P-51's vs. Me-109's and Fw-190's

[wmaxt]

Soren,

The problem with those numbers is that except for the climb and top speed they are static design numbers. There have been hundreds of aircraft that never achieved the theoretical promise of the design and a few that have exceeded it. If the point made above about the fuel is valid then the actual Speed/Climb numbers were also unavailable and we are still looking for Performance figures to compare. Anything else is assumption.

As pointed out above this debate has been going on for more than 60 years. I guess they must have been pretty damn close.

wmaxt

[DAVIDICUS]

Wmaxt said, "There have been hundreds of aircraft that never achieved the theoretical promise of the design and a few that have exceeded it."

I remember reading somewhere on this forum that the mechanics in the field had tweaked the R-2800 engines of some late war "D" model Thunderbolts. The engines were rated at 2,530hp at WEP but were developing about 2,700 horsepower as a result.

[Soren]

Only problem with those number is that they are for 1.98 ata and required C3 fuel. Consider the low fuel stocks in Germany at the time and the 190 had to use C3 it is questionable, how many of the K-4s in the 4 Gruppen that were suppose to convert to 1.98 really did so. The 4 Gruppen (I. / JG 27, III. / JG 2, III. / JG 53, IV. / JG 53) had only 91 operational K-4s as of April 9 1945. Testing of 1.98 started in Dec 1944 but was questionably cleared in early/mid March 1945. There was also much reliabilty problems with the DB605 which also puts into question the use of 1.98.

1.80 ata gave the K-4 a speed of 444mph

KK I only have one thing to say "do NOT rely on Mike Williams K-4 figures, they are flat wrong".

And as to the 1.98 boost issue: Back to the question of maximum allowed boosts, the already mentioned manual for the DB 605 DB/DC engines issued 5th December 1944, already the 3rd edition of it`s kind, notes the use of both 1.8 and 1.98ata for the DB/DC, respectively. According to the recordings of a meeting on the 20th January 1944, after unsuccessfull trials at Rechlin Test Centre, the clearance of 1.98ata was delayed until further testing is performed; particular interest is Gen. Ing. Paul`s criticizing Daimler Benz as it forwarded the clearance of 1.98ata boost directly to General Galland, General of the Fighter Arm, and the Technisches Ausendienst for 'diese Leistungen direkt der Truppe angeboten wurden und die Motoren umgestellt werden' or because it issued these boost (1.98ata) directly to the troops and set the engines to it. Further the document states that individual fighter-recons may be set to 1.98ata. Given the date of the manual and the meetings and their contents, we can be sure 1.98ata was already in use for some time during December until late January, when the boost was recalled for further testing with II./JG 11.


And note that In comparison to the Bf 109 K-4`s 10 minute limitation of running at maximum power, the Griffon 65 engine of the Spitfire XIV was limited to only 5 minutes at maximum power.

Originally Posted by wmaxt

Soren,

The problem with those numbers is that except for the climb and top speed they are static design numbers. There have been hundreds of aircraft that never achieved the theoretical promise of the design and a few that have exceeded it. If the point made above about the fuel is valid then the actual Speed/Climb numbers were also unavailable and we are still looking for Performance figures to compare. Anything else is assumption.

wmaxt

Well the point about C-3 fuel isnt correct, as it 'was' used.

[Soren]

Originally Posted by DAVIDICUS

Wmaxt said, "There have been hundreds of aircraft that never achieved the theoretical promise of the design and a few that have exceeded it."

I remember reading somewhere on this forum that the mechanics in the field had tweaked the R-2800 engines of some late war "D" model Thunderbolts. The engines were rated at 2,530hp at WEP but were developing about 2,700 horsepower as a result.

It certainly wasnt impossible to tweak them that much, but it would be very rare.

[FLYBOYJ]

Originally Posted by Soren

It certainly wasnt impossible to tweak them that much, but it would be very rare.

If I remember right I think as a field mod water injection and different cylinder heads were installed that might of increased the HP of these engines.

[lesofprimus]

Not as rare as u might think... My Grandfather told me that ALL the Corsairs in his VMF were tweaked out in more ways than one.... Every extra horsepower was cherished...

Some pilots and mechanics actually used logs books for tracking the different performance changes for the different adjustments they made... Boyington liked to have his aircraft pushing as many HP as was possible...

[wmaxt]

Soren,

How much C3 fuel was available overall and in the field? Any fuel was an issue late in the war. Your making a lot of assumptions and passing them on as facts.

David,

I also heard of a test program at P&W that ran several 2800s at well over 3,000hp for 250 continous hours each without a failure.

wmaxt

[DAVIDICUS]

It was my understanding as well that such "tweaking" was commonplace.

