Gas vs PSD
Lead Driver
Joined: May 2011
Posts: 5,775
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40 psi of air has a lot of oxygen in it. Next time you light up an acetylene torch, see how much that good old O2 helps it burn. And, add that 40PSI to the intake charge, which is normally 15PSI, so you have a net of 55PSI. Compress that at 12:1, or whatever a PSD uses for static compression, and you have more than three times the "naturally aspirated" dynamic cylinder pressure. With three times the O2, you have three times the power.
It's a "net positive" - the mechanical energy required to pump more O2 into the cylinders is outweighed by the mechanical energy "robbed" from the engine by driving the turbo.
If it only had to do with heat, why does a supercharger work? (see note below) The Detroit Diesel 6-71 blower exists for a reason.
*NOTE: Superchargers add to the rotational weight of the engine. Acceleration is directly effected. Turbos, not so much. They do rob power, but not directly, allowing faster spin up at the crank.
It's a "net positive" - the mechanical energy required to pump more O2 into the cylinders is outweighed by the mechanical energy "robbed" from the engine by driving the turbo.
If it only had to do with heat, why does a supercharger work? (see note below) The Detroit Diesel 6-71 blower exists for a reason.
*NOTE: Superchargers add to the rotational weight of the engine. Acceleration is directly effected. Turbos, not so much. They do rob power, but not directly, allowing faster spin up at the crank.
40 psi of drive pressure has absolutely nothing to do with intake pressure (boost). . . . . . . . . . . also, turbos dont "rob" the motor of heat (energy), they harness energy that would otherwise not be used. which is why turbos increase "thermal efficency"
do you know what drive pressure is? ? ?
for those that do. . .i can squash the debate with this next statement:
the bigger the pump, the more energy needed to operate it. right? the larger the turbo, the more energy needed for it to spool. . .these are laws of physics, not something im makin up. fact: as the turbo size increases, the drive pressure decreases. so, if drive pressure is what makes the turbo function, it would increase as turbo size increases. but it doesnt, it decreases. the larger turbos allow more pressure to be released past the turbine, resulting in less drive pressure, and more boost. AGAIN. . .drive pressure is a bi-product of thermal energy. . .smaller turbos = more DP and less boost. . .larger turbos = less DP and more boost. this statement of facts would defy the laws of physics if "pressure" (i.e. drive pressure) was the sole propellant of the turbo. but its not. . .without heat the drive pressure would never build. . .and if it did, it would merely spin the shaft enough to make some noise, not spin it to the 150-300,000 rpm that turbos operate.
Lead Driver
Joined: Jan 2006
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Likes: 5
40 psi of drive pressure has absolutely nothing to do with intake pressure. . . . . . . . . . .do you know what drive pressure is?
for those that do. . .i can squash the debate with this next statement:
the bigger the pump, the more energy needed to operate it. right? the larger the turbo, the more energy needed for it to spool. . .these are laws of physics, not something im makin up. fact: as the turbo size increases, the drive pressure decreases. so, if drive pressure is what makes the turbo function, it would increase as turbo size increases. but it doesnt, it decreases. the larger turbos allow more pressure to be released past the turbine, resulting in less drive pressure, and more boost. AGAIN. . .drive pressure is a bi-product of thermal energy. . .smaller turbos = more DP and less boost. . .larger turbos = less DP and more boost. this statement of facts would defy the laws of physics if "pressure" (i.e. drive pressure) was the sole propellant of the turbo.
for those that do. . .i can squash the debate with this next statement:
the bigger the pump, the more energy needed to operate it. right? the larger the turbo, the more energy needed for it to spool. . .these are laws of physics, not something im makin up. fact: as the turbo size increases, the drive pressure decreases. so, if drive pressure is what makes the turbo function, it would increase as turbo size increases. but it doesnt, it decreases. the larger turbos allow more pressure to be released past the turbine, resulting in less drive pressure, and more boost. AGAIN. . .drive pressure is a bi-product of thermal energy. . .smaller turbos = more DP and less boost. . .larger turbos = less DP and more boost. this statement of facts would defy the laws of physics if "pressure" (i.e. drive pressure) was the sole propellant of the turbo.
