Superchargers- how do they work?!?

[red admiral]

Figures from Rolls-Royce for Spitfire XIV

Super-chargergear Altitude(ft)Withoutexhaustthrust-Withexhaustthrust

MS 5,000 345 351
13,500FTH 388 400
23,500 373 399
FS
31,500FTH 419 454
40,000 377 424

 

[vanir]

Race engineering was an earlier hobby of mine, I'd like to add to the description of superchargers. Keep in mind my expertise is more automotive engines than aero engines, which have some different rules due to operating altitudes.

There are a few distinct types.
Roots type and centrifugal (compressor) type.
Exhaust driven and mechanically driven.
Clutched and direct drive.
Multiple stage and multispeed types.

All these can be easily divided into the two groups of roots and centrifugal.
Turbochargers and centrifgual compressors use identical construction, but different drives. They are the same thing and work differently from roots type blowers.

Roots type blowers are inefficient but mechanically uncomplicated.
Centrifugal blowers (including turbochargers) may be highly efficient but must be carefully tuned, set up and maintained.

Centrifugal blowers are the type generally used in aero engines. A turbosupercharger is essentially a two stage blower with the second stage driven by exhaust fumes. Multiple stage superchargers have both (or more) stages mechanically driven. The different stages may be two separate installations or one widened casing with two impeller sizings.
Multiple speed superchargers have one installation with a clutched or synchronised, multiple speed gear drive for it.
Turbochargers have extra piping and equipment and are generally larger, heavier and more complicated than mechanically driven compressors (until you start playing around with multiple stages and speeds, which can make a mechanical installation quite heavy and cumbersome).

Centrifugal superchargers rely upon an impeller to compress intake charge within a spiral casing. Tuning the impeller capacity to casing diameter provides the engine operating parameters at which maximum efficiency is attained. All centrigual blowers have a fairly narrow band of high efficiency, it may be say, 65% at 1000rpm/sea level, 110% at 2000rpm/sea level and 165% at 3000rpm/sea level, then 75% at 3500rpm/sea level. Change altitude you get a different effect. You might get 110% at 3000rpm/4000m and 140% at 3500rpm/4000m, but this is a problem if your motor redlines at 3200rpm.

Hence you have multiple stage superchargers, one small casing say, and one bigger, for high efficiency at low altitudes (roughly speaking), then regained efficiency at higher altitudes. This acts as if you are back at sea level for operating efficiency. At lower altitudes the high altitude impeller just doesn't spool up (ie. operates at something like 5% efficiency if that) so you don't have any detrimental effect from it. But hit the right altitude and it's like a kick in the guts for the motor.

Another way to improve supercharger efficiency is to use charge coolant. Water injection for example might lower the heating effect of compressing intake charge (which is a limiting factor on supercharger efficiency), so you might get a return of 185% at 3000rpm/sea level on your motor. Problem is the air intake being cooled actually reduces manifold pressure. It's a net gain in power, say 80hp in a 1000hp engine but reliability is vastly improved.

With actual boost systems fitted, like water injection there is a combination of wastegate adjustment and charge coolant. The Fw-190A system for example uses a two stop system operated by the pilot, the first stop adjusts the wastegate and the second stop activates a C3 fuel injector in the supercharger exhaust casing (used for charge cooling before MW-50 kits were available from the manufacturer in Jan44).

All centrifugal superchargers (including turbochargers) use a wastegate system to limit boost pressures at maximum power settings and engine speeds, particularly in the case of overspeeding the engine. This may be as simple as a pressure release valve located on the supercharger casing.
Yes I know it is mounted in the exhaust stream on turbochargers. It is on the casing in mechanical types for the same effect. No it is not a blow off valve, they're piped to the intake manifold proper. (just pre-empting arguments here)

So whilst supercharger efficiency at the higher boost pressure drops back a little (metered by the charge coolant), it now functions at 1.58ata instead of 1.42ata and gives a net gain of some 300hp, for a limited duration.

With multiple stage superchargers some sort of charge cooling is necessary, because intake is passing through two compressions and heats up quite a bit, dramatically reducing overall efficiency. Intercoolers and aftercoolers are the preferred method although in some cases water injection either substitutes or supplements.

With particularly light airframe engineering requirements like the Me-109 a few innovations were used to achieve the effects of multiple speed supercharging and aftercooling, in order to keep the weight down. A hydraulic drive system was used on the 605/603 motor impeller which acts like a multiple speed drive and increases best operating altitude by about 2000m, but without the extra mechanicals of a genuine multispeed system. MW-50 charge coolant was introduced in 1944 to also allow wastegate adjustment for higher, limited duration boost pressures in the later 605 motors (1.8ata and 1.92ata), for a net gain of 300-450hp without the weight expense of aftercooling.

For a complete mechanical setup, a high output engine using a turbosupercharger with intercooling just check out the sheer size and complexity of a P-47 engine layout.

