exhaust pressure versus boost pressure
Well, some really intelligent discussion topics to tackle.
First, lets tackle internal gates.
There is one nipple to supply boost pressure. Thus, this is the only reference to our engine directly. It does not care what the exhaust pressure is. A 7psi actuator will respond only when the pressure above the diaphragm is about 7psi above it's atmospheric pressure reference (it does not have a line leading to the exhaust system to reference exhaust pressure, thus it does not care) it will open. Technically, exhaust gas does apply a force to the flapper valve, as all molecules do even at atmospheric pressure they are applying a force to all matter around you. But the design/shape is such that this force is insignificant and it does not affect operation when the application is correct. If you have a 7psi wastegate spring, you will see 7psi on the boost gauge when it opens. If the exhaust gas pressure begins to increase, the boost gauge in your car will still say 7psi because the actuator/flapper is strong enough in this 7psi situation, there is no 1:1 or 1:2 correlation of spring vs. exhaust. If we could manually reduce the diameter of the exhaust manifold's plumbing to raise exhaust manifold pressure significantly, the boost gauge will still read 7psi in your car. The boost gauge does not care about the pressure in the exhaust, because it references the atmospheric pressure, just like the external gate does. The gate itself works in this situation because of it's design.
Externals gates also have a boost reference for a diaphragm, except that they posses an additional nipple, one on each side of the diaphragm, so the owner can choose what to reference, if not atmospheric. You could technically reference exhaust gas pressure if you wanted, they make a kit for that. But most do not, ahem, care to do that. Referencing the engine's boost pressure with respect to atmospheric is how it also opens if you leave the top nipple open.
Because a spring is involved, there is a non linear relationship with respect to the spring and its action holding shut the wastegate as you deviate from the manufacturer's tested/guaranteed performance (their disclaimer about the pressure on both sides being equal). The wastegate still doesn't care about the exhaust gas pressure in these situations because it is still technically only referencing boost pressure and atmospheric (or boost controller pressure, which is your own personal setting that is being reference, or "cared about"). The spring, on the other hand, is a non-linear expression of force which will vary from gate to gate, spring to spring, instance to instance (consider smaller openings will have less exhaust pressure driven force), and must be accounted for as an inherent property of having a a spring within the mechanism itself. Usually the action of a boost controller near the limit of the springs designated range is where this issue crops up; the owner is operating the spring outside of it's tested range and it is behaving inconsistent. In other words, if your desired boost and spring setting are not closely matched there will be a problem with wastegate duty cycle trying to achieve a desired boost, for the same reason that exhaust pressure influences wastegate opening: the design of the spring and it's dynamic range. The WG does not care because it still references boost/atmospheric and does this regardless of what spring we install. The spring is "extra help" to make sure it mostly stays tightly shut during closed operation settings, and If your spring is giving you trouble you change the spring because you care about the the behavior enough to do so, the wastegate is not the spring, it is the idea that pressure going against a reference (atmospheric) opens a valve somewhere, the spring comes out and changes as an feature of adjustment, whereas the wastegate is always just the wastegate.
In the real world, we rarely have any clue what our exhaust pressure is, and if we need more boost pressure we turn the **** until the spring is no longer behaving consistent, and then get a badder spring. A well plumbed/designed turbocharger setup is said to have 10 psi more pressure in the intake manifold as the exhaust manifold. Does that mean that it requires ten less psi of boost pressure to keep it closed? woudn't it overboost on everybody's setup exactly 1psi for every 1psi less of exhaust gas pressure than intake manifold pressure? You would never be able to buy a gate with a specific set psi because every setup generates different exhaust gas pressures. The reason they are somewhat consistent across the board on everybody's setup is because of the design of the spring, which accounts for this variability. Anytime anybody changed their turbine it would change the boost setting of their wastegate- and it does in theory, but not dramatically in a 1:1 fashion, it depends on the gate/spring/design.
First, lets tackle internal gates.