If you are saying that pressurised hot gasses are not spinning the turbo, what is?
Drive pressure is a product of the gases ability to flow through.
Depending on the exact setup and turbocharger etc, it will be different, but it will correlate to the work being done on the opposite end of the turbo, compressing air.
If you had an "imaginary" turbo with the exhaust side intact, but the air compressor side missing, you'd have almost zero back pressure until the thing grenaded, because it would have near zero load on it.
Lead Driver
Joined: Jan 2006
Posts: 6,267
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In essence, it is. The difference is that it operated at high RPM, and that it is driven by exhaust gasses instead of a belt.
In being driven by exhaust gasses, it is able to run very efficient as it is utilising hot pressurised exhaust gasses that would otherwise be dumped.
Cargo Master
Joined: Apr 2010
Posts: 3,274
Likes: 4
From: Seattle area
I have yet to post to this tread, but feel compelled to...for some strange reason. It's like the itch you get to touch a hot pan, just to see if it is hot and you can be quick enough to escape without a burn.
If you're hauling a house, then a diesel is the only way to go. But if you're hauling 8-10K pounds, the added costs are not worth it. Ford's V10s are lasting as long as their diesels and with their decreased maintenance cost and diesel being more expensive, the ROI is a very long time...
Do I miss my diesel? Yes, absolutely. Does my V10 haul like a diesel? No. But are the differences enough to justify the higher cost? For me, not even close.
If you're hauling a house, then a diesel is the only way to go. But if you're hauling 8-10K pounds, the added costs are not worth it. Ford's V10s are lasting as long as their diesels and with their decreased maintenance cost and diesel being more expensive, the ROI is a very long time...
Do I miss my diesel? Yes, absolutely. Does my V10 haul like a diesel? No. But are the differences enough to justify the higher cost? For me, not even close.
Lead Driver
Joined: Jan 2006
Posts: 6,267
Likes: 5
I have yet to post to this tread, but feel compelled to...for some strange reason. It's like the itch you get to touch a hot pan, just to see if it is hot and you can be quick enough to escape without a burn.
If you're hauling a house, then a diesel is the only way to go. But if you're hauling 8-10K pounds, the added costs are not worth it. Ford's V10s are lasting as long as their diesels and with their decreased maintenance cost and diesel being more expensive, the ROI is a very long time...
Do I miss my diesel? Yes, absolutely. Does my V10 haul like a diesel? No. But are the differences enough to justify the higher cost? For me, not even close.
If you're hauling a house, then a diesel is the only way to go. But if you're hauling 8-10K pounds, the added costs are not worth it. Ford's V10s are lasting as long as their diesels and with their decreased maintenance cost and diesel being more expensive, the ROI is a very long time...
Do I miss my diesel? Yes, absolutely. Does my V10 haul like a diesel? No. But are the differences enough to justify the higher cost? For me, not even close.
This further instils the fact that you run what works for you, and the next guy can run what works for him.
There is no "right" answer for everybody.
Lead Driver
Joined: May 2011
Posts: 5,775
Likes: 443
If you are saying that pressurised hot gasses are not spinning the turbo, what is?
Drive pressure is a product of the gases ability to flow through.
Depending on the exact setup and turbocharger etc, it will be different, but it will correlate to the work being done on the opposite end of the turbo, compressing air.
If you had an "imaginary" turbo with the exhaust side intact, but the air compressor side missing, you'd have almost zero back pressure until the thing grenaded, because it would have near zero load on it.
Drive pressure is a product of the gases ability to flow through.
Depending on the exact setup and turbocharger etc, it will be different, but it will correlate to the work being done on the opposite end of the turbo, compressing air.
If you had an "imaginary" turbo with the exhaust side intact, but the air compressor side missing, you'd have almost zero back pressure until the thing grenaded, because it would have near zero load on it.
Senior User
Joined: Jun 2011
Posts: 155
Likes: 2
Still, the turbo will operate better in a higher environment due to relative pressure at higher heat. However, the heat does nothing to create energy and spin the turbo. Again the 6.7L moved the exhaust manifolds into the engine valley, not for heating purposes, but to decrease the volume in the exhaust headers and up-pipes and reduce lag.
