Talk:Supercharger

Supercharged aircraft engines make LESS power below critical altitude?

"Below the critical altitude the supercharger is capable of delivering too much boost and must therefore be restricted lest the engine be damaged. Unless other measures are taken, this means that at least some of the power driving the supercharger is wasted. Also, due to the denser air at lower altitudes, the supercharger is not operating at its best efficiency, and this can cause an additional load on the engine. For the early years of the war this was simply how it was, and this led to the seemingly odd fact that many early-war engines actually delivered less power at lower altitudes. This was because the supercharger was still using up power to compress air that was not delivering any power back."

Looks like junk science to me, but I thought I'd ask for input before changing it. Most WWII aircraft engines used internal superchargers, where the carburetor or fuel injection master control is ahead of the supercharger intake. This means that all you have to do to avoid redlining the manifold pressure gauge is close the throttle a bit. Since closing the throttle means that lower pressure air is available to the supercharger, the supercharger should require less power to turn and it shouldn't result in any loss of efficiency. Thoughts? Shreditor 03:18, 4 March 2007 (UTC)

Since no one seemed to object I've rewritten this section Shreditor 04:36, 26 March 2007 (UTC)

Discrepencies Worth Attention

Notes

To make things easier (or potentially way more complex), 
I've also commented throughout the article.  I hope by bolding, 
my response will be obvious.  If you could, read every response 
before you comment, just because I think the whole picture helps 
explain my minor points. I hope it's fine that I slight formatted
everything for clarity.  LostCause 09:09, 30 September 2006 (UTC)

To make things easy I have interspersed my comments in italics 
inside your origional post below.--=Motorhead 00:21, 19 September 2006 (UTC)

To me, the supercharger article offers quite a bit of useful information, but I believe it isn't being precise enough in the information it presents. There is great confusion among most people, probably even me, about the specifics of terminology and function of superchargers. My interest of the subject extends outside of the automotive realm so it may provide a different perspective to help completely explain supercharging. I am no expert, though...just an observer.

Its an evolving process. In time I suppose lots of detail will appear in the article.

From my understanding of the subject, there are two distinctions that aren't being considered here. Boost and "Pressure" are two separate things.

Actually the common understanding of Boost would be the pressure reading from a guage comparing the inlet systems pressure to the outside air pressure, otherwise known as guage pressure. It’s the positive difference between the two that would be called boost .

I agree with you on this one. I was trying to differentiate between increasing manifold pressure and increasing an engine's massflow rate, which I still think are two different, but related items. A thing I think we should clarify is the inlet systems pressure. Do you mean the manifold air pressure (pressure acting on intake valves) or the deck pressure (pressure acting on throttle plate). You could be running 100psi of boost in deck pressure, and only pulling 14.7 psi in MAP...I assume though that you mean MAP.

It's pretty commonly understood that the higher compression ratio an engine has, the better its efficiency becomes. Assuming equal density and rpm, a 50cc engine running a CR of 15:1 should put out more power than a 150cc engine running at 5:1. Higher pressure/temperature increases an engine's fuel efficiency. Look at different engine's SFC if you want. Diesel fuel is more dense, but diesel engines still attribute much of their efficiency to high CR's. Therefore, I don't think "pressure" can be discounted. Boost is the mass flow rate of the air. More air, more fuel, more power. Boost isn't the whole story, though.

Regarding compression ratios Id like to introduce a little used term here, EXPANSION RATIO. Compression ratio should really be considered an expansion ratio. It is this expansion that give the increase in efficiency not the compression. We put up with the problems of a high compression ratio in order to get the benefits of the high expansion ratio. In your thumbnail example a CR of 15:1 has a theoretical fuel conversion efficiency of 47% while the CR of 5:1 is 33% That’s about 1/3 more efficient, So youd need more than 50cc to equal the power of the 150cc. In the same engine going from 5:1 to 15:1 would increase power by roughly 1/3.

IF ONLY boost would be the mass flow rate but it is not. Boost is the easily measured pressure difference between the inlet and atmosphere. It includes pressure due to heat increase as well as the extra mass. Mass flow is hard to measure and that is the reason we settle for boost pressure instead. But it has misleading pitfalls due to the heat created pressure present. Accurate mass flow would be better. As you say “More air, more fuel, more power.” Mass flow would tell you how much more not pressure.

I didn't know about Expansion Ration (nice to know, though), but regardless aren't we still concerned with CR. Unless we are dealing will Atkinson Cycle engines or something, ER seem like they can only be derived from CR. Also, according to your example, wouldn't the 50cc output more power if it is 14% more efficient? Or am I missing the link between efficiency and power output. It seems like pulling 14% more energy out of the fuel, you'd develop ~14% more power.

I agree with you regarding boost. I'll expand later on my orignal intent.

I think what you didn’t consider is specific power output. Power per unit volume.Your example didn’t account for it, you mentioned bulk power only. As such a 50cc engine has a long way to go to catch a 150cc engine, neglecting the scale effect that allows smaller engines to produce more power due to increased “revability”.

Superchargers are used to increased air's density, but they can only do that through pressure. Therefore, superchargers are only concerned with pressure, and they should be treated as such. Intercoolers are only concerned with temperature, and should also be treated as such. Ofcourse, the engineer is concerned with both. An engine with a red hot intake manifold @300psi pressure delivering equal density as a normally aspirated engine is still supercharged. Super, "above", is referring to sea level pressure, because superchargers don't deal with density...they physically can't.

Superchargers are not concerned with pressure they are concerned with air delivery. Not quite the same thing. They do increase density. Boost pressure is only a byproduct of the heat increase and extra air delivery. We only use the easily obtained boost pressure readings as a general guide.There are many examples of increasing turbo boost with no increase in power because the extra boost came at the expense of more heat and that is where the extra pressure came from. Inter/aftercoolers remove that excess heat which reduces pressure and allows more ACTUAL air to enter. 15psi boost with an inter/aftercooler is not the same as 15psi boost without.