There is one nipple to supply boost pressure. Thus, this is the only reference to our engine directly. It does not care what the exhaust pressure is. A 7psi actuator will respond only when the pressure above the diaphragm is about 7psi above it's atmospheric pressure reference (it does not have a line leading to the exhaust system to reference exhaust pressure, thus it does not care) it will open. Technically, exhaust gas does apply a force to the flapper valve, as all molecules do even at atmospheric pressure they are applying a force to all matter around you. But the design/shape is such that this force is insignificant and it does not affect operation when the application is correct. If you have a 7psi wastegate spring, you will see 7psi on the boost gauge when it opens. If the exhaust gas pressure begins to increase, the boost gauge in your car will still say 7psi because the actuator/flapper is strong enough in this 7psi situation, there is no 1:1 or 1:2 correlation of spring vs. exhaust. If we could manually reduce the diameter of the exhaust manifold's plumbing to raise exhaust manifold pressure significantly, the boost gauge will still read 7psi in your car. The boost gauge does not care about the pressure in the exhaust, because it references the atmospheric pressure, just like the external gate does. The gate itself works in this situation because of it's design.
Externals gates also have a boost reference for a diaphragm, except that they posses an additional nipple, one on each side of the diaphragm, so the owner can choose what to reference, if not atmospheric. You could technically reference exhaust gas pressure if you wanted, they make a kit for that. But most do not, ahem, care to do that. Referencing the engine's boost pressure with respect to atmospheric is how it also opens if you leave the top nipple open.
Because a spring is involved, there is a non linear relationship with respect to the spring and its action holding shut the wastegate as you deviate from the manufacturer's tested/guaranteed performance (their disclaimer about the pressure on both sides being equal). The wastegate still doesn't care about the exhaust gas pressure in these situations because it is still technically only referencing boost pressure and atmospheric (or boost controller pressure, which is your own personal setting that is being reference, or "cared about"). The spring, on the other hand, is a non-linear expression of force which will vary from gate to gate, spring to spring, instance to instance (consider smaller openings will have less exhaust pressure driven force), and must be accounted for as an inherent property of having a a spring within the mechanism itself. Usually the action of a boost controller near the limit of the springs designated range is where this issue crops up; the owner is operating the spring outside of it's tested range and it is behaving inconsistent. In other words, if your desired boost and spring setting are not closely matched there will be a problem with wastegate duty cycle trying to achieve a desired boost, for the same reason that exhaust pressure influences wastegate opening: the design of the spring and it's dynamic range. The WG does not care because it still references boost/atmospheric and does this regardless of what spring we install. The spring is "extra help" to make sure it mostly stays tightly shut during closed operation settings, and If your spring is giving you trouble you change the spring because you care about the the behavior enough to do so, the wastegate is not the spring, it is the idea that pressure going against a reference (atmospheric) opens a valve somewhere, the spring comes out and changes as an feature of adjustment, whereas the wastegate is always just the wastegate.
In the real world, we rarely have any clue what our exhaust pressure is, and if we need more boost pressure we turn the **** until the spring is no longer behaving consistent, and then get a badder spring. A well plumbed/designed turbocharger setup is said to have 10 psi more pressure in the intake manifold as the exhaust manifold. Does that mean that it requires ten less psi of boost pressure to keep it closed? woudn't it overboost on everybody's setup exactly 1psi for every 1psi less of exhaust gas pressure than intake manifold pressure? You would never be able to buy a gate with a specific set psi because every setup generates different exhaust gas pressures. The reason they are somewhat consistent across the board on everybody's setup is because of the design of the spring, which accounts for this variability. Anytime anybody changed their turbine it would change the boost setting of their wastegate- and it does in theory, but not dramatically in a 1:1 fashion, it depends on the gate/spring/design.
Last edited by kingtal0n; Dec 6, 2015 at 02:04 AM.
9 Second Club
Joined: Nov 2003
Posts: 13,616
Likes: 185
From: Norn Iron
Most internal gate cans have only 1 pipe...not all though. You can get them with attachments on both sides so you can blow open or closed.
