Dude, go look at a friggin turbo. Don't study theory. Forget theory. Theory is crap without practical and real world application.
The gases don't expand in the turbine chamber. If they did, they'd blow those tiny blades apart. Expanding gases create a positive pressure. Pressure alone doesn't spin a turbo. It's the pressure differential between the manifolds and the exhaust port that causes the turbo to spin.
Turbines spin because the air is flowing through the blades. The more air that flows, the faster the turbine spins. All the thermal expansion occurs in the COMBUSTION CHAMBER of the motor. Then, when the exhaust valves are openned, this expanded gas is forced out of the combustion chamber by the upwards moving piston. So all the gases are already expanded as far as they can be. Now they are moving out of the combustion chamber into the exhaust manifolds. But there's more air coming right behind it. And the only place it has to go is out through the turbine. So the blades in the turbine are forced to spin. Because the air in the exhaust manifolds is now slightly pressurized with relation to the air on the other side of the turbine.
btw: a heat pump is NOT a turbo. And vice versa.
heat pump: http://home.howstuffworks.com/question49.htm
A heat pump is an air conditioner that contains a valve that lets it switch between "air conditioner" and "heater." When the valve is switched one way, the heat pump acts like an air conditioner, and when it is switched the other way it reverses the flow of Freon and acts like a heater.
I guess you might want to ask for your money back for that 4 week course. Use it to buy a book called "Maximum Boost: Designing, Testing, and Installing Turbocharger Systems" by Corky Bell. Once you start reading it, you might have a better understanding about turbochargers and how they work in vehicular applications.
You are wrong and Ball is right. Read any engineering book on turbomachines. Its expansion accross the turbine that provides the great part of drive force. You are offering a highly simplified view of how a turbo works. Corkey Bell is an engineer but he is also writing in a way that laypeople can easily understand.
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I agree. howstuffworks.com is a great site for the basics. But it doesn't go into detail about properly sizing turbos, understanding A/R ratios, spool up times, etc. But for the basics (which is how they work), it's great. It explains completely how a turbo functions and what it's purpose is.
If you really want to understand turbos and how to properly size a turbo on both the exhaust and intake side, you get the book I mentioned by Corky Bell. It explains a lot more about them as far as properties of adequate sizing and proper cooling of intake charging as well as flow capabilities.
I have written and published stuff on how turbos work as well that goes into more detail than corkey bells book. In fact I have several articles on turbo sizing in several major magazines. I think I have a pretty decent working knowlege on applications of turbos and so do some of my friends who design turbos for a living.
You have to take how things work with a gain of salt, its written so a grade school or Jr high level kid can understnad and glean the basics from it. My stuff was written so a high school student that knows some algebra could understand it.
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What books have you written and what publications have you been published. I am genuinely interested in knowing how and why I'm wrong and what the truth is.
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What books have you written and what publications have you been published. I am genuinely interested in knowing how and why I'm wrong and what the truth is.
Read Classic Motorbooks SCC's engine and powertrain handbook, the gist of stuff is in their.
Its not expanding in the turbine like releasing heat energy, its accross the turbine and extracting heat energy this way. I suggest the before mentioned watson and genoda book specficaly for turbos or any collage engineering text on turbomachines.
You need some higher level math but not alot and they are also boring reads unless you are an engineer or a student and maybe even then. Unfortunatly their are no entertaining high level books on the subject but HP wants me to write one. Turbos for dummeys or something like that.
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Sorry man, but I'm right. How-Stuff-Works is a kiddie site at best. Ask anybody worth a salt on this site, such as Mike K., how a turbo really works. Exhaust gas velocity accounts for about 30% of how a turbo uses exhaust gas energy. The rest is caused by thermal expansion of exhaust gases in the turbine chamber. A turbo is essentially a heat pump.
Here is my $.02 to this.
Quote:
Originally Posted by B@lliZtiK
You got that backwards. A turbo uses heat energy, so it can actually make the exhaust after it a bit cooler.
I agree that a turbo uses heat energy (exhaust gases are forced through the turbine) but could you explain in more detail why it makes the exhaust a bit cooler? Did I read you right? I know that boost (very high), IC, A/F, timing affect how much heat is produced in the exhaust gases.
Quote:
Originally Posted by Marc Z31
[i]Yes, the turbo uses exhaust to power itself, but because of the increased backpressure, it makes the exhaust VERY hot. [i]
Backpressure as I know it is cause by the turbo piping (Length, angle, IC design, exhaust manifold) and exhaust system (precats, cats). I like the way this is stated,
"Pressurized air is then forced into the engine. Since pressurized air has more oxygen per unit volume (PV = nRT), there is more opportunity for combustion. This additional oxygen can either accompanied by additional fuel for increased power or in some diesel applications, the advantage is in the excess oxygen which allows for cleaner and more complete burning of the fuel, resulting in reduced emissions and increased efficiency."
