WGA Question

[4sfed]

Hey everyone.

My apologies if is answered somewhere, but a search didn't reveal it to me.

Can someone clarify/confirm how the WGA works?  I'm assuming that vacuum holds the WGA open and when vacuum drops low enough it allows the turbo to build boost that is routed to the engine.  If so, I'm assuming the higher the PSI rating, the faster the turbo starts building boost.  Obviously there's a point of diminishing returns....just wanting to make sure I understand the theory.

Also, what's the stock WGA rated at?  I see EPP's WGA rated at 7 psi and I'm wondering how this compares to stock.

Thanks in advance,
S

 

[ZSHO]

The stock pressure is 5 psi IIRC!  Z

Page 162 +
Good Info can be found here!  Z

https://drive.google.com/file/d/1VkJM9I721ybIDRvniEtIgKh-1zKZAS4F/view?usp=drivesdk

 

[ajpturbo]

Hey everyone.

My apologies if is answered somewhere, but a search didn't reveal it to me.

Can someone clarify/confirm how the WGA works?  I'm assuming that vacuum holds the WGA open and when vacuum drops low enough it allows the turbo to build boost that is routed to the engine.  If so, I'm assuming the higher the PSI rating, the faster the turbo starts building boost.  Obviously there's a point of diminishing returns....just wanting to make sure I understand the theory.

Also, what's the stock WGA rated at?  I see EPP's WGA rated at 7 psi and I'm wondering how this compares to stock.

Thanks in advance,
S

I think Z is correct at bout 4-5 psi...But I think you need some turbo boost control theory school.


Vacuum is NEVER part of this boost control system..On some of the newer ecoboosts it is.


Look at the line that comes from the charge pipe to the boost solenoid...It's always under pressure. The Wastegate is held shut by a spring in a canister with a diaphragm that pushes on the wastegate actuator arm. At 0% duty cycle all of the air in that hose goes through the solenoid, because it's an "normally open" type solenoid, and that pressure pushes on the diaphragm and spring in the canister and the gate opens and lowers boost.


Now if the wastegate duty is 100% the solenoid is acting as a bleed valve and releasing as much air possible, which is making less pressure available to push on that spring in the canister and the wastegate will remain closed which keeps boost higher.

 

[sm105k]

Hey everyone.

My apologies if is answered somewhere, but a search didn't reveal it to me.

Can someone clarify/confirm how the WGA works?  I'm assuming that vacuum holds the WGA open and when vacuum drops low enough it allows the turbo to build boost that is routed to the engine.  If so, I'm assuming the higher the PSI rating, the faster the turbo starts building boost.  Obviously there's a point of diminishing returns....just wanting to make sure I understand the theory.

Also, what's the stock WGA rated at?  I see EPP's WGA rated at 7 psi and I'm wondering how this compares to stock.

Thanks in advance,
S

I think Z is correct at bout 4-5 psi...But I think you need some turbo boost control theory school.


Vacuum is NEVER part of this boost control system..On some of the newer ecoboosts it is.


Look at the line that comes from the charge pipe to the boost solenoid...It's always under pressure. The Wastegate is held shut by a spring in a canister with a diaphragm that pushes on the wastegate actuator arm. At 0% duty cycle all of the air in that hose goes through the solenoid, because it's an "normally open" type solenoid, and that pressure pushes on the diaphragm and spring in the canister and the gate opens and lowers boost.


Now if the wastegate duty is 100% the solenoid is acting as a bleed valve and releasing as much air possible, which is making less pressure available to push on that spring in the canister and the wastegate will remain closed which keeps boost higher.

I was watching that on my datalogs and have it real time on my Livewire.  So basically the higher percentage the more the gate is open and bleeding boost correct?

 

[ajpturbo]

Hey everyone.

My apologies if is answered somewhere, but a search didn't reveal it to me.

Can someone clarify/confirm how the WGA works?  I'm assuming that vacuum holds the WGA open and when vacuum drops low enough it allows the turbo to build boost that is routed to the engine.  If so, I'm assuming the higher the PSI rating, the faster the turbo starts building boost.  Obviously there's a point of diminishing returns....just wanting to make sure I understand the theory.

Also, what's the stock WGA rated at?  I see EPP's WGA rated at 7 psi and I'm wondering how this compares to stock.

Thanks in advance,
S

I think Z is correct at bout 4-5 psi...But I think you need some turbo boost control theory school.


Vacuum is NEVER part of this boost control system..On some of the newer ecoboosts it is.


Look at the line that comes from the charge pipe to the boost solenoid...It's always under pressure. The Wastegate is held shut by a spring in a canister with a diaphragm that pushes on the wastegate actuator arm. At 0% duty cycle all of the air in that hose goes through the solenoid, because it's an "normally open" type solenoid, and that pressure pushes on the diaphragm and spring in the canister and the gate opens and lowers boost.


Now if the wastegate duty is 100% the solenoid is acting as a bleed valve and releasing as much air possible, which is making less pressure available to push on that spring in the canister and the wastegate will remain closed which keeps boost higher.

