How would the Fw190 have performed with the BMW 8028 engine with two-stage supercharger?

[Hardrada55]

Supposedly the BMW P.8028 engine with a two-stage supercharger offered no significant increase in performance over the Fw190A with the standard two-speed BMW 801, and that is why use of this engine was not pursued. I can see that being true, for lower altitudes particularly. But, what kind of performance could have been expected from a Fw190 with the BMW 8028 engine with the two-stage supercharger providing 1550hp at higher altitude, say, 23,000 ft or 7,000m?

 

[tomo pauk]

Supposedly the BMW P.8028 engine with a two-stage supercharger offered no significant increase in performance over the Fw190A with the standard two-speed BMW 801,

Who made that claim?

But, what kind of performance could have been expected from a Fw190 with the BMW 8028 engine with the two-stage supercharger providing 1550hp at higher altitude, say, 23,000 ft or 7,000m?

The BMW 801S offered a 20 km/h increase of speed over the 801D on a Fw 190, with about 180 HP advantage under 6 km. At 9 km, it offered 35+ km/h more - good superchargers matter.
Perhaps we can gain another 30-40 km/h above 8 km, ie. a bit greater speed than what the 190D-9 did? Gains in rate of climb over the 801D-powered Fw 190s would've been substantial above 7 km.

 

[Hardrada55]

I read that the reason the BMW P.8028 was not produced and used in the Fw190 was because it "failed to demonstrate a worthwhile increase in performance".

 

[tomo pauk]

I read that the reason the BMW P.8028 was not produced and used in the Fw190 was because it "failed to demonstrate a worthwhile increase in performance".

Where have you read that?

 

[Macandy]

Most fighting over the Eastern Front was under 15,000ft

 

[tomo pauk]

Most fighting over the Eastern Front was under 15,000ft

How that helps the fellow member asking the question in the 1st post here?

 

[Hardrada55]

Where have you read that?

Response #4 In any event not a primary source.

BMW P.8028

What configuration, R14 or R18 was this engine? Anyone know the capacity? Supposedly 1550hp at altitude(?).

www.secretprojects.co.uk

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A new heart for the shrike - the search for new Fw 190 engines

In 1942, the Fw 190 had already entered service on all fronts. It had proven to be a formidable fighter, sweeping away the obsession with aerodynamically clean and light inline-powered airframes and making other nations all over the world rethink their design philosophies. To keep the Fw 190 comp...

forum.warthunder.com

 

[Shortround6]

Problem the Germans had with 2 stage superchargers was the fuel and cooling.
The Germans could not use the same level of boost without detonating. And this is not just the total level of boost but the amount of multiplication over the ambient air.
Say you want to use about 15lbs of boost, at sea level you need to compress the air 2.0 times (rounding off a small bit) but at 23,000ft you need to compress the air about 4.95 times. Yes, the 2nd stage comes in handy, but the highly compressed air will be much hotter than the sea level air after compression so we need an inter cooler. and we still won't get down to temps at sea level.
It is also going to require several hundred HP to power the 2 stage so we need to burn more fuel or accept the difference in power, better than not using the 2nd stage but not quite the gain hoped for?
Now granted the air is a bit colder but the air at 23,000ft is about 84% as dense as the air is 18,000ft so we need more air (more drag) just to cool the engine that is making the same amount of heat in the cylinders even though 100-200hp less is making it to the propeller. Assuming the pane is making the same speed at both altitudes.

Wright never made a high altitude R-2600 engine. The R-3350 had a lot of problems. P & W used both intercoolers and water injection (and 100/130 fuel) to get high performance from the R-2800 and then redid the entire engine (new cylinder fins and cylinder heads) to get the engines for the P-47M & N and the engines in the F4U-4.

Liquid cooled engines had an easier time but did have limitations.

The Germans had a lot to juggle trying to 2 stage supercharge the BMW radials. Maybe a better intercooler would have allowed more power, but a better intercooler might require more cooling air creating more drag? Maybe they need more cooling airflow for the engine itself ? maybe they need a crapload more water/alcohol. maybe they need two of those solutions at the same time.

 

[tomo pauk]

Response #4 In any event not a primary source.

Thank you.

Problem the Germans had with 2 stage superchargers was the fuel and cooling.
The Germans could not use the same level of boost without detonating. And this is not just the total level of boost but the amount of multiplication over the ambient air.

Fuel used on Fw 190s was as good as the current-best Allied hi-octane fuel.
The BMW P.8028 was supposed to use intercooler between the auxiliary stage and engine-stage compressors.

(to all BTW - seems like that engine never flew. Did it even made to the test bench?

