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#1, the reduction happened with the switch to the Merlin 134/135When that reduction of boost took place?
That's very interesting. What source confirms +25 psi boost for post-war Sabres?
Jumo 213E and F were outfitted with 2-stage superchargers, and were still using 87 oct fuel.
Can you point out to the sources for both of the claims?#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.
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
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.oldmachinepress.com
Hmmm, maybe I missed something in the arc of the thread but:No Sabre ever made more the +10lbs without water injection.
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?
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,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.
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?
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.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.
View attachment 702310
The 11lbs rating needed 150 grade fuel.
View attachment 702313
View attachment 702312
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.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
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.
Since one mark of engine could be used in several different aircraft the engine maker did not generally list RAM or intake differences.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.
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.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