Wow, this is a bigger can if worms than I thought it would be. This thread just might become a sticky for info for those less versed in turbocharger operation and theory.
Thanks Mike K., Spongerider, James, and anyone else who came in here to back up my cause. Couldn't have done it without you.
__________________
1992 Yamaha FZR 1000. 145 Hp, all stock..
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!
Supercharger is a totally different drive system, and completely different in operation.
As far as blowing on a turbo with compressed air, sure you can do that, and you'll get a few thousand rpm out of it, but I doubt you realize just exactly how fast a turbine spins under expanding exhaust gases. Try over 100,000 rpm, and thats just in a stock boost application. Closer to 160,000 rpm for high level boost. You won't get that kind of rpm simply blowing air on a turbine blade.
__________________
1992 Yamaha FZR 1000. 145 Hp, all stock..
Its heat and expansion that provides most of the drive force for the turbine. They are not POP lituature but textbook level stuff. Or ask any ME or third year engineering student. This is striaghtfoward, not bizzaro technospeck.
How does heat and expansion drive the turbo? Where is the heat generated from? What is expanding? If this is such a simple concept, it should be very easy to explain. So please enlighten us.
__________________ 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
How does heat and expansion drive the turbo? Where is the heat generated from? What is expanding? If this is such a simple concept, it should be very easy to explain. So please enlighten us.
Did you miss what Mike Kojima said earlier?
Quote:
Originally Posted by Morpower2
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.
__________________
Wait a minute. Surely you know this. In the combustion chamber.
Exactly! And that's the point. Ignore that other crap about thermal expansion and heat energy. AIR drives the turbo. Plain and simple.
The large volume of air is created in the combustion chamber from the air and fuel taken in at much lower temperatures (like, 1000 degrees lower) and pressurized and ignited thus becoming a much larger volume at much greater temperatures. And this inturn driving the turbo.
There is no combustion, no pressurizing, and no heat expansion taking place in the turbo itself.
my original post that started this whole thing:
Quote:
Originally Posted by AZ-ZBum
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.
Your reply:
Quote:
Originally Posted by B@lliZtiK
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.
__________________ 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
Exactly! And that's the point. Ignore that other crap about thermal expansion and heat energy. AIR drives the turbo. Plain and simple.
The large volume of air is created in the combustion chamber from the air and fuel taken in at much lower temperatures (like, 1000 degrees lower) and pressurized and ignited thus becoming a much larger volume at much greater temperatures. And this inturn driving the turbo.
There is no combustion, no pressurizing, and no heat expansion taking place in the turbo itself.
my original post that started this whole thing:
Your reply:
I see your missing some parts of the system though. Combustion takes place in the engine, the exhaust is forced out into teh exhaust manifold. There is a little bit of expansion of exhaust gases there. From there, the exhaust gases go into the feed tube to the turbine chamber, where the space is very limited. The exhaust gases come out into the turbine chamber, and since it is larger than the feed tube, the gases expand and release heat energy. This is why turbos are located so close to the exhaust manifold, to preserve the heat energy factor. If you notice, in the 80s, some turbo cars, such as the GN prototypes, actually had the turbo located on TOP of the engine, with several feet of exhaust pipe in between the exhaust manifold and the turbo itself. This killed efficiency and turbos on such cars did not work as well. If it were simply a matter of blowing air, turbos could be located as far back as the muffler and still work perfectly fine. But they are not. If you notice, every turbo is loctaed as close as it can be to the head, and using heat energy is the reason for it. Turbo packaging is a nightmare for any engineer, thay have to balance location with efficiency and emissions compliance. Placing a turbo where it is is not because it's convenient, it's because it's necessary for proper operation and emissions.
__________________
1992 Yamaha FZR 1000. 145 Hp, all stock..
If it were simply a matter of blowing air, turbos could be located as far back as the muffler and still work perfectly fine. But they are not. If you notice, every turbo is loctaed as close as it can be to the head, and using heat energy is the reason for it.
__________________ 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
Az-Zbum, I think your trying to over simplfy things.
But a turbo is a very simple device.