I think I'm looking at this from a different perspective than you. Assuming you are a car enthusiast, we have (slightly) different ideas of the use of "supercharging." As far as I know, blowers were developed for (diesel?) trains during the turn of the century to allow the engines to "breathe" better; that is, to improve the efficiency of the intake valves. Supercharging came about mainly through aviation. The goal wasn't reducing intake restrictions, but rather to "normalize" the aircraft (normalizing is achieving sea level pressure at altitude). To normalize an aircraft, you can only do two things (as far as I know). Increase the pressure, or lower the temperature. Logically, superchargers (or normalizers) can only physically compress the air (assuming blowers are relegated to "air delivery"). Intercoolers (aftercoolers) can logically only lower the air's temperature. Technically, you don't stick a supercharger on an aircraft to increase the intake's density. Instead, you install and supercharger and an intercooler to do the job. It's really just minutia, but its a difference.

In aircraft didn’t they also use supercharging for extra takeoff power? In that case it would be the same application as in car engines, to raise the intake mass flow for more power. Even in a normalizing role it raised the intake mass flow beyond what is avalible from the thin high altitude atmosphere alone. In any case and in every case the goal is greater power via greater mass flow through the engine, however that is achieved.

(I should point out here that “Intercooler” properly applies to a cooler which is in between superchargers in a compound sequential system while “aftercooler” applies to a cooler in-between the supercharger and the engine.It has become common to refer to what is actually an aftercooler as an intercooler.)

By the way your getting Suspiciously close to the etymology with your “Super, "above", is referring to sea level pressure”- better watch that!! It might be considered bizarre hehe''

Interesting about the intercooling difference. I think a distinction should be made on the page if we are referring to aftercooling or intercooling. Just because common use has dumbed down the nomenclature doesn't necessarily mean we should continue the act here. Regarding super, the only reason I regard it that way is due to its ties to aircraft, rather than cars. In an aircraft, that's literally what a supercharger does.

Despite overlapping capabilities, superchargers deal with pressure, blowers deal with boost. Generally, dragsters use blowers because they are using fast-revving, big displacement engines that require a lot of air. Dragsters aren't interested in increasing their CR, they are generally already on the verge of the engine's stress threshold...they want their engines to breath. Blowers overcome the restriction of the carburetor and intake valve's small size. Blowers began life in large-scale industrial equipment, with equally large-scale engines. Imagine an engine breathing through a straw and then breathing through a large pipe. They are both designed to compress the same amount of air, but the engine breathing through the pipe is the only one capable of acquiring the amount needed.

The term BLOWER refers back the the origin as you say but when used in that way they cannot be considered as providing boost. They simply deliver air under low pressure. The words blower and supercharger are now interchangable in most segments of the supercharger genre. When applied to an engine for the purpose of increasing power there is no difference so there are no overlapping capabilities.

Like my perspective on intercooling, I think we should make the distinction despite common usage being different. I think a blower does what you think a supercharger does. This is the main thing I was trying to make a distinction with. Blowers deal with "mass flow rate" and superchargers deal with "pressure." I think we should dispel the myth that they are the same. A blower still increases power, it just does it in a different way.

What the fuck.... ?

These are all terms which are used to decribe the same device in common slang. Blower, supercharger, lung, huffer, supe(yuk!)are all interchangable terms used to describe it. They are just words. A supercharger simply crams more air into an engine than it can inhale on its own. Period. Certainly there will be a pressure increase and a change in temperature but the main thing is that more air is crammed into the engine. That’s what a supercharger does.

As far as nomenclature, remember most of this stuff evolved through aviation: · Turbocharger: An exhaust driven compressor used to increase an engine's manifold pressure at or up to 30inHg (sea level). · Turbosupercharger: An exhaust driven compressor used to increase an engine's manifold pressure above 30inHg (above sea level). · Normalizer: A compressor geared to the engine that is used to increase an engine's manifold pressure at or up to 30inHg (sea level). · Supercharger: A compressor geared to the engine that is used to increase an engine's manifold pressure above 30inHg (above sea level). · Turbocompound: A turbine-powered drive shaft geared to an engine's crankshaft. Turbo- always refers to turbine driven, almost always by the exhaust stream.

Super- always refers to pressures above sea level.

Remember that with superchargers, density is the goal, but pressure is the tool.

I still think this list will help understand my perspective

Ofcourse, in real life everything isn't that cut and dry. I want to hear your guys' response, but I'm going to post a revised version in the coming days unless I hear from someone. I do realize I wrote around 8 paragraphs...sorry. LostCause 03:54, 18 September 2006 (UTC)

lost exhaust power

"In addition the power in the exhaust would otherwise be wasted." No. In the Hawker Hurricane the exhausts were angled to provide some additional thrust, and when this was done there was a small but tactically significant increase in performance. PML.

Someone has since reflected this in a parenthetical. Steve Summit 23:19, 15 July 2005 (UTC)

These exhausts are called ejector exhausts and they were developed by Rolls-Royce at Hucknall. They were used in most UK inline-engined WW II high-performance aircraft and were reckoned to be worth an extra 150 hp in thrust at 300 mph. That was the main reason RR didn't use turbocharging in its engines, as the loss of the thrust derived from these exhausts wouldn't have offset the gain in power at the propeller shaft. Ian Dunster 10:52, 4 September 2006 (UTC)

I find the later claim difficult to believe. Given that the supercharger itself used up about 150-300 hp and added 600-800 (depending on mark) at critical altitude, it seems unlikely that the 150 hp from the ejector stacks was anything more than a "we might as well". I've always felt that the primary reason they didn't use turbos was that Stanley Hooker was extremely successful in supercharger design, and the gains from moving to a tubro would be offset by the huge development effort needed to bring it to service. Note, for instance, that the Germans made widespread use of ejector stacks throughout the war, yet were desperate to get turbochargers into service (unsuccessfully). One can also look at the US experience, which was certainly successful in terms of GE's engineering, but generally unsuccessful in operation terms with the exception of the bombers where they had the room to easily pipe the gasses. Do you have historical references for this, ones that couldn't be read as RR appologizing? Maury 14:05, 4 September 2006 (UTC)

It's from an article on the RR Merlin by Bill Gunston in an issue of Aeroplane Monthly from about 1982 - I'll see if I can find it again. Ian Dunster 23:56, 4 September 2006 (UTC)

Found it:

It stemmed from a meeting at Air Ministry (sic) in mid-1940 attended by Lovesey and Hooker. Rex Pierson, chief designer of Vickers-Armstrongs, had produced a pressure cabin to be flown in a special high-altitude version of the Wellington. With great difficulty, Bristol were working on a turbo-supercharged Hercules to power this aircraft, but the programme was judged so important that Rolls were asked to produce a turbocharged Merlin. This was studied at length, but the ejector exhausts so painstakingly perfected at Hucknall for day fighters were worth about 150 h.p. in forward thrust and this would be thrown away, quite apart from the problems of weight and unreliability. Hooker argued the case for an alternative solution: to fit two supercharger rotors in series to form a two-stage supercharger. The main problem was that the high compression would make the air so hot its density would be reduced, and with it the achieved power, besides promoting detonation in the cylinders. The answer was an inter cooler heat-exchanger between the supercharger and the cylinders, in the same kind of water/glycol circuit as the cylinder blocks.

