I don't understand how some planes ended up being so fast

[tomo pauk]

The service figures you quote are for engine service ratings achieved well after WW2. In 1945 they were bench figures just like the BMW801F.
...
Either way the difference is marginal. Sleeves thicken a cylinder.

5th May 1945 - Centaurus V making 2650 HP: link. If you believe that a 2560 cu in engine running at 2700 rpm will equal a 3270 cu in running at same RPM, in same year, on same reliability, I have Brooklyn bridge on sale.
Cylinder thickness has next to ne bearing on engine diameter.

German engines often are quoted at their sea level power. At about 1500m their rated power will be greater than the sea level power. This is inevitable in engines that choke of the supercharger pressure. Im thinking the 801TS produced 2200 at sea level and a little higher at rated altitude.

Minus the power to drive the fan, minus the difference of PS vs. HP. BTW - there is yet to emerge a test where the BMW 801S makes more than 1.7 ata (< 2000 PS) in service trim.

 

[Shortround6]

The service figures you quote are for engine service ratings achieved well after WW2. In 1945 they were bench figures just like the BMW801F.

well after WW II (1948?) you got the 230-260 series Hercules around 2000hp for take-off. One of them with a two speed supercharger (most had single speed) was rated at 1840hp at 13,250ft military power.
The 100-120 were pretty much end of war engines (1945-46)

 

[pbehn]

The sleeve valve was a response to a problem Sir Harry Ricardo himself had noted which was that poppet exhaust valves were getting so hot they would start causing pre-ignition as engine performance grew. This stimulated the development of sleeve valves in Britain some with one and some with two sleeves. There were even several automobiles in production that used them.

Sodium cooled exhaust valves, better springs and a myriad of refinements overcame the issue of the poppet valves.

At one point US researchers promoted the idea of installing a sleeve in a poppet engine to reduce fuel consumption, piston wear and pollution. Apparently the motion of the sleeve at top and bottom dead centre maintains the hydrodynamic oil film which reduces friction and prevents stiction. Oddly poppet valves had developed to the point that the idea of cutting a port into the sleeve to aspirate the engine via the anti-friction sleeve was not seen as an advantage.

The Sleeve valved Bristol Hercules and Centaurus offered no diameter advantage over the contemporary R-2600, R2800, R-3350, BMW801.

Looking at a cutaway of the Sabre shows that an enormous amount of space was allocated to the cylinder head, so much I question whether it even reduced the height of the cylinder and head assembly over a poppet valve system. The Sabres advantage may have come from the balance its horizontally opposed design offered and the high RPM this allowed.

I suspect the 3000hp Sabre probably would have given tempest a speed of around 430mph at sea level because the 2600hp version got to 410 on 150 PN fuel.

Fw 190D with plane old Jumo 213A (an engine the same weight as the Sabre were running at 2 ATA boost (about 2310hp over the 1.75 ATA 2100hp engines) so the Sabre was winning but 2.2 ATA must have been around the corner for the advanced versions of the Jumo engine which were expected to achieve 2700hp and that with a refined intercooled two stage 3 speed supercharger.

By that time jets were offering 520 mph at sea level and by the end of 1945 had exceeded 600mph. So the Sabre won a technical war it was maybe by 10%-15% over similar sized engines with single stage supercharger but that the margin would be less when inter cooling was added.

Obviously the money went to the jet.

Great post Koopernic, there are all sorts of theoretical advantages to a sleeve valve and also disadvantages. Theoretically it could be made more powerful and more economical due to better gas flow and scavenging. In the seventies I read a sort of "what if" article which speculated that if engines had started off as sleeve valve and had been producing and researching them for twenty to thirty years all over the world they could well have been much better than poppet valve engines. If jets had not existed or succeeded then Rolls Royce were looking at two stroke designs with reciprocal sleeve valves.
Rolls-Royce Crecy - Wikipedia

 

[grampi]

or course the premise matters. the original post made no distinction about a normal p47. it should have been pointed out as an extraordinary claim with no extraordinary proof. In what world should anybody begin a discussion of anything on a false premise.

So you don't believe ANY version of the P-47 did 500 mph?