Quote:
Originally Posted by Az-Zbum
[i]Turbo will also smooth it out and act as a preliminary muffler. But it will still be very loud. [i]
True but my Greddy SP make my Twin Turbo sounds stock.
Quote:
Originally Posted by Az-Zbum
B@lliZtiK: I think you should read about how turbos work again. They do NOT use heat energy or thermal expansion to drive the turbine blades. They are simply driven off the exhaust gas flow. Nothing more.
I think you were missing his point? The exhaust gases push the turbine blades which in turn forces the compressor (cold side) to force air to compress. This compression occures in the combustion camber so that more air can fit in the same volume (more O2, bigger bang, more heat) . It's a cyclic cycle of sorts.
Of course this is my opinion which based on my experiance of reading, seeing, and working on my Z. So please don't hurt me!!
You need some higher level math but not alot and they are also boring reads unless you are an engineer or a student and maybe even then. Unfortunatly their are no entertaining high level books on the subject but HP wants me to write one. Turbos for dummeys or something like that.
I have a degree in electrical engineering and was doing calculus in 6th grade, so I don't think it will get over my head. Thanks.
__________________ Disclaimer:
One thing you'll find about me is that I can be very helpful to people who take their time to ask complete questions with good grammar and punctuation. I'm also a real ass to people who don't show at least a little effort in their posts. Z31 Registry Z32 Registry
You are supposed to be an engineering student! A turbo does not make the exhaust hotter! That would be violating the laws of thermodynamics. In fact it makes it around 300 degrees F cooler!
The turbine extracts energy from the exhaust flow. Some of the drive power is expansion and mass flow accross the turbine, The conversion of heat to drive power. Some is pulse energy due to the tuned effects and harmonics of the system. Some is even accoustic energy. Look at some of your books on turbo machines.
Turbos run a higher EGT Pre turbine all things being equal mostly due to the ideal gas law and backpressure but they are in no way making the exhaust hotter, in fact they make the exhaust cooler.
Thermal expansion is for Jet turbin engines!Air comes in it is mixed with fuel and ignited. Once it is ignited it expands (builds pressure layman's term) then it has to exit somewhere. It is exited through another set of fins, which inturn speeds up the intake turbin which forces more air in which makes a bigger volume explosion which does what you may ask? speeds up theintake even more.
Now the point to this is that fuel is introduced into this chamber to create thermal expansion inside a jet engine.
A TURBO is feed by? AIR
Thats right AIR, you can turbo charge any car with a compressed air tank with enough volume to feed the turbo. Heck you force out cold air and the Turbo will still spin. If you don't believe that go to the dollar store a by miniture wind-mill. Light a fire under it and see if it turns faster as you blow the hottest air you can come up with on it. I with you on this one AZ-ZBUM, Let me guess a belt driven supercharger uses the heat off the belt to turn it faster. Exhaust has to come out, a turbo utilizes the free outcoming AIR to turn a wheel. ROCKET SCIENCE!
Thermal expansion is for Jet turbin engines!Air comes in it is mixed with fuel and ignited. Once it is ignited it expands (builds pressure layman's term) then it has to exit somewhere. It is exited through another set of fins, which inturn speeds up the intake turbin which forces more air in which makes a bigger volume explosion which does what you may ask? speeds up theintake even more.
Now the point to this is that fuel is introduced into this chamber to create thermal expansion inside a jet engine.
A TURBO is feed by? AIR
Thats right AIR, you can turbo charge any car with a compressed air tank with enough volume to feed the turbo. Heck you force out cold air and the Turbo will still spin. If you don't believe that go to the dollar store a by miniture wind-mill. Light a fire under it and see if it turns faster as you blow the hottest air you can come up with on it. I with you on this one AZ-ZBUM, Let me guess a belt driven supercharger uses the heat off the belt to turn it faster. Exhaust has to come out, a turbo utilizes the free outcoming AIR to turn a wheel. ROCKET SCIENCE!
B@lliZtiK: I think you should read about how turbos work again. They do NOT use heat energy or thermal expansion to drive the turbine blades. They are simply driven off the exhaust gas flow. Nothing more.
A turbo is simply an air pump. It is driven by air. It drives air.
All the other parts about thermal properties and pressures and everything else goes into determining the efficiency of a turbo.
Why is this so hard to understand?
Quote:
Originally Posted by chimmike
you're wrong man. Go read Maximum Boost by Corky Bell. That's a turbocharging book, not the stupid howstuffworks website.
Why do you think people thermal coat turbos? To maintain the maximum amount of heat inside the turbine as possible to decrease lag.