From: Classic Aero Engines - No 6 Part 2 The Rolls-Royce Merlin by Bill Gunston - Aeroplane Monthly - May 1983 issue.

The 300 mph figure was mentioned somewhere else but I can't remember where. Ian Dunster 01:51, 5 September 2006 (UTC)

The British didn't use turbosuperchargers because of the weight, not because of the 150hp loss. As Hooker said, "problems of weight and unreliability." were the true deathnail of turbosuperchargers. The Americans used turbos, but only on some of their largest fighters and bombers. The P38's notorious fork-tail came about because the turbo's made the Allison V-1710's so long, the engine pods would have otherwise hit the conventional cruciform tail. Take a look at the P-37 for an example of the turbo's size.

P37 illustrating the excessively large turbosupercharger installation.

The P-47, the largest front-line fighter, used turbos, but the P-51, which was much smaller, used a two-stage supercharger. Bombers like the B-17 and B-29 could stomach the weight and complexity. I think exhaust ejectors only "create" about 150hp by reducing backpressure and acting as additional forward thrust...I believe their effect was pretty negligable though, much less than an effective turbo setup. The picture from the USAF Museum at Dayton, Ohio demonstrates the enormous size of early turbochargers.

The turbos we know today are much different than the turbos of the 40's. LostCause 23:08, 17 September 2006 (UTC)

A more serious flaw in the claim that "the power in the exhaust would otherwise be waisted" is discussed in the "Power usage" section below. To summarize, this claim fails to account for a turbocharger turbine raising the exhaust pressure and thus drawing power from the engine in the exhaust stroke. In the end, a turbocharger costs an engine as much in power as a well-tuned supercharger; the primary advantage of a turbocharger is efficiency in sub-optimal conditions, which may have been less relevant in a WWII fighter. Moosesheppy 12:35, 11 June 2007 (UTC)

"More cons of supercharging"

This section requested copyediting, but first I think it needs some fact editing. It states that turbochargers start up faster and are smaller, but earlier sections made the opposite claims. In fact the entire last section might not be necessary, since it's really a list of "pros of turbochargers", not "cons of superchargers". If all of the cited superiorities of turbochargers are adequately reflected in the Turbocharger entry, they don't need to be repeated here. Steve Summit 23:26, 15 July 2005 (UTC)

On the whole I agree with your points Steve. I've copyedited this section and corrected some of the facts (ref: twin turbo/sequential turbo), but I'm also verging on the view that perhaps this article would be better off without this section. Robotmannick 06:23, 20 July 2005 (UTC)

"???"

Is the type of Blower thats on a lot of modified Muscle cars on here

Yes. All the types of "blower" are discribed here. Some pictures might be good to clarify that.--=Motorhead 12:47, 2 April 2006 (UTC)

WWII Detour

What's with the detour into WWII aircraft discussion? I understand its slight relevance to superchargers per se, but shouldn't it really have its own page?

The WWII aircraft stuff would be an important part of history/development of superchargers. I dont know if it warrants a seperate article but it certainly adds perspective here.--=Motorhead 12:47, 2 April 2006 (UTC)

Supercharger technology was really pushed to its extremes in World War II aircraft design, then the turbine engine came along and negated all that research and innovation. Due to cost and reliability considerations, modern general aviation aircraft rarely use superchargers. So, I realize it may look like a large tangent in a relatively small article, but to discuss the way supercharging was applied to aircraft, a discussion of World War II era military aircraft is really all that is needed. Shreditor 04:48, 7 March 2007 (UTC)

Jet engine supercharging

Supercharging has little meaning when applied to jet engines. The compressor has more to do with compression rather than overfilling the chambers. Although the parts are similar the application is totally different and I don't see how it can be called supercharging in the same sense because the engine wont run at all without a compressor. I think the section should be removed or qualified.--=Motorhead 03:32, 11 April 2006 (UTC)

Agreed, the concept of supercharging in the context of jet engines is 100% redundant and nonsensical. I'm deleting the section. The "super" in supercharging means "above" something, and that "something" is the ambient air density that a naturally aspirated piston engine is supplied with from the atmosphere. Of course there are no naturally aspirated jet engines, as the compressor is an integral part of their basic function. Vessbot 20:28, 28 December 2006 (UTC)

Filling beyond capacity.

User:Motorhead keeps adding the concept that 'filling something beyond it's physical capacity' is supercharging. This bizarro-land physics. The 'capacity' of something is either it's volume - or maybe the mass of something it can hold...whichever definition you use for this rather vague term, I don't see how you can 'exceed' it. What's going on is that by using higher pressure air, you can put more oxygen molecules into the chamber than at 'normal' air pressures. That's what a supercharger does - but this isn't filling something beyond it's capacity...it's filling it to exactly it's capacity - but at a higher than ambient pressure. We need to keep the words used in this article on a solidly scientific basis - and for that reason I'm RE-reverting Motorhead's change. SteveBaker 14:08, 13 June 2006 (UTC)

User:SteveBaker aparently has not heard of a volumetric efficiency of, for example, 150%. What could this mean? Could be that a standard volume of lets say 500cc is charged with 750cc of mixture at standard pressure. This it the way cylinder filling is specified. I did not invent it. We are speaking of SUPERCHARGING and in this context when volumetric efficiency exceeds 100% that means the cylinder now holds more than its capacity. The word itself is defined as SUPER (over) CHARGE. If it were specified as User:SteveBaker suggests then there would never be anything other than 100% volumetric efficiency. What good would that do? At idle=100%VE at 1/4 throttle=100%VE at full throttle and at all RPMS= 100% ????? That is the only possible result. Supercharging works by increasing Volumetric efficiency. Perhaps User:SteveBaker can rewrite the definition to satisfy every subtle detail. If not then someone wanting to learn about this topic will need a basic understanding of what is happening inside the engine. Not some disconnected incomplete facts.--=Motorhead 00:32, 15 June 2006 (UTC)

