could the Allison engine have done what the Rolls Royce Merlin did?

[Piper106]

Don't:
Upon further research: "It was found that Allison-powered F-82 models (C models) demonstrated a lower top speed and poorer high-altitude performance than earlier Merlin-power versions." The C model used Allison V-1710-100 engines. Only 20 production F-82B models were made using the British designed Merlin engine.

Per Dan Whitney in "Vee's for Victory"
XP-82 was to be powered with the Packard Merlin V-1650-23/25
XP-82A would have the Allison F32R/L V-1710-119/121 (Aircraft cancelled)
P-82B Allison offered the F33 R/L engine but the planes were produced with Merlin engines.
P-82C and P-82D were P-82B aircraft modified to add radar.
P-82E and P-82G originally to be Allison F36R/L V-1710-143/145 later changed to the Allison G6R/L also designated V-1710-143/145.

The F32 engine was two stage super charged with charged cooled after the engine stage (2 nd) supercharger, and Bendix SD-400 speed density (single point) injection. War emergency Rating was 2100 HP up to 4000 feet (grade 150 fuel required), 1720 HP at 20700 feet, and 1200 HP at 30000 feet. The G6 engines was however without the aftercooler but adding ADI (water) injection. The G6 was rated 2250 HP with water injection, and similar ratings at altitude as the F32..

 

[tomo pauk]

Per Dan Whitney in "Vee's for Victory"
XP-82 was to be powered with the Packard Merlin V-1650-23/25
XP-82A would have the Allison F32R/L V-1710-119/121 (Aircraft cancelled)
P-82B Allison offered the F33 R/L engine but the planes were produced with Merlin engines.
P-82C and P-82D were P-82B aircraft modified to add radar.
P-82E and P-82G originally to be Allison F36R/L V-1710-143/145 later changed to the Allison G6R/L also designated V-1710-143/145.

The F32 engine was two stage super charged with charged cooled after the engine stage (2 nd) supercharger, and Bendix SD-400 speed density (single point) injection. War emergency Rating was 2100 HP up to 4000 feet (grade 150 fuel required), 1720 HP at 20700 feet, and 1200 HP at 30000 feet. The G6 engines was however without the aftercooler but adding ADI (water) injection. The G6 was rated 2250 HP with water injection, and similar ratings at altitude as the F32..

I don't think that G6 have had similar ratings at altitude as the intercooled F32. We're probably looking at under 1000 HP at 30000 ft for the G6 - the similar V-1710-121 (F28) was making 930 HP at 3200 rpm at 30000 ft, and a bit less than 1700 HP at 17000 ft.

 

[Piper106]

I don't think that G6 have had similar ratings at altitude as the intercooled F32. We're probably looking at under 1000 HP at 30000 ft for the G6 - the similar V-1710-121 (F28) was making 930 HP at 3200 rpm at 30000 ft, and a bit less than 1700 HP at 17000 ft.

The F28 had the 9-1/2" engine stage impeller turned by 8.1:1 step up gears and the 7.23:1 gears in the auxiliary stage. The G6 had a 10-1/4" engine stage impeller turned by 7.48:1 gears with 8.03:1 auxiliary stage gears. For the G6 engine Whitney states (page 280): "The Military rating was set at 1250 HP and 30000 feet, a deviation from the intended 32500 feet. Allison then went on to achieve the intended altitude rating." Maybe the actual performance was lower, but that is what Whiney states based on a source letter from Allison to Air Materiel Command.

 

[GregP]

Hi Tomo,

If you check Graham White's Allied Aircraft Engines of World War II, the Allison V-1710-143 (G6R) had a rating at 1600 hp / 3200 rpm / Sea level, and 1250 HP / 3200 rpm / 30,000 feet. But I do not see an engine performance chart, so I couldn't say what the critical altitude is or at what altitude it dropped off to what level.

Graham has about a page and quarter of Allison references, but hard data on the G-series seems to be a bit thin, probably due to being at the end of pistons / beginning of jets era.

