Which nation was able to develop the best aircraft engines? I included categories for inline and radial types as these were parallel but very different types. I'm leaving out jet and rocket engines as they really had little impact on the war.

OK, OK - I blushingly admit to waving a Union Jack on this one. I honestly do believe that the Rolls-Royce Merlin is one of the most amazing internal combustion engines ever built ( and I also rate the Napier Sabre as a brave effort of engineering - I just can't imagine how they got it to work at all....)

I also admire the DB engines and the Wright Cyclone.....but my vote is for the British.....

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While I'm somewhat loathe to simply proclaim the British best at inline and the US at radials, these two nations arguably did produce the best of each category.

The British between Rolls Royce and Bristol produced some remarkably efficent inline engines. But, not without their difficulties, particularly the various sleeve valve engines like the Sabre. What strikes me most about the Merlin and other RR products was how this company could match componets in a way the US seemed at a loss to do.
That is, the Merlin matched an engine to a very efficent supercharger and carburation system that made for great overall performance. Allison with their V-1710 series never seemed able to do the same. Suprisingly, at lower altitudes there wasn't much difference in performance between the two; it was just when they got above about 15,000 feet that the Merlin continued to perform well while the Allison lost its "guts."
Germany, like Britain, had some excellent engine designs the DB 600 series were good performers but much heavier than their Allied counterparts. While this made for a strong engine, it made for a poorer performance per pound than the Allies were getting out of their motors.
The US really shines in the radial category. From about 1935 on while the Europeans developed more efficent inline engines for racing and high performance military aircraft the US was building very efficent radials for the commercial and transport market. One of the late war tour-de-force radials certainly has to be P&W's R 2800 Double Wasp four banked 28 cylinder engine. P&W succeeded in putting two Wasp engines togeather back to back in a way many others tried unsuccessfully to couple two engines to a single drive.
The other area where the US led was in supercharging using exhaust driven superchargers. No other nation came close to putting this system to such widespread use.
The Soviets and Japanese simply are not in this race. Both rely heavily on imported technology in their engines. The Soviets made heavy use of both French Hispano Suiza 12Y variants and US radial engine dirivatives while the Japanese likewise turned to US and German technology for much of their engine development.
The French had a few potential winners in engines like the Gnome Rhone 14 series radial but never got the chance to apply it.
In looking at this sort of technology one also has to remember that the Allies benefited greatly from superior metallurgy and chemical processes available to them. While both the Western Allies and Germany used water and methanol-water injection in engines for improved performance at lower altitudes the Germans alone turned to Nitrous Oxide for high altitude performance. This was due primarily to a lack of the fuel additives and octane levels the Allies could obtain far more easily. In 1944 most Allied fighters were running 100 to 130 octane with Tetraethyllead and other additives to boost octane while the Germans were generally limited to 87 octane or more occasionally 93 octane fuels that lacked these chemical boosters.

I don't know much about the air but I have read many accounts of the Rolls Royce Engine being superior so I chose that. Also, didn't the Mustang start out with the RR?

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I thought that the Mustang was originally outfitted with a different engine, and later was given it's RR engine and became the fighter we all know and love {till the change, I remember the P51 being listed as an 'under-achiever'}. Is this accurate, or am I once again missing something?

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The Mustang started life with an Allison engine the same as in the P-40.

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The Mustang was only really built because the RAF put out an order for a fighter it was initially supposed to use the Merlin but if i remember rightly the plane wasn't quite right so the early ones did'nt have it. Someone rightly said the aircraft used the Allison which was VERY similar to the Merlin but it never quite worked. I might add by the end of the war the engine worked great.

Vote for the Rolls-Royce Merlin as well...

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I had to vote also for the British for inline, and the U.S. for radial.

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How about the Italians?

Looks like that is the concensus so far . Robert

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If I remember my history correctly, the British purchasing commission was originally looking for Curtiss P-40 Kittyhawks - they approached North American Aviation with a request to build P-40's under license from Curtiss. North American really didn't want to build under a license from Curtiss, and, instead, proposed to design and build an entirely new fighter. After some last minute (overnight?) preliminary design work by 'Dutch' Kendleberger. The Brits agreed, under the stipulation that production could begin within 4 months (!!!) - an exceedingly short time for a new design. Kendleberger agreed and immediately proceeded with detailed design. The airframe was designed around the Allison V-1710-39, the same engine that powered the P-40.