If force induction relied on heat transfer, superchargers would not operate. A superchargers screws are turned by a crank and a pully. A turbo compressor spins off exhaust pressure.
Take the pressure off the trubo, and just apply heat. The turbo will not spin. The force of pressure upon the exhaust vanes, creates the motion that drives the compressor wheel. Be that exhaust gas, compressed air, the wind, air flow simply drives that wheel. Thermal Transfer of heat does not build boost, you can heat that compressor housing all day.
What creates the increased lag of a larger turbo, is the additional volume of air that must be first moved into the exhaust housing and then build up the pressure necessary to drive the compressor wheel. That increased volume takes additional time to build pressure. Two additional factors with a larger turbo, the size and weight of the vanes in the exhaust side, and the larger compressor wheel with additional drag and resistance. Also larger turbos are designed to operate at a higher boost pressure, and the trade off is that lag off the line.
If force induction relied on heat transfer, superchargers would not operate. A superchargers screws are turned by a crank and a pully. A turbo compressor spins off exhaust pressure.
Take the pressure off the trubo, and just apply heat. The turbo will not spin. The force of pressure upon the exhaust vanes, creates the motion that drives the compressor wheel. Be that exhaust gas, compressed air, the wind, air flow simply drives that wheel. Thermal Transfer of heat does not build boost, you can heat that compressor housing all day.
What creates the increased lag of a larger turbo, is the additional volume of air that must be first moved into the exhaust housing and then build up the pressure necessary to drive the compressor wheel. That increased volume takes additional time to build pressure. Two additional factors with a larger turbo, the size and weight of the vanes in the exhaust side, and the larger compressor wheel with additional drag and resistance. Also larger turbos are designed to operate at a higher boost pressure, and the trade off is that lag off the line.
Lead Driver
Joined: Jan 2006
Posts: 6,267
Likes: 5
drive pressure is a measurement of the restriction the turbo is causing. .
And the restriction the turbo causes is because of the work it is doing.
.just like boost pressure is a measurement of restriction the intake tract is causing. .
Boost pressure is a measurement of absolute air pressure. Nothing more or less.
.a larger turbo takes more energy to spool, hence the increased "lag" experienced. the drive pressure will always decrease as turbo size, and lag, increases.
It might take longer to spool, but once it is running, the forces being applied to the exhaust turbine should equal the forces exerted on the compressor side. Minus friction losses, as for any machine.
its impossible to make the argument that drive pressure is what operates the turbo. like ive said a few times now, drive pressure is a bi-product of the release of an enormous amount of unused btu (thermal energy) from the motor.
Yes, you are right. Drive pressure is a by product of an engine. Unused hot pressurised gasses drive the turbo. I'm not saying heat has nothing to do with it, I'm saying that pressure is solely responsible for operating the turbo. It may be HIGHER pressure because of wasted engine heat, but the turbocharger runs on air pressure.
sure, drive pressure alone would spin the turbo, but without the enormous amount of energy (heat) it wouldnt be enough to pressurize the enormous volume of the intake tract (intercooler, cylinder head, piping) to a substantial amount. its almost silly to think that drive pressure alone could provide the energy needed to spin a turbine at 150-300,000 rpm.
And the restriction the turbo causes is because of the work it is doing.
.just like boost pressure is a measurement of restriction the intake tract is causing. .
Boost pressure is a measurement of absolute air pressure. Nothing more or less.
.a larger turbo takes more energy to spool, hence the increased "lag" experienced. the drive pressure will always decrease as turbo size, and lag, increases.
It might take longer to spool, but once it is running, the forces being applied to the exhaust turbine should equal the forces exerted on the compressor side. Minus friction losses, as for any machine.
its impossible to make the argument that drive pressure is what operates the turbo. like ive said a few times now, drive pressure is a bi-product of the release of an enormous amount of unused btu (thermal energy) from the motor.