(Please sign your comments with four tilde characters so we all know who you are and when you wrote)

A volumetric efficiency of 150% means that if your combustion chamber has a volume of V liters then your compressor took 1.5xV liters of air at ambient pressure and squished it down into V liters at some pressure above ambient and shoved it into the V liter cylinder. You havn't filled the cylinder "beyond it's capacity" of V liters - what is inside the chamber is precisely V liters of compressed air - that's in no way beyond the chamber's capacity...look - it's holding it just fine! So I completely understand the concept of how the supercharger works and that air is compressed and so on and so forth. All I'm complaining about is the language you used (twice) to describe it. The concept of filling something beyond what it can hold is kinda meaningless - and is simply not what's going on here - so we shouldn't say so. If you tried to fill something beyond it's capacity - the contents would have to overflow or something. In this case, the pressure merely rises - and it all fits just fine. I'm sure both you and I understand perfectly what's going on - it's just that the wording of your explanation of it was bogus. I think my present wording explains things quite nicely. SteveBaker 05:16, 14 June 2006 (UTC)

Bogus? You will have to delete the word supercharge itself if so because the word itself means exactly what I said it means. The latin root of Super from 2 different sources is…

super- beyond

super- more than

Charge means to fill or load. To supercharge means to load or fill beyond or more than filled. The orgin of this word is its meaning. The meaning of supercharge is to overfill.

I explained it from that angle for several reasons.

-It is correct.

-In technical writing the first paragraph should contain as much as possible the whole topic in a nutshell in the simplest wording possible which conveys the meaning.

-In writing for the public it must be kept in mind that almost ALL readers should be able to understand it. It has been said that you should write at a third grade level if you want 80% of the population to understand it. I didn’t do that, opting instead for a FOURTH grade level hehe. I think that an interested kid will read your definition and think…”what does pressure have to do with it?? What the heck IS pressure anyways? I don’t get it!”. I try not to write for people who already know the stuff. I want people who DON’T know it to read and understand it on their own terms as much as possible. To satisfy the semantic sense of the tech heads in exchange for losing the interest of some curious kid or other person is a waste of time. (I don’t know why people can’t recall what it was like BEFORE they knew. Maybe that’s why we have so many crappy teachers! They can’t recall what it was like NOT to know.)

-The word supercharged has been co-opted by the corporate advertising leaches. We have Supercharged razors and turbo stereos and all manner of ridiculous stuff to contend with, all of which has infiltrated into the myth surrounding the word and is carried with the reader to this little article which I hoped would blow away the fog of bullshit and set them on the clear path. I took the opportunity to explain what the word itself really means which ties in nicely with the actual content of the article.

I don’t disagree with your wording but then, I already know the topic. I think your wording is more like a refinement of the basic definition not the simple definition appropriate for the beginning reader. Make things too high-falootin and you lose the beginners. Maybe you like to preach to the converted but I do not. I like dem FRESH souls!! Muhaaaaa! Muhaaaaa!--=Motorhead 02:02, 15 June 2006 (UTC)

If we have to write to the level of someone who doesn't know what 'pressure' is - then we need to say "Supercharger make car go fast." - because anything more technical than that would be incomprehensible to your theoretical audience. You're saying that we can't use words like 'pressure' - but we can use words like 'compressor', 'cylinder', 'pump', 'combustion chamber' and such. That's not just not reasonable. Furthermore, using the latin/greek derivation of the name 'supercharger' to justify your position would be akin to saying that the article on computers (from the latin word for 'counting' via the word 'accounting') has to say "Computers are machines for counting" or "Computers are machines to solve accountancy problems". You wouldn't say that a T-Rex was "King of the Terrible Lizards" when in fact it was neither a lizard nor either particularly terrible nor king of anything. That the name 'supercharger' doesn't accurately reflect it's function is neither here nor there. We didn't get to choose it's name - but irrespective of what it's name is, it's job is to compress air and stuff it into the combustion chamber. It increases the pressure of the incoming air - that's a simple enough concept - and if it isn't then let's add links to words like 'pressure' so anyone who doesn't know what it means can click on it and find out. SteveBaker 19:29, 15 June 2006 (UTC)

"Supercharger make car go fast." hmmm not bad! not bad at all! Sums it up quite well. Of course your free to delve into any technical depth you can back up later in the article. The first paragraph however should be general and explain in a nutshell what the topic is about in terms understood by all.

At its core all a computer does is add and shift binary digits into and out of registers on command. Thats about it, so counting is not far off. The word supercharger is entirely appropriate for the device latin root and all. "he that does not know where he comes from, knows not where he is going" --=Motorhead 23:59, 15 June 2006 (UTC)

At its core, all a computer does is move electrons from one place to another. At its core, all a computer does is add and shift binary digits? At its core, a computer is a machine for following rules? Just how low should your description go? The answer is that you have to give the USEFUL answer - if you write for a person of below average IQ/knowledge then you end up with an encyclopedia that smart people will find painful to use. On the other hand, if you write at the level of college professors, many people will be unable to understand the article at all. So the best you can hope to do is to write for the average reader and provide copious links for people to follow if they don't understand basic english words like 'pressure'. SteveBaker 19:11, 27 August 2006 (UTC)

All this because you don't like the etemology of the word supercharger being included in the article. I have seen more than one request on talk pages for the etemology of terms used in wikipedia.

for the record...

super- from L. adverb and preposition super "above, over, on the top (of), beyond, besides, in addition to," from PIE base *uper "over" (cf. Skt. upari, Avestan upairi "over, above, beyond," Gk. hyper, O.E. ofer "over," Goth. ufaro "over, across," Gaul. ver-, O.Ir. for), comparative of base *upo "under."

charge c.1225, from O.Fr. chargier "load, burden," from L.L. carricare "to load a wagon, cart," from L. carrus "wagon" (see car). Meaning "responsibility, burden" is c.1340 (cf. take charge, 1389; in charge, 1513), which progressed to "pecuniary burden, cost" (1460), and then to "price demanded for service or goods" (1514). Legal sense of "accusation" is 1477; earlier "injunction, order" (1380s). Sense of "rush in to attack" is 1568, perhaps through earlier meaning of "load a weapon" (1541). Electrical sense is from 1767. Slang meaning "thrill, kick" (Amer.Eng.) is from 1951. Charger "horse ridden by officer in the field" is from 1762. Chargé d'affairs was borrowed from Fr. 1767.