A multispeed impeller drive essentially increases the operating altitude of the motor a little. To raise the operating altitude a bit more, you put in another gear. Multiple stages put the intake charge through another process of compression.

 

[kool kitty89]

A turbosupercharger is essentially a two stage blower with the second stage driven by exhaust fumes.

This isn't necesarily ture. The term turbosupercharger was used simply to refer what is now usualy called just a turbocharger. Turbo-supercharging may refer just to the use of a turbosupercharger, but since in operational WWII US context there was always an "engine supercharger" any turbocharging would have a mechaicaly driven supercharger stage as well.


Something that often gets mixed up is two-stage and two-speed superchargers. (though this has pretty much been adressed here already, these are some pretty common mistakes made in literature which can be confusing)
As mentioned a 2-stage supercharger has 2 impellers with one feeding into the other; there are several configurations of this, usually 2-speed and always multi-speed.
With a multi-speed supercharger (usually 2-speed), it can be single stage. Take the Merlin XX, using a 2-speed supercharger. (single stage is implicit)
There are also cases like the DB 601, 605, and 603 which had variable speed supercharger driven by a fluid coupling and didn't have a finite gear ratio.

With 2-stage supercharger there are several different configurations: the one used on the Merlin had both impellers driven by a common shaft with 2 gear settings. The US engines (partiularly Pratt and Whitney) had the standard single-stage single-speed "engine stage" mounted to the back of the engine, along with a significantly larger external stage with multi-speed gearing. (neutral, low blower, and high blower)

THere were also some cases with both stages of a 2-stage supercharger having individual multi-speed gearing, but I don't know if these saw operational use. (I believe some German engines used this configiration expirementally)

 

[seesul]

the more posts in this thread the more I learn, thx guys!

 

[HoHun]

Hi Vanir,

>(used for charge cooling before MW-50 kits were available from the manufacturer in Jan44).

Do you have any source for the January 1944 introduction (or any introduction at all)?

>All centrifugal superchargers (including turbochargers) use a wastegate system to limit boost pressures at maximum power settings and engine speeds

In aero engine applications, mechnically-driven superchargers typically use a throttle instead. I'm aware of wastegate configurations only for turbo-supercharged engines.

>With particularly light airframe engineering requirements like the Me-109 a few innovations were used to achieve the effects of multiple speed supercharging and aftercooling, in order to keep the weight down.

This had nothing to do with weight - the system was already used in the DB 601, and it was later adopted by Allison and used in a fighter as heavy as the F-82.

Regards,

Henning (HoHun)

 

[vanir]

This isn't necesarily ture. The term turbosupercharger was used simply to refer what is now usualy called just a turbocharger. Turbo-supercharging may refer just to the use of a turbosupercharger, but since in operational WWII US context there was always an "engine supercharger" any turbocharging would have a mechaicaly driven supercharger stage as well.

In engineering a turbocharger is a layman introduced term that appeared somewhere along the way for what is just a supercharger. That said, so is "turbosupercharger" and you are quite correct. As a layman's term it doesn't really describe any particular piece of engineering, it just became a popular term for a particular supercharger setup, like turbocharger did. I appreciate what the common terminology means in the US and thankyou for the input. It makes some American aero publications I've been reading make more sense (about the D-motor for instance).

It's probably a similar thing with turbojet and turbofan, which evolved really as layman's terms for various bypass and whatnot, I wouldn't be surprised if jet/turbine engineers pull their hair out over that. "Turbojets" frequently used bypass too, for cooling purposes. Then you have high bleed, low bypass turbofans and oh my god I don't even know what I'm talking about

Popular use of certain terminology is by no means universal, a good point and one for the reader to keep in mind.

Do you have any source for the January 1944 introduction (or any introduction at all)?

Let's see. Mercedes Benz AG archives, Stuttgart (second hand, cited by the comprehensive DB605 homepage of an enthusiast).
Joe Baugher.
I'll have to look up others. I've read repeatedly the 801D-2 had always been intended to mount MW-50, but production of the kits was delayed unexpectedly. I presume C3 injection was introduced as a stop gap. I've seen no primary source documentation...but for one.

A graph of comparative performance (I can attach) which shows A-8 (801D), A-9 (801TS), Ta-152C-1 (603LA) and Ta-152H-1 (213E) performance curves at sondernotleistung. The A-8 has a very interesting graph showing two different maximum performance settings, one for 1.58ata and one for 1.65ata. The A-9 has just 1.65ata. Keeping in mind C3 injection is not as an effective charge coolant as MW-50...this could be consistent with the two performance curves representing both C3 injection and MW-50 use for the 801D motor in the A-8.

It's a lot of assumptions, isn't it.

Do you have references/documentation to the contrary? I'm open to a qualified correction, as always. I want to know, rather than claim but I do simply speak freely as at the best information at my disposal. No offense is intended.