Yes, you are right. Drive pressure is a by product of an engine. Unused hot pressurised gasses drive the turbo. I'm not saying heat has nothing to do with it, I'm saying that pressure is solely responsible for operating the turbo. It may be HIGHER pressure because of wasted engine heat, but the turbocharger runs on air pressure.
sure, drive pressure alone would spin the turbo, but without the enormous amount of energy (heat) it wouldnt be enough to pressurize the enormous volume of the intake tract (intercooler, cylinder head, piping) to a substantial amount. its almost silly to think that drive pressure alone could provide the energy needed to spin a turbine at 150-300,000 rpm.
I'm sure a turbocharger could be made to run off cooled condensed exhaust gasses, for discussion sakes, but I don't think it would make sense when we can use the hot high volume gasses right from the engine.
I realise the heat is what makes the turbocharger system efficient. But that has nothing to do with anything except the volume of gasses are greater passing though the unit.
To make my point, imagine injecting water into the exhaust manifolds, the temperature goes way down, but as it creates steam, the pressure is still there, and bang, you have a turbocharger running without the same heat.
Of course this is not 100% true, but you can see that heat alone does nothing, it is, like you said, a by product.
If you took 2 identical turbochargers, partially blocked off the compressor sides to simulate work, and then on one you gave it 40 PSI @ 0 deg air, and the other one 40 PSI @ 1000 deg air, they would both make the exact same boost, because the forces exerted to the vanes is identical. 40 lbs is 40 lbs.
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Cargo Master
Joined: Jan 2005
Posts: 2,413
Likes: 11
Why is it silly? I'm not agreeing or disagreeing w/ you. You built your vane surfaces and their angles to get the most use of the force going thru them. So its the heat off of combustion that turns the turbine and not the pressureized spent gases leaving the heads? Interresting to say the least.
Lead Driver
Joined: Jan 2006
Posts: 6,267
Likes: 5
If I remember right, combustion gasses out the manifolds are roughly 10 x the volume of the air that goes in, at WOT.
Of course theres lots of variables, but that is what I was told.
Most of that volume is because of heat expansion, I can't remember how much.
In any case, it is simply a lot of hot air, pushing vanes on the turbo.
89F2urd, I think that you're thinking of a jet engine setup, where without heat, nothing will happen. In that usage, the compressor is lower velocity high pressure, and the exhaust is low pressure, high velocity, so when you introduce heat in the burner and the unit is spinning, it runs as an engine.
While the turbocharger is considered an engine itself, in diesel engine usage, things are different, specifically the "Burner" being an engine itself able to create directional pressure.
In the way you describe it's operation, would be somehow taking the exhaust heat, and using it as the "fuel" for the turbocharger to run on, which is theoretically possible but using totally different equipment.
Of course theres lots of variables, but that is what I was told.
Most of that volume is because of heat expansion, I can't remember how much.
In any case, it is simply a lot of hot air, pushing vanes on the turbo.
89F2urd, I think that you're thinking of a jet engine setup, where without heat, nothing will happen. In that usage, the compressor is lower velocity high pressure, and the exhaust is low pressure, high velocity, so when you introduce heat in the burner and the unit is spinning, it runs as an engine.
While the turbocharger is considered an engine itself, in diesel engine usage, things are different, specifically the "Burner" being an engine itself able to create directional pressure.
In the way you describe it's operation, would be somehow taking the exhaust heat, and using it as the "fuel" for the turbocharger to run on, which is theoretically possible but using totally different equipment.
Senior User
Joined: Jul 2010
Posts: 336
Likes: 1
yes, lets talk about all of them. . . .
you only grazed the surface of reasons diesel is more efficient than a gasser. . .you stated that diesel fuel contains more energy (btu) than gasoline, which is correct. a gallon of gasoline contains 125,000 BTU, while a gallon of diesel contains 147,000 BTU. thats a 15% increase in BTU rating for diesel vs gas. . .but, thats not where the efficiency battle ends. the nature of compression ignition is superior to spark ignition in every way. diesels are 30-50% more thermally efficient than gasoline motors. why? ill put it in terms all the gassers can understand.
high compression makes the motor more efficient, right? if you bumped your compression up from 9:1 to 11:1 you would make more power, and your mileage would increase. of course, you'd have to run 93, but the fact remains you'd have a more efficient motor. diesels are between 16.5-17.5:1 for their compression ratio, which makes them leaps and bounds more efficient than their gasoline counterparts. diesels resistance to ignition is the REASON such high compression ratios can be utilized. even race fuel (c116) is limited to compression ratios nowhere near that of a run-of-the mill diesel engine. . .all on top of the already superior BTU rating makes the diesel that much more efficient.
