Trouble with Twin Spool Up

In my case I have a tial 38mm wastegate. I put two springs into it which would make it open at 19psi. I also put a adjustable boost elbow fitting in the turbo on the high pressure side going to the side of the wastegate so I could bleed off high pressure to adjust wastegate actuation pressure. If I want it to open at 25psi or whatever I just screw in the allen screw in the elbow. The other tube that runs to the top of the wastegate is connected to the lower pressure side between both turbos. This lets the wastegate only see what pressure the small turbo is making. In my experience exhaust drive pressure has not affected the opening of the wastegate, only boost has any affect. However I haven't ever run a 50mm wastegate which has much more valve surface area. I still doubt drive pressure will push your valve up, I strongly recommend running as high of a spring rate as possible to prevent valve flutter. For me the highest spring rate I could run for maximum adjustability was 19psi.
 
I dont know if this is the case but if you are running a e-bay 50mm wastegate which came with a 10psi spring you need to get rid of that wastegate and get a quality one. Cheap wastegates will not work right and will only give you problems.
Make sure you have the wastegate plumbed correctly, the side port is high pressure, the top port is pressure from the primary turbo.
 
no cheapy china crap for my truck! tial wastegate here. i will try and set it up that way. i will need to get another spring to raise the pressure, and change my tubing configuration a bit, but we will see. and i really need to get a smaller ht3b turbine housing too!
 
How are you guys plumbing in your external wastegate?

I'm building a set of twins with an external 50mm gate. The gate is on the exhaust manifold and is hot piped back into the hot pipe going into the primary.

I have a 8psi spring installed. I've noticed that the gate opens pretty fast, maybe I have to put in heavier springs. I probably going to have to run two adjustable pressure regulators just to get the open properly. One pressure reg for the bottom pressure tap and one for the top pressure tap.
 
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