And the original question is a little vague, and answer would be better answered with pictures and/or google no doubt lol
But as there are so many ways to configure boost control, there is no single answer one way or another unless he knows what way he wants to configure his system, for which he needs to know what sort of outcome he is expecting, which depends on the application, which depends on motor/turbos etc blah blah blah.
Well, some really intelligent discussion topics to tackle.
First, lets tackle internal gates.
There is one nipple to supply boost pressure. Thus, this is the only reference to our engine directly. It does not care what the exhaust pressure is. A 7psi actuator will respond only when the pressure above the diaphragm is about 7psi above it's atmospheric pressure reference (it does not have a line leading to the exhaust system to reference exhaust pressure, thus it does not care) it will open. Technically, exhaust gas does apply a force to the flapper valve, as all molecules do even at atmospheric pressure they are applying a force to all matter around you. But the design/shape is such that this force is insignificant and it does not affect operation when the application is correct. If you have a 7psi wastegate spring, you will see 7psi on the boost gauge when it opens. If the exhaust gas pressure begins to increase, the boost gauge in your car will still say 7psi because the actuator/flapper is strong enough in this 7psi situation, there is no 1:1 or 1:2 correlation of spring vs. exhaust. If we could manually reduce the diameter of the exhaust manifold's plumbing to raise exhaust manifold pressure significantly, the boost gauge will still read 7psi in your car. The boost gauge does not care about the pressure in the exhaust, because it references the atmospheric pressure, just like the external gate does. The gate itself works in this situation because of it's design.
Externals gates also have a boost reference for a diaphragm, except that they posses an additional nipple, one on each side of the diaphragm, so the owner can choose what to reference, if not atmospheric. You could technically reference exhaust gas pressure if you wanted, they make a kit for that. But most do not, ahem, care to do that. Referencing the engine's boost pressure with respect to atmospheric is how it also opens if you leave the top nipple open.
Because a spring is involved, there is a non linear relationship with respect to the spring and its action holding shut the wastegate as you deviate from the manufacturer's tested/guaranteed performance (their disclaimer about the pressure on both sides being equal). The wastegate still doesn't care about the exhaust gas pressure in these situations because it is still technically only referencing boost pressure and atmospheric (or boost controller pressure, which is your own personal setting that is being reference, or "cared about"). The spring, on the other hand, is a non-linear expression of force which will vary from gate to gate, spring to spring, instance to instance (consider smaller openings will have less exhaust pressure driven force), and must be accounted for as an inherent property of having a a spring within the mechanism itself. Usually the action of a boost controller near the limit of the springs designated range is where this issue crops up; the owner is operating the spring outside of it's tested range and it is behaving inconsistent. In other words, if your desired boost and spring setting are not closely matched there will be a problem with wastegate duty cycle trying to achieve a desired boost, for the same reason that exhaust pressure influences wastegate opening: the design of the spring and it's dynamic range. The WG does not care because it still references boost/atmospheric and does this regardless of what spring we install. The spring is "extra help" to make sure it mostly stays tightly shut during closed operation settings, and If your spring is giving you trouble you change the spring because you care about the the behavior enough to do so, the wastegate is not the spring, it is the idea that pressure going against a reference (atmospheric) opens a valve somewhere, the spring comes out and changes as an feature of adjustment, whereas the wastegate is always just the wastegate.
In the real world, we rarely have any clue what our exhaust pressure is, and if we need more boost pressure we turn the **** until the spring is no longer behaving consistent, and then get a badder spring. A well plumbed/designed turbocharger setup is said to have 10 psi more pressure in the intake manifold as the exhaust manifold. Does that mean that it requires ten less psi of boost pressure to keep it closed? woudn't it overboost on everybody's setup exactly 1psi for every 1psi less of exhaust gas pressure than intake manifold pressure? You would never be able to buy a gate with a specific set psi because every setup generates different exhaust gas pressures. The reason they are somewhat consistent across the board on everybody's setup is because of the design of the spring, which accounts for this variability. Anytime anybody changed their turbine it would change the boost setting of their wastegate- and it does in theory, but not dramatically in a 1:1 fashion, it depends on the gate/spring/design.
First, lets tackle internal gates.