 

[Koopernic]

Great post Koopernic, there are all sorts of theoretical advantages to a sleeve valve and also disadvantages. Theoretically it could be made more powerful and more economical due to better gas flow and scavenging. In the seventies I read a sort of "what if" article which speculated that if engines had started off as sleeve valve and had been producing and researching them for twenty to thirty years all over the world they could well have been much better than poppet valve engines. If jets had not existed or succeeded then Rolls Royce were looking at two stroke designs with reciprocal sleeve valves.
Rolls-Royce Crecy - Wikipedia

If turbojets hadn't been possible giant airliners would be winging their way across the ocean probably as 2 stroke diesels or possibly petrol engined. The usual problem with two strokes is the fuel mixture loss during scavenging. This can be overcome with direct injection. One then has the problem of determining the air fuel ratio because some of the charge is mixed with exhaust air. Using a pre chamber relaxes both octane requirements and the stoichiometric limits for reliable ignition. The pre-chamber can initiate reliable ignition while any pre-ignition or knocking is soon snuffed by oxygen starvation.

It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.

History of the sleeve

https://www.newcomen.com/wp-content/uploads/2012/12/Chapter-6-Hassell.pdf

 

[pbehn]

If turbojets hadn't been possible giant airliners would be winging their way across the ocean probably as 2 stroke diesels or possibly petrol engined. The usual problem with two strokes is the fuel mixture loss during scavenging. This can be overcome with direct injection. One then has the problem of determining the air fuel ratio because some of the charge is mixed with exhaust air. Using a pre chamber relaxes both octane requirements and the stoichiometric limits for reliable ignition. The pre-chamber can initiate reliable ignition while any pre-ignition or knocking is soon snuffed by oxygen starvation.

It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.
https://www.newcomen.com/wp-content/uploads/2012/12/Chapter-6-Hassell.pdf

Good post and attachment Koopernic, I must confess when I was involved in tuning two strokes I didnt give a monkeys toss about fuel efficiency or economy By some strange twist of fate I ended up with one of the fastest Suzuki X7s ever raced in UK in production clases, many good racers who had switched to Yamaha RD250s asked me what I had done to it, so I asked the tuner (Terry Becket) what he did and he said "same as all the others". Even in the 1980s two strokes were still in some ways a black art. However that was just top speed, my X7 lost ten yards at least coming out of every corner, even in lower capacity classes torque across a broad range rules the roost.

 

[wuzak]

It is possible to use exhaust gas measurements to determine the airfuel ratio. I think the Merlin relied on engine RPM, exhaust temperature and ambient pressure to determine fuel rates. There was no intake flow measurement.

Doubtful.

Early Merlins used a carburetor which uses the air flow to determine the air:fuel ratio. Later versions used an injection carburetor - which also used the air flow to determine the air:fuel ratio.

Pressure Injection Carburetors – Typical Injection Carburetor

Also, modern engines that use the exhaust to determine air fuel ratios use a sensor which detects excess oxygen in the exhaust. This can be used to adjust the air:fuel ratio.

And, if you look at a typical Merlin exhaust installation you would notice that there are no feedback mechanisms for exhaust temperature.

 

[wuzak]

The BMW801 is also significantly more powerfull than the Hercules. The BMW801 ended the war at about 2000hp for the 801D and 801TS at 1.62 ATA with the 801TS being able to operate at 1.82 ATA and 2350hp for emergencies. The 801 competed with the centaurus. The 801F version could have produced 2600hp.

The Rolls-Royce Vulture could have made 2500hp+ and had a diameter of 48". Well, it did on test in 1941.

The Daimler Benz DB 604 was rated at >2600hp, diameter I am not sure, but probably less than the Vulture.

The Merlin could have produced 2600hp also. The RM.17SM did just that in 1944. During tests it also ran over 2300hp (less boost, more rpm). The RM.17SM was type rated at 2200hp MS and 2100hp FS in 1945. Without ADI (which the V-1650-9 used to achieve similar numbers).

 

[Koopernic]

The Rolls-Royce Vulture could have made 2500hp+ and had a diameter of 48". Well, it did on test in 1941.

The Daimler Benz DB 604 was rated at >2600hp, diameter I am not sure, but probably less than the Vulture.

The Merlin could have produced 2600hp also. The RM.17SM did just that in 1944. During tests it also ran over 2300hp (less boost, more rpm). The RM.17SM was type rated at 2200hp MS and 2100hp FS in 1945. Without ADI (which the V-1650-9 used to achieve similar numbers).

Cynic?

The BMW 801F was delayed but scheduled for production in April 1945, BMW was forced to supply the BMW 801TS instead as an interim. It had promised the 801F or "similar" engine. Because the 801TS was lighter than the 801F and the Fw 190A9 had its centre of gravity built around the BMW 801F the Fw 190A9 had weights applied to the propeller to balance the aircraft. It got that close to production it effected the airframe.

