Alright, here the big deal.

My turbo actuator with internal wastegate (turbo is T25 style) was boosting a very constant 8 psi with my DX1.5 exhaust system. Now, I upgraded to 2.5 straight and it is now boosting 13-14psi ! ! !

Question 1:
Now, I need something to make the turbo boost lower. I heard you can lenghted the rod (how many inch?) or you can get a manual boost controller ! !

Question2:
Now, how can a manual boost controller lower the boost level ? ? actually, I am running a freeflow tube from the charge pipe nipple to the actuator nipple. Now, if a put a boost controller, all it can do is lower the air flow, right? So how can i reduce the amount of boost if at freeflow, my actuator is not even opening enought!

Thanks

 

i believe a boost contoller opens the wastegate slightly as boost reaches "maximum set" level.

you are boosting more now because your exhaust has less backpressure and lets the turbo spin faster. Unless the fabricator forgot to add a down pipe (j/k)

 

You cannot use a manual boost controller to lower your boost. You can only use them to increase the boost.

You need to lengthen the rod on your wastegate, and the only way to know how much is trial and error.

 

for your first question, going to a bigger diameter downpipe reduces back pressure and allows the turbo a cleaner less interupted path and hence the turbo spools faster. It's kinda the theory behind going from an open downpipe to connected one. I went from just under 10 psi with the open downpipe to just over 7 with the downpipe connected. This has been my experience with this kinda stuff.

As for the second question, boost controllers can only raise the boost because for the most part, it's restricting the amount of air that flows to the diaphram and then this in turn means that more boost is needed to push the diaphram open so yah, it can only raise the boost and not lower it.

As for lengthening the arm, what that does is slightly opens the wastegate flapper valve so that it bleeds off exhaust pressure and so that more exhaust pressure is needed to open the wastegate flapper valve, hence the higher revs or more turbo lag.

If I'm wrong on any of these feel free to correct me but from what I've experienced, this is what I have concluded.

 

Well done LUDE.

I am using a T25 and am boosting 10 psi with the stock actuator rod with a 2 1/4" exhaust with no cat.

I am using a threaded wastegate actuator rod and with it lengthened roughly 1/4" the boost drops to 8psi but it takes longer to spool. So obviously there is a trade off.

Best bet for you is to make your rod threaded. I adjust mine all the time so better do it right the first time.

 

A pic I saved