the boost going to the bottom of the gate lets the spring do its job if the top port is open to atmosphere and you give a boost reference to the bottom you will make spring pressure. if you restrict the pressure to the bottom with the top open to atmosphere you will increase boost.
we can control the pressure to the wastegate so a wga with a weaker spring can still hold boost to redline because we are controlling the pwm of the solenoid.
for more precise control you use presure to the top of the gate against the pressure in the bottom of the gate to make more boost. if you wanted to make more boost pressure you would need c02 to the top of the gate to take control.backpressure in the exhaust will limit the wastegate so depending on how much backpressure is in the manifold it will limit the total pressure seen in the intake as it will overcome the pressure in the top of the gate
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No boost applied to the bottom of the gate and no boost applied to the top of the gate--> spring pressure holding it closed
Full boost applied to the bottom of the gate and the top of the gate --> spring pressure holding it closed
I get that part.
But....
First off, I trust you guys, 'cause I know your products are awesome, not trying to piss you off, just want to learn something here!
So back to the but
Full boost top and bottom is still going to be "better" for the spring than boost on the bottom and less than boost at the top...
That's my thinking.
the boost going to the bottom of the gate lets the spring do its job if the top port is open to atmosphere and you give a boost reference to the bottom you will make spring pressure. if you restrict the pressure to the bottom with the top open to atmosphere you will increase boost.
we can control the pressure to the wastegate so a wga with a weaker spring can still hold boost to redline because we are controlling the pwm of the solenoid.
for more precise control you use presure to the top of the gate against the pressure in the bottom of the gate to make more boost. if you wanted to make more boost pressure you would need c02 to the top of the gate to take control.backpressure in the exhaust will limit the wastegate so depending on how much backpressure is in the manifold it will limit the total pressure seen in the intake as it will overcome the pressure in the top of the gate
First off, I trust you guys, 'cause I know your products are awesome, not trying to piss you off, just want to learn something here!
So back to the but
Full boost top and bottom is still going to be "better" for the spring than boost on the bottom and less than boost at the top...
That's my thinking.
No problem, we're trying to get to the bottom of all this too.
Yes, full boost top and bottom would be better than boost on the bottom and less boost on the top.
But, it would be the same as no boost on bottom and no boost on top.
I think you are missing that if the solenoid is completely closed, you will have 0 boost at the bottom of the gate and 0 boost at the top of the gate. That is the same as full boost on top and full boost on bottom.
Can someone answer my question on 25psi? Will the boost box be capable of 25psi on an externally wastegated turbo?
Yes, you can do 25 psi with the boost box as long as your wastegate can do that. It is the same as any other boost controller. It will depend on your wastegate, not the controller.
No problem, we're trying to get to the bottom of all this too.
Yes, full boost top and bottom would be better than boost on the bottom and less boost on the top.
But, it would be the same as no boost on bottom and no boost on top.
I think you are missing that if the solenoid is completely closed, you will have 0 boost at the bottom of the gate and 0 boost at the top of the gate. That is the same as full boost on top and full boost on bottom.
But when it's closed, the only thing holding the wastegate shut, is the spring.
So in other words, you can only hold 9psi.
I'm confused...
But when it's closed, the only thing holding the wastegate shut, is the spring.
So in other words, you can only hold 9psi.
I'm confused...
Yes, the only thing holding it shut is the spring, but you can hold a lot more than 9 psi with just the spring.
A "9 psi spring" means that it will open when 9 psi is applied to the bottom of the gate to push it open.
With nothing pushing it open, it will require a lot more pressure from the exhaust manifold to force it open. But, eventually it will open. The amount of pressure in the manifold that is required to open it depends on the surface area ratio. If it is a 3x smaller exhaust valve than diaphragm, then it will open at 27 psi of exhaust pressure.... 4x .... 36 psi..... 5x would be 45 psi...
Cool. We need to put up a thorough explanation of all this with cutaway pictures and 3-d models.
Now, there is one more vacuum hose configuration that we haven't really gone in depth about that might do better.
If you setup the hoses such that at 0% duty cycle you had:
full boost to the bottom of the gate and vent to atmosphere on the top
and then at 100% you had:
full boost to the top of the gate and vent to the atmosphere on the bottom
In theory, that configuration should allow you to hold much more boost than either of the two configurations we have been discussing. But, it requires a 4 port solenoid or two solenoids.
We will be getting one of those setups going and see what happens...
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