There is one nipple to supply boost pressure. Thus, this is the only reference to our engine directly. It does not care what the exhaust pressure is. A 7psi actuator will respond only when the pressure above the diaphragm is about 7psi above it's atmospheric pressure reference (it does not have a line leading to the exhaust system to reference exhaust pressure, thus it does not care) it will open. Technically, exhaust gas does apply a force to the flapper valve, as all molecules do even at atmospheric pressure they are applying a force to all matter around you. But the design/shape is such that this force is insignificant and it does not affect operation when the application is correct. If you have a 7psi wastegate spring, you will see 7psi on the boost gauge when it opens. If the exhaust gas pressure begins to increase, the boost gauge in your car will still say 7psi because the actuator/flapper is strong enough in this 7psi situation, there is no 1:1 or 1:2 correlation of spring vs. exhaust. If we could manually reduce the diameter of the exhaust manifold's plumbing to raise exhaust manifold pressure significantly, the boost gauge will still read 7psi in your car. The boost gauge does not care about the pressure in the exhaust, because it references the atmospheric pressure, just like the external gate does. The gate itself works in this situation because of it's design.
Externals gates also have a boost reference for a diaphragm, except that they posses an additional nipple, one on each side of the diaphragm, so the owner can choose what to reference, if not atmospheric. You could technically reference exhaust gas pressure if you wanted, they make a kit for that. But most do not, ahem, care to do that. Referencing the engine's boost pressure with respect to atmospheric is how it also opens if you leave the top nipple open.
Because a spring is involved, there is a non linear relationship with respect to the spring and its action holding shut the wastegate as you deviate from the manufacturer's tested/guaranteed performance (their disclaimer about the pressure on both sides being equal). The wastegate still doesn't care about the exhaust gas pressure in these situations because it is still technically only referencing boost pressure and atmospheric (or boost controller pressure, which is your own personal setting that is being reference, or "cared about"). The spring, on the other hand, is a non-linear expression of force which will vary from gate to gate, spring to spring, instance to instance (consider smaller openings will have less exhaust pressure driven force), and must be accounted for as an inherent property of having a a spring within the mechanism itself. Usually the action of a boost controller near the limit of the springs designated range is where this issue crops up; the owner is operating the spring outside of it's tested range and it is behaving inconsistent. In other words, if your desired boost and spring setting are not closely matched there will be a problem with wastegate duty cycle trying to achieve a desired boost, for the same reason that exhaust pressure influences wastegate opening: the design of the spring and it's dynamic range. The WG does not care because it still references boost/atmospheric and does this regardless of what spring we install. The spring is "extra help" to make sure it mostly stays tightly shut during closed operation settings, and If your spring is giving you trouble you change the spring because you care about the the behavior enough to do so, the wastegate is not the spring, it is the idea that pressure going against a reference (atmospheric) opens a valve somewhere, the spring comes out and changes as an feature of adjustment, whereas the wastegate is always just the wastegate.
In the real world, we rarely have any clue what our exhaust pressure is, and if we need more boost pressure we turn the **** until the spring is no longer behaving consistent, and then get a badder spring. A well plumbed/designed turbocharger setup is said to have 10 psi more pressure in the intake manifold as the exhaust manifold. Does that mean that it requires ten less psi of boost pressure to keep it closed? woudn't it overboost on everybody's setup exactly 1psi for every 1psi less of exhaust gas pressure than intake manifold pressure? You would never be able to buy a gate with a specific set psi because every setup generates different exhaust gas pressures. The reason they are somewhat consistent across the board on everybody's setup is because of the design of the spring, which accounts for this variability. Anytime anybody changed their turbine it would change the boost setting of their wastegate- and it does in theory, but not dramatically in a 1:1 fashion, it depends on the gate/spring/design.
WG do not reference exhaust pressure. Just because the spring is affected by exhaust pressure on a particular design doesn't mean that the WG is referencing exhaust pressure, nor does it mean that all wastegates are affected by the pressure equally. The amount of influence exhaust pressure has on the spring varies from gate to gate, spring to spring, since the amount of surface area presented to the exhaust changes as gate size changes, the amount of force applied by the same exhaust gas pressure will also change.