oh it doesnt end there. . . .now we can move on to the injection systems. any gasser fan drooling over fords new 6.2's potential can mainly thank direct injection for the efficiency boost those motors have over the older fords. not only is the injector directly in the combustion chamber, its injected at a much higher pressure for better atomization. diesels have utilized direct injection for decades now. and, by nature of the fuel, diesel can injected at a MUCH higher pressure than even the most sophisticated gasoline injection systems (direct gasoline injection). direct diesel injection ranges from pressures of 4000 psi (first direct injection motor) to 36,000+ psi of the new common rail engines. the gasser would be lucky to see 400 psi. . . whats this mean? higher pressures equate to higher atomization coefficients. better atomization = higher efficiency. its the physical characteristics of gasoline that limit it to low pressure injection cycles. high pressure gasoline does not only make it much less stable, its "cleaning" characteristics are amplified and an injector that could withstand such abuse would be impossible/too costly to produce.
is that it? NOPE. . .the compression ignition diesel makes its power at 1/2 the rpm of a motor with similar displacement powered by gasoline. this means less fuel is needed to make the power. . . .equating to a more efficient motor.
a diesel motor is 30-60% more thermally efficient than a similar sized gasoline motor. this DOES NOT take into account its higher btu rating, and lower rpm power band. this just means more of the heat generated by the combustion translates into hp vs just leavin through the exhaust. if you combine the higher btu rating of diesel, its thermal efficiency stats, and the lower rpm needed to produce the same power (1/2 the rpm), you are lookin at a motor that is 50-100% more efficient than its gas brothers. this equates to a 50-100% boost in mpg over a gasoline counterpart.
so the argument of fuel cost vs efficiency is bogus to say the least. diesel and premium has lingered around 4.00 a gallon where i am. at this cost, diesel is 20-30 cents more than regular. thats a 5-7.5% increase in cost. if reg gasoline was 50% less, you could have a viable argument. 5-7.5% cost in fuel / gallon isnt even worth talkin about when the diesel is getting +50% better mileage (at least). . .its still a savings of 45-42.5% for even a modestly efficient diesel.
you only grazed the surface of reasons diesel is more efficient than a gasser. . .you stated that diesel fuel contains more energy (btu) than gasoline, which is correct. a gallon of gasoline contains 125,000 BTU, while a gallon of diesel contains 147,000 BTU. thats a 15% increase in BTU rating for diesel vs gas. . .but, thats not where the efficiency battle ends. the nature of compression ignition is superior to spark ignition in every way. diesels are 30-50% more thermally efficient than gasoline motors. why? ill put it in terms all the gassers can understand.
high compression makes the motor more efficient, right? if you bumped your compression up from 9:1 to 11:1 you would make more power, and your mileage would increase. of course, you'd have to run 93, but the fact remains you'd have a more efficient motor. diesels are between 16.5-17.5:1 for their compression ratio, which makes them leaps and bounds more efficient than their gasoline counterparts. diesels resistance to ignition is the REASON such high compression ratios can be utilized. even race fuel (c116) is limited to compression ratios nowhere near that of a run-of-the mill diesel engine. . .all on top of the already superior BTU rating makes the diesel that much more efficient.
oh it doesnt end there. . . .now we can move on to the injection systems. any gasser fan drooling over fords new 6.2's potential can mainly thank direct injection for the efficiency boost those motors have over the older fords. not only is the injector directly in the combustion chamber, its injected at a much higher pressure for better atomization. diesels have utilized direct injection for decades now. and, by nature of the fuel, diesel can injected at a MUCH higher pressure than even the most sophisticated gasoline injection systems (direct gasoline injection). direct diesel injection ranges from pressures of 4000 psi (first direct injection motor) to 36,000+ psi of the new common rail engines. the gasser would be lucky to see 400 psi. . . whats this mean? higher pressures equate to higher atomization coefficients. better atomization = higher efficiency. its the physical characteristics of gasoline that limit it to low pressure injection cycles. high pressure gasoline does not only make it much less stable, its "cleaning" characteristics are amplified and an injector that could withstand such abuse would be impossible/too costly to produce.
