Dude! I never said "air moves towards the supercharger because of the presence of a vacuum".
That's what you're saying. Remember?
Ah! I get it now. You're trying the old Bugs Bunny routine. Duck Rabbit Duck Rabbit Duck Rabbit Duck Duck ..... BOOM!!

Still not man enough to admit you're wrong? Even though someone else has pointed out that you are?
That's OK. I understand how small people can be. I can accept you for all your "smallness"

How can not understanding some lame slang expression, that is not used by anyone I know, somehow negatively reflect on my ability to debate you into the ground?
That's just typical of your rather flaccid logic.

Can't say anything on topic to prove your point so you just stoop to petty name calling.
You da Man!

 

This guy still does... (obe... is this you?)

 

No no, remember I'm the one that doesn't understand the expression.



Besides, I still have "awl muh teefus".


Sorry, had to edit out the pic. Once was enough.

 

You earlier claimed to have answered my question at least three times, but I still can't find it: WHY does air move toward the supercharger? And to follow up: would air move toward the supercharger if you disconnected its outlet?

How am I not "man enough" to admit I am wrong when you yourself have confirmed I am right? Go read my original contention, then apply your eventual response:

"What you're trying to prove is that a supercharger can create a vacuum. Well duh! It's a pump." - obehave

Regarding "some lame slang expression" not used by anyone you know, that is not surprising. Why should I expect you to be familiar with a concept defined by Euclid, in the 4th century BC, and still very much in use today, as 14,000 hits on Google confirm. Perhaps a High School philosophy or debate class would enlighten you. Hell, any High School class would enlighten YOU.

 

Hammer,

Unfortunately on this forum there's people who will demand proof if I were to directly tell you what the line is doing. Rather than stir up all of that speculation, I'm asking any reader of this thread to take 45 seconds of their time to find out for all of us. Since you're the "Switzerland", maybe if you could tell us your findings, people will believe.

I still don't think the BMW engineers said "Hans, we've got some extra resources here, so let's think of putting something on the car that has no useful purpose whatsoever."

 

Why don't you read the info I posted prior too. I really didn't want to get involved but your beating a dead horse and don't seem to understand what the hell your talking about..

So read this first (page 2) http://auto.howstuffworks.com/supercharger1.htm

 

Are you finished..??

Great...did you see the parts that says "Superchargers increase intake by compressing air above atmospheric pressure, without creating a vacuum".

I believe thats the end of discussion. You really should have nothing left to say but just incase....

I understand your frustration as your trying to understand this and it is rather complex...i am not trying to insult you.

Exercise 1. Find any room fan (turn it off). Stand behind it and blow hard. What happens? The blades moved right (providing the fans size was relative to your breathe). Was there a vacuum? OF CORSE NOT! You just blew on it.

Exercise 2. Same as exercise one but put something like a piece of paper on the otherside of the fan. Now blow. Again the fan moved which in turn caused the paper to move.

Exercise 3. Same as 2 but take the fan out of the equation. You Just blew on a piece of paper right?

Why am I doing this to you? Picture the paper is the engine. Your mouth is the intake and the fan was the supercharger. With or without the fan (charger) the air (intake) still reaches the paper (engine). The only difference is that when your breathe spun the fan which in turn pushed the air to the paper harder. It did not however suck the air from your mouth faster which would be the vacuum your trying to justify that does not exist.

Now to conclude. Obviously there is no one sitting on your car blowing into the intake. The car must have a way to collect the air it needs on its own. If you read howstuffworks you will see that a 4 cylinder car has an "intake" stroke. This stoke among other things is when the piston goes down and...yes...here it is...CREATES A VACUUM which draws in the air from all the twist and turns of your intake system beginng at your little foam filter!!


Hope that helps you understand a little man....I wouldn't want to be on the recieving ide of Obe's wrath!!!!

 

Why are you so insistent on muddying up the thread. Simply state your opinion on the function of the vacuum line and be done with it. I have probably had more dirt under my nails in the last year than you have had in your entire lifetime. So please don't lecture me.

 

Nothing in that article contradicts what I have stated. You could misconstrue this statement: "Superchargers increase intake by compressing air above atmospheric pressure, without creating a vacuum. This forces more air into the engine, providing a "boost."" They are talking about vacuum on the outlet side of the supercharger, not the inlet side. Again, if you disconnect the supercharger outlet, air will still be SUCKED into the supercharger, because it creates vacuum to pull air. To wit: "The rotor of the compressor can come in various designs, but its job is to draw air in, squeeze the air into a smaller space and discharge it into the intake manifold."