Is that simple and short enough to read? You might try being a little less rude.
If not then here is an even simpler one.
If I have 100 wastegates, all of them set to 7psi, and I sell them to 100 different customers with 100 different engines, 99 of them will open at 7psi, and 0 of them will have identical exhaust gas pressures. The gates I sold do not care what the customers exhaust gas pressure are, I sold them a 7psi gate they got a 7psi gate /thread
Here Ill say it another way:
As engine RPM increases, and power increases, exhaust gas pressure also increases until the gate opens. If this changed the way the wastegate referenced (or controlled) boost pressure, then boost would decrease as engine rpm increased in a linear fashion.
Last edited by kingtal0n; Dec 6, 2015 at 11:11 AM.
Changing Names
Joined: Feb 2013
Posts: 236
Likes: 1
Can sombody please inform this person that if you "disconnected all lines going to the wg" that it would ruin the engine? I think he is just a troll trying to ruin somebodys engine. I can see only one situation where exhaust pressure drives open the gate without a reference and such a scenario would be uncontrolled, undesirable, and has zero application in the real world. I would also hardly call that "operation" since the word entails a certain amount of control. A WG without any lines (no reference to anything) would be highly uncontrolled, it would not be operating, it would be unpredictable and ruin the engine.
WG do not reference exhaust pressure. Just because the spring is affected by exhaust pressure on a particular design doesn't mean that the WG is referencing exhaust pressure, nor does it mean that all wastegates are affected by the pressure equally. The amount of influence exhaust pressure has on the spring varies from gate to gate, spring to spring, since the amount of surface area presented to the exhaust changes as gate size changes, the amount of force applied by the same exhaust gas pressure will also change.
Is that simple and short enough to read? You might try being a little less rude.
If not then here is an even simpler one.
If I have 100 wastegates, all of them set to 7psi, and I sell them to 100 different customers with 100 different engines, 99 of them will open at 7psi, and 0 of them will have identical exhaust gas pressures. The gates I sold do not care what the customers exhaust gas pressure are, I sold them a 7psi gate they got a 7psi gate /thread
Here Ill say it another way:
As engine RPM increases, and power increases, exhaust gas pressure also increases until the gate opens. If this changed the way the wastegate referenced (or controlled) boost pressure, then boost would decrease as engine rpm increased in a linear fashion.
WG do not reference exhaust pressure. Just because the spring is affected by exhaust pressure on a particular design doesn't mean that the WG is referencing exhaust pressure, nor does it mean that all wastegates are affected by the pressure equally. The amount of influence exhaust pressure has on the spring varies from gate to gate, spring to spring, since the amount of surface area presented to the exhaust changes as gate size changes, the amount of force applied by the same exhaust gas pressure will also change.
Is that simple and short enough to read? You might try being a little less rude.
If not then here is an even simpler one.
If I have 100 wastegates, all of them set to 7psi, and I sell them to 100 different customers with 100 different engines, 99 of them will open at 7psi, and 0 of them will have identical exhaust gas pressures. The gates I sold do not care what the customers exhaust gas pressure are, I sold them a 7psi gate they got a 7psi gate /thread
Here Ill say it another way:
As engine RPM increases, and power increases, exhaust gas pressure also increases until the gate opens. If this changed the way the wastegate referenced (or controlled) boost pressure, then boost would decrease as engine rpm increased in a linear fashion.
A gate will open without reference
And a whole new post because I care so much troll.
My initial post literally says "technically" because of the rare instances where exhaust pressure gets out of control (why is it so high to begin with?) and over-rides the spring setting. When we initially buy the wastegate, most of us do not know how much exhaust pressure the engine is going to produce, and so this never factors into the question. If we need a 15psi gate we buy a 15psi gate, not a 30psi gate. We can always change the spring or turn the ****. Thus, we do not care what the exhaust gas pressure is. Our wastegates "cares" about nothing because it is just a mechanical device, so it was wrong of me to reference this piece of machinery as if it could actually "care or not" which lead to holes for argument (anybody could argue when you say if something cares) so I will be more careful not to claim that parts can "care" in the future to prevent this situation.