Another confusing thing about the 801, MW-50 issue is that I've noted recent American sources in particular, even among engineers refer only to MW-50 use and seem completely unaware of the C3 injection system. But at the same time documentation of the use of C3 injection in the 801 is taken from US examination of probably an F-8.

This boost system has caused me more headaches than any other factor about WW2 aircraft. Just trying to figure out exactly what it was, how it worked, what its specifications were, what its particulars are.

Please, by all means, put this one to bed.

In aero engine applications, mechnically-driven superchargers typically use a throttle instead. I'm aware of wastegate configurations only for turbo-supercharged engines.

Safest bet is to look them up at engineering sources but I'll explain amid my own meagre comprehension.
Wastegate is the term describing valves mounted within the supercharger casing to release unusable or dangerous pressures. All superchargers from the roots GM 6:71 diesel type to the turbosupercharger of a P-47 Thunderbolt have them.
Adjusting the wastegate adjusts boost under given conditions, say full throttle and maximum operating speed. On an engine driven supercharger it is mounted to the impeller housing. On an exhaust driven supercharger it is mounted in the exhaust stream driving the impeller. The key point is that by adjusting this valve, you adjust boost pressure at a given condition.
A US document at Luftwaffe experten clearly describes the manual operation of the wastegate in the mechanically driven BMW 801D supercharger, for attaining the higher boost pressures used in conjunction with C3 injection.

This had nothing to do with weight - the system was already used in the DB 601, and it was later adopted by Allison and used in a fighter as heavy as the F-82.

I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one. This is consistent with the full throttle heights for these engines in conjunction with altitude performance graphs and low altitude outputs.
It is noteworthy I began with the assumption the hydraulic drive was used on all 600-series engines, but was repeatedly and markedly corrected as I (unsuccessfully) sought a blueprint for the 601 engine/supercharger.

Since the present assumption appears consistent with all available data, naturally I would nevertheless gladly accept any documentation, particularly blueprints of the 600/601 supercharger displaying a hydraulic drive. It is however listed as mechanical at various aero/engineering sites, where the 605 and 603 are specifically stated as hydraulic and innovative.

 

[vanir]

Just to clear up another potential problem...about wastegates. On a roots type blower these are simply a pressure release valve tapped in. The reason I made the earlier distinction with centrifugal blowers is that on these it is more likely to be a more complicated driver/pilot adjustable valve system termed wastegate. Turbochargers always have complicated wastegates even if automatically controlled, because of the need to vary the release of exhaust pressure at different operating speeds.

 

[HoHun]

Hi Vanir,

>In engineering a turbocharger is a layman introduced term that appeared somewhere along the way for what is just a supercharger.

What Koolkitty pointed out is that the turbo-supercharger was always used in connection with an engine-driven supercharger stage in US engines of WW2. It was not a terminology remark.

>Let's see. Mercedes Benz AG archives, Stuttgart (second hand, cited by the comprehensive DB605 homepage of an enthusiast).

You were talking about the BMW 801. Re-quoting:

"The Fw-190A system for example uses a two stop system operated by the pilot, the first stop adjusts the wastegate and the second stop activates a C3 fuel injector in the supercharger exhaust casing (used for charge cooling before MW-50 kits were available from the manufacturer in Jan44)."

So it's BMW documentation I'd like to see.

>Do you have references/documentation to the contrary?

You claim MW 50 for the BMW 801, you bring documentation. I'm quite aware of the countless claims for MW 50 in popular books, but haven't seen anything backing it up, ever. There is quite a community of researchers on the various internet fora, and I know they have been looking for information on MW 50 for years - in vain, as far as I'm aware.

>A US document at Luftwaffe experten clearly describes the manual operation of the wastegate in the mechanically driven BMW 801D supercharger, for attaining the higher boost pressures used in conjunction with C3 injection.

Well, bring it here. I believe you must be misreading something as the increased boost ("Erhöhte Notleistung") was invoked by a manually operated valve, but it affected the operation of the BMW's Kommandogerät computer, not simply that of the supercharger.

>I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

The DB 601 had the same hydraulical supercharger drive as the DB 605. See attached manual page ...

Regards,

Henning (HoHun)

 

[vanir]

Hi Vanir,

>In engineering a turbocharger is a layman introduced term that appeared somewhere along the way for what is just a supercharger.

What Koolkitty pointed out is that the turbo-supercharger was always used in connection with an engine-driven supercharger stage in US engines of WW2. It was not a terminology remark.

>Let's see. Mercedes Benz AG archives, Stuttgart (second hand, cited by the comprehensive DB605 homepage of an enthusiast).

You were talking about the BMW 801. Re-quoting:

"The Fw-190A system for example uses a two stop system operated by the pilot, the first stop adjusts the wastegate and the second stop activates a C3 fuel injector in the supercharger exhaust casing (used for charge cooling before MW-50 kits were available from the manufacturer in Jan44)."