is that it? NOPE. . .the compression ignition diesel makes its power at 1/2 the rpm of a motor with similar displacement powered by gasoline. this means less fuel is needed to make the power. . . .equating to a more efficient motor.
a diesel motor is 30-60% more thermally efficient than a similar sized gasoline motor. this DOES NOT take into account its higher btu rating, and lower rpm power band. this just means more of the heat generated by the combustion translates into hp vs just leavin through the exhaust. if you combine the higher btu rating of diesel, its thermal efficiency stats, and the lower rpm needed to produce the same power (1/2 the rpm), you are lookin at a motor that is 50-100% more efficient than its gas brothers. this equates to a 50-100% boost in mpg over a gasoline counterpart.
so the argument of fuel cost vs efficiency is bogus to say the least. diesel and premium has lingered around 4.00 a gallon where i am. at this cost, diesel is 20-30 cents more than regular. thats a 5-7.5% increase in cost. if reg gasoline was 50% less, you could have a viable argument. 5-7.5% cost in fuel / gallon isnt even worth talkin about when the diesel is getting +50% better mileage (at least). . .its still a savings of 45-42.5% for even a modestly efficient diesel.
Moderators, act accordingly. I never was that blunt with the insults.
You forgot, (like you guys always do) to include the cost of maintaining the diesel and its highly inflated purchase price. 50% better mpg doesn't make up for $5-8k more when you buy it and 3-5 times the servicing costs. It would literally take 15-20 years of ownership to equal out.
Even then, how much is a complete V10? $2400 for a rebuilt long block. What's a 6.0 worth these days? $5k for a short block and a whopping $7200 for a long block. Who wants to go out of pocket for a 6.0 10 years down the road when the warranty is up? I could literally buy a used V10 truck in nice shape for the price of a 6.0L long block engine. Who could actually afford to come out of pocket for something like that? Not many. I certainly will not. EVER.
Lead Driver
Joined: May 2011
Posts: 5,775
Likes: 443
Without thermal energy there would be absolutely no operation of the turbo whatsoever. If drive pressure was the sole propellant of a turbo. . . .a rear mounted turbo like the ones so popular in vettes/f bodies would never spool. . . .the volume between the turbo and the motor is too great and drive pressure is a fraction (very small one) of what it would be if the turbo was right next to the motor. Its not that air/exhaust passing through the turbo is doing nothing to move the turbo (in fact i never said it didnt)o. . .its that the turbo was specifically designed to harness some of the copious amounts of thermal energy leftover from combustion. THERMAL ENERGY IS THE ONLY ENERGY SOURCE AVAILABLE FOR THE TURBOS OPERATION. heat. The drive pressure is a physical biproduct of the heat converting to work. Without heat, there would be no function. Without heat, there would be no drive pressure. Because it converts heat into motion (just like the internal combustion engine) it increases the thermal efficiency of the motor. (Increases the amount of energy absorbed.from combustion)
A supercharger doesn't increase.thermal efficiency like turbos do. In fact, the increase is about 1/2 that of a turbo. Turbos use heat directly to spin them. They're directly subject to tremendous amounts of raw thermal energy. Superchargers, while still driven by thermal energy, are not directly subject to it. Superchargers harness hp (work) that was already converted from thermal to kinetic by the combustion / crank. . .this is why they don't increase thermal efficiency like turbos do. The same amount of waste heat is being tossed out. . .the efficiency gains come from a volumetric efficiencey coefficient of much greater %. A turbo doesn't need something else to provide the work input (hp to drive), but acts just like the internal combustion.engine and converts heat from the combustion to create its motion. Just like the motor converts heat from combustion into motion.