Turbos mainly spool off THERMAL EXPANSION.
In a perfect world where there is no heat soak, turbos would be lag free because there would be no loss of heat in the system.
Thermal expansion? WTF? Bull crocky.
Do you understand what THERMAL EXPANSION is? It's when a material expands because of heat. Air expanding in a closed system makes the system pressurized. Pressure alone does NOT spin a turbo. Heat alone does not spin the turbo. Heat and pressure together still don't spin the turbo. Heat has absolutely nothing to do with spinning a turbo. The difference in pressures between the two sides causes the turbo to spin. This is because air is now flowing through the turbine blades. And the air on the manifold side is pressurized because the air is being forced out of the cylinders by the pistons coming up and the valves being open. The turbo doesn't cause air to expand inside the turbine. That is done in the cylinders. The air is completely expanded before it even gets to the turbo. The turbo is driven off this moving air. And because the air is going from a pressurized state to a lower pressure state, the air is cooler than when it got in. Which is why the air on the exhaust is lower than in the manifolds (we're still talking over 1000 degrees though).
People thermal coat turbos to keep heat out of the engine bay and in the turbo. Keeping the heat inside the turbo makes it more efficient. It also makes it so you don't cook anything in your engine bay. Why do you think Z32TTs have such crappy wiring harnesses after a few years? It's because the turbos are packing into such a tight engine bay that the heat has no where to go but the engine compartment.
As defined in Maximum Boost. Lag: Lag is the delay between a change in throttle and the production of noticable boost when engine rpm is in a range in which boost can be achieved. Turbine: The turbine is the fan driven by the engine's exhaust gases. It is often called the "hot" side of the turbocharger.
Lag is caused because someone put too big a turbo on a motor and there are not enough exhaust gases at that RPM to create a positive pressure on the compressor side. This can be because the turbine fan is too large, the compressor fan is trying (unsuccessfully) to pressurize too much air, or the engine just isn't moving enough air because it isn't spinning at sufficient RPMs yet.
This isn't rocket science. A turbo is an air pump. Air drives it on the turbine side. It drives air on the compressor side. The engine feeds the air that drives the turbine side. The environment feeds the air that the compressor drives. The coimpressor drives the air that the engine needs. And the cycle continues.
You can't put a big compressor on a small turbine and expect it to work. You can't put a small compressor on a big turbine and expect it to work. You can't put a small compressor and turbine on a 12L diesel and expect it to work. Likewise, you can't put a large compressor and turbine on a 3.0L V6 and expect it to work. This is where the math comes in.
Certain sized turbines require a certain amount of air to drive them and can only flow a certain amount of air max. Same with compressors. And none of this affect the basic principal of the turbo. Air driving air.
All the efficiencies and heat exchanging is what is calculated. And you have to calculate the correct turbine blades and compressor blades sizes and housings to make them produce usable boost.
Repeat after me:
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
__________________ Disclaimer:
One thing you'll find about me is that I can be very helpful to people who take their time to ask complete questions with good grammar and punctuation. I'm also a real ass to people who don't show at least a little effort in their posts. Z31 Registry Z32 Registry
Thermal expansion is for Jet turbin engines!Air comes in it is mixed with fuel and ignited. Once it is ignited it expands (builds pressure layman's term) then it has to exit somewhere. It is exited through another set of fins, which inturn speeds up the intake turbin which forces more air in which makes a bigger volume explosion which does what you may ask? speeds up theintake even more.
Now the point to this is that fuel is introduced into this chamber to create thermal expansion inside a jet engine.
A TURBO is feed by? AIR
Thats right AIR, you can turbo charge any car with a compressed air tank with enough volume to feed the turbo. Heck you force out cold air and the Turbo will still spin. If you don't believe that go to the dollar store a by miniture wind-mill. Light a fire under it and see if it turns faster as you blow the hottest air you can come up with on it. I with you on this one AZ-ZBUM, Let me guess a belt driven supercharger uses the heat off the belt to turn it faster. Exhaust has to come out, a turbo utilizes the free outcoming AIR to turn a wheel. ROCKET SCIENCE!
You are being a typical internet "expert" you are stating opinion like its fact. I am speaking about known facts that are what any ME studies in school, its not rocket science.
Its heat and expansion that provides most of the drive force for the turbine. Read some of the things I suggested and then you will see how turbos work. They are not POP lituature but textbook level stuff. Or ask any ME or third year engineering student. This is striaghtfoward, not bizzaro technospeck.
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A turbo is simply an air pump. It is driven by air. It drives air.
Repeat after me:
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
A turbo is an air pump. Nothing more. Nothing less.
Well, its an energy recovery device as well.
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Thanks.
