP at S.L.


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## gjs238 (Sep 17, 2012)

The P40Q got the coal mine, the P-63 got the shaft.


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## Mike Williams (Sep 17, 2012)

oldcrowcv63 said:


> Anyone have a time to climb chart for the P-40F? or know where I can find one? I have the tables but they only go to 25,000 ft. I'd like to know the ToC to 30,000 ft.



Hello oldcrowcv63,

You might find the following of interest: Memorandum Report on P-40F, AAF No. 41-13601, Performance Test

See also: 




(click image to enlarge)


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## GregP (Sep 18, 2012)

The first charts posted in here are pretty far off reality. Did they come from some gaming site?

In reality, the planes are all pretty close, with the Allison-powered P-40N being among the best, and certainly the fastest.

1. P-40B: top speed 352 mph on 1,040 HP (1710-33), climb rate 14.5 m/s initial.
2. P-40E: top speed 360 mph on 1,150 HO (1710-39), climb rate 10.7 m/s initial.
3. P-40F: top speed 364 mph on 1,300 HP (1650-1), climb rate averaged 8.8 m/s to 6,100 m (wish they gave initial climb rate!)
4. P-40N: top speed 378 mph in 1,200 HP (1710-81), climb rate 11.4 m/s initial.

Since the 1650-1 was a single-stage Merlin, what difference was expected? If they had used a 2-stage, multi-speed Merlin .... maybe it would have been interesting. Of course, then, to be fair, they'd have to fit an Allison with a competitive system (aux stage or turbo). That might have needed a different airframe ...

I see that some of this has been commented on by others but, really, the Merlin-powered P-40F was no better than the Allison-powered one, unless a 2,000 foot ceiling difference was being deemed important. I doubt seriously that anyone wanted to fight a P-40 at 30,000+ feet anyway. the real question of interest would be a comparison at 10,000 - 15,000 feet, where it was employed in combat. 

Since they installed a single stage Merlin, I'm pretty sure nobody expected it to be better by any significant amount. Maybe that was the point of the exercise ... to demonstrate the equivalence of the two installations. That it certainly did.


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## tomo pauk (Sep 18, 2012)

Hi,



GregP said:


> The first charts posted in here are pretty far off reality. Did they come from some gaming site?



IIRC Ho Hun was the creator of those.



> In reality, the planes are all pretty close, with the Allison-powered P-40N being among the best, and certainly the fastest.
> 
> 1. P-40B: top speed 352 mph on 1,040 HP (1710-33), climb rate 14.5 m/s initial.
> 2. P-40E: top speed 360 mph on 1,150 HO (1710-39), climb rate 10.7 m/s initial.
> ...



If it's not too much of trouble for you, I'd like to see the source for the 378mph figure for the P-40N.



> Since the 1650-1 was a single-stage Merlin, what difference was expected? If they had used a 2-stage, multi-speed Merlin .... maybe it would have been interesting. Of course, then, to be fair, they'd have to fit an Allison with a competitive system (aux stage or turbo). That might have needed a different airframe ...
> I see that some of this has been commented on by others but, really, the Merlin-powered P-40F was no better than the Allison-powered one, unless a 2,000 foot ceiling difference was being deemed important. I doubt seriously that anyone wanted to fight a P-40 at 30,000+ feet anyway. the real question of interest would be a comparison at 10,000 - 15,000 feet, where it was employed in combat.



USA have had to do something with their 1/3rd of the Packard Merlins. Plus, making 1100 HP at 18000 ft vs. 1150 at 12000 ft was an expedient way to improve high altitude performance of the P-40s. You can check out the charts at the US 100000 book to see how the -F outperforms the -E above 18000 ft. Something like 40 mph difference at 22000 ft. 
At 12000 ft, the -F has almost 200 HP more on disposal vs. the -E. So saying that it was no better than the Allison powered planes is not correct.
I'm comparing the -F with -E, and not with -N, since -N was about 15 months later than the -F, and some 20 months later than the -E.



> Since they installed a single stage Merlin, I'm pretty sure nobody expected it to be better by any significant amount. Maybe that was the point of the exercise ... to demonstrate the equivalence of the two installations. That it certainly did.



Looks like they installed what they had?


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## wuzak (Sep 18, 2012)

GregP said:


> 1. P-40B: top speed 352 mph on 1,040 HP (1710-33), climb rate 14.5 m/s initial.
> 2. P-40E: top speed 360 mph on 1,150 HO (1710-39), climb rate 10.7 m/s initial.
> 3. P-40F: top speed 364 mph on 1,300 HP (1650-1), climb rate *averaged 83.8 m/s to 6,100 m* (wish they gave initial climb rate!)
> 4. P-40N: top speed 378 mph in 1,200 HP (1710-81), climb rate 11.4 m/s initial.



Wow..the P-40F had a climb rate 8 times that of the P-40E!




GregP said:


> Since the 1650-1 was a single-stage Merlin, what difference was expected?



The -1 was a single stage 2 speed Merlin. It had the improved supercharger of the Merlin XX, so its performance would theorteically be moved higher in altitude. Because ofthe 2 speed supercharger the loss of performance at lower altitudes would have been minimised.




GregP said:


> If they had used a 2-stage, multi-speed Merlin .... maybe it would have been interesting. Of course, then, to be fair, they'd have to fit an Allison with a competitive system (aux stage or turbo). That might have needed a different airframe ...



Certainly a turbo system or the Allison 2 stage system would have required a lot of work on the P-40 airframe. The 2 stage Merlin was not much longer than the original Allison, but quite a bit heavier. Some weights would have to have been readjusted, and extra cooling would have been required. 




GregP said:


> I see that some of this has been commented on by others but, really, the Merlin-powered P-40F was no better than the Allison-powered one, unless a 2,000 foot ceiling difference was being deemed important. I doubt seriously that anyone wanted to fight a P-40 at 30,000+ feet anyway. the real question of interest would be a comparison at 10,000 - 15,000 feet, where it was employed in combat.




It would appear that the P-40F had roughly the same performance as the E at the E's best altitude, but the F's best altitude was about 8000ft higher. (P-40E 342mph @ 11,400ft, 340mph @ 15,300, P-40F 350.5mph @ 12,800ft, 364.5mph @ 19,270ft).

http://www.wwiiaircraftperformance.org/P-40/P-40E_40-384_PHQ-M-19-1300-A.pdf
http://www.wwiiaircraftperformance.org/P-40/P-40F_41-13601_PHQ-M-19-1440-A.pdf
P-40 Performance Tests




GregP said:


> Since they installed a single stage Merlin, I'm pretty sure nobody expected it to be better by any significant amount. Maybe that was the point of the exercise ... to demonstrate the equivalence of the two installations. That it certainly did.