I have the pleasure of having a friend who overhauls Allison engines, and he has a number of G-series engines available for overhaul as well as all the manuals to do it. He made a hybrid F/G engine for Reno a couple of years back and he put it into Graham Frew's Yak-3 for the races. Graham won Bronze, silver, and transferred into Gold. But the Hybrid engine had cooling problems due to the small size of the radiator in the Yak, and he finished with a standard 100-series Allison up front. Anyway, the hybrid engine definitely sounded WAY more powerful than a garden-variety Allison when Graham took off. Everyone noticed that part!

 

[gjs238]

Yes, but does the 2-stage Allison still have a lower parts count than the Merlin?

 

[GregP]

Yes. The Auxiliary supercharger has very few parts. It is basically a casting with an impeller and some bearings and bolts and a driveshaft to turn it ... and not very many parts altogether.

 

[wuzak]

Yes. The Auxiliary supercharger has very few parts. It is basically a casting with an impeller and some bearings and bolts and a driveshaft to turn it ... and not very many parts altogether.

And a fluid coupling.

 

[ThomasP]

Around 500 additional parts for the auxiliary stage supercharger and required power take-off unit. This does not include the carburetor and such since it would be needed for a single stage anyway. It also does not include the mounting accessories needed to attach the auxiliary supercharger to the airframe.

 

[tomo pauk]

The F28 had the 9-1/2" engine stage impeller turned by 8.1:1 step up gears and the 7.23:1 gears in the auxiliary stage. The G6 had a 10-1/4" engine stage impeller turned by 7.48:1 gears with 8.03:1 auxiliary stage gears. For the G6 engine Whitney states (page 280): "The Military rating was set at 1250 HP and 30000 feet, a deviation from the intended 32500 feet. Allison then went on to achieve the intended altitude rating." Maybe the actual performance was lower, but that is what Whiney states based on a source letter from Allison to Air Materiel Command.

You're right, I stand corrected.

 

[GregP]

You are right, Wayne. I have helped assemble one for cleanup and paint, but it was on a stand by itself. We didn't connect it to an engine because nobody ordered one for purchase. The P-63 was going to run an E-series engine alone, and that is what we were working on. I only saw it because I was curious and asked about it.

 

[MACHIA]

If the V1710-E27 would have been developed further and put into production it would have been the ultimate V12 engine rated at about 2,800 hp at the prop !
Came to late and the alloys available at the time in the turbo couldn't stand up to the temperatures.

 

[ronjon]

Good question.
Specifically, did the intrinsic design of the V-1710 preclude development of it's supercharger in the ways that the Merlin supercharger developed?
Multi-speed, multi-stage, water cooling, etc.

Looking at the P-38's high altitude performance, being properly turbo- (and presumably super-) charged proves the Allison could do what the Merlin could, and it probably had a lot more room to explore and exploit its potential. The Army told Allison to either stop or not start 2nd stage supercharger development as this was to be handled exclusively by the GE turbocharger, which didn't work out for the P-39 because of packaging issues - there just wasn't enough room for the ductwor, I suppose, due to the engine placement. I'm trying to research if the A-36 and P-40 were ever intended to be turbocharged, or were they meant to be low-altitude craft exclusively,and be fine w the 1st stage impeller.

 

[Shortround6]

Curtiss had at least a better idea of what it took to turbo charge an engine than most.
Not saying that they were 100% right, just that they had actually done it.

13 YP-37s.

You need a lot of extra cubic feet of volume to fit the turbocharger, intercooler and duct work into the plane.
The XP-39 was clear example of trying to stuff too much into too small a bag.

North American may or may not have had drawings for a turbo charged Mustang/A-36 (although why you would turbocharge a dive bomber escapes me)
But we can pretty much be sure that it would NOT have fit into the existing fuselage out lines.

 

[GregP]

In the turbocharged systems the turbo compensated for altitude, and that's all it did. And the integral supercharger was there to boost the intake charge above atmospheric (sea level) pressure. Which they did.

