Just a question?
How do you introduce exhaust gas (EGR) into a turbo charged inlet manifold?
Internal pressure will be between 9 to 14 psi in the inlet manifold and the exhaust outlet pressure even before the turbine will be about equal(has to drive the blower)
So how does the exhaust gas get into the inlet manifold against a positive pressure?
The exhaust gas that goes back in doesn’t go through the turbo, it goes through the EGR valve into the EGR cooler and runs over the top of the engine into a Y pipe, meeting the cooled air from the intercooler just before it goes into the inlet manifold. The engine continually pushes EG through the EGR valve into the EGR cooler with each exhaust stroke, so eventually the pressure will be high enough to merge the EG with the fresh air. There’s a ton of sensors measuring and metering the EGR and opening or closing the EGR valve and varying the pitch on the turbine blades giving more, or less boost in the VGT so that one doesn’t overcome the other.
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Bking:
Just a question?
How do you introduce exhaust gas (EGR) into a turbo charged inlet manifold?
Internal pressure will be between 9 to 14 psi in the inlet manifold and the exhaust outlet pressure even before the turbine will be about equal(has to drive the blower)
So how does the exhaust gas get into the inlet manifold against a positive pressure?
Many truck will run closer to 2 bar boost pressure and some more than that.
What pressure is there in the exhaust manifold? Theres gonna be 2000psi in the cylinder on the power stroke? Maybe a tenth of that when the exhaust valve opens? Thats still 200 psi. And weve seen gases blowing past a tiny hole in a faulty head/manifold gasket so isnt that believable? So 200psi is about 12 bar. As the exhaust gases move into a long and widening system the pressures will drop but it`s still gonna be “substantial” enough.
Above is just “back of a ■■■ packet” stuff except for lifting the 2000psi from here: fuel trials on a 14ltre ■■■■■■■■ Peak pressure is about -ish- 14Megapascals or 2000 psi.
pdfs.semanticscholar.org/203f/b … 6cf8fc.pdf
Table on page 19.
I am of course open to correction on any of that!
Wow newmercman, that was so interesting I actually read both parts of the double post!
Well thank you, I’ve fixed it now, god knows what went on there, it took ages to submit the post and it didn’t show up when i checked the thread to see if it had gone through.
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newmercman:
The exhaust gas that goes back in doesn’t go through the turbo, it goes through the EGR valve into the EGR cooler and runs over the top of the engine into a Y pipe, meeting the cooled air from the intercooler just before it goes into the inlet manifold. The engine continually pushes EG through the EGR valve into the EGR cooler with each exhaust stroke, so eventually the pressure will be high enough to merge the EG with the fresh air. There’s a ton of sensors measuring and metering the EGR and opening or closing the EGR valve and varying the pitch on the turbine blades giving more, or less boost in the VGT so that one doesn’t overcome the other.Sent from my SM-G950W using Tapatalk
Still got to put exhaust gas into a pressurised inlet manifold .How does it overcome turbine pressure?
At no point do you ever get inlet manifold negative pressure or you would strangle the engine.And its no good being “eventually” high enough EGR is supposed to be “allways” there when needed.
The pitch of the blades never alters its the volute that changes by way of a variable cone to change the boost pressure.
Cannot figure out why they need a VG turbo any way when a pressure controlled waste gate is far more effective.
But there again its all about the money as usual.
When you give it the beans, the egr valve closes.
Eric Rambler:
When you give it the beans, the egr valve closes.
Is that on the Vauxhall Corsa?
Bking:
newmercman:
The exhaust gas that goes back in doesn’t go through the turbo, it goes through the EGR valve into the EGR cooler and runs over the top of the engine into a Y pipe, meeting the cooled air from the intercooler just before it goes into the inlet manifold. The engine continually pushes EG through the EGR valve into the EGR cooler with each exhaust stroke, so eventually the pressure will be high enough to merge the EG with the fresh air. There’s a ton of sensors measuring and metering the EGR and opening or closing the EGR valve and varying the pitch on the turbine blades giving more, or less boost in the VGT so that one doesn’t overcome the other.Sent from my SM-G950W using Tapatalk
Still got to put exhaust gas into a pressurised inlet manifold .How does it overcome turbine pressure?
At no point do you ever get inlet manifold negative pressure or you would strangle the engine.And its no good being “eventually” high enough EGR is supposed to be “allways” there when needed.
The pitch of the blades never alters its the volute that changes by way of a variable cone to change the boost pressure.
Cannot figure out why they need a VG turbo any way when a pressure controlled waste gate is far more effective.
But there again its all about the money as usual.
The inlet pressure (pressurised by the turbo) must always be less than that of the exhaust, upstream of the turbo.
The turbo surely can’t give more pressure than it receives can it?
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Yes it could, the hot and cold sides of the turbo have different sized turbines and housings, in simple terms they’re like the drive train on a push bike, a bigger turbine on the hot side and a smaller one on the cold side, the VGT is basically a Derailleur, as the pitch changes it increases or decreases pressure.
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newmercman:
Yes it could, the hot and cold sides of the turbo have different sized turbines and housings, in simple terms they’re like the drive train on a push bike, a bigger turbine on the hot side and a smaller one on the cold side, the VGT is basically a Derailleur, as the pitch changes it increases or decreases pressure.Sent from my SM-G950W using Tapatalk
Yep.
You’re right if course.
A turbo could compress a smaller volume of air to a higher pressure. And the exhaust from an engine really is always more than the air intake.
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Franglais:
newmercman:
Yes it could, the hot and cold sides of the turbo have different sized turbines and housings, in simple terms they’re like the drive train on a push bike, a bigger turbine on the hot side and a smaller one on the cold side, the VGT is basically a Derailleur, as the pitch changes it increases or decreases pressure.Sent from my SM-G950W using Tapatalk
Yep.
You’re right if course.
A turbo could compress a smaller volume of air to a higher pressure. And the exhaust from an engine really is always more than the air intake.
The exhaust gas speeds up as it flows through the turbine so its pressure falls, it gives up energy in driving the turbine. As explained above the advantage of a VGT over a wastegated unit is that changing the ‘effective size’ of the turbo to make best use of the exhaust volume is more thermally efficient than just dumping excess gas through a wastegate. An efficient VGT should ‘match’ the engine over a wider range of rpm/accelerator settings.