The point of the exercise was to use the V-1650-1s that the USAAF were getting under the terms of the Packard agreement (1/3 of Packard production was to go the the USAAF).


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## wuzak (Sep 18, 2012)

GregP said:


> 1. P-40B: top speed 352 mph on 1,040 HP (1710-33), climb rate 14.5 m/s initial.
> 2. P-40E: top speed 360 mph on 1,150 HO (1710-39), climb rate 10.7 m/s initial.
> 3. P-40F: top speed 364 mph on 1,300 HP (1650-1), climb rate averaged 83.8 m/s to 6,100 m (wish they gave initial climb rate!)
> 4. P-40N: top speed 378 mph in 1,200 HP (1710-81), climb rate 11.4 m/s initial.



What is the source for these figures Greg?


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## GregP (Sep 18, 2012)

Boy Kreighund, are your numbers for the Allisons in post # 16 somewhat misleading or what?

You picked 2-stage engines in the -93, -109, -117, and -121. The first three are E motors (driveshaft engines) and are P-63 engines. The last one is an F28 (F motors had propellers mounted) and only 4 were built for the XP-40Q, so it was an oddball. The real numbers are as follows:

E11 (1710-93): 1,325 HP for TO; 1,180 HP @ 21,500 feet; 1,800 HP WER. 2,521 built.
E22 (1710-109): 1,425 HP for TO; 1,100 HP @ 28,000 feet; 1,750 HP WER. 222 built.
E21 (1710-117: 1,325 HP for TO; 1,000 HP @ 25,000 feet; 1,800 HP WER. 2,237 built.
F28 (11710-121): 1,425 HP for TO; 1,100 HP @ 28,000 feet; 1,700 HP WER. 4 built.

So, you can see that the Allison didn't do too badly when you consider that the low HP ratings were all at altitude, where ALL WWII engine had somewhat lower ratings than at sea level.

Oh yeah, numbers from Dan Whitney's Vee's for Victory. We regularly get the sea level takeoff numbers from the the E and F engines we build and ship today (single stage, no aux stage), and can get better if anyone wants to race an Allison. Bring money; it ain't cheap. Nobody wants to fly their warbird these days IFR at 20,000 + feet; they'd rather fly VFR and play fighter pilot than waste their gas straight and level flying IFR. One last point, most of our single-stage E and F have a WER rating of about 1,600 HP @ 3,000 RPM. You can get more if you blip the RPM up to 3,200 or 3,400.

We have 5 or more tractor pullers who run them regualrly at 4,000 - 4,500 RPM. They get great HP and stomp all over the Merlin tractors in Europe. The European Tractor Pull Association tried to outlaw the Allison by limiting aircraft engine tractors to 1650 cubic inches and we simply made an Allison V-1650 and continued to beat them. They gave up and re-allowed the V-1710. We have one customer in the Netherlands who has been running our Allisons on the same tractor for 6+ years at 4,500 RPM+ with nothing but regular maintenance (oil changes, clean the screens, change plugs, etc.). He just ordered a sparre engine because he is expecting one to break. So far, it hasn't, but he wants to be covered in case.

If anybody really WANTS a two-stage Allison, we have two auxilliarly stage superchargers ready for overhaul and sale. We can even deliver a turbo setup if anyone really wants one. So far, nobody does since they stay at VFR altutudes.


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## GregP (Sep 18, 2012)

Sorry Wuzak, typo as I'm sure you know. I went back and corrected it and noted that in the edit note area. The P-40F average 8.8 m/s to 6,100 m. The references didn't give an initial climb rate for the F but rather a time to 6,100 m. It would be handy if they had a standard climb test so we could campare apples to apples, wouldn't it?

Source? http://en.wikipedia.org/wiki/Curtiss_P-40_variants. I know Wiki isn't generally all that great, but a quick check with some of my other references shows the same numbers for the variants. I'm sure you can check yours, too.

Let's see, a reference for the P-40N top speed. How about Curtiss P-40N Warhawk - Manufacturer was Curtiss (USA), or Curtiss P-40N Kittyhawk, or Variants P-40N. I could go on, but three is enough, I think. Also, our museum flies a P-40N and it WILL go that fast (TAS, not IAS), even with someone like me in the back seat looking at the ASI. Faster if they go to 3,200 or 3,400 rpm! ... as they have done in the past.

They made 13,739 P-40's. If the F was so good, how come they only made 1,082 of them and phased it out for later P-40 models? Personally, I like the P-40F without the carburetor scoop on top of the cowling. But it wasn't much of an improvment over the Allison version and nobody fought P-40's at high altitude unless there was no other option. It's hard to believe there wasn't a better plane for combat at altitudes over 15,000 feet! My bet on the questiomn above is they stopped making the single-stage Merlins and concentrated on 2-stage units. if so, why didn't they try a 2-stage Merlin in a P-40?

Of course, if they had a 2-stage, multi-speed supercharged version of the Merlin in it, that might have been different, as stated above. I'd like to have seen that model built and tested. Maybe it would have lived up to Don Berlin's intentions. I'd imagine that if true, it would have been a good performer, but maybe not quite as good as high-altitude P-51's or P-47's. I'd still like to know.

I read somewhere years ago that Don Berlin had been allowed to make ONE 2-stage P-40 just so he could prove it out. But I can't find that reference again and cannot remember if it was a 2-stage Allison, a turbocharged Allison, or a 2-stage Merlin. I wasn't into the engines at the time and simply cannot recall. If anyone out there definitely knows, please post! It hardly matters if only one was made, but would be an interesting footnote for the sake of the knowledge.


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## wuzak (Sep 18, 2012)

GregP said:


> Variants P-40N.



This site has a lower top speed listed.



> One 1200 hp Allison V-1710-81 twelve-cylinder liquid-cooled engine. Maximum speed 208 mph at 5000 feet, 325 mph at 10,000 feet, *343 mph at 15,000 feet*. Maximum climb rate was 2120 feet per minute at 5000 feet, 2230 feet per minute at 10,000 feet.



Perhaps the difference between the V-1710 having WEP and not?

Also, note that the P-40N is a lightweight version, with lighter structure and 2 fewer guns, and so is not directly comparable with the P-40F.


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## wuzak (Sep 18, 2012)

GregP said:


> The P-40F average 8.8 m/s to 6,100 m. The references didn't give an initial climb rate for the F but rather a time to 6,100 m.



This report has an initial climb rate of 2100ft/min (10.7m/s) at sea level and a peak climb rate of 2210ft/min (11.2m/s) at 9600ft.