"As the meshing lobes spin, air trapped in the pockets between the lobes is carried between the fill side and the discharge side." When you remove air from one place, a vacuum is formed.

"A twin-screw supercharger operates by pulling air through a pair of meshing lobes..."

"A centrifugal supercharger powers an impeller -- a device similar to a rotor -- at very high speeds to quickly draw air into a small compressor housing."

Air is sucked, pulled, drawn, etc. by means of the VACUUM created by the supercharger on the inlet side. Air moves from high to low pressure, ceterus paribus.

 

No offense, but you don't seem to understand why air moves. Turn on a hair dryer, and put your hand over the intake. Feel the vacuum? Tape an empty toilet paper tube to the inlet. Air moves down the tube because of the vacuum created by the fan, which I believe is set up as a paddle-wheel type blower. This captures little pockets of air and moves it toward the exhaust. As air is removed from the inlet, the resulting low pressure draws more air in, just as the moving lobes of a roots supercharger capture pockets of air, move them, dropping pressure to move more air in.

 

OK you and Obe both have me screwed in the head now! Thanks a bunch!

I am trying to defend something I am not 100% sure of. It seems like you 2 are possibly speaking of different things (intake versus outlet). I am backing out and FYI I tried the dryer thing and it worked...but so did my paper / fan thing.

I no longer no what the hell I was trying to say in the first place so i am gonna scrape what little dignity I have left and get out of this thread!!!

Thanks to both of you ( I think) cause I'm pretty sure i figured something out...i just don't know what it was!!!

 

Why should I state an opinion when there's facts to be stated. However, no matter how much I type the facts, nothing will convince you and others.

Assumptions are like...well you know...

Wait, first you ask me to tell you things, then you tell me not to tell you things... Please make up your mind.


When you've got some facts as to what is happening on that line and you post them here, then we will discuss further.

 

I think you are right about OB and I speaking of different things. If you read my original post, it is more clear.

Your paper/fan thing is an odd example. If you look at it in terms of why the air is moving, it flows like this: Your diaphram squeezes your lungs, forcing the air out your mouth (from now higher lung pressure to lower atmospheric pressure). The air continues moving primarily by virtue of momentum (and some stacked pressure retained immediately around your mouth). The fan blades turn because they act like wings as the air moves past them (please don't make me go through how wings work, but the fan doesn't spin very well this way because of the angle of attack and the diffuse airstream). Then the air strikes the paper and pushes it.

 

I went to a drag race yesterday and decided to get the UBER PROs their opinions about a vacuum in a supercharger.

One guy, who was really helpful, took me over to his car and showed me that there is a pretty big vacuum in his supercharger, so big that I could see it! (A Dirt Devil to be exact)



Man... that guy wasn't lying either!

I'm convinced.

 

Thanks saifa I appreciate the attempt. Sorry he turned on you.

Thank you for going to the effort of trying to learn. The fact that you grasped the basic info right off the bat is cool.
If you really want to get a dizzy amount of information read the book I recommended earlier. The one DialM obviously hasn't read.

TBH. I haven't been mad for a second. At one point in my life I worked with the mentally handicapped. We would hire them for summer jobs. I found in my experience that you just need to find a way to break concepts down into pieces that fit their view of the world.
Once they "got it" it was a joy to see the light come on.
I hope to do the same for DialM.
Do not, do not allow his behaviour to put you off questioning and learning.

 

You're F'n killing me

Long response on the way so hang on. Had to take a break

 

Thanks for clearly proving you don't know what you're talking about.

Twin screw and centrifugal SC works very, very differently than roots/eatons do. To bring them into this discussion just muddies the water.

Let's leave those designs for another lesson and stick to the question at hand.

While you're at it please do email the good folks at HowStuffWorks and clear that little bit up for them.

Ceteris parabus(proper spelling) means if I recall right " all things being the same". What does all things being the same have to do with air moving from high to low pressure. How can that ever change? It's a physical constant so that will always be the same.

Braccae tuae aperiuntur

 

I said can create a vacuum. In a particular application. Just not in the application we're discussing.

What does the slang term have to do with this debate. I took philosophy in high. Psych and philosophy in college. You assertion that I would have learned this expression in those classes is obviously flawed. Just like your supercharger argument.