My initial post literally says "technically" because of the rare instances where exhaust pressure gets out of control (why is it so high to begin with?) and over-rides the spring setting. When we initially buy the wastegate, most of us do not know how much exhaust pressure the engine is going to produce, and so this never factors into the question. If we need a 15psi gate we buy a 15psi gate, not a 30psi gate. We can always change the spring or turn the ****. Thus, we do not care what the exhaust gas pressure is. Our wastegates "cares" about nothing because it is just a mechanical device, so it was wrong of me to reference this piece of machinery as if it could actually "care or not" which lead to holes for argument (anybody could argue when you say if something cares) so I will be more careful not to claim that parts can "care" in the future to prevent this situation.
So sad
You don't have a clue with any yours posts and are misleading people who actually want to learn
First you make the case an IAT sensor is pointless
Now telling exhaust pressure has nothing at all to do with WG operation.
Little less posting.... Little more reading
You don't have a clue with any yours posts and are misleading people who actually want to learn
First you make the case an IAT sensor is pointless
Now telling exhaust pressure has nothing at all to do with WG operation.
Little less posting.... Little more reading
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Verdad Gallardo This is exactly what I have been saying! It will open due to exhaust pressure- yes, but not because it is referencing exhaust pressure! Exactly my point! If the gate has NO REFERENCE, then EXHAUST PRESSURE is not a reference.
lol. technicality that made me be politically correct. You think you are getting me on a technical issue but it is I who is standing behind the real technical issue through engineering perspective. I am not experienced with the design of wastegates, I will not hide this fact and have made no attempt to do so.
So sad
You don't have a clue with any yours posts and are misleading people who actually want to learn
First you make the case an IAT sensor is pointless
Now telling exhaust pressure has nothing at all to do with WG operation.
Little less posting.... Little more reading
You don't have a clue with any yours posts and are misleading people who actually want to learn
First you make the case an IAT sensor is pointless
Now telling exhaust pressure has nothing at all to do with WG operation.
Little less posting.... Little more reading
I think my post count is low enough I qualify to make a few. Now I am seriously starting to doubt your ability to do simple math.
Just dont think you can swing at me without getting hit back. You can keep it friendly or we can play games.
Last edited by kingtal0n; Dec 6, 2015 at 11:32 AM.
Seriously are you that dense? What do you think the spring in the WG is opposing? Unicorns?
The WG is directly referenced to exhaust pressure /story
Let's dumb it down a bit for you.
Please explain this?? According to you exhaust pressure means nothing. I can't wait to see this response
The WG is directly referenced to exhaust pressure /story
Let's dumb it down a bit for you.
Please explain this?? According to you exhaust pressure means nothing. I can't wait to see this response
Take a gate setup with a 4lb rated spring.... Unhook all reference to the diaphragm.
It will operate strictly on reference to exhaust pressure and the spring.
Instead of 4psi. It is going to be running in the ballpark of 8psi boost, but functioning still the same only trying to hold a set exhaust pressure
It will operate strictly on reference to exhaust pressure and the spring.
Instead of 4psi. It is going to be running in the ballpark of 8psi boost, but functioning still the same only trying to hold a set exhaust pressure
show me one place that I said exhaust pressure means nothing. I have been speaking about it since the first post as it influences operation, my entire position hinges on the fact that this is not a factor when we purchase gates. The OP was new to turbos and was asking about exhaust pressure. My knee-jerk instinctual answer was for him not to worry about exhaust pressure (not to care about it. Not to worry that the wastegate might care about it), because we do not know or care about exhaust pressure, and it would take quite the rare situation he is very unlikely to encounter as a novice to turbos in which the wastegate would care about exhaust gas pressure. Thus, the use of the word technically in my sentance, to cover these rare instances.
Conversely, when I said what I said earlier, I meant it: if you have a 5psi spring, the wastegate opens at 5psi, even if the engine is off and there is no exhaust pressure. It also opens at 5psi if the engine is on, and there are several extra psi of exhaust pressure. It doesnt care if there is any exhaust or not. You can operate a wastegate with it in your hands.