GregP said:


> Also, our museum flies a P-40N and it WILL go that fast, even with someone like me in the back seat. Faster if they go to 3,200 or 3,400 rpm! ... as they have done in the past.



Earlier P-40s with earlier V-1710s would not have had 3200rpm allowed, let alone 3400rpm. As Tomo pointed out, the N was more than a year after the F.





GregP said:


> They made 13,739 P-40's. If the F was so good, how come they only made 1,082 of them and phased it out for later P-40 models?



Engine availability.





GregP said:


> Personally, I like the P-40F without the carburetor scoop on top of the cowling. But it wasn't much of an improvment over the Allison version and nobody fought P-40's at high altitude unless there was no other option. It's hard to believe there wasn't a better plane for combat at altitudes over 15,000 feet!



There was....and that's why they didn't get more Merlins.

The USAAF were getting only a portion (1/3) of Packard production, and when the P-40 was coming on-line so was the P-51B.





GregP said:


> Of course, if they had a 2-stage, multi-speed supercharged version of the Merlin in it, that might have been different, as stated above. I'd like to have seen that model built and tested. Maybe it would have lived up to Don Berlin's intentions.



Don Berlin really wanted the 2 stage Merlin for the P-40. But would it have been worth the effort?

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## krieghund (Sep 18, 2012)

GregP said:


> Boy Kreighund, are your numbers for the Allisons in post # 16 somewhat misleading or what?



I believe the question was about the engine in the XP-40Q being the same as installed in the P-63?

The data I provided gave the answer, no it was from a different series but had similar powers, I wasn't concerned about production numbers.

This is the V-1710-119 in the Mustang. This would have worked in the 'Q' as well, to bad they didn't allow the use of the ADI when flight testing this aircraft.


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## Jabberwocky (Sep 18, 2012)

I don't know if I've ever seen the 378 mph figure in primary documentation, certainly not in testing data. Generally speaking, tested P-40Ns seem to max out at about 360 mph, with the lowest figures down under 350 mph and the best at about 365 mph.

Remember though that the performance of test aircraft varied wildly. The RAF and USAAF P-40F tests have top speeds as high as 374 mph in one test with a cleaned up example and as low as 342 mph in RAAF tests with a war-weary example.

The RAAF and RAF operated a lot of P-40Ns and I've got a few of their service tests on hand. The best speed data I have on hand from their testing is the following:

August 1943 RAAF data sheet:

364 mph at 17,200 feet for P-40N (unidentified sub-type, V-1710-81, MP not given)
312 mph at sea level, conditions as above

October 1943 RAF data 

359 mph at 12,000 ft with P-40N-1 with V-1710-81 at 52" manifold pressure (5 minute war emergency)

March 1944 RAAF testing

344 mph at 17,000 ft for a P-40N-5 with V-1710-81 at 44" manifold pressure (15 minute military power)
352 mph at 9,200 ft for P-40N-5 with V-1710-81 at 57" manifold pressure (5 minute war emergency)

Undated RAAF data sheet

310 mph at 1000 ft, for P-40N with V-1710-81 at 55" manifold pressure (5 minute war emergency)
359 mph at 10,000 ft, conditions as above

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## krieghund (Sep 18, 2012)

Referring back to my previous post #16 here is the Spec curve of the P-63 with those three referenced engines..............enjoy from WWII Performance Website


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## Shortround6 (Sep 18, 2012)

The P-40N designation actual covered a variety of aircraft depending on block number. The 378mph speed _MAY_ apply to a very early block number (200 made?) with 4 guns, restricted ammo, one fuel tank taken out, hand starter only, small battery, one bomb fuel rack(?) and some other tricks and suing WER at 10,000ft. Later block numbers with 6 guns, electric starters and other "luxuries" but back back in and three bomb racks (even if empty) were down to the 343mph figure at 15,000ft. Supercharger would not provide any WER at that height UNLESS the engine was OVER revved. Engines capable of over revving to any significant extent without drastic shorting of life were the so called 12 counter weight crankshaft engines. Some late P-40Ns may have gotten these crankshafts from the factories, some may have gotten them at overhaul. Greg would know much better than I but many restored warbirds may use these crankshafts now. They will fit in most of the older blocks (?). 

As Jabberwockey has said, a lot depends on aircraft condition. a good putty job and sanding, a good coat of "gloss" paint and a good wax job could be worth 10-15mph vrs even a decent flat camo standard factory finish let alone a well worn front line aircraft. 

Basically the US was getting 1/3 of the Merlin production, they needed some way to use them. Sticking them in the P-40 was one way and at the time, very late 1941 to mid 1942, the Allisons _in production_
were topping out at 12,000ft and under. The Merlin in high gear offered 5-8,000 more altitude. At 20,000ft an F was 20-25mph faster than an E. Unfortunately the enemy fighters improved even more.


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## Mike Williams (Sep 18, 2012)

The following reports should shed some light on P-40N performance and go some way to explain the varying data noted:

Memorandum Report on P-40N, No. 42-9987: Flight Tests.
Memorandum Report on P-40N, No. 42-105241: Performance Tests


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## GregP (Sep 18, 2012)

Thanks you Jabberwocky! The performance of individual aircraft DID vary quite a bit. And the only people who much ever saw the absolute maximum speed were test pilots. NOBODY flew them at that speed, except in a dive, when away from the home airfield since they wanted to get back in one piece. The "combat speed" was generally about 50 - 80 mph slower than maximum straight and level speed. To me, "combat speed" is the cruise speed plus any acceleration produced after combat was joined, until combta broke off. Of course, they went faster if they dived out of combat, but then ... it broke off, didn't it? Unless someone followed, and that did happen on a few occasions.

I don't much care of the P-40N was a year later; it was in the P-40 family and counts. Any of the E, F, or G Allisons could easily get to 3,200 or 3,400 rpm. Any of our E, F, or G models can and sometimes do. The earlier models could, but the nosecase would overheat if it stayed there for very long since it wasn't designed for it. The F and G were and the E didn't have a nose case at all; it turned a driveshaft. 

Personally, I think the real bread and butter combat P-40's of WWII started with the E. The earlier ones, about 1,723 or so ... possibly a few more ... of over 13,000 built, were somewhat developmental. Just my opinion.


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## oldcrowcv63 (Sep 20, 2012)

Greyman said:


> A&AEE test I have for a Kittyhawk II (V1650-1) at 8,910 lb and at 2,990 rpm indicates:
> 
> 28,000 feet in 18.5 minutes
> 30,000 feet in 21.8 minutes
> ...



Thanks, GM, That's pretty much what I was looking for.