In engines without turbocharger the supercharger was to do both. It did this by being spun faster (different gearing). Unfortunately this meant that the engine couldn't take the boost the supercharger was capable of delivering at lower altitudes, so the intake had to be throttled to prevent overboosting.

A supercharger can be used to compensate for altitude, increase sea level horsepower, or both. If you elect to use it for both, some of the boost is used for the horsepower increase and the rest of the possible boost is used for altitude compensation. Naturally, if you use it for both, the critical altitude will be lower than if you used it all for altitude compensation alone. And, if you use all the supercharger boost for more horsepower, you can overboost, But even if you don't, there isn't any boost left for altitude compensation, and the horsepower just falls off with altitude normally.

A turbocharger is no different from a supercharger; both are compressors. In fact, many use the exact same compressor design. It's just that one is driven by the engine (supercharger) and the other is driven by exhaust gases (turbocharger). Likewise, you can use the boost any way the designer wants to use it ... for altitude compensation alone (call turbo-normalizing), for more horsepower alone, or for both. Again, if you use it for both, then there is less boost available than if you turbo-normalize it.

Let's say you have 10 psi of boost. If you turbo-normalize, then you can make sea level horsepower way up high. But if you use 4 psi of it to increase horsepower, that only leaves 6 psi of boost for altitude compensation. It won't go as high as it will with all 10 psi of boost used for altitude compensation, before running out of boost and losing power with altitude gained.

Pretty simple qualitatively. No so simple quantitatively, as the guys at Bell Aircraft found out for themselves.

 

[Reluctant Poster]

Looking at the P-38's high altitude performance, being properly turbo- (and presumably super-) charged proves the Allison could do what the Merlin could, and it probably had a lot more room to explore and exploit its potential. The Army told Allison to either stop or not start 2nd stage supercharger development as this was to be handled exclusively by the GE turbocharger, which didn't work out for the P-39 because of packaging issues - there just wasn't enough room for the ductwor, I suppose, due to the engine placement. I'm trying to research if the A-36 and P-40 were ever intended to be turbocharged, or were they meant to be low-altitude craft exclusively,and be fine w the 1st stage impeller.

The first statement doesn't stand up to close scrutiny, no Allison ever matched the performance of a 100 series Merlin. There is no evidence that the Army stopped Allison from working on 2 stage supercharging. Allison were building test models in 1942. The problem is that Allison didn't think about actually fittingly it into existing aircraft. This is in stark constrast to Rolls Royce who designed a very compact 2 stage arrangement for the Merlin and extensively redesigned the Griffon to allow it to fit into Merlin engined aircraft.

 

[Reluctant Poster]

Too bad that NACA found it fit to test and suggest improvements for the V-1710 in 1946.

Actually, NACA was working on the V-1710 in 1942.

From the NASA website:

SP-4306 Engines and Innovation: Lewis Laboratory and American Propulsion Technology

"Ben Pinkel, one of the NACA's leading propulsion experts, directed the NACA's research on the exhaust gas turbine, another name for the turbo supercharger. Pinkel had come to the NACA in 1931 from the University of Pennsylvania with a degree in electrical engineering. In 1938, when Pinkel was appointed head of the Engine Analysis Section, it had a staff of three. By 1942, Pinkel's division had expanded to over 150 people. Although facilities were lacking at Langley, as soon as the Cleveland Laboratory was ready, Pinkel's Thermodynamics Division launched a strong program to improve exhaust gas turbines. In a talk to the staff, all of whom, he humorously remarked, demonstrated the principle of "heat in motion," Pinkel illuminated the importance of their work to the war effort. Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."17​ Testing in 1939 by Ben Pinkel, Richard L. Turner, and Fred Voss confirmed the predictions of a German, Hermann Oestrich, who suggested that the horsepower of an engine could be increased by the redesign of the nozzles of the airplane's tailpipes. The Power Plants Division became an advocate of "exhaust stacks" added to the tailpipes of aircraft. Once they were adopted by the aircraft manufacturers, they led to dramatic increases in performance fighter planes, including the North American P-51 and the British Spitfire.1"​