The 2580hp was intended as a service rating. It wasn't a test stand experiment to detect vibration or heat load.

The 801F remained somewhat as an abstract engine in which new strengthened components were developed that then turned up in production in interim engines. A specific power of 2600hp out of 2600 cubic inches was not exceptional for an engine running on 100/130 + Water Injection. The R2800 achieved 2800hp on 100/130 plus water. The BMW801 was also a highly developed engine, with much modification based on experience.

Production of the engine was supposedly held up by tooling issues since everything was highly modified.

There was also a BMW801TH supplied at the same time as the TS. The TH had provision for Nitous Oxide.

I doubt that the BMW801F had it been produced in 1945 would have been put into Fw 190 airframes. The Jumo 213 reduced drag over the total airframe by 13%, promised more power and had a fully developed two stage supercharger with intercooler. It gave the speed at all altitudes the Luftwaffe needed to take on Griffon Spitfires, Tempest V, P51H and P47N on an equal level.

The core of the of the 801F engine would have turned up in the turbo charged BMW801TQ on Ju 388 etc and maybe Ju 88G1 night fighters,

The 801 was reaching the end of its development potential but 2600hp was realistic. It just couldn't make the Fw 190 airframe competitive. The Jumo 213 and DB603L could.

 

[Koopernic]

Doubtful.

Early Merlins used a carburetor which uses the air flow to determine the air:fuel ratio. Later versions used an injection carburetor - which also used the air flow to determine the air:fuel ratio.

Pressure Injection Carburetors – Typical Injection Carburetor

Also, modern engines that use the exhaust to determine air fuel ratios use a sensor which detects excess oxygen in the exhaust. This can be used to adjust the air:fuel ratio.

And, if you look at a typical Merlin exhaust installation you would notice that there are no feedback mechanisms for exhaust temperature.

My description was a little off but in essence correct. They didn't measure air mass flow but computed it from pressure ratios of the inlet to exhaust pressure and inlet temperature. That's all the data you need if you have the correct physical laws.

Read the section on the SU "Skinners Union" carburettor which was really an injection system.
Aircraft Carburetors and Fuel Systems: A Brief History - 09

In essence they use an engine map the way some motorcycles do only they used levers, cams and hydraulic fuel pressures to do the computations.

"Skinners Union (SU) and Rolls-Royce Speed-Density System

A speed-density carburetor system does away with the carburetor venturi, replacing it with an engine driven fuel pump that delivers the fuel to either the intake eye of the supercharger or divides it into individual fuel charges that are injected directly into the engine cylinder. Atmospheric pressure and the mass of air passing through the unit combine to control the fuel pump.

Rolls-Royce wanted to use the speed-density method of controlling the fuel-air ratio. It found that the Skinners Union carburetor division of the Morris group had already manufactured a reciprocating swash-plate pump, although it was much too small for the purpose. Rolls-Royce then invited SU to produce a larger pump of the same design, and to develop a control system for it with Rolls-Royce. SU engineers came to the Rolls-Royce plant, and received engine specific data of what the fuel supply produce under all operating conditions. The volume of fuel pumped with the SU swash plate pump can vary from no fuel to full fuel by changing the angle of the swash plate, similar to the method used to control the pitch of a helicopter's rotor blades. In the case of the fuel pump, intake and exhaust manifold pressure, intake manifold temperature and engine speed combine to control the swash plate angle.

Rolls-Royce later developed its own speed-density system that was mechanically simpler than the SU device. In the Rolls-Royce system, the feed pump supplied fuel at a constant pressure to two jets in parallel. A tapered needle valve operated by a pressure capsule measuring the pressure difference between the intake and exhaust manifolds controlled the size of one jet. The other jet was controlled a tapered needle valve connected to a temperature-sensitive device in the intake manifold. The fuel pressure drop across the pair of jets acted on one side of a flexible diaphragm that was loaded by the action of an engine-driven centrifugal governor on the other; the diaphragm operated a valve regulating fuel flow as the two forces balanced against one another on the diaphragm. Rolls-Royce was much more involved in the development of these speed-density systems than it had been in the development of float-type carburetors it used before."