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## GregP (Sep 22, 2012)

Yeah, if you're only turning 39" of MAP and 2,600 rpm, the P-40 flies fine but doesn't sparkle at all. 3,250 feet per minute is WAY better than 1,900 fpm, huh? Try climbing at 65" and 3,200 rpm. The climb rate will be just fine and right there with a P-51. 

57+" MAP and 3,000 rpm makes a BIG difference. Either way, it still rolled better than most US aircraft in WWII.

Also, almost any late Allison can pull 75+" of MAP if needed and can get to 3,600 rpm without trouble. The prop may have some stress, but the engine can DO it. Ours do, today ... right now, and anytime. Heck, we even have the props, hubs, and brush assemblies for the Curtiss Electric prop! Want to race? We can get you 120+" of MAP with an Aux stage supercharger (G6) and you can make some serious HP in your P-40! We even have the gun synchronizer assemblies if required ... and they WORK. Of course, it is tough these days to find P-40 engine mounts. We have them, too. Heck, the P-40 is more rare today than the P-51, and probably worth more money.


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## pinsog (Sep 22, 2012)

GregP said:


> Yeah, if you're only turning 39" of MAP and 2,600 rpm, the P-40 flies fine but doesn't sparkle at all. 3,250 feet per minute is WAY better than 1,900 fpm, huh? Try climbing at 65" and 3,200 rpm. The climb rate will be just fine and right there with a P-51.
> 
> 57+" MAP and 3,000 rpm makes a BIG difference. Either way, it still rolled better than most US aircraft in WWII.
> 
> Also, almost any late Allison can pull 75+" of MAP if needed and can get to 3,600 rpm without trouble. The prop may have some stress, but the engine can DO it. Ours do, today ... right now, and anytime. Heck, we even have the props, hubs, and brush assemblies for the Curtiss Electric prop! Want to race? We can get you 120+" of MAP with an Aux stage supercharger (G6) and you can make some serious HP in your P-40! We even have the gun synchronizer assemblies if required ... and they WORK. Of course, it is tough these days to find P-40 engine mounts. We have them, too. Heck, the P-40 is more rare today than the P-51, and probably worth more money.



What could the 1942 and 1943 Allison engines have done as far as MAP and RPM? What are you guys doing different today that they weren't doing during earl WW2 when the Germans and Japanese(especially the Japs) were giving the P40 such a bad time?

Why didn't the early Allisons try to pull as much MAP and RPM as your engines?


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## Shortround6 (Sep 22, 2012)

The old engines didn't have the 12 counterweight crankshaft until very late in the war. 

The older engines weren't balanced as well apparently. Pistons and connecting rods not as closely matched for weight? 

There may have been small but important changes to the supercharger. Changing the inlet guide vanes may be worth a few inches of MAP. 

The ability to pull 72-75 in of MAP is very dependent on altitude and which set of supercharger gears are in the engine. 

There is also the difference between test stand and flight. Many engines show a difference of several thousand feet of altitude between climb and level flight (high speed) pressure limits. You may be able to get 72-75in at sea level and doing 300+ mph level flight. Slowing to 140-160mph for best climb may see several in of MAP disappear.


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## pinsog (Sep 22, 2012)

Shortround6 said:


> The old engines didn't have the 12 counterweight crankshaft until very late in the war.
> 
> The older engines weren't balanced as well apparently. Pistons and connecting rods not as closely matched for weight?
> 
> ...


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## bob44 (Sep 22, 2012)

> I guess my question is, should they have been able to get alot more out of the Allison, early in the war, with their available technology? Or did they do all they could do?



Possibly. But this takes development. Add a two stage supercharger, or turbocharger, intercooler/aftercooler, a pressure carb. Is a good start.
Also, you need an aircraft for this engine, something that is simple for the pilot to operate, with automatic controls, that will help manage the engine.

A problem with the Allison, from what I have read, was the uneven fuel distribution in the intake. Some cylinders too much fuel, some too little fuel. If this was known early in the engine's life, I do not know. Otherwise the Allison was a very tough engine.


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## Shortround6 (Sep 22, 2012)

You had several things going on at once. The early "C" engines in the P-40B&C (Tomahawks) had a problem with the propeller reduction gears. Some of the other parts may not have been the equal of even a 1941/42 manufactured engine. 

Fuel was another big "_IF_" factor in the early part of the war. The Allisons were developed using US spec 100 octane fuel. This is different than either British 87 octane or British 100 octane. British 87 octane fuel had a fair amount of "aeromatics" in it and performed better (allowed higher boost)than than _some_ 87 octane fuel but it was never really measured. American 100 octane fuel had very little allowable ( 2% max) "aeromatics" and while a richer mixture allowed a bit more boost there was no real _jump_ in allowable boost pressures. In fact a few batches of US 100 octane gas performed at _worse_ than 100 octane rating when running rich.
British 100 octane fuel at the time of the BoB and shortly after had 20% aeromatics _minimum_ and while not tested for a while, it performed much better under rich conditions than lean. Once they did come up with test procedures and and a rating system it was found that most batches of British 100 octane had a rich mixture response of between 115-120PN. Or 100/115-120. Once they had that figured out the British began specifying 100/130 fuel. The US meanwhile shifted to a 100/125 fuel specification. 

Sorry to be a bit long winded but it helps explain why British units in North Africa could use higher boost numbers than the US army approved for it's identical engines at the same time. While few people were using 75in of boost at the time a lot of them were running way over the "BOOK" numbers of 40-44 in MAP. Some claim ( and others say they didn't) The Flying Tigers used some rather high boost settings too, but I don't know were their fuel was coming from. British or American stocks? This fuel discrepancy carried over into the P-40E's at least and maybe into the P-40Ks. At some point in 1942 the British and Americans standardized on the 100/130 fuel specification. Trying to use 60-70 in of boost on 1940 US 100 octane fuel could be a very _iffy_ proposition. Given ideal conditions you might get away with it. Less than ideal might mean pushing into the 50s could wreck the engine. 

As far as other "technology" goes a number of parts were changed along the way, Crankshafts went from "plain" to shot peened to shot peened _and_ Nitrided (early 1942) for an almost doubled allowable stress level, and that is before the 12 counter weight crankshaft shows up in early 1944. Other parts like connecting rods changed. Valve springs changed on the later engines. Even the way the crankcases were cast was changed. 
Trying to wind an early engine _AS BUILT_ to 3400-3600rpm could (and often did) result in disaster. Doing it to a rebuilt engine using late model internal parts could very well be a different story.

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## GregP (Sep 22, 2012)

The engines we build today are mostly later series and perform to stock levels. The rated rpm is 3,000 but the design was good for a LOT more. We have some customers who run them at 4,500+ rpm, but not in airplanes.