So it's BMW documentation I'd like to see.

>Do you have references/documentation to the contrary?

You claim MW 50 for the BMW 801, you bring documentation. I'm quite aware of the countless claims for MW 50 in popular books, but haven't seen anything backing it up, ever. There is quite a community of researchers on the various internet fora, and I know they have been looking for information on MW 50 for years - in vain, as far as I'm aware.

>A US document at Luftwaffe experten clearly describes the manual operation of the wastegate in the mechanically driven BMW 801D supercharger, for attaining the higher boost pressures used in conjunction with C3 injection.

Well, bring it here. I believe you must be misreading something as the increased boost ("Erhöhte Notleistung") was invoked by a manually operated valve, but it affected the operation of the BMW's Kommandogerät computer, not simply that of the supercharger.

>I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

The DB 601 had the same hydraulical supercharger drive as the DB 605. See attached manual page ...

Regards,

Henning (HoHun)

I take it there's some reason you're looking for a fight? Surely a bar brawl would be more satisfying than a web argument with a sincere poster.

I have to go to work in five hours, so I'll answer all your questions tomorrow. You have so very many questions, but it's such a lonely place at the top, yes?

It's alright mate. Take it all in stride. You're being argumentative. Chill.

 

[HoHun]

Hi Vanir,

>I take it there's some reason you're looking for a fight?

If you can't handle a simple request for sources without taking it as a personal challenge, maybe you should stay on the safe side and don't make any doubtful claims - or better, don't make any claims at all.

>I have to go to work in five hours, so I'll answer all your questions tomorrow.

As far as I'm concerned, no need to - you're going to be on my ignore list by then.

Kind regards,

Henning (HoHun)

 

[kool kitty89]

I have read of a supercharger waste gate in some circumstances, but this would only make sense with a fuel injected engine. Otherwise you'd be blowing fuel-air mixture out the waste gate. (the carburator sprays fuel into the supercharger)

And in any case it would make more sence to use a throttle configuration to limit the boost. Also limiting RPM will also limit boost as the supercharger's rpm is dependant on the engine rpm. (at a given supercharger gear stetting, of course the DB supercharger vairies its speed independently but that solves the other issues in its self)

I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

Perhaps you were thinking of the DB 600, which certainly did use a gear driven (2-speed iirc) supercharger. (it also used a pressure carburetor instead of fuel injection)


It was also my understanding that MW 50 was never used operationally on the BMW 801, it had been in testing and was proposed for kits iirc, but this was dropped due to problems with its use in this engine. (iirc fractures/microfractures were found in the cylinders after its use)

 

[vanir]

Hi Vanir,

>I take it there's some reason you're looking for a fight?

If you can't handle a simple request for sources without taking it as a personal challenge, maybe you should stay on the safe side and don't make any doubtful claims - or better, don't make any claims at all.

>I have to go to work in five hours, so I'll answer all your questions tomorrow.

As far as I'm concerned, no need to - you're going to be on my ignore list by then.

Kind regards,

Henning (HoHun)

No no no, you see the appropriate response should have been, "I'm sorry friend, I didn't mean to make it seem like I was having a dig at you."

Then I would have said, "No trouble buddy. No harm done."

But you've decided to remain wholly argumentative and confrontational from the first to the last. We do not know each other, there is no reason for you to have trolled the way you have. My posting within the thread has been nothing but open, thoughtful and considerate.

As far as I'm concerned, no need to - you're going to be on my ignore list by then.

I've seen you do nothing but take apart posts and reference other people's efforts on three forums now. I've yet to witness a single original thought from you. Your word carries no weight with me and I thankyou for saving me the trouble.

 

[vanir]

My apolegies to the thread poster. The discussion was how superchargers work, I do believe other interests should qualify their own threads by those concerned.

I have read of a supercharger waste gate in some circumstances, but this would only make sense with a fuel injected engine. Otherwise you'd be blowing fuel-air mixture out the waste gate. (the carburator sprays fuel into the supercharger)

And in any case it would make more sence to use a throttle configuration to limit the boost. Also limiting RPM will also limit boost as the supercharger's rpm is dependant on the engine rpm. (at a given supercharger gear stetting, of course the DB supercharger vairies its speed independently but that solves the other issues in its self)

I should give a little background. I have been modifying/building race engines in my garage on and off for 20 years and running them at places like Calder Park raceway. I've messed with Eaton superchargers, two types of centrifugal, turbos, water injection, fuel as a charge coolant (to cool blowers vanes/impeller mostly) and SU/injection carbs.

The reason I tell you this is because, a) I'm unqualified and at all times open to correction upon any point...preferrably by suitably qualified material sources
This would largely be because, b) I may mess up terminology, but generally know what I'm talking about at least visually/mechanically.

