Adjustable Internal Wastegate Issues

[Freise]

I've got an Isis RS3871, it comes with an adjustable internal wastegate, supposedly adjustable from .5bar to 1.5bar.

I didn't realize it came with an adjustable wastegate, so when I figured that out I decided to do the research, learned that the way you adjust it is by extending the actuator arm to lower boost, and shortening it to raise boost. Everything that I look at suggests that the lengthen/shortening of the actuator arm controls boost by pre-loading the spring. If the spring is slightly compressed (rod shorter) = more boost pressure to open wastegate and vice versa.

Anyways, so I leave the arm in the "stock" setting to see where I'm starting from. I do a 5th gear low rpm pull so that I can watch boost slowly increase, make sure everything is safe. It begins spooling and by about 2800 reaches about 11psi and stops climbing, took it to about 3500rpm.
I try a 2nd gear run, and as soon as I hit the throttle boost goes right past 11, let off at 19psi

My first assumption is maybe I just wasn't able to spool it past 11psi in 5th gear due to low rpm, so I adjust the rod, and lengthen it by about 6 rotations. I do a 5th gear pull again, this time it hits about 8psi and stops. Do a 2nd gear run and it flies right past 8, keeps going up! Let off at 16+!

So i tried adjusting the length of the actuator arm to where it is parallel with the wastegate flap. In other words, there is virtually no tension on the arm. I assumed this is the lowest boost setting. Again, 5th gear run, I'm pegging 5psi. But as I push higher rpms, it flies past 5psi and keeps climbing, I can easily take it up to 15psi or more.


If I lengthen the actuator arm any further, the wastegate flap will not sit closed. Is that something I'm going to have to live with in order to see less boost??? Or does it sound like the wastegate isn't working right? (FYI did extensive boost leak test, no leaks!)


TL;DR Turbo will hit a "limit" of boost in lower rpms, will keep climbing very quickly in higher rpm. Not sure if I don't understand basics of adjustable wastegate or wastegate is broken in some manner.

[OrangeVirus1]

Is the line for the wastegate connected to a Vacuum source or boost only source?

Sounds like the wastegate can't feed off enough gas in the upper RPM

[Biggamehit]

check the diaphragm with regulated air.

[derass]

as mentioned, make sure you are using a dedicated pressure source, either from the compressor housing or hot pipe.

i have an HKS adjustable actuator on my 2781 and messed with it a bit to get it right. i found that with too much preload, boost pressure would spike in the lower gears. the revs, and therefore volume of exhaust gas, increase faster than the actuator can open.

do your pulls in 4th gear, this is the 1:1 gear ratio.

its possible that the actuator you have is simply 1.5bar (~20psi) opening pressure.

[Mikester]

Get a good EBC and your problems will be solved (With a 3871, you do NOT want a MBC).

An adjustable actuator arm is only going to give you a 'coarse' adjustment for when the wastegate starts to open... It is not a standalone boost controller. When the wastegate starts to open, this does not mean you won't continue to build boost. You really need an EBC.

[Freise]

-It is connected via compressor housing.

-I'm not sure what you mean by check the diaphragm with regulated air... I've hooked my air compressor up to the vacuum line and the flap opens with compressed air

-The weird thing is that I see a difference as I mess with it; as I lengthen the adjustable rod, then I am seeing the "limit" change, and it changes as it should... The biggest concern is that the arm is adjusted to the point to where any further length will actually prevent the flap from fully closing. I don't have to preload the spring at all in order to attach the arm, and thus I assumed this should be the theoretical lower limit...

Everything I read and the symptoms I have scream that the wastegate is not large enough to bypass enough exhaust to control boost, but this setup is like this from their factory, I just find it really hard to believe they would engineer it with an internal wastegate that is far too small (I guess the point of this thread is, do I need to get over that??!)

-While I've never considered an EBC... I'd honestly be worried that it would be putting a band aid over a broken leg. I want to be sure that everything is working the way it is suppose to be, and I have a feeling that something isn't right. I've gone through reviews, theres even a thread here on zilvia, no one mentions this flaw, so either something is wrong or everyone is converting to external or running an EBC and I'm just retarded for trying this setup lol

[whose5that]

I am having a similar issue with my setup, at one time the actuator got removed, and i believe the stock preload from factory was messed up. Now im having a hard time finding the right preload for the actuator. And having issues with how slow the boost builds, itll build continuously but very slowly.

Im not sure if i has to do with the adjustment of my bov either.

does shortening the rod of the actuator, where you have to pull the rod on the wastegate flap, increase or decrease boost?