The thing is, the American engineers and Army acceptance peoplpe were very conservative. The Allison can pull over 100" of Mercury MAP, but was rated VERY conservatively and tested conservatively. You almost can't FIND a test report at over 57" of MAP and 3,000 rpm .... but we can easily get 75"+ and 3,400 - 3,600 rpm if we want. We CAN get to 115" of MAP for a race engine. Most owners don't becasue there is almost no reason to do so.

The entire point is, when we DO, the engine handles it very well!

The Allison is tougher than the Merlin and holds a tune-up MUCH longer; MUCH more trouble-free. NOTHING wrong with a Merlin; you get what you expect to get with one, no argument there. It's just that you get so much MORE than you expect with a well-overhauled and properly-tuned Allison. We have several in Jurca Spitfire replicas and they give 95+% of the performance of the real aircaft despite having only a single stage supercharger rather than a 2-stage unit. If they had an equivalent two-stage, they'd kick-butt, and do anyway in tractor pulls where sea level performance is important.

No single-stage ALlison is great at 25,000+ feet compared with a 2-stage Merlin, but the aux-stage and turbo models were ... and ARE. ALL Alisons were VERY comparable to the single stage Merlins, particularly from a serviceability standpoint. They were VERY good engines hamstrung by a government committee that controlled the ordes. if they order a V-1710-39, thath's what you deliver ... not some BETTER engine. To do that would violate the contract.

In the post-war unlimited hydroplanes, the merlins that eventually took over from the Allisons were all 2-stage units. The single-stage Merlins mostly lost to the sinlge-stage Allisons. Guy Lombardo was the US Champion for 1946 - 1949 and won EVERY trophy on the circuit with Allisons. I have two pistons from one of his Championship-winning boats. When Merlins "took over," they were the 2-stage units and won mostly due to lack of knowledge of how to tune-up Allisons.

When they made the movie "Madison," Joe Yancey built the Allisons for the 20+ old hydroplane boats in the movie. He built them to STOCK configuration and they almost all ran 20+ mph faster than they did in "back-in-the-day" competion during the filming of the movie simply becasue the guys trying to "hot rod" the Allisons didn't know what they were doing. They ALSO put over 70+ hours on most of the boats during the filming and the engines never broke.


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## RCAFson (Sep 23, 2012)

Shortround6 said:


> You had several things going on at once. The early "C" engines in the P-40B&C (Tomahawks) had a problem with the propeller reduction gears. Some of the other parts may not have been the equal of even a 1941/42 manufactured engine.
> 
> Fuel was another big "_IF_" factor in the early part of the war. The Allisons were developed using US spec 100 octane fuel. This is different than either British 87 octane or British 100 octane. British 87 octane fuel had a fair amount of "aeromatics" in it and performed better (allowed higher boost)than than _some_ 87 octane fuel but it was never really measured. American 100 octane fuel had very little allowable ( 2% max) "aeromatics" and while a richer mixture allowed a bit more boost there was no real _jump_ in allowable boost pressures. In fact a few batches of US 100 octane gas performed at _worse_ than 100 octane rating when running rich.
> British 100 octane fuel at the time of the BoB and shortly after had 20% aeromatics _minimum_ and while not tested for a while, it performed much better under rich conditions than lean. Once they did come up with test procedures and and a rating system it was found that most batches of British 100 octane had a rich mixture response of between 115-120PN. Or 100/115-120. Once they had that figured out the British began specifying 100/130 fuel. The US meanwhile shifted to a 100/125 fuel specification.
> ...



On page 7:

http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf

there's an example of a p-39 trying, and failing, to use 70in of boost, on US fuel.

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## tomo pauk (Sep 23, 2012)

GregP said:


> The engines we build today are mostly later series and perform to stock levels. The rated rpm is 3,000 but the design was good for a LOT more. We have some customers who run them at 4,500+ rpm, but not in airplanes.
> 
> The thing is, the American engineers and Army acceptance peoplpe were very conservative. The Allison can pull over 100" of Mercury MAP, but was rated VERY conservatively and tested conservatively. You almost can't FIND a test report at over 57" of MAP and 3,000 rpm .... but we can easily get 75"+ and 3,400 - 3,600 rpm if we want. We CAN get to 115" of MAP for a race engine. Most owners don't becasue there is almost not reason to do so.
> 
> The entire point is, when we DO, the engine handles it very well!



Hi, Greg,
IMO, stating what today's piston engines are able to do, and then drawing the conclusions about ww2 era engines is just messing the thread. It's what the V-1710 was able to do vs. Merlin/V-1650, during the war time. 



> The Allison is tougher than the Merlin and holds a tune-up MUCH longer; MUCH more trouble-free. NOTHING wrong with a Merlin; you get what you expect to get with one, no argument there. It's just that you get so much MORE than you expect with a well-overhauled and properly-tuned Allison. We have several in Jurca Spitfire replicas and they give 95+% of the performance of the real aircaft despite having only a single stage supercharger rather than a 2-stage unit. If they had an equivalent two-stage, they'd kick-butt, and do anyway in tractor pulls where sea level performance is imnportant.



What altitude is where those 95% of the performance is reached? SL, 15000 ft, 30000 ft?



> No single-stage ALlison is great at 25,000+ feet compared with a 2-stage Merlin, but the aux-stage and turbo models were ... and ARE. ALL Alisons were VERY comparable to the single stage Merlins, particularly from a serviceability standpoint. They were VERY good engines hamstrung by a government committee that controlled the ordes. if they order a V-1710-39, thath's what you deliver ... not some BETTER engine. To do that would violate the contract.



Single stage Allison is worse above 15000 ft than the single stage Merlin, period. 2 stage engine was capable to do in 1944 what the 2 stage Merlin was capable to do in 1942. The turbo V-1710, in order to reach what the 2 stage Merlin was doing, needed much more space weight. 



> In the post-war unlimited hydroplanes, the merlins that eventually took over from the Allisons were all 2-stage units. The single-stage Merlins mostly lost to the sinlge-stage Allisons. Guy Lombardo was the US Champion for 1946 - 1949 and won EVERY trophy on the circuit with Allisons. I have two pistons from one of his Championship-winning boats. When Merlins "took over," they were the 2-stage units and won mostly due to lack of knowledge of how to tune-up Allisons.



Nobody in RR was interested in development of the 1-stage Merlins past, say, mid 1942? 



> When they made the movie "Madison," Joe Yancey built the Allisons for the 20+ old hydroplane boats in the movie. He built them to STOCK configuration and they almost all ran 20+ mph faster than they did in "back-in-the-day" competion during the filming of the movie simply becasue the guys trying to "hot rod" the Allisons didn't know what they were doing. They ALSO put over 70+ hours on most of the boats during the filming and the engines never broke.