I should make a self correction, in fact the only reason I dug my heels in about it was because I was being trolled.
When I say "wastegate" for a supercharger I should really say simply "pressure release valve." It is just that this is very different from a blow off valve. It is very much like a turbocharger wastegate and it performs the same function: to prevent too much pressure build up inside the supercharger casing.

Truth is on a supercharger they're usually only adjustable by opening the hood and using a spanner. Usually it's just an elaborate bolt on the casing, a pressure valve just like a steam cooker. Turn it, you adjust it.

If I didn't have to pay my renewal for Engine Analyzer (ahem, $700!!!!), I'd show you some graphs of various centrifugal outputs (I've even got a model of a Merlin II, I think, in there).

They have ratings the same as turbos, very similar to the roots type cfm system but different. Different sizes for different engine capacities, different tuning for different operating conditions. It's a pretty narrow band of maximum efficiency, 2-3000rpm if you size it a little too well. What you do is size one for a much greater requirement than you need, allowing for some efficiency reduction such as less than perfect inlet/exhaust manifolding, modelled ignition/valve timings, fuel quality and so on. Put all that aside and still have it geared to pump a little more boost than you need.
All high performance centrifugal fitments will feature this, only domestic commercial products notably differ. Then you put a pressure release valve sized for the maximum boost you actually intend to use.

Result: wider efficiency band, say 3500-4500rpm above 110% blower efficiency. Actually iirc it's the volumetric efficiency of the engine itself which is improved this way, the blower still has its regular efficiency. Point is still same.

Description: detuned race engine for high performance application.

So, on all high performance engines using centrifugal superchargers, even where the supercharger is directly driven mechanically, the supercharger itself is rated for higher boost than the maximum normal (dry) boost of the engine.

Let me put this another way, in saying that you are correct KK. Boost is a product of engine rpm as this is mechanically driving the impeller. The throttle can to a degree limit boost as engine speed is the product of horsepower and drag (ie. in simple terms, prop pitch and other things associated with a reciprocal engine). However "opening the throttle wider" cannot make the impeller provide more boost than the speed/capacity at which the engine speed (horsepower/drag) is dictating. It's confusing because it's a circular argument, but in engineering terms is sound. This is for "special, extra boosting" systems. You need more boost to raise the rpm, but you need more rpm to raise the boost...unless the supercharger makes more boost than the engine normally uses at full throttle to begin with.

Hence my above, unfortunately long winded and somewhat confusing descriptions.

Oh I might add. I've mounted carburettors both ahead of and after supercharging. On centrifugal superchargers it is better to mount them after and use something like SU carbs. On roots types it's better to mount them before and use injector plates.

 

[vanir]

I do apolegise to the mods if multiple posting is not allowed. Please advise me if this is the case, as I searched the FAQ and found nothing saying so.

Perhaps you were thinking of the DB 600, which certainly did use a gear driven (2-speed iirc) supercharger. (it also used a pressure carburetor instead of fuel injection)

Quoted referencing:
Green, William. The Augsburg Eagle: A Documentary History - Messerschmitt Bf 109. London: Macdonald and Jane's Publishing Group Ltd. 1980. ISBN 0-7106-0005-4
Smith, J R and Kay, Anthony L. German Aircraft of the Second World War. London: Putman Company Ltd. 1972 ISBN 0-370 00024-2

"DB 601A, partially sectioned General characteristics
Components
Valvetrain: Two intake and two sodium-cooled exhaust valves per cylinder actuated via a single overhead camshaft per cylinder block.
Supercharger: Gear-driven single-stage single-speed centrifugal type supercharger"

And yet...I have just found a cutaway rendition of a DB-601N motor which clearly labels a fluid drive coupling (hydraulic driven supercharger).
These are the facts, not entirely sure what to make of them.
Thoughts, comments?

It was also my understanding that MW 50 was never used operationally on the BMW 801, it had been in testing and was proposed for kits iirc, but this was dropped due to problems with its use in this engine. (iirc fractures/microfractures were found in the cylinders after its use)

You may very well be perfectly correct here, and this description certainly sounds highly authoritive. Please can anyone settle this question with any kind of sound documentation? Where's Crumpp when you need him?

 

[vanir]

Actually, nevermind, I speak far too arbitrarily and toss way too many ideas around on forums I know full well are prone to flaming by veteran members. I could speak the way I do if I was around at site formation or came with references, but I wasn't and didn't, so I can't.

My sincere apolegies to all browsers. The best way to learn about superchargers is to look them up at suitable engineering sites and academic sources. Don't accept heresay (mine or anybody's) or "historical documentation" about anything at face value, half the time if it even got interpreted right, it's either incomplete or completely misunderstood by the presenters. Go with hard science, your own research, replicated models and working reproductions. A system gleaned by inferrence which physically works simply has to be more accurate than one strictly outlined, which just plain doesn't, if that system originally worked in the first place. The laws of physics haven't changed since 1940. Point two, there are regional terminologies, propaganda, historical perspectives and industrial secrets to consider. The entire period surrounding World War Two was after all, a wartime environment.

