BarnOwlLover
Staff Sergeant
#1, the reduction happened with the switch to the Merlin 134/135
#2 the Sabre VIII was rated to run 25 lbs of boost, but was post war.
Jumo 213 vs. Napier Sabre
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#2 the Sabre VIII was rated to run 25 lbs of boost, but was post war.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
German engines were designed to operate on lower octane rating, so they were functioning in the designed range.
Can you point out to the sources for both of the claims?
BarnOwlLover
Staff Sergeant
Napier H-24 Sabre Aircraft Engine
The Naiper Sabre was the last H engine designed by Frank Halford. From a troubled start, the complex Sabre ultimately produced more power for its displacement than any other WWII aircraft engine.
oldmachinepress.com
List of Rolls-Royce Merlin variants - Wikipedia
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
Napier H-24 Sabre Aircraft Engine
The Naiper Sabre was the last H engine designed by Frank Halford. From a troubled start, the complex Sabre ultimately produced more power for its displacement than any other WWII aircraft engine.
List of Rolls-Royce Merlin variants - Wikipedia
en.wikipedia.org
The source appears rather unwilling to confirm your statements:
"..it appears to have remained an unbuilt project. The engine was forecasted to have a military rating of 3,350 hp (2,498 kW) and be capable of 25 psi"
The engine never existed on anything but paper. I`ve got a lot of the surviving Sabre documentation and I cant see anything about the VIII.
No Sabre ever made more the +10lbs without water injection.
Calum covered the Sabre.Napier H-24 Sabre Aircraft Engine
The Naiper Sabre was the last H engine designed by Frank Halford. From a troubled start, the complex Sabre ultimately produced more power for its displacement than any other WWII aircraft engine.
List of Rolls-Royce Merlin variants - Wikipedia
'Merlin' book by RR Heritage Trust notes +25 psi for the Merlin 133 and 134, pg. 177 and 178.
Mike Williams
Senior Airman
- 572
- Oct 19, 2006
Hmmm, maybe I missed something in the arc of the thread but:
Also, both Pierre Clostermann and Ronald Dennis wrote of operational use of +13 lbs boost & 3850 rpm with the Sabre.
BarnOwlLover
Staff Sergeant
OK, so I was wrong about the Sabre, not the end of the world.
But every source I've read (including the two DH Hornet books I've referenced) do say that the Merlin 134/135 was derated to 18 lbs boost for normal operations. If it wasn't for the boost reduction, why make new variants? I do believe that the 134/135 did also introduce minor changes to the carb, but why, one, derate the engines if that happened, or two, if that didn't actually happen, why introduce new mark numbers for what seems to be 99% the same engine?
But every source I've read (including the two DH Hornet books I've referenced) do say that the Merlin 134/135 was derated to 18 lbs boost for normal operations. If it wasn't for the boost reduction, why make new variants? I do believe that the 134/135 did also introduce minor changes to the carb, but why, one, derate the engines if that happened, or two, if that didn't actually happen, why introduce new mark numbers for what seems to be 99% the same engine?
wuzak
Captain
I don't know that they were derated, but probably restricted in operation post war, as the extra performace wasn't necessary and would probably shorten the life of the engine.
There were often new mark numbers for Rolls-Royce engines when there were even minor changes. They may have used a different type of injection system, have extra accessories, etc.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Hornet had two engines, so the limitation was most likely due to that particular application.
R-2800 2400 RPM Bore 5.8" Stroke 6" Piston speed 2400 fpm Total cylinder area 475.6 sq. in. Piston Speed X Area = 1.14 million
Merlin 3000 RPM Bore 5.4" Stroke 6" Piston speed 3000 fpm Total cylinder area 274.8 sq. in. Piston Speed X Area = 0.82 million
213J 3700 RPM Bore 5.9" Stroke 6.5" Piston speed 4008 fpm Total cylinder area 328.1 sq. in. Piston Speed X Area = 1.32 million
Sabre 4000 RPM Bore 5.0" Stroke 4.75" Piston speed 3166 fpm Total cylinder area 471.2 sq. in. Piston Speed X Area = 1.49 million
R-4360 2800 RPM Bore 5.75" Stroke 6" Piston speed 2800 fpm Total cylinder area 727.1 sq. in. Piston Speed X Area = 2.04 million
I tend to look at these things as air pumps. Turning at a given RPM, how much air can they pump? This assumes a lot of things that ain't necessarily so, such as equal BMEP for all engines, and equal volumetric efficiency. For example, the 213J doesn't get to a good volumetric efficiency until it gets 4 valves per cylinder, and different compression ratios and different supercharging schemes all give different BMEPs. But this gives a (very) rough estimate of development potential.