All fine and well, but again, no bearing to the time frame, and hence to the topic of the thread.


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## Shortround6 (Sep 23, 2012)

Thank you. The report is dated Dec of 1942, The actual flying tests may have been some months earlier? 

Of interest is not only was engine detonating with the attempt at 70in for take-off or sea level but that 52in of MAP could only be maintained until until 4500ft at climb speed. 

Power charts for some early model Allison's are available and use NO RAM at all so flying even at climb speed would show an improvement. The -33 engine used in the P-40B&C and Tomahawks was good for 1090hp at 3000rpm at 38.9 in MAP at 13,200ft. At 5,000ft the engine was good (assuming it did not blow up and these early engines did NOT have the improvements of the later engines) for 1440hp at 3000rpm and just over 52in MAP. Continuing down to sea level the engine should have made just under 1700hp at 61in of MAP. Getting more than 61in of MAP requires either forward speed providing RAM or over revving the engine or both. This engine had the 8.77 supercharger gears and any Allison engine using the 9.5in dia impeller and the same (or 8.80?) gear is going to give about the same pressures at the same altitudes. Differences in carburetors, inlet manifolds, backfire screens and inlet guide vanes on the supercharger inlet can affect things a bit. Big changes are the supercharger gears. With the 7.48 gears used in the A-36 there is little chance the engine could make 70 in at any altitude or speed. With the 9.60 gears used in late model Allisons getting to 70-75 in at low altitudes in fairly easy. Surviving is a lot harder. 

Impeller speeds at 3000 rpm for the 7.48 gear is 22440rpm. for the 8.80 gear it is 26400rpm and for the 9.60 gear it is 28800rpm. power to drive the supercharger goes up with the square of the speed. approximately 30% of the power is turned into heat in the intake charge. The hotter charge is less dense and doesn't give the proportional power increase and the hotter charge is more likely to detonate. Allison was afraid that units that were used to operating at 56in and above with the 8.80 gears would wreck engines running those pressures with the 9.60 gears.


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## Dan Fahey (Aug 12, 2018)

Would love to revive this conversation.
Some questions..
The Reno Races over the last few years have a P40, P51A and think a P38 taking laps.
There was a comment that the 3 blade prop of the Mustang and Warhawk limited the top speed.
Can a modern day Allison be built to compete with the super Unlimiteds?
Would that require a different propeller?
What HP could be expected?
Would operating at 3200/3400/3600 rpm be doable?

Conversations with Chris Fahey with Planes of Fame.
He noticed the P51A climbed a bit better than the P51D to 10000 ft.
This is when they were doing photo ops.

Then again do not know what octane they were regulated to use.
Think they all use the 100LL as standard for most of their flying.

Dan


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## Shortround6 (Aug 12, 2018)

Dan Fahey said:


> The Reno Races over the last few years have a P40, P51A and think a P38 taking laps.
> There was a comment that the 3 blade prop of the Mustang and Warhawk limited the top speed.
> Can a modern day Allison be built to compete with the super Unlimiteds?
> Would that require a different propeller?
> ...



A newer prop might well be beneficial. However as a general rule of thumb the higher you go the more prop you need. at sea level on a 59 degree day you can use a much smaller prop than at 20,000ft even for the same power. Air density at Reno altitude and well over 100 degrees IS????

A modern day Allison might be able to compete with the unlimiteds but it needs a much different supercharger to do it. It also needs a much different cooling system. It would certainly require a new propeller as you are now dealing with 3-4000hp and not 1200-1500hp. 
Using the 12 counter weight crankshaft is a start for high RPM but for how long??? 

Greg may have better answers



> Conversations with Chris Fahey with Planes of Fame.
> He noticed the P51A climbed a bit better than the P51D to 10000 ft.
> This is when they were doing photo ops.



Here you need information on the two planes involved. The P-51A was lighter in military form than the P-51D. 
As "warbirds" are they carrying weight to simulate guns/ammo? 
I don't believe anybody is still flying with self sealing tanks/liners (they deteriorate over time and become a hazard=blocked fuel lines/filters) 
Armor? new radios? 

and are both pilots accurately reporting rpm and boost used in the climb?


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## Dan Fahey (Aug 12, 2018)

Shortround6 said:


> A newer prop might well be beneficial. However as a general rule of thumb the higher you go the more prop you need. at sea level on a 59 degree day you can use a much smaller prop than at 20,000ft even for the same power. Air density at Reno altitude and well over 100 degrees IS????
> 
> A modern day Allison might be able to compete with the unlimiteds but it needs a much different supercharger to do it. It also needs a much different cooling system. It would certainly require a new propeller as you are now dealing with 3-4000hp and not 1200-1500hp.
> Using the 12 counter weight crankshaft is a start for high RPM but for how long???
> ...



Well earlier conversations commented that the D was about 1000 lbs lighter in civilian trim.
Don’t think they are using full tanks of fuel either. 
Then again modern day radios are a lot lighter than the tube with heavy transformers.
Be interesting redesigning the Mustang cockpit with modern instruments!

Figured the P51A flying at Reno was using 100 LL octane fuel for the Silver and Gold Races.
Hitting 350 mph laps. Which seems consistent with WW2 tests.
The P40 was not far behind.

Lot of new Allison FAA upgraded approved parts are available.
Because the original equipment is gone or worn out.
So new ones got manufactured.

Reading about the tractor pull races using Allison’s.
Figured those upgrades could be used for Reno coming up in mid September!

Was the oil system in the Allison high pressure low volume or low pressure high volume?

Dan


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## FLYBOYJ (Aug 13, 2018)

Folks, understand that the the P-40 and P-51A ( and similar heat aircraft) are there more for show. Look at the qualifying times and their final placings in the unlimited. BTW comparing lap speeds at Reno to original testing is like comparing apples to bowling balls.

2017 Unlimited Qualifiers

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## FLYBOYJ (Aug 13, 2018)

Dan Fahey said:


> Lot of new Allison *FAA upgraded approved parts* are available.



Hmmmm... Please explan


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## Dan Fahey (Aug 14, 2018)

FLYBOYJ said:


> Hmmmm... Please explan


What was said in the Allison engine builders web site!
They remanufactured the parts and got FAA certifications.
Plus exceeded original factory specification!
Www.aceallisons.com


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## FLYBOYJ (Aug 14, 2018)

"Upgraded FAA approved parts." The correct term.