 

[Koopernic]

Good post and attachment Koopernic, I must confess when I was involved in tuning two strokes I didnt give a monkeys toss about fuel efficiency or economy By some strange twist of fate I ended up with one of the fastest Suzuki X7s ever raced in UK in production clases, many good racers who had switched to Yamaha RD250s asked me what I had done to it, so I asked the tuner (Terry Becket) what he did and he said "same as all the others". Even in the 1980s two strokes were still in some ways a black art. However that was just top speed, my X7 lost ten yards at least coming out of every corner, even in lower capacity classes torque across a broad range rules the roost.

Never ridde nmotor cycles much except for a few 50cc step throughs while on holiday. They still give you that "born to be wild" song in the head. Might take up Segway racing.


In the 1990s Ralph Sarich developed a compressed air direct fuel injection system that could develop a stratified charge that was rich across the spark plus but lean elsewhere. This system could make a 2 stroke superior to 4 strokes though it is applicable to all cycles. It was perfect for two-stroke cars but entrenched conservatism prevented an uptake. It in essence worked like the crecy.

Ralph Sarich -- Fuel injector

It was taken up by Evinrude for their outboard motors, a maritime environment is not a place for valve gear. The patent may have gone to a motorcycle manufacturer.

They do use oxygen sensors and fuel sensors in the exhaust but these are required for catalytic converters anyway.

 

[pbehn]

Never ridde nmotor cycles much except for a few 50cc step throughs while on holiday. They still give you that "born to be wild" song in the head. Might take up Segway racing.


In the 1990s Ralph Sarich developed a compressed air direct fuel injection system that could develop a stratified charge that was rich across the spark plus but lean elsewhere. This system could make a 2 stroke superior to 4 strokes though it is applicable to all cycles. It was perfect for two-stroke cars but entrenched conservatism prevented an uptake. It in essence worked like the crecy.

Ralph Sarich -- Fuel injector

It was taken up by Evinrude for their outboard motors, a maritime environment is not a place for valve gear. The patent may have gone to a motorcycle manufacturer.

They do use oxygen sensors and fuel sensors in the exhaust but these are required for catalytic converters anyway.

Two strokes were running in to problems of safety, noise and emissions even before economy and power output became an issue.

 

[Denniss]

BMW 801TH contains the 801F engine
BMW 801TS contains the 801S engine
BMW 801TU contains the 801Q-2 engine = a D-2 with larger/better armored oil tank/cooler and provision for injection systems
The T designation is for "Triebwerksanlage", an engine complete will all parts to simply attach to an airframe using quick change mounts.
Never heard of the Fw 190 A-9 designed around/for the F-engine or requiring additional ballast at prop, this was an A-8 with a similar-weight but more-powerful engine. Later A-8 already got nose-heavier due to switching D-2 for slightly heavier Q-2 engine

EDIT: typo fixed - TU with Q-2 engine, not TQ with Q-2 engine, matching numbers of engine and M/T types was rare

 

[fastmongrel]

Unfortunately the theory didn't work out in practice. The Hercules being larger in diameter the Gnome-Rhone 14N/R (and the 14K derivatives ) that used the same bore and stroke. Difference in diameter compared to the Wright R-2600 was also minor although the Wright used a 4.8mm shorter stroke (but bigger bore)

The 14N was a very light engine compared to other 14 cyl radials, the postwar Snecma R developments gained a lot of weight and got a little bit bigger in diameter.

 

[Shortround6]

Thank you. The reason for bringing in the Gr 14N was that it used the same bore and stroke as the Hercules and would be a good comparison for the claim that a sleeve valve would offer a smaller diameter.
The BMW used a 6.15in stroke (156mm) vs the 6.5 in (165mm) stroke of the Gr 14N and Hercules. This isn't the 100% explanation of the difference in diameters, the R-2600 used a 6.3215 (160mm) stroke. However I believe it shows my point that this "theoretical" advantage of the sleeve valve didn't work out in practice.

The Snecma R started pre-war as the Gr 14R but they didn't have enough time to get it into production although it powered one or more prototypes, most famous being the Bloch 157.

 

[fastmongrel]

The reason for the Bristol sleeve valve engines diameter being bigger than expected originally was that the Junk Head needed a lot of extra finning as power increased.

You can see the depth of the Junk Head from the above wikipedia picture. From the Junk Head sealing rings to the top of the fins is about the same as a normal push rod and poppet valve system from head gasket to rocker cover.

 

[Shortround6]

Also please note that the sleeve rises several inches above the the "head" surface. The ports, when closed are above the combustion chamber.

