Internal wastegate operation.

[Todd W]

I am currently running an A5K with an industrial t-4 turbine housing. My wastegate is currently not hooked up in any way.the Big brass looking head with the brass nipple where you attach the boost line is open to the atmosphere.

My question, is this the way a person would see the most boost for a gated turbo. Or does boost to this brass thing somehow aid in keeping the wategate shut until desired boost opens the gate? would just capping the brass nipple be any different?

The reason i ask is that i am seeing less boost with this tighter housing than I got with the original housing. I did also add a bigger cam at the same time i did the housing swap which could account for the change. I also added a lot more fuel and whether I have the pump set up really heavy or light on fuel the boost never goes over 50. Only difference is amount of smoke, and the truck runs better with less fuel.

 

[Todd W]

Anyone??

 

[Charles]

You said cam...

Everything from before is out the window.



However.....

The thing you are referring to is the Actuator. There is a diaphragm inside that little "can" that has a spring pre-load that works to hold the rod tight and keep the wastegate "flapper" sealed inside the turbine housing. By applying boost to the actuator port you introduce pressure to the diaphragm that works to oppose the spring force, decreasing the pre-load holding the gate closed. As boost rises this will eventually allow the gate to open various amounts depending on spring pressure, rod adjustment and exhaust drive pressure.

With the actuator "signal" line not connected (signal is nothing more than a boost line from the manifold) the gate is operating purely on drive pressure. If the rod is not tensioned excessively, the gate will still blow open due to exhaust drive pressure exceeding the force the actuator spring can withstand.

However, the rod can usually be adjusted tight enough that it will render the gate inoperable. In this case it will never open and boost pressure should increase if it were opening some amount before.

If you want to increase boost farther with the line disconnected, and you're fairly sure that the gate is still opening at present, then tighten the linkage rod to increase the pre-load until the gate is either inoperable, or your desired boost is reached.