I'm curious about this as I could not find any Type Certificate Data Sheet for the V-1710. Most if not all unlimiteds are running in Experimental category. FAA approval for any change in configuration would only happen if modifications are restricted on their aircraft's operation letter. Ace Allison's is not listed as an FAA repair station so I'm wondering on what basis this guy is making this claim. Maybe Greg has some info.


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## GregP (Aug 14, 2018)

With regards to post#41, a P-39 trying and failing to use 70" MAP, the date of the report is Oct 1942. Grade 150 fuel wasn't widely available until after summer 1944. I'm guessing the P-39 was running grade 100/130 fuel. Not challenging the report at all, just noting the report date and when fuel was improved to grade 150.

Reference here: 150 Grade Fuel Summarized below.

USAAF Materiel Command held a "Conference on National Advisory Committee for Aeronautics Test Program to Investigate 150 Grade Fuels" on 27-28, January 1944. It was concluded that "The program outlined should permit conclusive data to be obtained and should indicate the relative advantages of the various high octane fuel components for the preparation of satisfactory rich and lean rating fuels. It should also indicate the military value of these fuels for long range patrol or bombardment operation". It was recommended that "the program outlined should be carried out as expeditiously as is possible".

With regard to Post #48 above, ACE Allisons: They make/made new parts because they don't have any originals to speak of. I have seen at least a eight ACE Allisons while taking them apart. My recommendation is to use genuine Allison parts when you can, and they ARE available, including piston rings.

If you are serious about an Allison, ask ACE's Bud Wheeler what his Allison guarantee is and what constitutes engine abuse. Ask him to seat the rings on a run stand before he ships it. Ask him if he'll ride in it with you. Then go ask Joe Yancey (Yancey Allisons) and/or Jose Flores (Vintage V-12s). Might as well get info from several builders. Decide for yourself and good luck whatever the choice is. Last, post pics of your new Allison chariot!

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## Kevin J (Aug 15, 2018)

GregP said:


> With regards to post#41, a P-39 trying and failing to use 70" MAP, the date of the report is Oct 1942. Grade 150 fuel wasn't widely available until after summer 1944. I'm guessing the P-39 was running grade 100/130 fuel. Not challenging the report at all, just noting the report date and when fuel was improved to grade 150.
> 
> Reference here: 150 Grade Fuel Summarized below.
> 
> ...


From what I've read on the Soviet experience with the P-39, WEP wasn't available for use until the P-39K.

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## Dan Fahey (Aug 16, 2018)

Jack Rouch built Merlin Engines for the Reno Mustangs with a lot of his modifications.
My original comment was the possibility of building a competitive Allison engine.
Would not be surprised that the remaining Allison engine builders have to manufacture unavailable parts.
And collaborate how and what to do and get them past FAA certification!


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## GregP (Aug 16, 2018)

Not sure anyone these days is running Roush parts on Merlins or Allisons. Would be great to find out, though.


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## FLYBOYJ (Aug 16, 2018)

Dan Fahey said:


> And collaborate how and what to do and get them past FAA certification!



There is NO FAA certification for experimental engine or engine parts unless there is a Type Certificate issued against that engine.


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## Dan Fahey (Aug 16, 2018)

FLYBOYJ said:


> There is NO FAA certification for experimental engine or engine parts unless there is a Type Certificate issued against that engine.


Merlin’s and Allison are not experimental engines!
Even though they are souped up!


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## FLYBOYJ (Aug 16, 2018)

Dan Fahey said:


> Merlin’s and Allison are not experimental engines!
> Even though they are souped up!


Evidently you know nothing about aircraft certification.

If they do not hold a Type Certificate Data Sheet (issued by the FAA) they cannot be installed in an aircraft unless that aircraft is certificated under EXPERIMENTAL category. There is no FAA certification process for the manufacture of these engines (or their parts) unless a TCDS is issued. The FAA may issue on a case-by-case/ individual aircraft basis a requirement for inspection if any part of the airframe or engine is modified under the individual aircraft's operation specifications and experimental airworthiness certificate.

So far I have not found a TCDS for either the Merlin or Allison

Again, for certification and civilian operational certification purposes, these aircraft (to include engines and propellers) are EXPERIMENTAL


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## GregP (Aug 16, 2018)

Joe Yancey built up a racing Allison for an Australian Yak last year flown by Graeme Frew. Graeme's number, 35, was taken directly from Burt Munro's (World's Fastest Indian) motorcycle.






I have been asked by Joe not to disclose what was done to built up the engine and I won't. The issues they had centered around the fact that the Yak's radiator was NOT up to the task of cooling the Allison at race power levels. It ran hot EVERY time they ran it.

They had to put back in Graeme's stock Allison due to heat issues and finished last in the Gold final, but their goal was to get to Reno and compete. They managed to get bumped out of Bronze and transferred to Silver, then transferred to Gold. They not only competed, they bumped two classes and finished the Gold class! That's pretty good for a first attempt, I'd say. They never got to race the Allison that was built up for the task due to too small a radiator.

It may or may not happen again, but everyone who heard Joe's racing Allison was impressed. The best comment came from Matt Nightengale. He said to Joe that he had never heard an Allison sound like that before after Graeme's first takeoff. Graeme climbed out at about a 30° angle, but quickly came back with a hot engine!

I'd love to say more about his race engine, but Joe is my friend and he has specifically asked me not to do so.

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## MACHIA (Aug 16, 2018)

Marshall_Stack said:


> Does anyone know anything about the engine for the XP-40Q? All I have read is that it had a two-stage supercharger and a higher rated Allison. Was this the same arrangement as the P-63?


From earlier reading I recall an Allison V1710 1,475 hp was used and the P-40Q and attained a speed of 422 mph in straight and level flight . The V1710’s used in the P-38’s were of the same horsepower . Although I’m not sure that this engine was installed in the P-63 . Anyone care to comment on that ?


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## Big Jake (Aug 16, 2018)

Firstly, if the aircraft and engine are "as built" and conform with the Type Certificate then the aircraft can be registered in Limited or Restricted categories, not necessarily Experimental. This also applies to Warbirds. Through the years, many alterations were allowed by the FAA on Warbirds. 
Secondly, in Reno some Warbirds are "Stock" (certified in Limited or Restricted categories), very limited in the way of modifications, or "Experimental" (the "Big Guns".) As far as I remember, a stock one never won an un-limited race in Reno - just didn't have the performance.
Thirdly, you cannot build a P-51 or a Merlin engine from scratch unless you own the Type Certificate and have a production authorization from the FAA. All the engines and aircraft in circulation have an original placard from the original manufacturer. You can build a new aircraft around a placard but you have to be careful - you need to show the Feds that it is a "restoration" or "major repair"... In addition to a number of fighters, right now a "new" B-17 is being built basically from scratch following this method.
If you change an engine on an aircraft and that new engine is not on the aircraft Type Certificate - talk to the FAA first. 
My two cents...


