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Re: Allison vs. Merlin.
Also, concerning your comments about a Merlin-powered P-51A...that is exactly what happened, except we called it the P-51B/C.
Not too much difference between the A and the B/C. Main one was the powerplant!
Elvis
Pilots claim that contemporary Spitfires were matched in turn performance of the P-40B, but that the P-40 fell behind in performance when the SpitV came out.
a problem with the Merlin/P-51 dream is timing.
In 1938-39 the Merlin was a single speed-single stage engine that showed little difference in potential from the Allison. A two-speed single stage version was on offer but in it's original form it showed very little difference in altitude performance over the single speed (the most common single speed version being optimized for high altitude work). It is not until Hooker does his bit that things improve for the Merlin and that is about the middle of 1940. The improved single speed engines (40 series) and two speed engines (XX or 20 series) engines are what is first contracted for with Packard. The American versions power the P-40F. Please note introduction dates for the P-40F and then figure performance for a P-51 with that engine and not the later 2 stage engines.
Work starts on the 2 stage Merlin engine but Allison has started work on a 2 stage engine at the end of 1938!
It takes Rolls-Royce several years to get the two stage engines into production and sharing info with Packard and Packard doesn't deliver any real quantity of 2 stage engines until 1943. These are the -3 and later Packard Merlins.
Allison has development problems with their 2 stage supercharger and development is slower. A good engine once developed it reaches production just a little too late to have any real impact on the war (same could be said of the P&W R4360 on which work started in 1940)
In April 1942 2,000 two stage Allison engines were ordered. The V-1710-47´s critical altitude was 22,400ft. Early 43 seems doable IF someone make an effort to get the engine ASAP.
Spit V it's the contemporary of P-40B, there is some wrong in the claim
and afaik there was little difference in turn within Spit I and V
How were the Daimler-Benz DB series of engines performing during these times?
If the DB's were performing as well or better, how was that being achieved?
Hmm, not sure of that either. From what i read the P-40 could turn with spits and dive with 109s, it just suffered in climb.
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The Early DB engine's superchargers didn't perform any better or worse than the superchargers on the early Merlins and Allisons. The larger displacement, slower turning DB engines didn't need as much boost to make their rated power however. A Merlin using 6lb of boost is running at 1.4 Ato as is an Allison at just 42in. The more boost used to make rated power the lower the ceiling a given pressure ratio supercharger is going to work. Once the British and Americans start going to 12lbs of boost or 50in plus of manifold pressure to make rated power either the altitude performance suffers (or more accurately low altitude performance improves but high high altitude does not) or improved superchargers are needed.
The Germans with their lower manifold pressure needs can keep up the pressure to higher altitudes using the same basic supercharger. The Germans did improve their superchargers too as the war went on. A better impeller or a different diffuser design or even just a better inlet geometry could give small but useful improvements without any out change in appearance or weight.
Why do you want to pay RR 6,000 $ per engine if the V-1710 just needs an aux. stage supercharger and an intercooler to be as good? The Allison was stuck with the lesser supercharger not because of technical reasons but because the USAAF did not want a better one. They had 100% faith in the turbocharger and even objected to Allison developing altitude rated engines.
So I guess it comes down to the old adage, "there's no replacement for displacement?"
I assume the DB engines were heavier as well?
If so, it sounds like they performed very well despite the weight - while not suffering the supercharger/turbocharger issues.
Re my post #275Could the Allison have been bored out to ~2000 CID
...
Alternately, what if we had bought the patent for the RR Griffon with its huge 36L displacement?
I still think it's a shame NAA didn't consider building a P-51 around itGriffon was to late for US planes, since R-2800 Merlin already filled the needs perfectly
Could the Allison have been bored out to ~2000 CID (similar to the R-1830 becoming the R-2000)? An Allison V-2000 could have had a pretty high critical altitude if it was possible. I know the engine types are different, and I am asking for even more, but could it be done?
Alternately, what if we had bought the patent for the RR Griffon with its huge 36L displacement?
Could the Allison have been bored out to ~2000 CID?
Umm, well, OK...If the bore spacing was big enough to allow it, it might have been possible, if the bore spacing wasn't big enough then you are dealing with essentially a new engine
The Early DB engine's superchargers didn't perform any better or worse than the superchargers on the early Merlins and Allisons. The larger displacement, slower turning DB engines didn't need as much boost to make their rated power however. A Merlin using 6lb of boost is running at 1.4 Ato as is an Allison at just 42in. The more boost used to make rated power the lower the ceiling a given pressure ratio supercharger is going to work. Once the British and Americans start going to 12lbs of boost or 50in plus of manifold pressure to make rated power either the altitude performance suffers (or more accurately low altitude performance improves but high high altitude does not) or improved superchargers are needed.
The Germans with their lower manifold pressure needs can keep up the pressure to higher altitudes using the same basic supercharger. The Germans did improve their superchargers too as the war went on. A better impeller or a different diffuser design or even just a better inlet geometry could give small but useful improvements without any out change in appearance or weight.
Umm, well, OK...
assuming that there was some spare diameter, how would this affect the mechanical strength issue?
If you can get a back-copy of 'Aeroplane' from May 2005 (VE Day Special) there is an article called 'Developing Power' all about DB and the 109
From 1934 to 44 power of the DB went from 850 hp to 2,000 hp
A lot of this was due to Water and Methanol - MW50 - and N2O or Nitrous Oxide.
MW50 - This is another way of getting round the Detonation problem - especially without High Octane fuels to hand. It also increases the Fuel/Air Mass that you can cram into a cylinder
N2O - 25% increase in power at Altitude due to releae of Oxygen from the Nitrous Oxide
This is *still* something of a secret held by DB - even to this day
Exactly.a problem with the Merlin/P-51 dream is timing.
In 1938-39 the Merlin was a single speed-single stage engine that showed little difference in potential from the Allison. A two-speed single stage version was on offer but in it's original form it showed very little difference in altitude performance over the single speed (the most common single speed version being optimized for high altitude work). It is not until Hooker does his bit that things improve for the Merlin and that is about the middle of 1940. The improved single speed engines (40 series) and two speed engines (XX or 20 series) engines are what is first contracted for with Packard. The American versions power the P-40F. Please note introduction dates for the P-40F and then figure performance for a P-51 with that engine and not the later 2 stage engines.
Work starts on the 2 stage Merlin engine but Allison has started work on a 2 stage engine at the end of 1938!
It takes Rolls-Royce several years to get the two stage engines into production and sharing info with Packard and Packard doesn't deliver any real quantity of 2 stage engines until 1943. These are the -3 and later Packard Merlins.
Allison has development problems with their 2 stage supercharger and development is slower. A good engine once developed it reaches production just a little too late to have any real impact on the war (same could be said of the P&W R4360 on which work started in 1940)