Slant Six Forum :: Turbo or Blown???

This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. In fact, the pressure differential accross the turbine should be minimal. As you compromise the system design, the pumping action becomes more of a factor. When you start using pumping action, turbo efficiency starts to go way down.

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I don't question what you're saying, but the heat energy must somehow be converted into mechanical energy; that is accomplished by the expansion of the hot gasses across the turbine rotor. Heat energy is useless until it is converted to mechanical energy.

Hey michb don't want to sound rude and all but, heat does nothing for a turbo but destroy it. If you push antartic air through a turbos drive impeller at 20 below the compressor side would still spin. I've worked on diesel for over 12 years and the old 2 stroke ran a turbo on each manifold (v-6, v-8 detroit ) and a root super charger on top. The turbos were there only to push the exhaust out. I'm not being rude so please do not be offended.

This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine.

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I'm not so sure it's heat that drives the turbo...........

When the turbo is close to the exhaust port, the exhaust is as hot as it can be......

The exhaust also as the greatest volume possible because of the heat.

There's more volume of air to spin the turbo, and that's what I think makes turbos more efficient closer to the exhaust port.

As the exhaust moves down the pipe, it cools down; less volume of exhaust to spin the turbo, less efficient.

So let me get this right, MitchB says that it takes 80hp to create 10lbs of boost from a belt driven certifical supercharger on 5.0 Mustang. But for some strange reason it dosen't take 80hp to create 10lbs of boost when a certifical supercharger is driven by exhaust gases.

How can this be?

Author:	valiantfreak [ Sun Mar 26, 2006 6:11 pm ]
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Panic, More silly stupid comments? Don't you know (after your 40 years of doing this) that if you don't have something nice to say, don't say anything at all? If what I have to say doesn't interest you, then why make comments like this and waste your time? Like you stated before, I am only interested in serious statements. So far, you have only contributed drivel meant to intimidate. I thought we are all on the same team here on this website? Now, I could make disrespectful comments like yourself, for example, I can accept that you write stuff like that and hide behind a computer and feel like you are getting the better of someone and feel special. However, in person, you would definately be swallowing some teeth. But I won't, because I'm not like that. If you must be disrespectful, please don't post here. I had a serious question that obviously you misinterpreted.

Author:	panic [ Sun Mar 26, 2006 8:09 pm ]
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However, in person, you would definately be swallowing some teeth? Would you like my address?

Author:	Hyper'72Valiant [ Sun Mar 26, 2006 10:16 pm ]
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omg!!! Break it up, break it up. Cory

Author:	dakight [ Mon Mar 27, 2006 4:37 am ]
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Quote: This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. In fact, the pressure differential accross the turbine should be minimal. As you compromise the system design, the pumping action becomes more of a factor. When you start using pumping action, turbo efficiency starts to go way down. I don't question what you're saying, but the heat energy must somehow be converted into mechanical energy; that is accomplished by the expansion of the hot gasses across the turbine rotor. Heat energy is useless until it is converted to mechanical energy.

Author:	mopardemon71 [ Mon Mar 27, 2006 10:53 am ]
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Hey michb don't want to sound rude and all but, heat does nothing for a turbo but destroy it. If you push antartic air through a turbos drive impeller at 20 below the compressor side would still spin. I've worked on diesel for over 12 years and the old 2 stroke ran a turbo on each manifold (v-6, v-8 detroit ) and a root super charger on top. The turbos were there only to push the exhaust out. I'm not being rude so please do not be offended. This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. [quote][/quote]

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Turbo or Blown??? https://slantsix.org/forum/viewtopic.php?t=16697	Page 2 of 3

Author:	mcnoople [ Mon Mar 27, 2006 11:37 am ]
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Just use a turbo. Mounting a cent supercharger isn't simple the brackets have to be very stout. Can't we all just get along

Author:	panic [ Mon Mar 27, 2006 12:22 pm ]
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I agree on the brackets, supposedly this is the biggest cause of complaints. But - it's easier to double up on the plates, add stiffeners, etc. than to construct a whole exhaust system - which also needs brackets. Where it looks feeble - it's obvious - add some metal and extra attachment points, it's really easy. A centrifugal is also much more likely to work the first time. Don't like it? Change the pulley. If you guess wrong on turbine A/R, you need a new housing (from a smaller motor will produce good boost with high backpressure, from a larger motor the reverse). If you guess really wrong, you need a whole turbo. My choice for cheap: Eaton M112 from a Ford Lightning etc. on eBay for $200., add your own MS EFI.

Author:	MitchB [ Mon Mar 27, 2006 2:09 pm ]
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Quote: Quote: This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. In fact, the pressure differential accross the turbine should be minimal. As you compromise the system design, the pumping action becomes more of a factor. When you start using pumping action, turbo efficiency starts to go way down. I don't question what you're saying, but the heat energy must somehow be converted into mechanical energy; that is accomplished by the expansion of the hot gasses across the turbine rotor. Heat energy is useless until it is converted to mechanical energy. A turbo does WORK. It uses the heat ENERGY to perform this work. The heat energy is converted into rotational inertia of the compressor wheel. The work is performed when the compressor wheel moves the intake charge into the engine. Whether you use a crank deiven compressor or a heat driven compressor, you still use energy to perform work. You have the wrong concept when you think the temperature drop (and energy conversion) across the turbine occurs because of the expansion of gasses. This is not correct with regard to the mechanism or principle on how a turbo works. Mitch