I was watching that on my datalogs and have it real time on my Livewire.  So basically the higher percentage the more the gate is open and bleeding boost correct?

No......The higher the percentage the more air the boost solenoid is bleeding off which means there will be less pressure acting on the wastegate actuator arm which means the wastegate is staying closed more.....The wastegate doesn't bleed boost, it allows exhaust to bypass the turbine wheel.

 

[sm105k]

Thanks Brad, I get what you are saying.

 

[4sfed]

I think Z is correct at bout 4-5 psi...But I think you need some turbo boost control theory school.

Vacuum is NEVER part of this boost control system..On some of the newer ecoboosts it is.

Look at the line that comes from the charge pipe to the boost solenoid...It's always under pressure. The Wastegate is held shut by a spring in a canister with a diaphragm that pushes on the wastegate actuator arm. At 0% duty cycle all of the air in that hose goes through the solenoid, because it's an "normally open" type solenoid, and that pressure pushes on the diaphragm and spring in the canister and the gate opens and lowers boost.


Now if the wastegate duty is 100% the solenoid is acting as a bleed valve and releasing as much air possible, which is making less pressure available to push on that spring in the canister and the wastegate will remain closed which keeps boost higher.

Okay....so this question came from an assumption that the external wastegate controlled max boost, and the internal wastegate controlled when the boost comes on.  My assumption was that the internal wastegate was open until the throttle was pressed far enough to allow the internal wastegate to close, closing the bypass.

 

[4sfed]

Okay....so this question came from an assumption that the external wastegate controlled max boost, and the internal wastegate controlled when the boost comes on.  My assumption was that the internal wastegate was open until the throttle was pressed far enough to allow the internal wastegate to close, closing the bypass.

So...are the wastegates always open until a demand for boost is made?  If not, how is the engine not under constant boost?

Just trying to get my head around how this works.  I understand the basic idea of forcing air in the engine, just not familiar with how the wastegate systems actually work (other than obviously releasing pressure).

 

[geophb]

-Wastegate is on the turbine side and is held closed by a spring until boost over comes spring pressure. Once boost reaches that pressure it bypasses the turbine, thus limiting boost. IN THEORY if you have a 5# wastegate spring, the max boost you can make is 5#.

-BOV just dump boost when throttle blade is closed so it doesnt backfeed the compressor and try to spin it backwards (surge).

-Wastegate spring wont affect spool time. Since Wastgate is always closed until boost hits certain pressure. 

-Engine wont be under constant boost because there is not enough exhaust flow at low load/idle conditions to spin the turbine fast enough to make boost.  Example: Blowing on a toy pin wheel. Harder you blow the faster it spins. You can demand whatever you want but until you blow harder, it wont spin faster.  ;D

I assumed Wastgate percetage PID meant that was how much the wasgate was open, but it means the opposite?

 

[ajpturbo]

Wastegate duty cycle % is the duty cycle of the solenoid

 

[geophb]

Wastegate duty cycle % is the duty cycle of the solenoid

Soooo, if wastegate duty cycle stayed at 100% all the time the wastgate will never see boost? Similar to not even having it hooked up, and will never open?

 

[ajpturbo]

Wastegate duty cycle % is the duty cycle of the solenoid

Soooo, if wastegate duty cycle stayed at 100% all the time the wastgate will never see boost? Similar to not even having it hooked up, and will never open?

Well not entirely. If you don't have the vac line that comes out of the solenoid hooked up the wastegate will never open and you will over boost...It needs reference

 

[4sfed]

-Wastegate is on the turbine side and is held closed by a spring until boost over comes spring pressure. Once boost reaches that pressure it bypasses the turbine, thus limiting boost. IN THEORY if you have a 5# wastegate spring, the max boost you can make is 5#.

Okay, I'm with you on everything you said except the 5# thing.  It sounds like our WGA is 5-ish #'s stock.  How can we make 9# or 14#, if the WGA opens at 5#?

 

[geophb]

-Wastegate is on the turbine side and is held closed by a spring until boost over comes spring pressure. Once boost reaches that pressure it bypasses the turbine, thus limiting boost. IN THEORY if you have a 5# wastegate spring, the max boost you can make is 5#.

Okay, I'm with you on everything you said except the 5# thing.  It sounds like our WGA is 5-ish #'s stock.  How can we make 9# or 14#, if the WGA opens at 5#?

The boost solenoid bleeds boost off the line to the wastegate. So rough example: if your making 10psi and the solenoid is bleeding 5 psi off the pressure line to the wastegate then the wastgate is only seeing 5 psi, and starting to open (with a 5psi spring)

 

[4sfed]

The boost solenoid bleeds boost off the line to the wastegate. So rough example: if your making 10psi and the solenoid is bleeding 5 psi off the pressure line to the wastegate then the wastgate is only seeing 5 psi, and starting to open (with a 5psi spring)

Ah!  Okay...thank you.  That helps.

ALSO, I was confusing an external wastegate with the BOV.  I now realize they are not the same thing.

Thanks for your explanations and patience everyone.  We now return you to your regularly scheduled program.