As to that test, it was 3,600hp! The engine was a Series 57 (the engine that went into the "M" and "N" models) rated for 2,800hp at WEP.

From: http://home.att.net/~historyzone/Sev...Republic7.html

Right out of the starting gate, the XP-47M was the horse to beat in terms of speed. The XP-47M proved to be nearly as fast as the XP-47J. 488 mph was obtained on at least one flight. The official maximum speed is 470 mph. However, over-boosting the engine could tweak another 15 to 20 mph out of the big fighter. Some may find this next tidbit hard to swallow, however, the test documents still exist.

During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens.

[FLYBOYJ]

Advancing the ignition timing, removing air filters, altering spark plug gap, shaving piston heads, and altering propeller tips are some of the field mods I heard mechanics did during WW2 to get more perfomance.

[cheddar cheese]

Originally Posted by DAVIDICUS

It was my understanding as well that such "tweaking" was commonplace.

As to that test, it was 3,600hp! The engine was a Series 57 (The engine that went into the "M" and "N" models) rated for 2,800hp at WEP.

From: http://home.att.net/~historyzone/Sev...Republic7.html

Right out of the starting gate, the XP-47M the horse to beat in terms of speed. The XP-47M proved to be nearly as fast as the XP-47J. 488 mph was obtained on at least one flight. The official maximum speed is 470 mph. However, over-boosting the engine could tweak another 15 to 20 mph out of the big fighter. Some may find this next tidbit hard to swallow, however, the test documents still exist.

During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens.

Wow, thats pretty amazing!

[Soren]

Originally Posted by wmaxt

Soren,

How much C3 fuel was available overall and in the field? Any fuel was an issue late in the war.

Not much, as there wasnt much fuel in the first place My point is, "It 'was' used".

Originally Posted by wmaxt

Your making a lot of assumptions and passing them on as facts.

No wmaxt, im not. And plz wmaxt, lets not get judgemental here !

Not as rare as u might think... My Grandfather told me that ALL the Corsairs in his VMF were tweaked out in more ways than one.... Every extra horsepower was cherished...

And it might very well be true, however not every P-47 or Corsair had its engine tweaked.. How many did ? Who knows..

[DAVIDICUS]

Soren said, "And it might very well be true, however not every P-47 or Corsair had its engine tweaked.. How many did ? Who knows.."

Well, no one said every Corsair or Thunderbolt underwent such "tweaking."

Les said all the aircraft in his Grandfather's VMF were modified. Thast doesn't mean every Corsair in the theatre of operations.

I understand that such tweaking was comonplace. As for how much additional horsepower could be generated, as you said, who knows? Achieving an extra 170 horsepower (2,700hp from 2,530hp) doesn't sound so improbable as to be a rare occurence per your statement that, "It certainly wasnt impossible to tweak them that much, but it would be very rare."

Again, however, as you have said, who knows?

[Soren]

Well, no one said every Corsair or Thunderbolt underwent such "tweaking."

I know, I was just pointing it out.

Les said all the aircraft in his Grandfather's VMF were modified. Thast doesn't mean every Corsair in the theatre of operations.

I know, and I said that it might very well be true..

I understand that such tweaking was comonplace. As for how much additional horsepower could be generated, as you said, who knows? Achieving an extra 170 horsepower (2,700hp from 2,530hp) doesn't sound so improbable as to be a rare occurence per your statement that, "It certainly wasnt impossible to tweak them that much, but it would be very rare."

You miss-understood me.. What I meant was that this "tweaking" of P-47D's was pretty rare, except later in the war where it became abit more common.

The 170hp increase in engine-power was easely possible for a good mech, no problem there.

[DAVIDICUS]

Soren said, "You miss-understood me.. What I meant was that this "tweaking" of P-47D's was pretty rare, except later in the war where it became abit more common."

I think the misunderstanding was on your part. All along, I was talking about the late war "D" variant.

I said, "I remember reading somewhere on this forum that the mechanics in the field had tweaked the R-2800 engines of some late war "D" model Thunderbolts. The engines were rated at 2,530hp at WEP but were developing about 2,700 horsepower as a result."

To which you responded, "It certainly wasnt impossible to tweak them that much, but it would be very rare."

When you said "them" you were clearly referring to the late war "D" model R-2800 engines described in my post.

[Soren]

No you miss-undertsood me, as you thought I was implying that an 170hp increase in engine power was hard to accomplish

Btw, I hadnt noticed you wrote 'late-war' -47D's, so there I actually miss- understood you.

It goes both ways

Anyway, we do agree with each other.