And speaking of development potential, try to imagine 24 of the 213J cylinders in an H (or X) configuration: Your figure of merit rises to 2.64 million.
You also need to consider power-to-weight ratio and frontal area.
Merlin 3000 RPM Bore 5.4" Stroke 6" Piston speed 3000 fpm Total cylinder area 274.8 sq. in. Piston Speed X Area = 0.82 million
213J 3700 RPM Bore 5.9" Stroke 6.5" Piston speed 4008 fpm Total cylinder area 328.1 sq. in. Piston Speed X Area = 1.32 million
Sabre 4000 RPM Bore 5.0" Stroke 4.75" Piston speed 3166 fpm Total cylinder area 471.2 sq. in. Piston Speed X Area = 1.49 million
R-4360 2800 RPM Bore 5.75" Stroke 6" Piston speed 2800 fpm Total cylinder area 727.1 sq. in. Piston Speed X Area = 2.04 million
I tend to look at these things as air pumps. Turning at a given RPM, how much air can they pump? This assumes a lot of things that ain't necessarily so, such as equal BMEP for all engines, and equal volumetric efficiency. For example, the 213J doesn't get to a good volumetric efficiency until it gets 4 valves per cylinder, and different compression ratios and different supercharging schemes all give different BMEPs. But this gives a (very) rough estimate of development potential.
And speaking of development potential, try to imagine 24 of the 213J cylinders in an H (or X) configuration: Your figure of merit rises to 2.64 million.
You also need to consider power-to-weight ratio and frontal area.
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
Well one is a "performance test" on 150 grade, not service use, and the other was +11 lbs which I had mistakenly put as 10,
If they used those ratings then there will be data-cards with that written on. I certainly have never seen one in the Napier
archive. You did get some "local" emergency allowances made for doodle-bug chasing, but with the understanding
of probably severely reduced engine life far below normal service acceptance. The Ministry pretty quickly gave up authorising
over-boosting of the Sabre for Doodlebug purposes because it just blew the engine up.
The 11lbs rating needed 150 grade fuel.
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The M134/135 differed from the M130/131 primarily in the introduction of a Corliss type throttle body for their SU fuel injection and the ignition being fixed. This info from the RR Merlin 100 book from RRHT. Stating different ratings could be confusion with the 18lb T/O rating, against the Emergency/Combat ratings of 20lb with 100/130 and 25lb in S gear with 100/150 fuel, but this would depend on the source info, which presumably does not say?
Of course, lower limits may have simply been used for Service requirements. Another possibility is the Naval use, where it is possible that the Navy did not chose to use 100/150 and the 100/130 ratings would apply. Additionally, the power difference between output at 25lb and 18lb would be in the region of 500hp.
As for the different mark numbers, the different engines would have specific application, installation and maintenance requirements that RR and the AID would define as requiring the different Mk numbers.
Eng
Mike Williams
Senior Airman
- 572
- Oct 19, 2006
More information on the Sabre IIB would be appreciated. I'm still unclear as to it's operational history. Certainly the Tempest V Aircraft Data Card dated 2.2.45 shows the Sabre IIB was cleared for 11 lb/3,850 rpm.
My understanding it that the Sabre IIB could operate at +11 with either 130 or 150 grade fuel.
That said, 150 grade fuel was used by Typhoons operating in Holland.
Sabre II engines were modified to Sabre IIB in Holland.