Design and production proceeded, and, incredibly, the prototype was completed in 117 days, and, using the same engine, outperformed the P-40 by 25 mph or so. The Brits immediately put in an order for 300 or so, and later doubled it. The major strong point of the design was it's incorporation of the laminar flow wing, which greatly reduced drag and was much more efficient than standard wing designs of the time. The airframe had great low altitude performance, but, as mentioned above, was rather anemic in the thinner air at higher altitudes, due primarily to the un-supercharged Allison engine.

North American approached the US Army, but other than their requirements to purchase a minimum number of airframes under Lend-Lease, weren't interested, and initially fitted them with dive brakes and used them as low level attack/dive bombers (A-36 'Apaches').

It was the Brits who initially tried the Merlin in the Mustang, and the rest, as they say, is history. Most production Mustangs were fitted with Packard built Merlins, constructed under license from Rolls Royce.

Probably WAAAY more than anyone really wanted to know.

-whatever

-Lou

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You could add that the Army in their "wisdom" built more P-40's than they did P-51's during the war.

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Well, after lurking around here for a long time I have to weigh in on this having turned some wrenches on round engines.

While the Merlin V-1650-3 is one of my favorite engines I would have to vote for the Wright Cyclone series.

Consider this:
The Merlin was rated at 1520 HP and developed 1400 HP at takeoff. Although it wasn't a serious issue the Merlin's weakness was that one bullet or piece of flak could put it out of action which is inherent in any liquid cooled engine.

The Wright R1820-65 developed 1200 HP, while the R3350-23 a double row 18 cylinder pumped out a staggering 2200 to 3700 HP depending on the model. The earlier model did have some dependability issues though.

Entering the scene a little too late for WW II was also the Pratt R2800 which was shoe horned into the F8F-2P Bearcat, pumping out 2100 HP and outperformed most of the early jet fighters.

All that said, I would have to go with the round engines first......and then the Merlin for inline.

Tch! Real planes have two wings and a round engine, and the epitome of this was the Polikarpov I.153 with his Shvetsov M-62, still flying today on the Polish PZL Dromader fire-fighters!!!!





How's that for longevity, eh?

If you want to go for a reasonably good round engine, single wing you might choose the F4U with his Pratt & Whitney R-2800 Double Wasp !!! This is still in service today as well with another fire-fighter, the Canadair 215 !!!

There was also the Goodyear Corsair, the F2G with the Pratt & Whitney R-4360 Corncob 28 cylinder engine. Now that was (is!!!) a sight to see! (and hear!!)

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Any guess how I voted?


I sheepishly admit to voting for only the radial category by mistake. My vote for inline would been for the British, given the amazing history of the Merlin.

One of the reasons the Messerschmitt was declared the most advanced fighter in the world was a couple of important innovations, like the fuel injection, fully automatic pitch control (not just constant speed), and the fluid drive coupling on the mechanical compressor, a unique quality which gave the Messerschmitt excellent performance up to the rated altitude of around 5.8km and even good performance at 7km. This is unusual in that the sea level outputs were on the whole similar to those at rated altitude, something other manufacturers including Rolls Royce hadn't achieved.

When comparing something like the single stage Merlin 45 to the DB-601E of that year we can see the figures for the rated maximum take off output of 1515hp and 1350PS (1330hp) hardly extrapolates their performance at low altitude aerial combat, with figures at around 2000m more in the region of 1350hp and 1450PS respectively, whilst at the rated altitude the Daimler was still putting out 1320PS whilst the Merlin had begun running out of puff back at 4500m. The simple fact there was no secret even whilst giving away turning rates, the Messerchmitt still retained better climb, dive and overall equivalent performance to the Mark V Spitfire at all altitudes, and at 5km or 2km it was better. Considering only some 40 fighters were assigned defence on the Channel Front (the slack taken up by flak crews), this leap in performance from the Emil is what made this possible whilst still retaining total air superiority over France. Later addition of the Fw-190 helped consolodate it.

But this advantage was to last only a year before the Merlin 45 received a new two-stage supercharger to produce the 60-series of the Mark IX. The DB-605 was then new and with its wide list of variants must be regarded at least equal in performance. Supercharger design was refined, or borrowed from the monstrous DB-603 for high altitude variations that had rated altitudes of up to 7.8km. A comparison would be the 1020hp Merlin 63 rated at 9km, with the DB-605AS weighing in at 1435PS at 8km and the same engine fitted with MW-50 boost returning 1800PS at sea level to the Merlin's 1565hp.

But the DB-605A had some serious reliability issues. It overheated and when it did the engine seals opened up, causing fires. When engine boosters like charge coolant were fitted engine life was tremendously reduced to as little as 12hrs adhering to strict operational guidelines. Otherwise the infamous Reich Defence interceptors could have a serviceability as littl