As for my posts, I have a fraction of experience with a bare handful of custom setups and half the time I'm partly trying to understand, and partly trying to sort my own thoughts.

I'm being far too authoritive and that's as childish as those veteran members who don't think anyone should try to understand any more than they do.

I'm going to opt out from here for a bit.

 

[RAM]

Hi everyone, new here and first message.

vanir:
I know HoHun from other forums and have to say that you have taken his remarks the wrong way. The way I read it, he just asked for some sources on some affirmations you made. That's all. I see nothing personal there...but oh well.

back on topic:

I'll have to look up others. I've read repeatedly the 801D-2 had always been intended to mount MW-50, but production of the kits was delayed unexpectedly. I presume C3 injection was introduced as a stop gap. I've seen no primary source documentation...but for one.

The information is right: since the A4 series, the Fw190 had provision to mount a MW50 injection system. But it was seldom used. In fact, it was used by only a handful of Fw190A4s doing fast jabo raids over south england, and for a short time only.

The reason for the Fw190s not mounting MW50 even while in theory they could is different. There was no special shortage of MW50 kits, mostly because the engine simply couldn't take it at first, and then a much more efficient system was used.
Methanol-Water injection is not exactly kind to the engines which use it. Its use degrades engine lifetime quite a bit. Still, and usually, the reduction of engine lifetime is still acceptable and down to decent time frames.

However with the BMW801D-2 as initially mounted on the Fw190A4, the kit was literally an engine killer. As I say with, say, the DB605AM, use of MW50 caused a decrease of engine lifetime, a nuisance, but something ground crews could take. In the initial BMW801D2 engines, a single use of the MW50 system forced a complete revision of the engine as soon as the plane landed (as almost every time MW50 was used, the engine developed a serious trouble with fouled plugs, along a lot of atrittion to engine components). I guess it's needless to say it, but you can't keep in service an operational plane which requires a full engine revision each time it uses its full power. And that was the case: the BMW by that time (late 1942) simply couldn't cope with the increased MPs associated with the use of MW50, and didn't take well the mixture itself.

So, the MW50 was dropped almost completely (some low level 190 jabos did use it over SE UK during 1943 briefly. But nothing else). There was no delay in the delivery of kits. The kit simply couldn't be used operationally.

As time passed by the engine was updated for increased MP tolerances, a result of the testing and later introduction during 1943 of Erhöhte Notleistung (C3 injection, don't confuse with C3- Einspritzung, a whole different system) in some A5 planes which required the engine to be run at 1.58/1.65ata, something which the BMW801D-2 wasn't initially able to stand, and the main reason why the engine couldn't take MW50 use very well.

After modifications had been done to the engine, the BMW801 could run at those manifold pressures without a hitch. In theory now the germans could've installed Alkohol-Einspritzung, or MW50 in the Fw190s, but the thing is that by then there was no need of MW50 in the Fw190. Erhöhte notleistung gave roughly the same power increase as MW50 could provide, and didn't have the corrosion problems associated with continuous use of MW50 ,was much easier to install, and required no extra weight/equipment installed on the plane (other than an extra fuel tank that the MW50 also needed, but full of Methanol-water mixture)

So while the plane still had provision for MW50 installation, it was not used because it simply offered nothing that the C3 injection already provided. The only reason why MW50 was ever used on Fw190s (after the 1943 jabo raids on england) was fuel economy. There are some affirmations about the Fw190A9s using MW50 instead of Erhöhte Notleistung as a fuel-saving measure (Erhöhte notleistung increased fuel consumption a lot, and C3 fuel was getting more scare by late war) with the plane getting similar or lower performances as those attained with Erhöhte notleistung, and a well known focke-wulf speed chart for the Fw190D9 shows that the Fw190D9 with Ladedruckhöhung (C3 fuel+C3 injection) had performances that surpassed those of the Fw190D9 with MW50 (B4 fuel+C3 injection).



As for:

I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

You are mistaking the DB601 with the DB600. The latter had a mechanically driven supercharger, the former's supercharger was of variable speed and acted on the same principle as those in the DB603/DB605.

 

[RAM]

Hi everyone, new here and first message.

vanir:
I know HoHun from other forums and have to say that you have taken his remarks the wrong way. The way I read it, he just asked for some sources on some affirmations you made. That's all. I see nothing personal there...but oh well.

back on topic:

I'll have to look up others. I've read repeatedly the 801D-2 had always been intended to mount MW-50, but production of the kits was delayed unexpectedly. I presume C3 injection was introduced as a stop gap. I've seen no primary source documentation...but for one.