Whew i didn't mean for.that to be so.long
A supercharger doesn't increase.thermal efficiency like turbos do. In fact, the increase is about 1/2 that of a turbo. Turbos use heat directly to spin them. They're directly subject to tremendous amounts of raw thermal energy. Superchargers, while still driven by thermal energy, are not directly subject to it. Superchargers harness hp (work) that was already converted from thermal to kinetic by the combustion / crank. . .this is why they don't increase thermal efficiency like turbos do. The same amount of waste heat is being tossed out. . .the efficiency gains come from a volumetric efficiencey coefficient of much greater %. A turbo doesn't need something else to provide the work input (hp to drive), but acts just like the internal combustion.engine and converts heat from the combustion to create its motion. Just like the motor converts heat from combustion into motion.
Whew i didn't mean for.that to be so.long
Lead Driver
Joined: May 2011
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Likes: 443
Without thermal energy there would be absolutely no operation of the turbo whatsoever. If drive pressure was the sole propellant of a turbo. . . .a rear mounted turbo like the ones so popular in vettes/f bodies would never spool. . . .the volume between the turbo and the motor is too great and drive pressure is a fraction (very small one) of what it would be if the turbo was right next to the motor. Its not that air/exhaust passing through the turbo is doing nothing to move the turbo (in fact i never said it didnt)o. . .its that the turbo was specifically designed to harness some of the copious amounts of thermal energy leftover from combustion. THERMAL ENERGY IS THE ONLY ENERGY SOURCE AVAILABLE FOR THE TURBOS OPERATION. heat. The drive pressure is a physical biproduct of the heat converting to work. Without heat, there would be no function. Without heat, there would be no drive pressure. Because it converts heat into motion (just like the internal combustion engine) it increases the thermal efficiency of the motor. (Increases the amount of energy absorbed.from combustion)
A supercharger doesn't increase.thermal efficiency like turbos do. In fact, the increase is about 1/2 that of a turbo. Turbos use heat directly to spin them. They're directly subject to tremendous amounts of raw thermal energy. Superchargers, while still driven by thermal energy, are not directly subject to it. Superchargers harness hp (work) that was already converted from thermal to kinetic by the combustion / crank. . .this is why they don't increase thermal efficiency like turbos do. The same amount of waste heat is being tossed out. . .the efficiency gains come from a volumetric efficiencey coefficient of much greater %. A turbo doesn't need something else to provide the work input (hp to drive), but acts just like the internal combustion.engine and converts heat from the combustion to create its motion. Just like the motor converts heat from combustion into motion.
Whew i didn't mean for.that to be so.long
A supercharger doesn't increase.thermal efficiency like turbos do. In fact, the increase is about 1/2 that of a turbo. Turbos use heat directly to spin them. They're directly subject to tremendous amounts of raw thermal energy. Superchargers, while still driven by thermal energy, are not directly subject to it. Superchargers harness hp (work) that was already converted from thermal to kinetic by the combustion / crank. . .this is why they don't increase thermal efficiency like turbos do. The same amount of waste heat is being tossed out. . .the efficiency gains come from a volumetric efficiencey coefficient of much greater %. A turbo doesn't need something else to provide the work input (hp to drive), but acts just like the internal combustion.engine and converts heat from the combustion to create its motion. Just like the motor converts heat from combustion into motion.
Whew i didn't mean for.that to be so.long
Lead Driver
Joined: May 2011
Posts: 5,775
Likes: 443
Hm
"Lol" really?
I used gasser parts, gasser comparisons, and gasser terminology to clear up what makes diesel powered compression ignited motors more efficient than gas powered motors. Its not my fault you took it out of context and got insulted. I am not and have not, in this thread, tried to insult anyone.
I used gasser parts, gasser comparisons, and gasser terminology to clear up what makes diesel powered compression ignited motors more efficient than gas powered motors. Its not my fault you took it out of context and got insulted. I am not and have not, in this thread, tried to insult anyone.
FTE Leadership Emeritus
Joined: Jul 2002
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From: Long Island USA
I am at work, so I'm only going to go so far into this, but...
On a naturally aspirated engine, rev it to 2000RPM and try to put your hand over the exhaust pipe. You're telling me that there's no pressure when you do this?
I know that's not what you're saying, but it would certainly seem based on a previous comment you made, that exhaust pressure in a naturally-aspirated engine is at atmospheric pressure, ie delta of zero. But put a restriction in there, and pressure rises. Even a muffler does given enough RPM.