If you can't deal with the way it is then maybe you can propose a new term and see if it catches on. I think the current term is perfect and its etemology enhances the understanding of the term.--=Motorhead 02:12, 29 August 2006 (UTC)

I have no problem with your etymology. There is no doubt where 'super' and 'charge' come from. However, modern usage of the word has changed. Nowadays it means something like "an air pump driven from the engine" as opposed to a turbocharger which is driven from exhaust gasses". My complaint with the original words that said that a supercharger fills something "beyond it's capacity" and that's just bullshit - it's meaningless - it's a scientific impossibility and it's most definitely not encyclopeadic - so it had to go. The capacity of the thing that the supercharger "fills" is not in any way exceeded - the pressure inside that thing merely increases. What the supercharger does is to increase the pressure of the air entering the engine. This is not a hard concept - and it is precisely what is going on. The etymology is slightly interesting if you are a historian of the English language - but it's irrelevent to the discussion of what a supercharger actually does. SteveBaker 12:52, 29 August 2006 (UTC)

I'm with Steve on this one, it's a misleading claim even if it isn't technically "incorrect" under all possible usages of the term. It should be removed, if it isn't already. Maury 20:59, 29 August 2006 (UTC)

You have no problem with the etymology? Yet the etymology is that the word literally means to overcharge or over fill. That’s simply the structure of the word. According to you the words supercharge, overcharge, overfill, overload, supersaturated and many others have to be struck from the language because "it's a scientific impossibility". Who's talking bullshit here?

By the way your contention that "What the supercharger does is to increase the pressure of the air entering the engine" is incorrect (not to mention DEAD WRONG if you want to nit pik as you do). It is charge DENSITY which must be increased NOT merely pressure. Pressure in a vessel can be increased with a temperature increase alone and not one iota of supercharge will have occurred. The DENSITY must increase in order for supercharging to occur and THAT "is precisely what is going on". Alcohol fuel cools the air and give a power increase due to the mild supercharge due to the increased density yet no pump at all is used. (Feel free to re write using the correct information and terminology.)

To User:Maury "It should be removed, if it isn't already." ... if you have not even read the article perhaps you should not comment. --=Motorhead 23:08, 29 August 2006 (UTC)

Etymology means the origins of the word - not the meaning. So the etymology (origins) of the word is as you say - but the meaning is not. There are many words in the English language whose etymology differs from the modern meaning. So - as I said - you are almost certainly correct about the etymology - but that's quite utterly irrelevent to what a Supercharger actually does. Should we say that the throttle strangles the airflow? Should the car battery be explained by analogy to 16th century field artillery? Should we talk about the tire as the attire of the wheels? We have ...from Latin centrum "center" and fugere "to flee"...centrifugal superchargers. Would you have us say that these superchargers work by running away in fear from the center? That's the etymology of centrifugal - but it's not the modern meaning.

No - we use modern meanings for modern words - and if we want to explain the etymology, that's a separate matter from the modern usage.

You said By the way your contention that "What the supercharger does is to increase the pressure of the air entering the engine" is incorrect (not to mention DEAD WRONG if you want to nit pik as you do). It is charge DENSITY which must be increased NOT merely pressure. - which is further proof that you completely misunderstand the physics of the matter. The only way to increase the density is to increase the pressure or decrease the temperature. The two are completely related (Boyle's law). I'm pretty sure that the supercharger doesn't work by cooling the gas - so it must be increasing the density by pushing up the pressure. Jeez - go read some 10th grade physics books. A supercharger is an air pump - it increases the pressure - and as a direct consequence, the density goes up. That means that there are more oxygen molecules going into the available space in the cylinder - which means you can burn more molecules of gasoline - which means you get more combustion products pushing down on the piston - and hence more torque. There is no black magic here - just some really basic physics. SteveBaker 00:42, 30 August 2006 (UTC)

Racecar tire pressures rise as the tires heat up. Do you suppose there’s a little supercharger doing it? Simply saying pressure alone does not describe what a supercharger does. Charge DENSITY does.

You seem to think that pressure is the be all and end all when in fact it is just a byproduct of the density increase. In fact charge cooling devices (intercoolers) are there to REMOVE the pressure component due to temperature rise. The result? LESS heat and pressure, MORE density, MORE power. So not all the increase in pressure is desirable is it? Yet you define the process as a function of pressure alone. You simple don’t understand the simple physics involved.

Heat a gas in a closed vessel and pressure rises without ANY increase in density at all. So your attempt to cover your error by relating pressure to density as if they were in locked step with each other fails. It becomes evident that you’re desperately trying to recover the unrecoverable! You can’t admit that it is DENSITY that is the controlling factor and NOT pressure. Better crack those 10th grade physics books again and see what you missed.

People who live in glass houses...

By the way I ACED all my high school science classes, I suspect you muddled through with C’s and maybe the odd B. I have taught a dozen students like you who acquire a knack for isolated bits and pieces but who never can see the big picture. They really don’t have the talent to put any of it to good use.

Note to others reading this “discussion”: There is something else going on here I suspect. The passage in question was deleted some 2 and a half months ago and yet user stevebaker is STILL whining about it like it was yesterday. Hurt feelings? I don’t know what it is but imagine how much could have been added to the article instead of pissing away time here. --=Motorhead 22:52, 30 August 2006 (UTC)

I obtained an honors degree in Physics from the University of Kent at Canterbury in 1977 and I earn a six figure salary doing physics - would you like me to post a picture of my degree certificate? But I forget what my high school grades were - so you might be right after all. Let's just leave out the "Filling beyond capacity" nonsense and we can end this pointless thread. SteveBaker 00:23, 31 August 2006 (UTC)

Guys, be respectful. I don't care if you aced all your high school exams, grew up as a prodigy, and obtained five Phd's...we're all human and make mistakes. I may be in kindergarten or a nobel peace prize winner...my background shouldn't make a difference. The validity of our arguments are at stake...we shouldn't resort to arguments of ad hominem to prove our idea's worth. Lets work cooperatively, not against each other.