The information is right: since the A4 series, the Fw190 had provision to mount a MW50 injection system. But it was seldom used. In fact, it was used by only a handful of Fw190A4s doing fast jabo raids over south england, and for a short time only.

The reason for the Fw190s not mounting MW50 even while in theory they could is different. There was no special shortage of MW50 kits, mostly because the engine simply couldn't take it at first, and then a much more efficient system was used.
Methanol-Water injection is not exactly kind to the engines which use it. Its use degrades engine lifetime quite a bit. Still, and usually, the reduction of engine lifetime is still acceptable and down to decent time frames.

However with the BMW801D-2 as initially mounted on the Fw190A4, the kit was literally an engine killer. As I say with, say, the DB605AM, use of MW50 caused a decrease of engine lifetime, a nuisance, but something ground crews could take. In the initial BMW801D2 engines, a single use of the MW50 system forced a complete revision of the engine as soon as the plane landed (as almost every time MW50 was used, the engine developed a serious trouble with fouled plugs, along a lot of atrittion to engine components). I guess it's needless to say it, but you can't keep in service an operational plane which requires a full engine revision each time it uses its full power. And that was the case: the BMW by that time (late 1942) simply couldn't cope with the increased MPs associated with the use of MW50, and didn't take well the mixture itself.

So, the MW50 was dropped almost completely (some low level 190 jabos did use it over SE UK during 1943 briefly. But nothing else). There was no delay in the delivery of kits. The kit simply couldn't be used operationally.

As time passed by the engine was updated for increased MP tolerances, a result of the testing and later introduction during 1943 of Erhöhte Notleistung (C3 injection, don't confuse with C3- Einspritzung, a whole different system) in some A5 planes which required the engine to be run at 1.58/1.65ata, something which the BMW801D-2 wasn't initially able to stand, and the main reason why the engine couldn't take MW50 use very well.

After modifications had been done to the engine, the BMW801 could run at those manifold pressures without a hitch. In theory now the germans could've installed Alkohol-Einspritzung (MW50) in the Fw190s, but the thing is that by then there was no need of MW50 in the Fw190. Erhöhte notleistung gave roughly the same power increase as MW50 could provide, and didn't have the corrosion problems associated with continuous use of MW50 ,was much easier to install, and required no extra weight/equipment installed on the plane (other than an extra fuel tank that the MW50 also needed, but full of Methanol-water mixture)

So while the plane still had provision for MW50 installation, it was not used because it simply offered nothing that the C3 injection already provided. The only reason why MW50 was ever used on Fw190s (after the 1943 jabo raids on england) was fuel economy. There are some affirmations about the Fw190A9s using MW50 instead of Erhöhte Notleistung as a fuel-saving measure (Erhöhte notleistung increased fuel consumption a lot, and C3 fuel was getting more scarce by late war) and in theory and if those affirmations are true (never seen anything that seriously backs it up) the plane getting similar or lower performances as those attained with Erhöhte notleistung, and a well known focke-wulf speed chart for the Fw190D9 shows that the Fw190D9 with Ladedruckhöhung (C3 fuel+C3 injection, no MW50 involved) had performances that surpassed those of the Fw190D9 with MW50 (B4 fuel+MW50 injection).



As for:

I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

Seems that you are mistaking the DB601 with the DB600. The latter had a mechanically driven supercharger, the former's supercharger was of variable speed and acted on the same principle as those in the DB603/DB605.

 

[RAM]

Hi everyone, new here and first message.

vanir:
I know HoHun from other forums and have to say that you have taken his remarks the wrong way. The way I read it, he just asked for some sources on some affirmations you made. That's all. I see nothing personal there...but oh well.

back on topic:

I'll have to look up others. I've read repeatedly the 801D-2 had always been intended to mount MW-50, but production of the kits was delayed unexpectedly. I presume C3 injection was introduced as a stop gap. I've seen no primary source documentation...but for one.

The information is right: since the A4 series, the Fw190 had provision to mount a MW50 injection system. But it was seldom used. In fact, it was used by only a handful of Fw190A4s doing fast jabo raids over south england, and for a short time only.

The reason for the Fw190s not mounting MW50 even while in theory they could is different. There was no special shortage of MW50 kits, mostly because the engine simply couldn't take it at first, and then a much more efficient system was used.
Methanol-Water injection is not exactly kind to the engines which use it. Its use degrades engine lifetime quite a bit. Still, and usually, the reduction of engine lifetime is still acceptable and down to decent time frames.