Those Sabre IIA's having Mod. No. Sabre/158 or 297 ("strengthened propeller reduction gear assembly") were converted to IIB's by the incorporation of a new boost control cam (Mod. No. Sabre/433) and a new boost control capsule (Mod. No. Sabre/435).
BarnOwlLover
Staff Sergeant
Doesn't explain why the 130/131 and 134/135 were rated for only a difference of 40 hp between them if the drop in boost should've meant a near 500bhp drop. There was an other thread on here where there was a comment wondering if the 2000+hp ratings for the Merlin 130 series was with 130 or 150 octane fuel, or was a sprint/WEP rating vs a max normal rating.
Of course, all official base ratings were probably made at sea level or whatever altitude the engine was being tested at, and don't really (or at least usually) account for things like ram air or even aircraft installation characteristics.
Hi, You really need to accurately quote the ratings you refer to. My data is the individual ratings in Lumsden's British piston engines, which shows the same ratings between the 130/131 and 134/135 marks.
I think I wrote that the different mark numbers were probably due to the physical differences between these different marks.
Eng
Shortround6
Major General
Since one mark of engine could be used in several different aircraft the engine maker did not generally list RAM or intake differences.
They did specify an altitude at which the engine would give the rated power (engine test cells air supply could be regulated).
All of the Merlin 130 series (from 130 through 135) were rated at the same power at the same altitudes except for the 134A and the 135A which were 20 or 15hp lower (depending on low gear or high gear) The difference was that the 134A/135A had modifications for low rpm cruise and after heating installed (prevents fuel puddling in the intake manifolds).
Take-off power was also a bit lower, 20hp at 18lbs of boost.
BarnOwlLover
Staff Sergeant
You yourself said in a previous post that dropping down to 18 lbs boost vs 25 lbs should've cost up to 500 bhp (I'm willing to account that it's a typo). On various sources, from Wikipedia to info in the two Hornet books I've referenced don't note that much of a discrepancy. They also don't note when or why the changes happened. You have to remember that the Hornet/Sea Hornet were the only aircraft to use the 130 series engines.
The 2070 hp for the 130/131 and 2030 for the 134/135 have been quoted forever in most sources I've read, be it internet or print. But then again, those sources also quoted incorrect overall lengths for the Hornet (37" 9" tail up for F1, 38" 3" for subsequent versions is the accurate figure) until the book Hornet & Sea Hornet: de Havilland's Ultimate Piston Engine Fighter came out about a decade ago (plans were found during he book's writing that were actual DH plans for the Hornet that had the correct info), and that the Sea Hornet NF21 had a top speed of 430 mph, instead of the correct 461 mph. I think that it's safe to assume that the newer info based on what are supposed to be more accurate sources should be correct or at least more accurate.
But even the newer sources quote the differing supercharger boost and power differences between the engines.
Shortround6
Major General
RR Heritage trust in the Book. "The Merlin in Perspective" gives 1980hp at 3,000ft using 25lbs in low gear. It gives 1830hp at 13,000ft in high gear. It gives 1640hp for take-off at 18lbs boost.
There are different ratings given here.
Somewhere there is chart for some Merlins but the chart is assuming that the plane is doing 400mph at all altitudes and using RAM.
Some of the 1945-46 numbers may have been a bit optimistic?
There are different ratings given here.
Somewhere there is chart for some Merlins but the chart is assuming that the plane is doing 400mph at all altitudes and using RAM.
Some of the 1945-46 numbers may have been a bit optimistic?
ThomasP
Senior Master Sergeant
I have info in my notes (copied from an official post-war manual) that states the following:
Merlin 100/101/104/130/131____+20 lb max boost with 130 grade
_____________________________ +25 lb max boost with 150 grade
Merlin 113/114________________+18 lb max boost with 130 grade
_____________________________ +25 lb max boost with 150 grade
I believe these boosts correlate with the info at the link Shortround6 just posted.
Merlin 100/101/104/130/131____+20 lb max boost with 130 grade
_____________________________ +25 lb max boost with 150 grade
Merlin 113/114________________+18 lb max boost with 130 grade
_____________________________ +25 lb max boost with 150 grade
I believe these boosts correlate with the info at the link Shortround6 just posted.
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