Like most bullies and losers you think attacking me on a personal level and avoiding the argument is the way to win. No matter how wrong you are if you can "beat me up" it makes you right. "Might makes Right" is a very medieval mentality.
Now I'm not going to bother debating the philosophical term with you. I'll just say you're right. Me not having heard of it or being familiar with it in now way demonstrates a lack of intellect or education.
Your being right on this point does not establish the corollary that it makes you right about the supercharger question.

I do find it amusing that you've chosen to lash out at saifa. Me I can understand but to insult him and by inference establish that you are, in your mind, correct whereas How Stuff Works is wrong is once again the actions of a bully. Lashing out in a childlike fit of temper thinking insults and false arguments make you right. Shouting louder makes you the winner.
Laughable at best but more like just sad.
BTW I posted a link to HowStuffWorks in post #22. Guess nobody but saifa bothered to try and educate themselves on this topic.

Now for the "answers";

Post # 38

B]Post # 49[/B] post # 56 Not really an answer but if you'd followed this advice you wouldn't be making this inaccurate assertion about superchargers
Post # 60 Post # 74Post # 79 I just like this so much I left the whole post in.

Post # 85 Post # 114That should do I think.
So once again you're wrong. I'm sure you won't see it that way.
So I am once again awaiting your uninformed response.


Still waiting for real answers to these questions

 

Funny post....I can understand how you feel right now.

saifa the examples you used were good but different.....to sum it up...the fan example is a aerodynamic example and the hair dryer is a pump example.

A jet engine not running will free wheel with the wind and once the starter is engauged and fuel is put to it they are giant vacuums.

The hair dryer is a great example of this debate.

 

It's been three days and no-one has reported back any findings whatsoever. Some say they already know what it's doing. Some say they conducted the above test. However no-one has reported their findings. What a bummer that so many want to "keyboard"-wrench and not actually talk about what it actually occurring in real life. I think the ol' saying is quite apropo here: You can lead a horse to water, but you cannot force 'em to drink.

 

Somehow, I don't think you will get them.

 

Thanks...I needed that

 

I'm arriving late to this party, and what an interesting party it has been... I think the confusion centers mainly on definition of the term vacuum, so let me share my theory (sorry, no hard data) and try to unmuddy the waters a bit. Let me know if this makes sense...

Turn on the hair dryer... air is moving, but if you measure the pressure at the inlet, it should be at atmospheric, i.e. no vacuum. Tape an empty toilet paper tube to the inlet. Air continues to move, and the inlet remains at atmospheric pressure. Put your hand over the intake end of the toilet paper tube... the inlet remains at atmospheric, but now you should have created measurable vacuum *inside* the tube because you're hand is an obstruction that the air cannot move around fast enough to remain at atmospheric pressure inside the tube.

Now think about a normally aspirated engine. At WOT, the engine is pumping air at maximum capacity, but measured inlet pressure is atmospheric, and measured intake manifold pressure should be nearly atmospheric because the throttle body is providing only minimal restriction to the pumping action of the engine and the air is able to move fast enough around the throttle body to resolve the pressure differential. At idle, still no vacuum at the inlet, however there is measured vacuum at the intake manifold because of the large obstruction posed by the nearly-closed throttle body (like your hand over the tube).

Now add the supercharger into the mix. At WOT, the engine is still pumping air at maximum capacity as before, but the supercharger is also pumping air and pumping it faster than the engine can ingest it, creating measurable boost on the outlet side of the supercharger. Supercharger inlet remains at atompsheric. At idle, the supercharger isn't doing much of anything because it's spinning slow enough as to be insignificant in creating boost. Measured intake manifold vacuum should be similar, if not identical, to a NA engine. This was obehave's hypothesis as well. Still, supercharger inlet pressure remains atompsheric.

So does the hair dryer, the NA engine, or the supercharged engine actually create measurable vacuum in front of the inlet? No. Measurable vacuum is only possible in back of an obstruction in the intake path, such as a mostly closed throttle body, or your hand over the toilet paper tube (or, I suppose, with an absolutely ridiculous pressure differential). The key word, of course, is "measurable" vacuum, because obviously a pressure differential is making the air move. It's just that the air moves so fast, it resolves the pressure differential almost instantly. This was obehave's point - there is no measurable vacuum at the inlet so how can you say a vacuum exists there? To say that a supercharger creates a vacuum at its inlet is not really accurate in engineering terms, nor in the way that the word is typically used in the automotive field.

Does that help?

 

Nice job with the under arm thing, but the teeth need a few mods.... maybe the eyes & where are the shirts available?