I've edited out my statement to enter it into a new section. LostCause 03:45, 18 September 2006 (UTC)

"Just when I think I'm out, they pull me back in!"-The Godfather- I thought (hoped) this thread was over. "Respectful" went out of this on the very first post as you can read above. It was all over the etymology of the word "supercharger" being included in the article and that’s all. It all comes down to "I say "TO MA TO" you say "TO MAT O"" that’s about it. Just a bunch of minutia gone wild! You raise a lot of points which should probably be covered in a different thread(s) as they are not quite on topic in this one.--=Motorhead 00:53, 18 September 2006 (UTC)

Sorry for continuing this thread. I'll repost under a new section. LostCause 03:45, 18 September 2006 (UTC)

Power usage

considering that super chargers are connected directly to the drive of the engine, some of that rotational force (torque?) must be lost in powering the supercharger unit. How much is lost, if any, and is it different for different types of charger?

Also what is the ratio or extra boost to power output of the engine if it is super charged?

many thanks

chris

Yes, there is a loss in driving any type of supercharger. The type of supercharger definitely determines how much is lost. The efficiency of the supercharger is a measure of how much will be lost by that particular unit. That’s why efficiency is such an important thing to know about a blower. Each type of supercharger has its own characteristic efficiency map. Drive losses can become incredibly high. In top fuel drag engines it amounts to more than 1000 horsepower lost to drive the blower.

The boost for a given power increase is basically proportional to the delivery of air to the intake (MINUS blower efficiency losses) compared to what is delivered by the atmosphere alone. If you double the airflow, power doubles (MINUS blower efficiency losses). Inefficiency in the blower causes a temperature rise in the air, masking some of the apparent boost so you have to account for the temperature rise when using boost pressure as a guide.

This topic would be a good addition to this article. --=Motorhead 23:10, 26 August 2006 (UTC)

I've seen figures of 2500 hp to drive the blower for a top fueler. Gzuckier 19:02, 27 August 2006 (UTC)

So have I and even higher figures but I stick with the conservative "more than 1000" because I know that it has been experimentally verified and not estimated. When you look at that drive belt, its hard to believe isn't it?. Spooky!--=Motorhead 02:22, 29 August 2006 (UTC)

Other types of chargers take different amounts of energy. I don't know the specific amount, but turbosuperchargers take energy from the engine by increasing backpressure. Most of a turbo's power comes from the exhaust gas, but it's not entirely "free" power. In the miller cycle engine, the supercharger robs the engine of power, but the energy it robs is more than compensated for by the smaller amount of energy the piston requires to compress the charge. By using less power to get the same job done, a supercharger in a miller cycle engine in a way actually contributes energy. There are different ways at determining the power a (super)charger consumes. In net power, superchargers contribute energy. When not considering energy output, they consume energy. Considering fuel, an engine may extract more or less energy from its fuel with a supercharger. Sometimes I hate dealing with this stuff, especially with nitpicky people (like myself), because it generally just feels like minutia...and it's easy to make a stupid mistake. That's my warning to whoever may read this that I am not a master of the subject and only know what I hear. That about sums up wikipedia though...Take it with a grain of salt. LostCause 00:31, 18 September 2006 (UTC)

I agree with LostCause to a large degree. I think the argument that a supercharger or a turbosupercharger 'robs' power from the engine is fairly ridiculous. To pump air into an engine requires power, and in a large engine (like a top fuel dragster's) it requires a LOT of power. That power has to be supplied by the engine one way or another. It can be supplied by the vacuum generated by the pistons (naturally aspirated engine), mechanically by belt drive (supercharger), or by the exhaust pressure (turbosupercharger). Of course there are some efficiency losses due to friction in the bearings and curves in the intake manifold, but the majority of the power required to turn the 'charger at speed is due to the air it's moving. That's not a 'loss', it's the 'charger doing its job. I've also never bought the argument that a turbo uses 'waste' power in the exhaust stream. The exhaust gases have to be removed from the engine, whether or not they push a turbo first. Inserting a turbo in the exhaust simply requires the engine to produce more pressure to evacuate the exhaust from the engine -- the engine supplies the same amount of power as it would to turn a supercharger, just supplies it differently. It's a simple matter of conservation of energy. If you want to move some air, into or out of an engine, you've got to supply power to do it. Middlenamefrank 02:48, 18 October 2006 (UTC)

I see what you are saying - and in the abstract, it does seem plausible (although 'conservation of energy' doesn't apply here because it's not a closed system) - but if what you suggest is true, why would anyone design a car to use a turbocharger rather than a supercharger? The common wisdom (which could certainly be false) is that the main benefit of a turbo over a supercharger is that it imposes a smaller load on the engine. If that isn't true - why put up with turbo lag, additional heat in the engine bay, heat transferred from the exhaust to the inlet air, etc? SteveBaker 22:06, 18 October 2006 (UTC)

Nuh uh. The energy in the exhaust stream is WAY more than is needed to simply remove the gases. And it's simply wasted. If it takes X amount of power to pump the air into the engine, and you extract the energy from the front of the crankshaft, then that's X amount of energy you no longer have available at the back of the crankshaft. If you extract that energy from the exhaust, then you are no longer subtracting that energy from the crank, and you have X amount of energy more available from the crank. Gzuckier 14:34, 19 October 2006 (UTC)

Gzuckier, how do you figure there is any energy 'wasted' in the exhaust? Sure, the exhaust air moves fast, but it has to because the engine must be evacuated for the next power cyle. Air has to be pumped both into the engine prior to combustion, and then out. Both of these require power, and the more air you want to move (so you can burn more fuel, to make the engine more powerful), the harder you have to work to move the air on both the intake and exhaust sides of the engine. Of course you can extract the power required to supercharge the intake from the exhaust stream, but that simply requires the engine to work harder to force the exhaust out. The power available in the exhaust stream isn't any more 'free' than the power available at the crank. If energy in the exhaust stream were free, why would the top fuelers use blowers rather than turbos?