Ok let's take this cherry of yours. And break it down so maybe possible you will follow
What you posted is absolutely incorrect
Please explain
"I am brand new to turbos" is all I need to see. If you are brand new to turbos, you do not care about what your exhaust pressure is, and your wastegate does not care either.
Edit (Dec.11) I think it important to realize the play on words here. Do not let this slip by: the wastegate is a mechanical part, and incapable of emotion. The wastegate cannot "Care" about anything.
Edit (Dec.11) I think it important to realize the play on words here. Do not let this slip by: the wastegate is a mechanical part, and incapable of emotion. The wastegate cannot "Care" about anything.
Last edited by kingtal0n; Dec 11, 2015 at 12:42 AM.
In the case of external gates, which have more surface area presented to the exhaust system, pressure in the exhaust system will exert more force on the valve. The manufacturer knows all about this, and they have designed the wastegate such that pressure from above is different than pressure from below. In other words, I believe that the underside of the diaphragm of an external gate is sized larger than the surface area of the valve which is exposed to the exhaust gas- such that pressure below the diaphragm has a larger effect towards opening the valve than pressure from exhaust gas. Larger surface areas mean larger forces are applied, so the manufacturer configures the gate to supply a consistent operation under a wide range of pressure differentials. For example a 15psi wastegate will open at 15psi when the exhaust gas pressure is 13psi or 17psi. The 4psi difference of exhaust pressure will not add or subtract 4psi from the intake manifold, because the exhaust gas pressure is not a reference for the gate through which it settles on a desired boost setting. The atmosphere is a reference, with which the gate compares the manifold pressure and decides when to open.
A gate will open without a reference. You can disconnect the actuator arm and have it swing wildly. What a great example. In that case, is exhaust gas acting as a reference? Technically the gate is referencing exhaust gas pressure, sampling it at high rate, and adjusting accordingly. In the same way it is also referencing gravity, intertia, these insignificant forces begin to play a role in the operation of devices when there are no other forces large enough to "take the reigns". So technically everything is a reference: air pressure, air temperature, air density, exhaust pressure, exhaust temperature, air speed, acoustic pressure waves, these references change the properties of the materials, and/or influence their movements in the case of the disconnected wastegate flapper. Under normal operating circumstances, as when the gate is properly installed and operating, these minor influences are not references for operation unless they get out of hand, thus the disclaimer on the ad. It could just as easily say "only where gravity is 9.8m/s^2"
Last edited by kingtal0n; Dec 6, 2015 at 12:12 PM.
. For example a 15psi wastegate will open at 15psi when the exhaust gas pressure is 13psi or 17psi. The 4psi difference of exhaust pressure will not add or subtract 4psi from the intake manifold, because the exhaust gas pressure is not a reference for the gate through which it settles on a desired boost setting.
/story
If this was the case.... There would be no reason for this note lol
A 15lb spring would make 15psi boost no matter if running at 3:1 or 1:1 drive pressure: boost if this was the case..... And it absolutely is wrong
Okay, prove it. Show me intake manifold vs exhaust pressure vs wastegate operation data in a 15psi application and you can have it. Otherwise... I am fairly certain that if manufactuers couldn't guarantee you a pressure setting, within reason, well it would be much more difficult to purchase the right gate. Because everybodys exhaust pressure changes as engine rpm changes, and everybodys engines are different. a 15psi gate works on a 4-cylinder application the same as a V8 application, and you cant tell me that they have identical exhaust pressures.
You seem to think that extreme high power instances qualify as "novice to turbochargers" relevant. The topic is about novice situations. Novices do not care about their exhaust gas pressure. Novices buy a 15psi gate and it references atmospheric pressure and opens at 15psi.
You seem to think that extreme high power instances qualify as "novice to turbochargers" relevant. The topic is about novice situations. Novices do not care about their exhaust gas pressure. Novices buy a 15psi gate and it references atmospheric pressure and opens at 15psi.