Superchargers?

It is not fair to criticize them for the lack of a two stage supercharger. The Szydlowsky-Planiol supercharger was sort of a stage and half or maybe a stage and 1/3. But it doesn't seem to have actually performed quite as claimed although a significant improvement over the Hispano supercharger used up until then.
The lack of a 2 speed supercharger is a little harder to excuse. A number of companies offered a variety of different supercharger gears on the same engines so the benefits of the different gear ratios was known. Several companies had experimented with 2 speed engines and Armstrong-Siddeley had one in production by the summer of 1937 if not a bit early and it was written up in the magazines of the day: 1937 | 2141 | Flight Archive

I would note that experiments are one thing and production engines are another, Bristol set world records with a 2 stage supercharged in the Bristol 138 aircraft : Bristol Type 138 - Wikipedia, the free encyclopedia

But never got a production 2 stage supercharger into service.

Several French companies announced power figures for new models of engines in 1939/40 but the versions of those engines offered for sale in 1946-48 were rated a bit lower in power or altitude or both than the pre-war engines despite the common availability of 100/130 fuel which didn't exist in 1940. Perhaps the engines were de-rated in the interest of longevity?

I am sure that the French engines would have advanced beyond what they were in 1940 if development continued but I think they were flogging a dead horse in 1940 with the Hispano 12Y and 12Z. Post war versions gained several hundred pounds, new cylinder heads with more valves, fuel injection and other improvements yet struggled to get beyond 1500hp or so. (Swiss, Spanish and French programs)

Shortround6 said:

It is not fair to criticize them for the lack of a two stage supercharger. The Szydlowsky-Planiol supercharger was sort of a stage and half or maybe a stage and 1/3. But it doesn't seem to have actually performed quite as claimed although a significant improvement over the Hispano supercharger used up until then.

The lack of a 2 speed supercharger is a little harder to excuse. A number of companies offered a variety of different supercharger gears on the same engines so the benefits of the different gear ratios was known. Several companies had experimented with 2 speed engines and Armstrong-Siddeley had one in production by the summer of 1937 if not a bit early and it was written up in the magazines of the day: 1937 | 2141 | Flight Archive

...I am sure that the French engines would have advanced beyond what they were in 1940 if development continued but I think they were flogging a dead horse in 1940 with the Hispano 12Y and 12Z. Post war versions gained several hundred pounds, new cylinder heads with more valves, fuel injection and other improvements yet struggled to get beyond 1500hp or so. (Swiss, Spanish and French programs)

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So basically you are saying that the French were remiss in not developing a two-speed supercharger, but even if they had, the HS 12Y/12Z engines were past their prime and a new engine needed to be developed, which makes sense considering the basic design goes back to 1928 with the 12N. Did the Russians ever come up with a two-speed supercharger for their variation of the 12Y? If so, do you know when?

Note that the drive for the two-speed supercharger developed for the Rolls-Royce Merlin X/XX series was based on pre-war design by the French Farman company, which licensed Rolls-Royce to use it in 1938.

ohogain said:

I'd like to switch topics slightly. I've read often that the French Hispano-Suiza engines were criticized for their lack of a two speed or two stage supercharger. Since France fell in mid-1940, is this criticism fair?

I only joined this forum yesterday as a result of a discussion I read that took place on this forum back in 2008 that I found while researching superchargers. To quote one of the comments from that thread:

Shortround6
I think people get confused as to what was low altitude and high altitude in the late 30s. in 1939 ANYTHING and EVERYTHING that did not have a turbo charger was "low altitude". There were NO workable 2 stage mechanical blowers in any country and the 2 speed single stage super charger was only 6-7 years old and the ONLY production engines with 2 speed superchargers were the British Armstrong Siddeley Tiger, Bristol Pegasus and Merlin X, The American Wright Cyclone (since 1937) and the P &W Twin Wasp (after the Cyclone), and the German inverted V-12s.

While behind the English and the Germans in the deployment of 2-speed superchargers, the French were beginning to use the Szydlowsky-Planiol supercharger on their 12Y-45 and had mounted a 3-speed compressor in 1938 on their 12Y-5.

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The swiss developed the MS.406 and its HS12 engine into a 1500hp 422mph fuel injected monster, so it would be wrong to assume the engine lacked development potential. The aircraft would be the Swiss Dornier D.3803 and the engine the Saurer YS-3, the name may be familiar from Formula F1.

Thanks Thommo,

In regards to the debate re BMW801 versus PW R-2800. I am asserting that the BMW engine wasn't inferior. The evolution of power in consideration of the fact that the R-2800 versus BMW 801 was 9.5% larger and had better fuel was about the same.

