New boost control problems

[WarWagon]

Bison 6265 turbo, it has a precision turbine housing and the waste gate hole is 1.5" the short tube to the external waste gate is also 1.5"
New 38mm waste gate now dumping to atmosphere, it has a 10lb spring in it.
I use a delux TurboXS boost controller that is NOT installed right now.

I used to have control of the boost with my old waste gate and the TXS booster controller in the past for 5 years.
My old waste gate had a diaphragm failure so I replaced the whole gate with a new one.
At the time my original waste gate was going bad I had repaired the exhaust leaks I didn't know about (cross over connections and some header cracks).
Ever since the waste gate failure and leak repair the boost has continued to be out of my control.
During my latest tests: boost hits 10psi and I hear the gate opening boost remains here for a moment then I hear the gate fully open and boost is 15psi now and climbing.. 20..25.28..30psi and that is when I get off it.
I've tried everything I can think of here. So am I having a waste gate too small issue now with most of the leaks repaired? If I wanted to only run 20psi the 38mm gate should still be enough for this turbo, I do plan on running 28-30+psi but the current contol issue has me messed up.

 

[bison]

It’s likely the location of the gate. I proved a 38mm worked just fine and we were able to get it down to the spring even with a 6766 on a 700hp (27-28psi)engine. Post picture of configuration


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[Boost231]

I'm trying to figure out what controller you have Installed if any since its confusing. Is this just on spring pressure?

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[WarWagon]

The gate is on the down pipe, I built the whole pipe it's been on this car from the beginning I'll post a picture in a few.
The boost controller is a manual bleeder type (coarse/fine) adjustable, it isn't junk and has been working great. It is not even on right now to eliminate that as problem.

 

[Boost231]

So you have the pressure source feeding directly to the Wastegate?

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[bison]

Do this and if you’re using a quality wastegate like this you will have zero problems with wastegate flow.


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[WarWagon]

Do this and if you’re using a quality wastegate like this you will have zero problems with wastegate flow.


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I can do that, I definitely don't have it there.
I see what's going on, you have your stainless plate over the hole between the down pipe to seal that off. You have a short section of looks like 1.5" pipe coming out at the same angle of flow.

 

[WarWagon]

Yes, the source is going right into the gate and the top port is open.
As it is right now:

 

[WarWagon]

It's the next day now but I moved the waste gate on Monday with no other changes and went for test drive. Boost was 10 for awhile then went to 25 and seemed to stay at 25 after a shift. Now I forgot to move the signal source on all these tests it was on the intake manifold. I moved it now today (Tuesday) the source is the compressor housing, I'll take it to work today and keep on testing. Hopefully with the source line and waste gate moved boost control works properly again.

I have my old waste gate that I put a new diaphragm in I can try as a last resort.

 

[WarWagon]

Had a nice drive to work in the Buick, really no change in control with the source at the compressor cover now. I'm sure the boost was stopping at 25

 

[WarWagon]

I installed my original waste gate that has a new diaphragm in it this morning. This one has a 7psi spring and I used new 1/4" ID hose from the compressor cover to the lower port on this gate. Testing this old gate combo on my way to work: holds 10psi for a few hundred rpm then creeps right back up to 25psi.
I still can't get boost under control,
I can borrow another Tial 38 gate to try out but I didt see any improvement/changes swapping between my two gates.
I verified that both of these gate valves move freely and hold open with pressure.

 

[TurboBuRick]

Something about the wastegaye is not flowing enough. Either the pipe or the gate itself.

 

[WarWagon]

That's what I was thinking however testing hasn't found the issue yet. I'm still certain everything is sized accordingly and Bison's testing confirmed a 38mm gate is plenty.
What else to do but try a 3rd different waste gate?

 

[TurboBuRick]

You have a sharp turn off the header to the gate. That should have a smooth merge. Can it work the way you have it? Yes but it will not be 100% efficient when you need to dump more boost.

Does your down pipe still have the integral “puck” gate? If so, Pull the block off plate plate and hook the factory gate back up with the external. Run both gates and see what results.

 

[WarWagon]

I built this down pipe from scratch and it's always been externally gated, I don't have any internal gate parts.
More testing to follow

 

[bison]

We used a Tial on the example I gave above. I have no data with anything other than Turbosmart or Tial gates


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[WarWagon]

^Thanks for the info Bison.
More testing was needed! On my way home the old original waste gate worked. After a few hits the boost settles at 10 on a 7 psi spring. Boost hit 15 for a moment then fell back down on a few more hits.
I think it's going in the right direction now and I can probably add the boost controller back in.

 

[WarWagon]

This thread can be locked down. Boost is under control with the current setup of the old waste gate and the boost controller back on.