Author:	MitchB [ Mon Mar 27, 2006 2:15 pm ]
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Quote: Hey michb don't want to sound rude and all but, heat does nothing for a turbo but destroy it. If you push antartic air through a turbos drive impeller at 20 below the compressor side would still spin. I've worked on diesel for over 12 years and the old 2 stroke ran a turbo on each manifold (v-6, v-8 detroit ) and a root super charger on top. The turbos were there only to push the exhaust out. I'm not being rude so please do not be offended. This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. Quote: I am very well aquainted on the engines you describe. The one and only reason Detroit Diesel used turbos on their 2 stroke engines was to reduce emissions!!! Besides, the turbos in the application you are talking about STILL used exhaust HEAT as it's primary source of energy. Look at Detroits later 4-stroke series 50/60 engines which did not use a roots blower - only one turbo. Where is the turbo mounted? RIGHT OFF THE EXHAUST MANIFOLD AS CLOSE TO THE EXHAUST PORTS AS POSSIBLE!!!. Mitch

Author:	MitchB [ Mon Mar 27, 2006 2:17 pm ]
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Quote: Hey michb don't want to sound rude and all but, heat does nothing for a turbo but destroy it. If you push antartic air through a turbos drive impeller at 20 below the compressor side would still spin. I've worked on diesel for over 12 years and the old 2 stroke ran a turbo on each manifold (v-6, v-8 detroit ) and a root super charger on top. The turbos were there only to push the exhaust out. I'm not being rude so please do not be offended. This does not account for the amount of work performed by a turbo. Heat is a form of energy. A turbo uses this energy to perform the work of compressing air into the engine. In a well designed system, most of the energy used by a turbo comes from the heat in the exhaust, not by the pressure differential caused by the pumping action of the engine. Quote: Oh yes, one other thing - the turbos did NOT push the exhaust out. They were used to force more air into the engine. This helped reduce emissions. Mitch

Author:	emsvitil [ Mon Mar 27, 2006 6:50 pm ]
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I'm not so sure it's heat that drives the turbo........... When the turbo is close to the exhaust port, the exhaust is as hot as it can be...... The exhaust also as the greatest volume possible because of the heat. There's more volume of air to spin the turbo, and that's what I think makes turbos more efficient closer to the exhaust port. As the exhaust moves down the pipe, it cools down; less volume of exhaust to spin the turbo, less efficient.

Author:	dakight [ Mon Mar 27, 2006 7:38 pm ]
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Quote: I'm not so sure it's heat that drives the turbo........... When the turbo is close to the exhaust port, the exhaust is as hot as it can be...... The exhaust also as the greatest volume possible because of the heat. There's more volume of air to spin the turbo, and that's what I think makes turbos more efficient closer to the exhaust port. As the exhaust moves down the pipe, it cools down; less volume of exhaust to spin the turbo, less efficient. Heat is a form of energy and hot gas has more energy than cool gas. The heat energy is converted to kinetic (mechanical) energy in the turbine and used to compress the incoming air/fuel charge. The mechanical Coincidentally, that compression heats the air fuel mixture which is then often passed through an intercooler to dump the excess heat.

Author:	grthigpen [ Mon Mar 27, 2006 8:27 pm ]
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i tried to explain earlier but seems that some are taking the law of physics out of context (only recognizing part of the equation). As i tried to explain earlier but got so much criticism i deleted my writeup I have decided to say it again. It heat that creates the volumne of air differential between intake and exhaust... quote from physics article: "No, heat doesn't create velocity. Heat creates volume. If you look at any of the physics laws for gasses, you will find that pressure and volume and heat are related. PV=NRT is a popular one, The V isn't for velocity, it is for Volume. The turbine housing is what creates the velocity. The scrolling design that reduces the volume of the exhaust chamber as it scrolls around causes the gasses to have to increase in velocity and pressure to maintain the same flow rate. Hotter gasses have more volume, thus requiring a higher A/R which in effect means that it starts at say 3" and scrolls down to approximately 1". Lower temperature gasses are denser and have less volume, so they require a lower A/R housing which would start at the same 3" volume, as the turbine housings use standard flanges, and scroll down to say 3/4". basically you speed up the already increased volumne of air (due to high heat) by reducing the feed diameter into the turbine which spins the turbine even faster and compresses the intake air that is cooler and denser even more and pressurizes the intake chamber. Also the closer to the heat source, the more efficient the turbo is. The drawback is the reduction of housing in the turbo is what creates the backpressure issue, very little is attributed to the necessary energy to spin the turbo so i have said it differently this time so maybe it can be understood. So i guess i will be told i am wrong again so be it.... lets go out and smoke some tires.....need new ones anyway haha Gene T

Author:	kesteb [ Wed Mar 29, 2006 9:02 pm ]
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So let me get this right, MitchB says that it takes 80hp to create 10lbs of boost from a belt driven certifical supercharger on 5.0 Mustang. But for some strange reason it dosen't take 80hp to create 10lbs of boost when a certifical supercharger is driven by exhaust gases. How can this be?

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Author:	emsvitil [ Wed Mar 29, 2006 10:56 pm ]
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Quote: So let me get this right, MitchB says that it takes 80hp to create 10lbs of boost from a belt driven certifical supercharger on 5.0 Mustang. But for some strange reason it dosen't take 80hp to create 10lbs of boost when a certifical supercharger is driven by exhaust gases. How can this be? Yes and no... In both cases it takes 80 hp to spin the supercharger/turbocharger. With the centrifugal the 80 hp comes directly from the engine. With the turbo the 80hp comes from the exhaust. But when it comes from the exhaust, you're extracting energy from a source that is usually lost out the tailpipe. So the turbo may only cause a 40 hp loss to the engine due to backpressure and pumping losses. The other 40hp came from the exhaust gasses. You'll find that exhaust gasses that come out the end of the pipe of the turbocharged engine will be cooler than the exhaust gasses coming out the end of the supercharged engine (the energy has to come from somewhere) (and don't argue the 40 hp, I'm just using that as an example..........)