I recently switched to an ATP O2 DP that integrates a Tial V44 External Wastegate Actuator and have some questions about why there are two pressure ports on them. I read somewhere that people leave the top port open to atmosphere and the bottom port was where I plumbed my MBC with a small bleed hole into the line. This setup seemed to be fine and the boost would rocket to setpoint without any problems with maybe a 2 psi spike.

Then I noticed that according to these directions I didn't install it right.

http://www.tialmedia.com/documents/w..._wginstall.pdf

Turns out the bottom port is supposed to get a boost source pre throttle plate and then you plumb the MBC with bleeder into the upper port. Well I did this and it seems like the boost will rocket up to around 20 psi and then have a delay as it reaches full boost with zero overshoot. Once full boost was reached the car was flying but that sudden hit of torque was now gone.

I think it came with a single 13 psi spring so I thought perhaps I may need that secondary spring for another 7 psi bringing it to a 20 psi base pressure. It appears that full boost signal to the WG delivers around 15 psi at lower RPM's and it evenly creeps to about 20 psi by redline which must be the max flow of the internal WG passages. I don't plan on ever running lower than 20 psi anyways so this setup will work fine for me.

So should I just switch it back to the "wrong" method and get that 2 psi spike and great torque hit or tinker with bleed holes and signal strength with it hooked up the official Tial way.

Who can explain what the dual port config is doing, and will one way work better for holding boost at high RPM's?

 

Apparently not very many people know about External Wastegates in the Evo X section, LOL. I switched back to just using the bottom port with the MBC and left the top port to atmosphere. The car has wicked spool again with maybe 1-2 psi spike and then steady right to 7000. I'll be running some Virtual Dyno plots to compare how much HP I've gained with the new combo, it definitely feels promising.

 

I think the dual-port setup is used for more advanced boost control systems that use a pressurizied source (higher than engine) to pressurize the top port. I'm guessing it would allow the use of a lighter spring to faster response, but still stay shut at high boost levels (by pressurizing the top port higher than the bottom). Just a guess based on the diagram. I have talked to a rally guy who has used a dual port and the aforementioned pressurized system.

 

the way my tial was setup from my civic before using an mbc was...get a boost source from the compressor housing of charge pipe... then from that line T it...one will go to the side of the external wg...then the other line from the T...that line will have the inline mbc...then route the line from mbc to the top...according to what i've searched before that will have much better and stable boost control..

it can be also from the boost source line then inline mbc then the side of the external wg..

let me know if this is still not clear i can create a diagram for ya later...