"Laboratory staff was less enthusiastic about its work on the Allison liquid-cooled engine. Although many of their research programs were simply a carryover of work begun at Langley, Army Research Authorization E-1 to improve the power output of the Allison-1710 engine was different. Issued in October 1942, it was the laboratory's first new research project. Hap Arnold, Chief of the Army Air Forces, counted on the Cleveland laboratory to assist in the redesign of the Allison supercharger and intercooler. Three engines were sent to the laboratory. Schey's division investigated the supercharger to give it better performance. Rothrock's division explored its limitations in terms of knock; Pinkel's division took on the problem of cooling. Moore's Engine Components Division improved the distribution of fuel and air in the carburetor.

The Allison engine, however, never met the expectations of the Army Air Forces. The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design. Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight."​

The full article:
ch2

 

[tomo pauk]

Actually, NACA was working on the V-1710 in 1942.

From the NASA website:

SP-4306 Engines and Innovation: Lewis Laboratory and American Propulsion Technology

Cool that they did.

Unfortunately, the article contains too much of questionable statements, some of them misleading:
- Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."

Once thought obsolete??? Each B-17 have had 4 engines, thus will need 4 turboes per ship. It was Boeing and GE that were instrumental in a B-17 having turbocharged engines, not the PP Division.

-The Power Plants Division became an advocate of "exhaust stacks" added to the tailpipes of aircraft. Once they were adopted by the aircraft manufacturers, they led to dramatic increases in performance fighter planes, including the North American P-51 and the British Spitfire.1"​

Leading to a reader to conclude that Spitire received a dramatic performance increase due to the advice on exhaust stacks received by PPD.

- Three engines were sent to the laboratory. Schey's division investigated the supercharger to give it better performance. Rothrock's division explored its limitations in terms of knock; Pinkel's division took on the problem of cooling. Moore's Engine Components Division improved the distribution of fuel and air in the carburetor.

Fine, although one would love to see the test reports from 1943.

- The Allison engine, however, never met the expectations of the Army Air Forces.

It certailny met them in 1940, when it enabled a 30+ mph jump in pursuit speed over the then-current pursuits. Also in the P-38. For engines that never met the AAF expectations, we can take a look at a few of the hy-per engines sucking the resources the V-1710 could've used.

- The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design.

Not listing the supposed basic flaws is a red flag.

- Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight."​

Seems like the P-47 never existed.​

tl;dr: When an institution writes their own history, it will be not the 1st nor the last time they migh twist the facts in order for themselves to look good.​

 

[Shortround6]

Hmmm, not a lot mention about the Continental 1430 which was actually the armies fair haired boy in disguise.
They didn't give up on it until 1944 while trying to beat the Allison engine.

and I have no idea of where this came from in Wiki, but the entry on the XI-1430 sounds like they were written by USAAC press release hacks.

Continental built the first I-1430 engine in 1938 and successfully tested it in 1939.[1]​ At the time it was an extremely competitive design, offering at least 1,300 hp (970 kW) from a 23-liter displacement; the contemporary Rolls-Royce Merlin offered about 1,000 hp (700 kW) from 27 L displacement,

and

In 1944 it was also tested in the McDonnell XP-67.[1]​

Interest in the design had largely disappeared by then; piston engines with the same power or greater ratings were widely available, the Merlin for example had improved tremendously and was offering at least 1,500 hp (1,120 kW), and the military and aircraft builders were already starting to focus on jet engines.

the 1430 managed to set fire to only two planes it was ever installed in. They built 23 of them and built it in or planed to build 13 different versions?

 

[drgondog]

Hmmm, not a lot mention about the Continental 1430 which was actually the armies fair haired boy in disguise.
They didn't give up on it until 1944 while trying to beat the Allison engine.

and I have no idea of where this came from in Wiki, but the entry on the XI-1430 sounds like they were written by USAAC press release hacks.