 

[tomo pauk]

...
The BMW 801F was delayed but scheduled for production in April 1945, BMW was forced to supply the BMW 801TS instead as an interim. It had promised the 801F or "similar" engine. Because the 801TS was lighter than the 801F and the Fw 190A9 had its centre of gravity built around the BMW 801F the Fw 190A9 had weights applied to the propeller to balance the aircraft. It got that close to production it effected the airframe.

The 2580hp was intended as a service rating. It wasn't a test stand experiment to detect vibration or heat load.
...

I'd kindly ask for sources for the statements quoted.

 

[Koopernic]

BMW 801TH contains the 801F engine
BMW 801TS contains the 801S engine
BMW 801TQ contains the 801Q-2 engine = a D-2 with larger/better armored oil tank/cooler and provision for injection systems
The T designation is for "Triebwerksanlage", an engine complete will all parts to simply attach to an airframe using quick change mounts.
Never heard of the Fw 190 A-9 designed around/for the F-engine or requiring additional ballast at prop, this was an A-8 with a similar-weight but more-powerful engine. Later A-8 already got nose-heavier due to switching D-2 for slightly heavier Q-2 engine

I've added two scans from a pair of of my reference Books. The first is The excellent Creek & Smith Book Fw 190 Volume 2, the second from Ju 388 by Christof Vernalken and Martin Handif because of its information on the 801E engine which is a bomber analog of the 801F AFAIKT.

Unfortunately I had taken some bad information from Wikipedia (calling the 801TJ-1 the 801TQ and confusing the TH and TU)

801C-2 1600hp at 900m
801D-2 1700hp at sea level (D series increased to around 1950hp shp around 1943 with C3 intake injection for emergencies)
801F(TH) 2400hp at sea level
801R(TR) 2000hp at sea level, 1950hp @ 5200m/17060ft, 1760hp @ 8600m/28220ft. Two Stage 4 speed inter-cooled engine for Ta 152C etc
801S(TS) 2000hp at sea level. Improved supercharger, altered SC gear ratios, straightened components.
801U(TU) 1730hp at sea level but significantly improved altitude performance over the D2 as it could maintain 1710hp to 18700ft

There are plenty of photos of Fw 190A9, their distinguishing feature is two air intakes, left and right.

The above are the military and takeoff power ratings not the higher ratings possible with WEP.

801E appears to be a bomber analog of the 801F and was also to be capable of 2400hp with either 150kg/hour of MW0 (pure water) or 250kg/hour of MW50.

801TJ-0 Turbo-Charged Intercooled engine used on Ju 388
801TJ-1 Turbo-Charged Intercooled engine but with improved turbo charger and 801E core.


***************
Notes
1 The 801F ie 801TH was flown in the Fw 190 V34 on 9 August 1943.
2 Focke Wulf Documents of August 1943 note that production series delivery of the 801TH probably won't commence till May 1945.
3 Focke-Wulf BMW will supply the improved BMW801TU and 801TS in the interim.
4 Increased emergency power (ie WEP) is not possible due to the weakness of the propeller gearbox

In regards to the 801E (bomber engine) which can be regarded as having the same issues in reaching 2400hp (2600hp WEP) AS THE 801F (fighter engine)

1 Gearbox not strong enough to handle increased power
2 Con rods not strong enough to handle increased power
3 Drive Shaft not strong enough to handle bigger propeller to handle increased power.
4 Electrical motor for pitch change mechanism needs more power to handle bigger and greater number of blades.

Id say the 801F and 801E were complete redesigns with stronger gearbox, con rods, stronger pistons, precision vacuum caste heads and likely bigger bearings. It sounds like everything needed strengthening and everything was "new production". I can't see the Fw 190A8 propeller absorbing 2600hp

Also noteworthy in the Ju388/Vernalen/Handig book is that production of the Jumo 213EB was beginning as production of modified inlet guide vanes for the Jumo 213EB had been made. The new vanes solved a surge problem at altitude.

BMW gave the Junker Ju 388 program priority for new stronger connecting rods. This means the Fw 190A would have lower priority, an indication the Fw 190A was being phased out.

Its clear the future for the Fw 190 lay with liquid cooled engines, they were already producing more power.

 

[Koopernic]

I'd kindly ask for sources for the statements quoted.

See my response to Deniss. The BMW801F(TH) was flown in the Fw 190V34 as early as Aug 1943.

The 801F can be regarded as analogous to the R-2800-57 which had a power rating of 1hp per cubic inch and was in essence completely engineered.

There was nothing wrong with the 801F, the Germans just couldn't set up production at that stage of the war, just a few of the more important components were transfered into the TS and TU