 

[Shortround6]

Fuel used on Fw 190s was as good as the current-best Allied hi-octane fuel.
The BMW P.8028 was supposed to use intercooler between the auxiliary stage and engine-stage compressors.

For some reason the Germans never used it like the Allies did.
They ran higher compression in the cylinders (except for the Jumo engines?) and they may not have run the engines as rich at full power.

I don't know if they had piston problems, or spark problems or if they didn't know quite what they had? (German fuel may have varied a bit more form batch to batch?).
There is no doubt that some German fuel was as good (or better than ) allied fuel, but the Germans don't seem to have increased their power ratings as much.
German fuel seemed to get better as the war went on but I don't know why, were they really trying for it or did changes in the raw materials (higher percentage of aromatic in synthetic fuel) give unintended results?

British in the 1930s were specifying around 20% aromatics even in 87 octane fuel because it gave better rich mixture response. They never figured out if it was 87/92 or 87/96 or what it was. They just knew it was better than 87 octane with a very low percentage of aromatics. They were looking for a similar improvement in 100 octane fuel over and above what "straight" 100 octane would give.

 

[tomo pauk]

For some reason the Germans never used it like the Allies did.
They ran higher compression in the cylinders (except for the Jumo engines?) and they may not have run the engines as rich at full power.

If we focus just on the big radials, some boost pressures to compare at high-octane fuel.
BMW 801D (fully rated): 1.42 ata, or 41 in Hg
801D in over-boost: 1.65 ata, or 47.80 in Hg
801S in over-boost: 1.82 ata, or 53 in Hg
R-2600-13 (1700 HP for t.o.): 43 in Hg for t.o. and 1st gear mil power, 44.5-45.5 in 2nd gear mil power
R-2600-20 (1900 HP for t.o.): 49 in Hg for take off, 43.5 in Hg for military rating
R-2800-43 (on B-26): 49.5 in Hg 1st gear mil power of 1920 HP (more for take off and 2000 HP)
Hercules VI: at 1st +7 psi (44.2 psi), later up to +8.25 psi (46.70 in Hg)
Hercules XVII: +10 psi (50.30 in Hg) per this test

Yes, BMW 801D indeed have had a higher compression ratio than these Allied engines.

 

[Macandy]

How that helps the fellow member asking the question in the 1st post here?

It explains why the RLM didn't see any milage in an alternative engine to the one already delivering outstanding service.

'What if…' a meaningless question if there isn't a question to be answered.

 

[Shortround6]

The R-2800-8 in the F4U-1 was good for 54in for take-off and 52.5-53.0 military.
With water injection it was good for 57.5-59.5 depending on supercharger gear.
Pretty much the same engine in the P-61 used 53in in neutral or high gear and 54 in in low gear for military power.
They used 60in in all gears for WER.
P-47s used 52-53 in until they got water injection. Initial water injection systems used 56in (and that was worth about 200-300hp depending on altitude"
Later installations used 64in for 2535hp.
This is on 100/130 fuel. and not using the C series engine.
Some later B-24 engines (R-1830s) were rated at 49in at altitude for 1255hp(?) .

A lot of radials were cooling limited.

 

[tomo pauk]

It explains why the RLM didn't see any milage in an alternative engine to the one already delivering outstanding service.

It does not.

'What if…' a meaningless question if there isn't a question to be answered.

Bye.

 

[tomo pauk]

The R-2800-8 in the F4U-1 was good for 54in for take-off and 52.5-53.0 military.

It have had an intercooler, and lower CR than the BMW 801D. Higher boost is to be expected. The 801S was thereabout with the -10, though - having better S/C was an improvement, as always.

With water injection it was good for 57.5-59.5 depending on supercharger gear.
Pretty much the same engine in the P-61 used 53in in neutral or high gear and 54 in in low gear for military power.
They used 60in in all gears for WER.

Water injection kinda moves goal post vs. what one airforce was doing with their high-octane fuel.

P-47s used 52-53 in until they got water injection.

Again the intercooler, with turbo doing a lot of work. Not what the 801D had.

A lot of radials were cooling limited.

Agreed.

 

[Shortround6]

Air cooled engines were most always limited by cooling. They were running closer to the edge than the liquid cooled engines. You could over-boost the liquid cooled engines and get more power, at least for a few minutes, before anything melted down. Liquid cooled engines might break (forces were too great) and at some point the extra heat was going to either allow the fuel to detonate (octane limit) or the extra heat was going to overpower the cooling system (cook the oil) .

The Air cooled engines might break but they were running a lot close to the heat limit to begin with.
The American radials were often running as fuel cooled engines. The F4U used 45 gallons an hour (0.75 gallons a minute) less fuel when the water injection was running than at military power despite making about 10-16% more power.