Sure the turbocharged variants of the PW-2800 were vastly superior in power above 25000ft but that came at the cost of over 600lbs of turbo charger and more for the airframe to house it. At low altitude I argued that the R-2800 was in fact inferior to the BMW801 in respect of the fact that at sea level even with 2600hp of water injected ADI the P-47D was still slower than a 1800hp let alone the 2000hp Fw 190A8. I know that's a bigger airframe but that's a lot more power. Even the 2800hp of the clipped wing P-47M didn't lead to a spectacular increase in speed at low altitude. I put this down to the high drag installation of the R-2800 which lacked the forced induction and tight cowling of the BMW 801 power egg. At high altitude drag became less important since at 20000ft air density is 50% while at 33000ft it is 33% but at low altitude the P-47 clearly suffered from drag.

BMW clearly could produce a turbo charged engine and they did in the form of the BMW 801TJ. It shows the same power densities as the R-2800 though it never had Water injection added this was planned and was designed for higher altitudes(which in my view was what delayed them). BMW were getting 2580 out of the 801F which means that an turbocharged version of this engine could develop that sort of power.

Given German shortages of nickel and chromium using large amounts of the material for turbochargers and their turbines and ducting doesn't make a great deal of sense given that engines using inter-cooled multistage superchargers could produce almost the same power at high altitude. That doesn't mean that the 801 was inferior, it just doesn't make sense to develop it, certainly not for fighters.

I don't accept the claims about the forced fan of the BMW 801 costing 80hp under all conditions. At 20000ft air density is 50% and you can't tell me the engine fan is still drawing 80hp. Likewise with dynamic effects from aircraft speed. The laws of physics don't usually work that constantly. I'm saying that the 80hp is already accounted for as for the data you provide above AFAIKT the exhaust stub issue was fixed on the Fw 190A6 leading to the extra power.

I note above that in the table above that as the aircraft speeds up that its power increases.

One can see a lag in BMW introducing power boosting methods by about 6 months over PW (mid 44 instead of early 1944 for increased pressure and C3 injection versus Water injection for the R-2800) but I suspect that if Canada and Mexico had of been populated by 400 million angry Germans sending over 3000 bombers and 6000 fighters aircraft per day and 20000 tanks that Pratt and Whitney might have a few delays as well.

Koopernic said:

The swiss developed the MS.406 and its HS12 engine into a 1500hp 422mph fuel injected monster, so it would be wrong to assume the engine lacked development potential. The aircraft would be the Swiss Dornier D.3803 and the engine the Saurer YS-3, the name may be familiar from Formula F1.

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The Saurer YS-2 was good for 1300 hp/2600rpm/5.7lbs at take-off and 1410 hp at 15,700ft on 93 octane fuel but weighed 1510lbs, single speed supercharger. Uses fuel injection.
Spanish Hispano 12Z-89 was good for 1300 hp/2800rpm/8.6lb at take-off and 1410 hp/2800rpm at 15,700ft on 92 octane fuel but weighed 1510lbs, single speed Szydlowsky-Planiol supercharger. Uses fuel injection.
The French 12Z-1 was good for 1800 hp/2800rpm/7.7lb at take-off, 1600 hp/2800rpm at 8,200ft, 1320/2800rpm at 26,200ft on 100/130 octane fuel but weighed 1367lb, two speed supercharger. Uses fuel injection.
Russian M-107A was good for 1600 hp/2800rpm/11.2lb at take-off, 1600 hp/2800rpm at 5,600ft, 1500 hp/2800rpm at 14,800ft on 95 octane fuel but weighed 1323lb, two speed supercharger. Uses carburetors.
Saurer YS-3 was good for 1500 hp/2800rpm/8.6lbs at take-off and 1600 hp at 15,400ft on 100/130 octane fuel weight not given, single speed supercharger. Uses fuel injection.
Saurer YS-4 was good for 1600 hp/2800rpm/8.6lbs at take-off and 1580 hp at 15,300ft on 100/130 octane fuel weight 1555lbs, variable speed supercharger. Uses fuel injection.

please note that ALL of these are post war engines (or pretty much) and that the Saurer YS-4 shows up in late 1947 or early 1948.
Please also note that the figures for the French engine are almost too good to be true. It had also disappeared from Wilkenson's "Aircraft engines of the World" 1948 edition, the one were the Saurer-3 4 show up. Getting 1500-1600hp at 15-16,000ft on 100/130 octane fuel from a 1500lb engine in 1947-48 doesn't really qualify as a "monster" engine.

Koopernic said:

Thanks Thommo,

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Thank you, I love debating about engines.