However with the BMW801D-2 as initially mounted on the Fw190A4, the kit was literally an engine killer. As I say with, say, the DB605AM, use of MW50 caused a decrease of engine lifetime, a nuisance, but something ground crews could take. In the initial BMW801D2 engines, a single use of the MW50 system forced a complete revision of the engine as soon as the plane landed (as almost every time MW50 was used, the engine developed a serious trouble with fouled plugs, along a lot of atrittion to engine components). I guess it's needless to say it, but you can't keep in service an operational plane which requires a full engine revision each time it uses its full power. And that was the case: the BMW by that time (late 1942) simply couldn't cope with the increased MPs associated with the use of MW50, and didn't take well the mixture itself.

So, the MW50 was dropped almost completely (some low level 190 jabos did use it over SE UK during 1943 briefly. But nothing else). There was no delay in the delivery of kits. The kit simply couldn't be used operationally.

As time passed by the engine was updated for increased MP tolerances, a result of the testing and later introduction during 1943 of Erhöhte Notleistung (C3 injection, don't confuse with C3- Einspritzung, a whole different system) in some A5 planes which required the engine to be run at 1.58/1.65ata, something which the BMW801D-2 wasn't initially able to stand, and the main reason why the engine couldn't take MW50 use very well.

After modifications had been done to the engine, the BMW801 could run at those manifold pressures without a hitch. In theory now the germans could've installed Alkohol-Einspritzung, or MW50 in the Fw190s, but the thing is that by then there was no need of MW50 in the Fw190. Erhöhte notleistung gave roughly the same power increase as MW50 could provide, and didn't have the corrosion problems associated with continuous use of MW50 ,was much easier to install, and required no extra weight/equipment installed on the plane (other than an extra fuel tank that the MW50 also needed, but full of Methanol-water mixture)

So while the plane still had provision for MW50 installation, it was not used because it simply offered nothing that the C3 injection already provided. The only reason why MW50 was ever used on Fw190As (after the 1943 jabo raids on england) was fuel economy. There are some affirmations about the Fw190A9s using MW50 instead of Erhöhte Notleistung as a fuel-saving measure (Erhöhte notleistung increased fuel consumption a lot, and C3 fuel was getting more scare by late war) with the plane getting similar or lower performances as those attained with Erhöhte notleistung alone.

Also, a well known focke-wulf speed chart for the Fw190D9 shows that the Fw190D9 with Ladedruckhöhung (C3 fuel+C3 injection) had performances that surpassed those of the Fw190D9 with MW50 (B4 fuel+MW50 injection), wich points out that C3 was as effective, or more, than MW50.

Long story short: the initial Fw190A4s coudn't take MW50 well because the engine was sensible to it's use and wasn't able to take the increased manifold pressures anyway. And when the engine was developed to stand those pressures, there was an alternative system available that required no special equipment or additional weight to be installed to the plane, so that system was used instead.

as you see, nothing to do with lack of MW50 kits...



As for:

I spent quite a bit of time and argument researching this particular issue. I'm open to correction, but gathered the 601 used a mechanically driven supercharger where the 605 and 603 used a hydraulically driven one.

You are mistaking the DB601 with the DB600. The latter had a mechanically driven supercharger, the former's supercharger was of variable speed and acted on the same principle as those in the DB603/DB605.

 

[tommayer]

Why does brake specific fuel consumption (bsfc) increase with altitude on mechanically supercharged (NOT turbo supercharged) P&W and CW radials? Example, from a manual for a GB-2 (Navy version of a Beech D-17S) equipped with a P&W R-985 AN1 or 3.
ALT MP RPM HP GPH BSFC
SL 28 2000 310 21 .407
9000 27 2000 300 25 .5

That's a deterioration in efficiency of over 20%. Any manual for any supercharged (NOT Turbocharged) WWII vintage radial will show the same pattern.
Many engine builders and pilots attribute the increase in fuel consumption to the power necessary to drive the supercharger. Maybe, but consider the following--1) The power charts show a constant power for a given manifold pressure and rpm, regardless of altitude. If it is costing a 20% fuel increase to compress the air with the mechanical supercharger, why is the effort NOT reflected in higher manifold pressure and/or rpm settings? You increase power either by increasing boost or rpm or both. 2) A given horsepower will move an airplane at roughly the same indicated airspeed, regardless of altitude. The indicated IAS in the GB-2, R-985 example given above varies by all of 2 mph between S/L and 9000MSL. Some 5000 hours in type allow me to say with reasonable certainty that the book is correct on both matters of fuel burn and indicated airspeed.
How come the big drop off in fuel efficiency?
Old Staggerwing Pilot

 

[red admiral]

For a single speed single stage supercharger like the R-985, the supercharger is taking pretty much the same amount of power all the time. However the amount of compression (or boost) applied increases up to it's critical altitude. Compressing a fluid increases it's temperature. This is bad for a fuel/air mixture as it won't combust as well in the cylinder. Ergo, you have to add more fuel to get the same amount of power.

I'm surprised about the difference being 20% though.

Most of the turbosupercharged setups had an intercooler which cooled the fuel/air mixture back down to a temperature at which it would combust better.