 

[Howard Gibson]

Most fighting over the Eastern Front was under 15,000ft

How about all the fighting against P-47 Thunderbolts at 30,000ft?

 

[Howard Gibson]

Problem the Germans had with 2 stage superchargers was the fuel and cooling.
The Germans could not use the same level of boost without detonating. And this is not just the total level of boost but the amount of multiplication over the ambient air.
Say you want to use about 15lbs of boost, at sea level you need to compress the air 2.0 times (rounding off a small bit) but at 23,000ft you need to compress the air about 4.95 times. Yes, the 2nd stage comes in handy, but the highly compressed air will be much hotter than the sea level air after compression so we need an inter cooler. and we still won't get down to temps at sea level.
It is also going to require several hundred HP to power the 2 stage so we need to burn more fuel or accept the difference in power, better than not using the 2nd stage but not quite the gain hoped for?
Now granted the air is a bit colder but the air at 23,000ft is about 84% as dense as the air is 18,000ft so we need more air (more drag) just to cool the engine that is making the same amount of heat in the cylinders even though 100-200hp less is making it to the propeller. Assuming the pane is making the same speed at both altitudes.

Wright never made a high altitude R-2600 engine. The R-3350 had a lot of problems. P & W used both intercoolers and water injection (and 100/130 fuel) to get high performance from the R-2800 and then redid the entire engine (new cylinder fins and cylinder heads) to get the engines for the P-47M & N and the engines in the F4U-4.

Liquid cooled engines had an easier time but did have limitations.

The Germans had a lot to juggle trying to 2 stage supercharge the BMW radials. Maybe a better intercooler would have allowed more power, but a better intercooler might require more cooling air creating more drag? Maybe they need more cooling airflow for the engine itself ? maybe they need a crapload more water/alcohol. maybe they need two of those solutions at the same time.

Fuel and cooling are separate problems.

In the Fw190, the BMW801's power fell off above 20,000ft. German fuel allowed something like 1.6Atm (48"Hg, 9RAFpsi) boost pressure. A two stage supercharger would have allowed the Fw190 to maintain that boost well above 20,000ft. To intercept USAAF B-17s, the Fw190 need to climb to 30,000ft, where the P-47s had a 50mph speed advantage. They needed the two stage supercharger.

Air heats up when compressed, so an inter-cooler would have helped. Given the Fw190's high altitude performance, anything would have helped.

 

[tomo pauk]

German fuel allowed something like 1.6Atm (48"Hg, 9RAFpsi) boost pressure.

Different engines were able to withstand different boosts. Air-cooled engines were not so good as the water-cooled types, high-compression engines less than low-compression engines.
BMW 801D, being of high compression and air-cooled, was unable to use as high boosts as the liquid-cooled low-compression engines, like the Merlin.

(all of this before we factor in the ADI systems to help out with bigger boosts)

 

[Thos9]

Problem the Germans had with 2 stage superchargers was the fuel and cooling.
The Germans could not use the same level of boost without detonating. And this is not just the total level of boost but the amount of multiplication over the ambient air.
Say you want to use about 15lbs of boost, at sea level you need to compress the air 2.0 times (rounding off a small bit) but at 23,000ft you need to compress the air about 4.95 times. Yes, the 2nd stage comes in handy, but the highly compressed air will be much hotter than the sea level air after compression so we need an inter cooler. and we still won't get down to temps at sea level.
It is also going to require several hundred HP to power the 2 stage so we need to burn more fuel or accept the difference in power, better than not using the 2nd stage but not quite the gain hoped for?
Now granted the air is a bit colder but the air at 23,000ft is about 84% as dense as the air is 18,000ft so we need more air (more drag) just to cool the engine that is making the same amount of heat in the cylinders even though 100-200hp less is making it to the propeller. Assuming the pane is making the same speed at both altitudes.

Wright never made a high altitude R-2600 engine. The R-3350 had a lot of problems. P & W used both intercoolers and water injection (and 100/130 fuel) to get high performance from the R-2800 and then redid the entire engine (new cylinder fins and cylinder heads) to get the engines for the P-47M & N and the engines in the F4U-4.

Liquid cooled engines had an easier time but did have limitations.

The Germans had a lot to juggle trying to 2 stage supercharge the BMW radials. Maybe a better intercooler would have allowed more power, but a better intercooler might require more cooling air creating more drag? Maybe they need more cooling airflow for the engine itself ? maybe they need a crapload more water/alcohol. maybe they need two of those solutions at the same time.

Wright never made a high altitude R-2600 engine.

A two-stage supercharged Wright R-2600-10 rated at 1,700 hp for takeoff and 1,380 hp at 21,500 feet powered the Grumman XF6F-1 Hellcat prototype (all subsequent Hellcats employed the P&W R-2800).