In regards to the debate re BMW801 versus PW R-2800. I am asserting that the BMW engine wasn't inferior. The evolution of power in consideration of the fact that the R-2800 versus BMW 801 was 9.5% larger and had better fuel was about the same.

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The fuel rating (in rich setting) was in the ballpark; the USA did not initially (1941) have had 100/130 fuel either. 100/120?
We can see that, good as it was, the BMW 801D was, from late 1942 on, making the same manifold pressure on C3 fuel as the DB-601E and Jumo 211F on B4 fuel in early 1942. In other words, the qualities of the C3 were not used up until Autumn of 1943 (experiments) or early 1944 (service use). 1.42 ata is about +5.5 lbs/sq in, or about 41 in Hg.
I'll cover inferiority/superiority down the post.

Sure the turbocharged variants of the PW-2800 were vastly superior in power above 25000ft but that came at the cost of over 600lbs of turbo charger and more for the airframe to house it. At low altitude I argued that the R-2800 was in fact inferior to the BMW801 in respect of the fact that at sea level even with 2600hp of water injected ADI the P-47D was still slower than a 1800hp let alone the 2000hp Fw 190A8. I know that's a bigger airframe but that's a lot more power. Even the 2800hp of the clipped wing P-47M didn't lead to a spectacular increase in speed at low altitude. I put this down to the high drag installation of the R-2800 which lacked the forced induction and tight cowling of the BMW 801 power egg. At high altitude drag became less important since at 20000ft air density is 50% while at 33000ft it is 33% but at low altitude the P-47 clearly suffered from drag.

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Leaving aside comparison between complete aircraft (that really belong to some other thread), few things:
- the main benefit of the turbocharged R-2800 was that it was there, working as advertised and when needed. Unlike handful of turbo BMWs, it was produced in like 10000 examples, and gave sterling service
-the P-47M did not have clipped wings
-the 'forced induction' of the BMW-801 gave more trouble than it was worth - the handful of Fw-190s (and I'm not talking about lighthened examples) with external intakes were better in high altitudes than those run-on-the-mill.

BMW clearly could produce a turbo charged engine and they did in the form of the BMW 801TJ. It shows the same power densities as the R-2800 though it never had Water injection added this was planned and was designed for higher altitudes(which in my view was what delayed them). BMW were getting 2580 out of the 801F which means that an turbocharged version of this engine could develop that sort of power.

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There is no doubt that there was plenty of unused potential in the 801. Quirk is that BMW was trying to develop like half a dozen engines in short span of time, and that was their undoing. Should've concentrated on the 801.

Given German shortages of nickel and chromium using large amounts of the material for turbochargers and their turbines and ducting doesn't make a great deal of sense given that engines using inter-cooled multistage superchargers could produce almost the same power at high altitude. That doesn't mean that the 801 was inferior, it just doesn't make sense to develop it, certainly not for fighters.

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The benefits of two-stage supercharging were known in Germany even before ww2 started. Alas, they took that path too late to matter, with Jumo 213E/F and DB-605/603L

I don't accept the claims about the forced fan of the BMW 801 costing 80hp under all conditions. At 20000ft air density is 50% and you can't tell me the engine fan is still drawing 80hp. Likewise with dynamic effects from aircraft speed. The laws of physics don't usually work that constantly. I'm saying that the 80hp is already accounted for as for the data you provide above AFAIKT the exhaust stub issue was fixed on the Fw 190A6 leading to the extra power.

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No one was claiming that 80 PS need to be deduced for every altitude. At 5.7 km, it was just 50 PS. The flight manual for A-5 and A-8 gives the same power, 1730 or 1440 PS, depending on supercharger gear.

I note above that in the table above that as the aircraft speeds up that its power increases.

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Guess you mean the use of ram effect? All the power figures I gave are without ram, that levels the playing field. BTW, if you take a look at the chart (link)for over-boosted A-5 (ie. a lighter and 'cleaner' sibling of the A-8), you will note that even with maximum ram (= max speed), the power is 1650 PS at 5.25 km. And 1900 PS at 400 m.

One can see a lag in BMW introducing power boosting methods by about 6 months over PW (mid 44 instead of early 1944 for increased pressure and C3 injection versus Water injection for the R-2800)

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Lag was much bigger. The single stage, B series R-2800-41 was capable in low gear for 52 in Hg (=2000 HP up to 1500 m), or 49.5 in Hg at 3500 ft (1920 HP); no ram. That would be ~1.79 ata and ~1.71 ata respectively. Power rating on 100/130 fuel. Those engines powered the B-26B and C. It took BMW some 2.5 years to equal or better this result with service engines, when 1.82 was available for 801S.
In high gear, up to 47 in Hg (=1.62 ata) was available for the -41 up to ~15000 ft; again, the BMW was able to equal or better this some 2 years for service engines. Link for R-2800-41/-43.