We aren't talking about how an ENGINE makes power. We're talking about how a turbo works. What drives it. What it drives. What it does. And what it is 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
Haha, I fully expected you to pull out that site. Most people do, who have no clue about how a turbo really works. Remote mounting is ok, but notice that none of those applications is yet on a car which has to pass emissions. None of those turbos is on a vehicle old enough yet. They will have problems when they come of age, mark my words. If you notice, the basic turbo provides 5 psi of boost. That far back, thats probably about it's maximum. Turbo "upgrades" can produce up to 20 psi? Heck, most stock turbos can do that normally. That right there tells me there's a major loss of efficiency. The guys that invented that system obviously have never paid attention to the fact that an exhaust system can lose 80% of it's heat through the pipe walls by the time it gets to the muffler. Thats why you can put your hand in front of an exhaust pipe and not get burned...... A turbo system like that does not work to the best of it's ability and will only cause problems later on.
__________________
1992 Yamaha FZR 1000. 145 Hp, all stock..
AZ, you're problem is, is that you are good at researching stuff on the internet, but you don't fully understandwhat you are reading. It's easy to pull sites out of anywhere to attempt to explain whatever you want, but you don't seem to understand that not everything on the net is the gospel truth. There's reason why people still write books. That turbo site that you just pulled out is the perfect example of what I'm talking about. Vehicle manufacturers have been placing turbos where they are for how many years now? And you don't think there's a reason for that? Some site that claims to have remote mounted turbos, now how many of those have you ever seen on any car. Only somebody who barely finished high school, with no engineering knowledge and no school time, and certainly no true automotive knowledge, will ever have one of those devices installed on their car.
You know what, go on with whatever you think your theories are concerning turbo knowledge, but know this. When you first came here, I respected you for your Z31 knowledge, and I still do. But your knowledge of operations is limited. Stick to what you know. Let the rest of us explain operations.
__________________
1992 Yamaha FZR 1000. 145 Hp, all stock..
Last edited by B@lliZtiK : Dec 30th, 2004 at 08:59 PM.
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.
A gas turbine engine works in this way, but not a turbocharger. EGT's are hotter on turbo cars because of the severely increased backpressure. The turbocharger works as a product of thermal expansion, but it does not actually have any sort of expansion inside of the turbocharger itself. All of the expansion happens in the combustion chamber, and as it passes through the exhaust manifold, it begins to cool actually. This is the reason racecars have heat wrap on the exhaust manifold, to keep the heat from passing to ambient air.
The air passing through the compressor housing is more dense and lesser in volume than the gas passing through the turbine side. Yes, the heat makes the turbo work, but there is only contraction of gasses in the turbo itself, from heat lost through exhaust manifolds and the turbine housing itself.
Haha, I fully expected you to pull out that site. Most people do, who have no clue about how a turbo really works. Remote mounting is ok, but notice that none of those applications is yet on a car which has to pass emissions. None of those turbos is on a vehicle old enough yet. They will have problems when they come of age, mark my words. If you notice, the basic turbo provides 5 psi of boost. That far back, thats probably about it's maximum. Turbo "upgrades" can produce up to 20 psi? Heck, most stock turbos can do that normally. That right there tells me there's a major loss of efficiency. The guys that invented that system obviously have never paid attention to the fact that an exhaust system can lose 80% of it's heat through the pipe walls by the time it gets to the muffler. Thats why you can put your hand in front of an exhaust pipe and not get burned...... A turbo system like that does not work to the best of it's ability and will only cause problems later on.
The 97 TA should have to pass emissions. Besides we aren't talking about emissions. We already know that turbos hinder emissions.
Most of them are only running 5 psi because they haven't upgraded their fuel systems. Most car manufacturers don't ship cars with fuel injectors that can handle twice as much fuel as the car should ever need (the Z31 is a perfect example). Why? Because it's harder to get more precise inections with larger fuel injectors at lower power requirements/rpms.
With reference to the air flow, air flow drives the turbine because of the pressure differential between the two sides of the turbine blades. I agree that the mounting location is not the most efficient and placing the turbo closer to the actual exhaust valves would be optimal, but it does work. There are plenty of dyno graphs up there to prove it.
The only reason I can see to keep the exhaust temps up is to maintain the highest pressures and thus, the highest volumes of air. But I fail to see how temps otherwise help the turbo spin.
How does a turbo require heat to work? What does heat do? How does it benefit the driving of the turbine? Or is it simply to keep the volume of air higher?
edit: I still don't have answers to these questions:
1. How does heat and expansion drive the turbo?
2. Where is the heat generated from?
3. What is expanding?
__________________ 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
Last edited by AZ-ZBum : Dec 30th, 2004 at 09:07 PM.