SteveBaker, I've wondered the same thing myself! In fact that's really why I posted the question, because I just don't understand why there are so many more turbo installations than blowers. The only real reasons I can come up with are 1) A turbo installation is an easier add-on than a blower. A manufacturer usually has to offer 'charged and non-'charged versions of the same engine, and they can share more parts in a turbo installation. Easier add-on is of course a boon for hot-rodders too. 2) A turbocharged car gets better gas mileage when it's not on boost. A blown engine is always boosting. That's a big factor for the manufacturers. 3) I think there's a "bad-boy" hot-rodder image to a supercharger which is okay for some production cars, but not for most. There are a lot of people who want a high-performance vehicle but not a refugee from a drag strip. 4) I wonder also if upper management at the manufacturers understands the real differences between the two. I'm an engineer (electronics) and I know how hard it can be to bring clear understanding to the decision-makers. 5) Finally, I think a turbo is easier to fit under the hoods of most vehicles. Although they could be designed differently than they are, most current supercharger designs add a lot of height to the top of the engine. You can route intake and exhaust tubing anywhere you want and stick a turbosupercharger wherever it fits. Middlenamefrank 20:25, 20 October 2006 (UTC)

It can be confusing when more than one phenomena are mixed together. In this case there are two regimes of flow, which occur sequentially.

Consider what happens when the exhaust valve opens before bottom dead center. The pressure in the cylinder forces the gas out into the exhaust system. The gas is moving at high speed yet the piston is still moving downward. Clearly the piston is not contributing to the gas movement at that time and therefore there is no mechanical loss. It is this portion of the cycle that contains the extra energy we would like to use to drive a turbine. If not used it is wasted (in the form of heat, noise and turbulence.)

Once the pressure has fallen and the piston is rising then the piston exerts force on the gas to evacuate the rest. This is where the mechanical loss occurs. However if you consider that the turbocharger will supply boost to the intake side which will add pressure pushing the piston down then that mechanical loss during the exhaust cycle can be nullified. Exhaust back pressure counteracted by the intake boost pressure leaves the blowdown energy. This is the energy that would be wasted.

In practice the exhaust back pressure is even less than the boost pressure pushing the piston down so that even the mechanical pumping loss can be partially recovered.

Top fuelers use positive displacement superchargers because engine response is absolutely critical to winning. Even the best turbo cannot match a roots in this regard. In addition, Top fuel engines pour gallons of fuel into the intake during a 4 second run. This huge volume of fuel in liquid form makes the inefficiency of the roots go to work vaporizing the fuel. In addition the large volume of fuel can be physically accommodated in a large roots blower where that large volume of fuel in a small turbo would choke it. Top fuel would love to use the free waste heat but can’t in the turbo format. It has been tried on more than one occasion. Don Prudomme spent a kings ransom on it but ended up saying “first you have none of it then you have all of it” it just didn’t work.--=Motorhead 15:12, 21 October 2006 (UTC)

Idea?

Just as an addition to the article above, if say you wanted to change the amount of boost for different RPM, is it possible to bolt a gear box, automatic or otherwise, between the driveshaft and the blower driveshaft to change the amount of torque used by the blower?

For example say I have a blower moving 2000cubic feet/min of air into the engine at 2000RPM ( i know that works out as 1 cubic foot per cycle which sounds alot, but its just for example purposes), if i want to double that at anytime, could i put a gearbox that changes from a ratio of 1:1 to 1:2 and double the amount of air intake at the same RPM?

or would adding a gearbox decrease the efficiency of the blower further?

many thanks

Chris (aka wouse101)

Adding a gearbox would cause an additional loss of a few percent depending on how good the gearbox is. It would be similar to simply changing the pullys for a different drive ratio except that the unused gears will consume some additional energy.

Increasing boost on a roots type blower will hurt efficiency. Simply turning the supercharger faster does not necessarily mean a loss of efficiency. It depends on the exact characteristics of the blower in question. There will be a sweet spot in the efficiency map for that particular blower and you may be moving it into or out of that sweet spot with smaller speed/boost changes, depending where it is. If you talk about doubling the boost I would say it certainly should mean a large loss in efficiency but may still produce a worthwhile increase in power at the expense of engine stress.

A bigger challenge would be to re optimize the rest of the engines systems to match the new boost level,Ignition, fuel etc.

Most things have been tried before and some catch on and most don't for various reasons. If you poke around you can find examples of this idea.

http://www.worldcarfans.com/news.cfm/newsid/2060519.006/country/gen_acf/general_acf/first-2-speed-supercharger-drive-system

Just ignore thier PR claims about being the worlds first!

I have added a general efficiency map in the article. If you have a look it will give you a better idea of how your changes will affect efficiency. Keep in mind that it refers only to the blowers pumping efficiency and does not include any drive losses at all. From it you can see that actually doubling the boost from almost any point will result in a heavy efficiency loss. Its just a question of diminishing returns.

--=Motorhead 12:29, 1 September 2006 (UTC)

A common trick of MINI Cooper'S owners is to replace the supercharger pulley with one that's 15% smaller. This spins the supercharger 15% faster and - amazingly - produces almost exactly 15% more peak horsepower on the dyno. So it is clear that the drive ratio of the superchargers on at least some common cars is less than optimal (probably there are emissions control or gas consumption issues to be considered, along with the life of the supercharger's bearings). It's hard to imagine that the extra complexity (and friction) associated with a teeny-tiny gearbox would be worth having. But many cars (like the MINI for example) have a bypass valve arrangement such that when the supercharger isn't needed, the airflow is routed past it so it's just spinning freely against no resistance. This reduces the load on the engine when the supercharger isn't needed - and improves gas consumption. I suppose you could get an effect somewhat akin to gearing the thing just by opening and closing that bypass valve incrementally instead of all at once. SteveBaker 21:21, 1 September 2006 (UTC)

Just for the curious, the reason the gearbox will be less efficient is due to friction. Basically anything in your engine compartment that generates heat externally is wasting energy. It probably is possible to design a CVT between the engine and supercharger and not encounter additional friction losses because equal amounts of material are in contact at all times. It is possible to overboost your engine, but that may require a larger supercharger rather than increased speeds. An engine can only handle so much stress and is bound to break something if pushed over that limit.