Two stage engines (R-2800-8, 10), used on fighters, were rated more aggressively, even without water injection. In low gear (or 'intermediate', as called by RAF), it was 54 in Hg (~1.9 ata) at 15500 ft (=1800 HP) and ~52.5 in (~1.81 ata) at (at least) 21000 ft for 1650 HP. That is military power (5 minute); please note that BMW-801D was allowed for only 3 min for Notleistung. In 1944, military power was allowed for 15 min of duration. And this is early 1942 we are talking about. At those 21000 ft, the BMW-801D was making about 1250 HP (a bit better than 1-stage R-2800), once cleared for 1.42 ata and 2700 rpm.
Water injection enabled up to 60 in Hg (and was flight tested for 65 in Hg) at 100/130 fuel. 60 in Hg is about 2 ata.

The C3 injection was used unly under 1000 m.

but I suspect that if Canada and Mexico had of been populated by 400 million angry Germans sending over 3000 bombers and 6000 fighters aircraft per day and 20000 tanks that Pratt and Whitney might have a few delays as well.

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As above - lack of focus was as much an issue as Allied bombing.

Aozora said:

Note that the drive for the two-speed supercharger developed for the Rolls-Royce Merlin X/XX series was based on pre-war design by the French Farman company, which licensed Rolls-Royce to use it in 1938.

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Very interesting. I was totally unaware of that fact. What can you tell me about the Farman 2-speed supercharger - a link, maybe?

Koopernic said:

The swiss developed the MS.406 and its HS12 engine into a 1500hp 422mph fuel injected monster, so it would be wrong to assume the engine lacked development potential. The aircraft would be the Swiss Dornier D.3803 and the engine the Saurer YS-3, the name may be familiar from Formula F1.

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The Swiss team in F1 are Sauber, not Saurer.

ohogain said:

Very interesting. I was totally unaware of that fact. What can you tell me about the Farman 2-speed supercharger - a link, maybe?

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Indeed I can:

http://www.wwiiaircraftperformance.org/100-octane/Development_of_Aircraft_Engines.pdf

A description of the Farman supercharger from Flight May 2 1935: Farman two-stage supercharger or



So it can be seen that the French could have had two-stage superchargers for their military aircraft engines in 1940.

Plus an interesting article from Flight 1943:

View attachment Aircraft Supercharger Development 1943.pdf

That was pretty interesting, thanks for posting!

tomo pauk said:

What I'm after is this: is there a one-stop on-line reference around? Specifically, I'm interested about supercharger systems used in piston engines, from late 1930s to late 1940s. Preferably, with as small flag-waving as possible

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I just found this book today on Google Books:

Development of Aircraft Engines: Two Studies of Relations Between Government ... - Robert Schlaifer - Google Books

Development of Aircraft Engines by Schlaifer and Heron. The discussion of the Merlin supercharger begins on page 219, but there are references about superchargers, how they work, and the history of their development scatter about consistently.

Thanks for the tip
The book can be dowloaded from here, one page at time, or complete if one has the password:

Development of aircraft engines Two studies of ... . - Full View | HathiTrust Digital Library | HathiTrust Digital Library

A bit about P&W two-stage compressors (though the power claimed, 1050 HP at 22500 ft, is a good deal optimistic; maybe with plenty of ram?):

tomo pauk said:

Thanks for the tip
The book can be dowloaded from here, one page at time, or complete if one has the password:

Development of aircraft engines Two studies of ... . - Full View | HathiTrust Digital Library | HathiTrust Digital Library

A bit about P&W two-stage compressors (though the power claimed, 1050 HP at 22500 ft, is a good deal optimistic; maybe with plenty of ram?):

View attachment 262183

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Attached is NACA Technical Note #794 on two-stage supercharging written in early 1941 by Richard E Buck of Pratt Whitney; this may have helped form the basis of Pratt Whitney's development of the supercharger:

View attachment Two-Stage Supercharging.pdf

Also attached is a 1940 research paper on the limits of single-stage superchargers

View attachment Limits of single-stage supercharging.pdf

first off let me say that you guys are the Kings of knowledge when it comes to all things plane or engine related.

but do have a question about turbo's and superchargers. what i would like is break down on the different's of the two type's. or was just a way to say the same thing with two words turbo and supercharger

snelson said:

first off let me say that you guys are the Kings of knowledge when it comes to all things plane or engine related.

but do have a question about turbo's and superchargers. what i would like is break down on the different's of the two type's. or was just a way to say the same thing with two words turbo and supercharger

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Supercharger = a compressor that is driven by a gearbox driven by the engine crankshaft. In an aircraft there may be two or even three or four speeds as well as two stages. Sometimes even infinitely variable drive.
There is a type of valve (butterfly valve corliss valve) that is regulated (usually automatically) to prevent excess pressure damaging the engine. The altitude this can be fully open is refered to as full throttle height.

