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External wastegate 2port vs single port

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I have tried searching the net but did not come up with a conclusive answer...

What is the exact difference between 2-port setup vs single (bottom) port setup on a external wastegate (using 3port max valve)?

Why are link/turbosmart refering to the 2port plumbing when net forces cancel eachother out?

Besides the obvious (Keeping dirt out of the top chamber)

Is there a difference in the bottom section leaking a small amount of air by the valve stem?

Hoping someone knowledgeable can enlighten me :)

Attached Files

Having the gate plumbed that way, the differential pressure across the diaphragm becomes that of the waste gate spring as you have Manifold pressure on the bottom of the diaphragm, and manifold pressure + spring rate on the top of the diaphragm. This should keep the valve well seated (unless the exhaust manifold pressure is high) until the boost control system starts to control the valve. The Boost control system also typically has less work to do as it is essentially only controlling the spring.

With manifold pressure only going to the bottom diaphragm, then you will have the gate starting to creep open once the pressure on the poppet valve exceeds the spring rate. This means that the maximum boost pressure that is achievable is that if the spring installed, and all that the boost control can do is assist in the opening of the gate to reduce pressure.

Thanks for ellaborating Stephen. Though it seems i have a lack of understanding this.

"Having the gate plumbed that way, the differential pressure across the diaphragm becomes that of the waste gate spring as you have Manifold pressure on the bottom of the diaphragm, and manifold pressure + spring rate on the top of the diaphragm. This should keep the valve well seated (unless the exhaust manifold pressure is high) until the boost control system starts to control the valve. The Boost control system also typically has less work to do as it is essentially only controlling the spring."

I understand that the differential pressure nets the spring pressure when full duty cycle. The same situation like bottom port setup if no duty cycle, unless i'm missing something? The poppet valve is rated to 120Psi / 827kPa so seems unlikely to me they go leaking?

For now, I can find myself in this explation:

https://gfb.com.au/tech/tech-articles/what-is-the-best-way-to-connect-a-3-port-solenoid-to-an-external-wastegate-bottom-port-only-or-both-ports/#:~:text=Using%20only%20the%20bottom%20port,the%20top%20of%20the%20diaphragm.

But it seems more likely i'm missing information / understanding

My purpose is not to start an argument I just like to get a torough understanding. Thanks :)

It doesn't have anything to do with the wastegate diaphragm leaking, it's because the valve itself is sitting in the exhaust manifold and like Stephen said, the manifold backpressure + boost on the bottom port can crack the wastegate open early and reduce the spool time. Connecting both ports help keeping the wastegate shut until the desired boost pressure is achieved.

I think the confusion may be from talking about 1 vs. 2 port EWG, but only showing a 2 port hose routing diagram.

When only using the lower gate port, you'd plumb the system differently so the pressure source goes into the boost solenoid, and some of that pressure can be diverted away from reaching the lower EWG port, allowing you to make boost great than the spring's rated pressure still, but this doesn't give you as much range to increase boost over spring pressure as 2 port EWG use does.

@Frank

How does connecting both ports (both pressurized) end up in a different situation then connecting only bottom port (not pressurized). That is the max boost (spool) setting for both. The remaining forces for both situations are spring force and backpressure?

@Mike

I have an understanding how both are plumbed (1 vs 2).

When you say diverting pressure from bottom (1port). It's the same situation as increasing pressure to top (2port). I'd like to know what differs for both situations. They both experience forces from backpressure / spring so leaving them outside of the equation.

In both situations the max boost / spool is when:

-No pressure is applied to bottom / top (1port)

-Pressure is applied to bottom+top (2port)

Both result in only spring pressure / backpressure remaining

Bram,

"How does connecting both ports (both pressurized) end up in a different situation then connecting only bottom port (not pressurized). That is the max boost (spool) setting for both. The remaining forces for both situations are spring force and backpressure?"

In pneumatics, Force is equal to Pressure * Area. The top of the wastegate has more area than the bottom because the valve shaft is attached to the diaphragm, and goes thru the bottom. That would be why you can have more force at the top than at the bottom.

Honestly, I use the bottom port only method most of the case, unless I can't achieve a certain boost pressure because the backpressure in the manifold crack the wastegate valve early and I don't want to change springs.

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