Another thing to consider is that air changes certain characteristics the faster you move and compress it. My guess is that the closer air particles inside the supercharger reach supersonic speeds, the sharper efficiency will decrease. I bring up this phenomena because it is the cause propellers lose efficiency when tip speeds exceed the speed of sound. It is surpassable, but impractical. The most likely reason owners of the Mini Cooper S are achieving such great results is that BMW intentionally underrated their superchargers for reliability issues. A general trend you see in aftermarket conversions is that the more performance you modify into your car, the more reliability/efficiency you remove. BMW is concerned with warranties and efficiency, owners are concerned with performance...the two travel opposite directions in relation with each other. LostCause 00:46, 18 September 2006 (UTC)

In the case of the MINI, BMW also sell their own 'John Cooper Works' kit that has a faster-spinning supercharger. I suspect that the reason for the less-than-optimal supercharger in the basic model is simply that they can charge you $5000 for the upgrade. (Versus about $200 to do the job yourself!) SteveBaker 13:44, 3 October 2006 (UTC)

Interesting. That's the old IBM trick from the 50s-60s up through their original PCs and ATs; deliberately cripple the lower priced version and charge more for an almost identical uncrippled version. For instance the 6 Mhz AT that was changable into an 8 Mhz by simply replacing the clock (screamingly fast!) which was followed by the 6 Mhz AT that was "fixed" so you needed to jump through hoops to upgrade it to 8 Mhz, just so IBM could sell the 8 Mhz AT. Gzuckier 20:32, 3 October 2006 (UTC)

In a related note, clutching the supercharger has been tried now and again. In the movie Mad Max for one thing, but I'm pretty sure that's phony; but some of the old Mercedes SSKs had a clutch for the supercharger, I believe. I imagine you'd need some sort of bypass as well. Gzuckier 14:36, 19 October 2006 (UTC)

As it happens, the Mad Max movie car is now owned by a friend of mine here in Texas - they call it "The last of the V8 Interceptors" - although that's not what it actually is. (Here it is at a local car show: [1] )...the supercharger most certainly works - and you can switch it on and off with a switch on the dash - although it's not the big obvious switch you see on the dash in the movie. The 4" wide toothed supercharger drive belt is insanely noisy - it's probably the loudest street car I've ever heard! SteveBaker 19:05, 19 October 2006 (UTC)

I love that car, although in the movie i thought he pulls up a big orange switch on the gear lever and then cuts to the charger spinning into life? -wouse101

It's been done, and it's in the article, under the WWII section Vessbot (talk) 09:40, 22 November 2007 (UTC)

Lancia cheating with their integrale?

Me again with another topic for you to debate.

Me and a friend were talking in the pub about the old Group B rally cars and how the cars design negated some of the rules and regualtions of what they could and couldn't do with their engines. I think a common one of the rules was that, if you had a turbocharger, you had a time penalty which was 1.4 x your engine size, off your time at the end of each stage.

Aparently there have been romours that on one particular event, Lancia enter their Integrale as supercharged, but aledgedly, it had both supercharger and turbocharger.

The idea was that the supercharger was within the rules of European Rallycross Championship the at that time, but the turbo was hidden out of the way somewhere in the car. the supercharge was supposed to provide a small boost in the low rev range before the turbo kicked in provided quite a fair bit of boost.

Is there any truth in this turbo+supercharging technique? or is it just poppycock?

another rumour was that they hollowed out the roll-cage and filled it N2O, but thats another story for the N2O board!:D

It's certainly possible to both supercharge and turbocharge at the same time. Whether Lancia did that is hard to know - but it seems really unlikely that they could have somehow hidden that from the Rally judges - so I'd call this BS. SteveBaker 00:09, 26 November 2006 (UTC)

fair enough. So apart from providing boost until the turbo comes in, are there any other pros and cons of using this method?Wouse101 10:49, 26 November 2006 (UTC)

The 'con' is extra weight and extra complexity - more things to go wrong...never a good thing for a rally car. But the claim here is that the supercharger was there to 'disguise' the fact that there was an illegal turbocharger - but the risk to a team like Lancia to be caught out with bare-faced outright and deliberate cheating - and for it being so very likely that a judge would inspect the car and find the illegal parts...it just doesn't seem credible to me. SteveBaker 16:13, 26 November 2006 (UTC)

Motorcycles

The Yamaha V-Max has a V-boost system which is a supercharger. Kicks in around 6000RPM on a V4 1200cc. Very dangerous in first gear but 11 seconds to 200Kph is good. In production for over 20 years. 83.70.239.47 04:11, 16 May 2007 (UTC)

Supercharger

This sentence seems confusing:

Due to the fact that the turbine speed is directly proportional to the RPM, pressure and flow output at low RPM is limited, thus it is possible for the demand to outweigh the supply etc.

Would this be a correct edit?

Due to the fact that the turbine speed is directly proportional to pressure and flow, output at low RPM is limited. Thus it is possible for the demand to outweigh the supply etc.

JohnSteb —Preceding unsigned comment added by 84.104.78.107 (talk) 10:16, 6 September 2007 (UTC)

The original sentence is correct in its original context except for the word turbine where it should read impeller. The confusion arises because the author used the term “centrifugal supercharger” at the start of the paragraph, referring to a mechanically driven centrifugal supercharger and NOT a turbocharger as might be suspected from just the above sentence. The term “supercharger” is too often (and annoyingly) used to mean a mechanically driven device while turbocharger is used to mean an exhaust driven device. The first paragraph of the article should clear this up. Clearing up popular misconceptions….. well that’s another matter.

In any case the pressure and flow is never directly proportional to the impellers rpm.--=Motorhead 16:45, 14 October 2007 (UTC)

Supercharger

This supercharger article is very well written.

.<a http://www.electricsupercharger.net;electric supercharger[/url]..

Scamcorp 21:03, 12 October 2007 (UTC)

Toyota Supra turbocharger

Rich6023 00:15, 14 October 2007 (UTC) This page states that the Toyota Supra's turbochargers work in parallel. The wikipedia page on the Toyota Supra states that they are sequential.

Suggested History Addition

This article has improved greatly from one year ago, but it doesn't feel complete. While this article does a good job covering the technical aspects and usage of superchargers, it lacks something fundamental - its history. The WWII section marginally covers the topic, but supercharging has a varied and interesting history. Just as x-planes hold the prestige of the jet/space age, supercharging holds a great deal of prestige in aviation's early days. Some great achievements that are forgotten, like the first flight over Mt. Everest, were only possible due to the supercharger. Some of the greatest test pilots and engineers advanced the concept and with it they pushed the limits of aircraft technology during the interwar period.

Having an understanding of where the technology came from, why it was developed, seems crucial in explaining this complex machine. The automotive industry didn't have the clout in the early 1900's to develop supercharging, it took a national effort with some of the greatest minds in science. It's akin to describing a car in great technical detail without mentioning Otto or Benz...describing an aircraft without mentioning Cayley or Lillienthal...teaching a student calculus without mentioning Liebnitz or Newton. LostCause 13:52, 16 October 2007 (UTC)