Continental built the first I-1430 engine in 1938 and successfully tested it in 1939.[1]​ At the time it was an extremely competitive design, offering at least 1,300 hp (970 kW) from a 23-liter displacement; the contemporary Rolls-Royce Merlin offered about 1,000 hp (700 kW) from 27 L displacement,

and

In 1944 it was also tested in the McDonnell XP-67.[1]​

Interest in the design had largely disappeared by then; piston engines with the same power or greater ratings were widely available, the Merlin for example had improved tremendously and was offering at least 1,500 hp (1,120 kW), and the military and aircraft builders were already starting to focus on jet engines.

the 1430 managed to set fire to only two planes it was ever installed in. They built 23 of them and built it in or planed to build 13 different versions?

Good points on 1430.In 1941 NAA rejected it because of cooling issues primarily, then like the auxilary 2S it was also too long.

 

[Reluctant Poster]

Cool that they did.

Unfortunately, the article contains too much of questionable statements, some of them misleading:
- Adding a turbo supercharger to the engine of the B-17 "Flying Fortress," once thought obsolete, had made it a high-speed, high-altitude airplane. "This caused considerable excitement at the time because there wasn't a pursuit ship in the air force that could keep up with it."

Once thought obsolete??? Each B-17 have had 4 engines, thus will need 4 turboes per ship. It was Boeing and GE that were instrumental in a B-17 having turbocharged engines, not the PP Division.

-The Power Plants Division became an advocate of "exhaust stacks" added to the tailpipes of aircraft. Once they were adopted by the aircraft manufacturers, they led to dramatic increases in performance fighter planes, including the North American P-51 and the British Spitfire.1"​

Leading to a reader to conclude that Spitire received a dramatic performance increase due to the advice on exhaust stacks received by PPD.

- Three engines were sent to the laboratory. Schey's division investigated the supercharger to give it better performance. Rothrock's division explored its limitations in terms of knock; Pinkel's division took on the problem of cooling. Moore's Engine Components Division improved the distribution of fuel and air in the carburetor.

Fine, although one would love to see the test reports from 1943.

- The Allison engine, however, never met the expectations of the Army Air Forces.

It certailny met them in 1940, when it enabled a 30+ mph jump in pursuit speed over the then-current pursuits. Also in the P-38. For engines that never met the AAF expectations, we can take a look at a few of the hy-per engines sucking the resources the V-1710 could've used.

- The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design.

Not listing the supposed basic flaws is a red flag.

- Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight."​

Seems like the P-47 never existed.​

tl;dr: When an institution writes their own history, it will be not the 1st nor the last time they migh twist the facts in order for themselves to look good.​

Agreed. The point that I was making is that NACA was working on the V-1710 through most of the war.

However, when I read your first quote, I don't think they are actually taking credit for turbocharging the B-17. It certainly wasn't considered to be obsolete.
Here is a more nuanced description of NACA involvement from NASA - WWII & NACA: US Aviation Research Helped Speed Victory

"Engine research did not receive very much public attention. One project NACA engineers often high-lighted was their work on the engines for the Boeing B-17 Flying Fortress. While testing the early B-17 prototypes, the Army had discovered that adding a turbo-supercharger would greatly improve the altitude and speed of the bomber. The Army ordered future B-17s be equipped with turbo-superchargers. Supercharger technology was not very well developed and Wright Aeronautical, makers of the R-1820 Cyclone engines used on the B-17, struggled with the requirements. This was precisely the kind of problem the engine lab was intended to work on. Eventually, the turbo-supercharger problems were resolved and the B-17, a true high-altitude, high speed bomber, went on to become one of the military's most successful bombers. The turbosupercharger was also used with great success in the Boeing B-29 Superfortress. The Wright R-3350 Duplex Cyclone that powered the B-29 also underwent extensive testing in the NACA's new Altitude Wind Tunnel at the engine lab."

To be fair to NACA they did a lot of research into superchargers and turbochargers in the inter war period. I have attached a NACA paper as an example.

The second quote certainly does try to take credit for the improved Spitfire exhaust stacks. NACA did test exhausts on a Spitfire V, but I am sure that Rolls Royce had done their own research into Merlin exhaust systems. I have attached a copy of the report