Turbosupercharger = a compressor that is driven by an exhaust gas turbine. The speed of the turbine is regulated by a waste gate valve that bleeds of excess exhaust. This is more effective than the gear driven supercharger alone but requires special high temperature alloys. Developed by an American called Sanford Moss who should've invented the jet engine as well. The altitude the wast gate is fully shut is the critical altitude, which is analogous tothe full throttle height.

Intercooler: = a heat exchanger that is placed between the engine and compressor to cool the air down thereby preventing preignition and knocking in the engine. Also reduces the workload in pumping in the air though it is actually throwing away energy.

Turbocompound = a gas turbine whose power is driven into the main engine crankshaft via a hydraulic coupling or some sort of infinitely variable drive. In this situation a mechanical supercharger is used. Turbocompounds don't need a waste gate, nor do diesels. Used in some diesel trucks as well as post war US piston engines.

The boost pressure is the pressure in the manifold of the engine.
WW2 Germans used atmosphere abbreviated as ATA so an unboosted engine was 1.0 ATA.
British used psig pounds square inch guage above the 14.2psi that was a standard atmosphere. Hence a Merlin running at 12psgi actually had 26.2psi (14.2 plus 12) in the manifold.
Americans used inches of mercury with 30 inches equaling 1.0 ata or 0 psig boost. 60 inches of Mercury would be called 2.0 ata or 14psig.

The power out put of the engine is approximately linearly proportional to the pressure. Double the pressure you double the power, roughly. There are odd little effects such as engines initially producing more power as they climb due to less exhaust back pressure, mechanical load of the supercharger, jet thrust.

Most cars that have superchargers like a Subaru WRX or Porche Carrera use exhaust driven turbo superchargers. The compressor is invariably a centrifugal rotary type. Such compressors are non linear.

A few cars like certain Mercedes Benz's models may use a "Kompressor" that is driven of the engine. This is G shaped scroll device, a positive displacement air pump, that produces an air flow proportional to engine RPM thereby helping preventing lag effects . One or two cars have used Lysholm twin scrolls or even roots blowers.

Felix Wankel, a German who invented the Wankel Rotary engine seen in Mazda RX8 cars invented the concept as a compressor. Rolls Royce actually built diesel Wankel Rotary engines supercharged by a Wankel Rotary Compressor.

snelson said:

first off let me say that you guys are the Kings of knowledge when it comes to all things plane or engine related.

but do have a question about turbo's and superchargers. what i would like is break down on the different's of the two type's. or was just a way to say the same thing with two words turbo and supercharger

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Both are super-chargers.

Simple "supercharger" usually refers to a mechanically driven one.

What is now often simply called a "turbo" refers to an exhaust driven supercharger.
Turbo refers to the turbine that gives the charge.
There are turbine type mechanical units but terminology makes reference to an exhaust driven supercharger simple by saying "turbo".

The difference is that simple.

is one really better than the other? i use to drive a ford diesel that had a turbo and it seemed to have some lag time from when you punched it till it really took off, but once it got rolling it gave a lot of power.

While turbo lag can affect cars and trucks it has a lot less effect in aircraft. In cars or trucks there is only one supercharger. It is either mechanical driven or a turbo and the turbos, for the most part, did have lag.

In aircraft, after about 1935/36, the planes with turbos had TWO superchargers, ONE turbo and ONE mechanical with the turbo feeding the the mechanical in a two stage system. While it may take time for the turbo to "spool up" this will be masked by the engine supercharger providing some immediate response, at least until full throttle or full RPM is reached. You also have the propeller acting as a 300-500lb flywheel depending on engine and propeller. You may, depending on actual cruise conditions, have the propeller changing pitch as the engine accelerates.

snelson said:

is one really better than the other? i use to drive a ford diesel that had a turbo and it seemed to have some lag time from when you punched it till it really took off, but once it got rolling it gave a lot of power.

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One serious drawback to a turbocharger is heat.

Now it is not as bad as it once was but the heat wears out any turbo unit, far, far sooner than any other engine related part.
As a Porsche mechanic once told me, it is not if, but when it will go out.