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## FLYBOYJ (Aug 16, 2018)

Big Jake said:


> Firstly, if the aircraft and engine are "as built" and conform with the Type Certificate then the aircraft can be registered in Limited or Restricted categories, not necessarily Experimental. This also applies to Warbirds. Through the years, many alterations were allowed by the FAA on Warbirds.
> Secondly, in Reno some Warbirds are "Stock" (certified in Limited or Restricted categories), very limited in the way of modifications, or "Experimental" (the "Big Guns".) As far as I remember, a stock one never won an un-limited race in Reno - just didn't have the performance.
> Thirdly, you cannot build a P-51 or a Merlin engine from scratch unless you own the Type Certificate and have a production authorization from the FAA. All the engines and aircraft in circulation have an original placard from the original manufacturer. You can build a new aircraft around a placard but you have to be careful - you need to show the Feds that it is a "restoration" or "major repair"... In addition to a number of fighters, right now a "new" B-17 is being built basically from scratch following this method.
> If you change an engine on an aircraft and that new engine is not on the aircraft Type Certificate - talk to the FAA first.
> My two cents...



There is no "Type Design" for the Merlin or Allison (let alone for the P-40 or P-51), as far as I could find. While you are correct about the Limited or Restricted categories, under those categories you are "Restricted or Limited" in operations or modifications but you CAN build a P-51 or Merlin if they don't have a TC to begin with.
Again - if a former military aircraft doesn't have a T/C and you want to put a "N" number on it (and race it) more than likely the feds are going to issue that pink piece of paper that says "EXPERIMENTAL."

http://rgl.faa.gov/Regulatory_and_G...b0dbf755726862581670074666f/$FILE/8130.2J.pdf


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## FLYBOYJ (Aug 16, 2018)

Looks like the P-51 has a "LIMITED" TCDS

http://www.calpacificairmotive.com/LTC-11__rev_5.pdf


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## FLYBOYJ (Aug 16, 2018)

FLYBOYJ said:


> Looks like the P-51 has a "LIMITED" TCDS
> 
> http://www.calpacificairmotive.com/LTC-11__rev_5.pdf


And I'll stand corrected, one for the P-40N. Both Limited

http://www.airweb.faa.gov/Regulator...90d673ee85c186257106006fd4ab/$FILE/LTC-18.pdf


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## Kevin J (Aug 16, 2018)

MACHIA said:


> From earlier reading I recall an Allison V1710 1,475 hp was used and the P-40Q and attained a speed of 422 mph in straight and level flight . The V1710’s used in the P-38’s were of the same horsepower . Although I’m not sure that this engine was installed in the P-63 . Anyone care to comment on that ?


You'd get an extra 20 mph out of a Spitfire without its armament, armour, rear view mirror, snow guard etc. So the speed seems plausible on the single stage engine that it was fitted with. Oops, I thought you wrote P-39Q.


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## FLYBOYJ (Aug 16, 2018)

FLYBOYJ said:


> And I'll stand corrected, one for the P-40N. Both Limited
> 
> http://www.airweb.faa.gov/Regulator...90d673ee85c186257106006fd4ab/$FILE/LTC-18.pdf



So going full circle - if you operate a P-40 or P-51 under those LTCDS and alter the type design, you'll more than likely have to certify the aircraft (to include the engine) under experimental category


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## Shortround6 (Aug 16, 2018)

Kevin J said:


> You'd get an extra 20 mph out of a Spitfire without its armament, armour, rear view mirror, snow guard etc. So the speed seems plausible on the single stage engine that it was fitted with.




trouble is that it wasn't a single stage engine and the 422mph wasn't done using 1425hp. 

see:http://www.wwiiaircraftperformance.org/P-40/XP-40Q2_Eng-47-1728-A.pdf

of which this is an excerpt. 





3200rpm and 75in of boost at 20,000ft were well beyond the capabilities of any single stage Allison.

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## P-39 Expert (Aug 17, 2018)

RCAFson said:


> On page 7:
> 
> http://www.wwiiaircraftperformance.org/japan/intelsum85-dec42.pdf
> 
> there's an example of a p-39 trying, and failing, to use 70in of boost, on US fuel.


Considering the takeoff rating of that engine was 44.5" it was not surprising that detonation would occur at 70". Surprised the engine didn't blow up.


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## GregP (Aug 17, 2018)

Hi FlyboyJ,

At the Planes of Fame, we operate now four P-51s: a P-51A, two P-51Ds, and the Voodoo air racer.

To my knowledge, Steve Hinton's P-51D (N7715C) is in the Standard category, Spam Can (N5441V) is in the Limited, the P-51A (N4235Y) is in the Experimental Exhibition category, and Voodoo (N551VC) is in the Experimental Racing Exhibition category.

No point here, just FYI.

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## FLYBOYJ (Aug 17, 2018)

GregP said:


> Hi FlyboyJ,
> 
> At the Planes of Fame, we operate now four P-51s: a P-51A, two P-51Ds, and the Voodoo air racer.
> 
> ...


Hi Greg;

Thanks for the info - yes, looked up the N number and it is Standard which means someone holds a TC for his Mustang shown as an F-51D. I looked high and low in the TCs annd only found those for a Limited. It looks like the basis for airworthiness was the old CAR 9 which were the rules back in the 1940s!


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## GregP (Aug 17, 2018)

If it means anything, Steve's P-51 was built up from parts of several Mustangs, but it was all done to original specs, including a propeller that still meets original diameter limits.

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## Old Jim (Aug 18, 2018)

Here is a list of LTCs.

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## FLYBOYJ (Aug 18, 2018)

GregP said:


> Steve Hinton's P-51D (N7715C) is in the Standard category.



The cobwebs cleared on me today - He may have a "Standard" airworthiness certificate but there are 7 classes of a standard airworthiness certificate:

Normal, Utility, Acrobatic, Commuter, Transport, Manned free balloons, Special classes

Under Special Classes:

Primary
Restricted
Multiple
Limited
Light Sport
Experimental
Special Flight Permit
Provisional

I bet he's either Restricted, Limited or Experimental


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## GregP (Aug 19, 2018)

Given your post, I'd suspect Limited. I seem to recall seeing that somewhere in the hangar. I quoted standard only because that's what an N-number FAA inquiry said. You'd think they would post the actual category, wouldn't you?

But, the FAA doesn't come across as "here to help," do they?

Also, the "Experimental Racing Exhibition" listing would then probably be simply imply "Experimental Exhibition," don't you think?

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