Comments in order:
1) Yes.
2) It might SEEM they are feeding on the exhaust heat. What is happening is the same principal used in air conditioners and refrigerators. Physical energy is used to create a pressure drop that lowers the temp of the coolant (exhaust gas).
So yes, the temperature of the exhaust is lower on a turbo'd engine compared to a naturally aspirated, given a similar HP/torque output. Or maybe even in terms of volume versus temp.
But did you factor in the heat output from the intercooler, AND under the hood? Or how much extra heat comes from the radiator because of the increased combustion pressures heating the cylinders?
3) Gas turbine - Wikipedia, the free encyclopedia
I've used this exact example as a reason why a turbo is NOT running on heat energy.
And, to be honest, it doesn't directly correlate to a turbo'd piston engine.
--
Again, a turbo'd engine who's power output is similar to a naturally aspirated engine most likely does have a lower exhaust temperature. Because of the pressure drop after the turbo. But the intake charge temp is much higher, necessitating an intercooler.
And I'm not completely sure, given the discussion so far, that anyone has taken the waste heat from the intercooler into account, nor the higher under-hood temps, nor anything else, except to say the exhaust is cooler.
Does a non-intercooled turbo engine produce similarly lower exhaust temps too?
And OK, I'll stipulate for the moment that the turbo'd engine is more thermally efficient in terms of raw BTUs emitted out the exhaust. But it's not using that heat as power to drive the turbo.
If anything, there's more going on in terms of smaller displacement meaning less overall friction in the engine because of smaller cylinders, less cylinders/less bearings, etc.
On a naturally aspirated engine, rev it to 2000RPM and try to put your hand over the exhaust pipe. You're telling me that there's no pressure when you do this?
I know that's not what you're saying, but it would certainly seem based on a previous comment you made, that exhaust pressure in a naturally-aspirated engine is at atmospheric pressure, ie delta of zero. But put a restriction in there, and pressure rises. Even a muffler does given enough RPM.
Thats how Turbo Chargers add Power - Super Chargers add power by the same manner, by forcing more air in (and having more fuel delivered).
What we are debating is that a Turbo engine is more thermally efficient.
Myself and '89F2urd (and some others) are contending that they are, and that for the most part Turbo's are driven off energy that in a N/A engine would be wasted in the form of exhaust heat.
So I will come back at you. How does a Gas Turbine engine work?
What we are debating is that a Turbo engine is more thermally efficient.
Myself and '89F2urd (and some others) are contending that they are, and that for the most part Turbo's are driven off energy that in a N/A engine would be wasted in the form of exhaust heat.
So I will come back at you. How does a Gas Turbine engine work?
1) Yes.
2) It might SEEM they are feeding on the exhaust heat. What is happening is the same principal used in air conditioners and refrigerators. Physical energy is used to create a pressure drop that lowers the temp of the coolant (exhaust gas).
So yes, the temperature of the exhaust is lower on a turbo'd engine compared to a naturally aspirated, given a similar HP/torque output. Or maybe even in terms of volume versus temp.
But did you factor in the heat output from the intercooler, AND under the hood? Or how much extra heat comes from the radiator because of the increased combustion pressures heating the cylinders?
3) Gas turbine - Wikipedia, the free encyclopedia
I've used this exact example as a reason why a turbo is NOT running on heat energy.
And, to be honest, it doesn't directly correlate to a turbo'd piston engine.
--
Again, a turbo'd engine who's power output is similar to a naturally aspirated engine most likely does have a lower exhaust temperature. Because of the pressure drop after the turbo. But the intake charge temp is much higher, necessitating an intercooler.
And I'm not completely sure, given the discussion so far, that anyone has taken the waste heat from the intercooler into account, nor the higher under-hood temps, nor anything else, except to say the exhaust is cooler.
Does a non-intercooled turbo engine produce similarly lower exhaust temps too?
And OK, I'll stipulate for the moment that the turbo'd engine is more thermally efficient in terms of raw BTUs emitted out the exhaust. But it's not using that heat as power to drive the turbo.
If anything, there's more going on in terms of smaller displacement meaning less overall friction in the engine because of smaller cylinders, less cylinders/less bearings, etc.