New Turbo Install, Odd Boost Issue

[kklobb]

FP Big28 -- 1997 GsT
550's

I can't seem to get boost down to less than 21ish PSI. Previously (T25) I built my own boost valve. I bought (joe p? maybe) a maual controller. I believe I just have enough tension on it to stop the ball from rattling. After that while looking under the hood, I saw a loose lock nut on the waste gate actuator (17 PSPI upgrade) rod. Did I need to adjust this? It was on tight (so I thought) when the turbo arrived.

I can't think of any reason as to why I can't control boost. I go from the compressor housing stock nipple to the controller (ball side), and then from the controller (bolt side) to the wastegate actuator.

I also believe I am hitting fuel cut at around 6k RPM if I am on it 3/4 throttle or better. It just flat falls on it's face and then it's fine until you get on it somewhat again.

Often I get a stumble (like a loose or split dump tube) when letting off the gas. I would assume that's due to the injectors and no tune, but many years ago I put a big16 on an old buddy's laser with 550's and don't remember a stumble or fuel cut issue.

It's not tuned, I have no logger or wideband. I plan to pay for it to be tuned and be done with it.

EGT's
have not exceeded 1450,
start up 800
warm idle 1,000
highway cruising 75 mph 12-1400 the temp stays at what ever teimp it's at when i let off to cruise.

thoughts or suggestions of where to start for my lack of boost control?

 

[drewvr4]

Post a picture of how you have the boost controller setup is it possible you have it backwards? I haven't check lately but is the arm on the wastegate adjustable?

 

[kklobb]

I'm certain the controller is hooked up correctly. it's not uncontrolled boost, it simply won't adjust below 21 PSI.

I have no clue about the actuator, I assume the only adjustment is for rod length.

 

[drewvr4]

correct but if you can adjust the length of the rod it also adjusts how much it takes to open the wastegate.

Maybe you just have a defective boost controller? Try running just a vacuum line to your wastegate with no boost controller and see if it still does it.

 

[ktmrider]

correct but if you can adjust the length of the rod it also adjusts how much it takes to open the wastegate.

Maybe you just have a defective boost controller? Try running just a vacuum line to your wastegate with no boost controller and see if it still does it.

+1, this will also tell you what the WG spring tension is ( might be stronger than 17psi ).
The arm itself cannot self adjust even if the locknut was loose as you need to turn the entire end attached to the flapper.
Like drewvr4 said, run the WG signal line direct from the source instead of thru the MBC and see what happens.

 

[kklobb]

boosting issue has to be in the controller. it's a slowboy manual ball and spring controller. anyone have any experience with these? I thought I had all the tension out of it, but maybe not.

The wastegate actuator spring is 17 pounds as that is what I boost to with the controller bypassed.

The boost issue I can work around and correct one way or the other. The other issue I have is a running problem.

I need to drive it a bit more to get more precise info, but it feels like I am hitting fuel cut. It runs fine until a certain RPM/Throttle position is reached. I do not believe it's a boost leak though.

my mods are

• 
  FP Big28
  550's RC
  3 inch exh
  RRE intercooler pipes
  Slow boy sidemount intercooler
  greddy BOV.

prior to turbo install, this issue was not present. thoughts, suggestions or starting points?

Thanks for the help!

I do not believe this is a boost leak though. the symptom does not occur to closer to the 5-6K RPM range and boost pressure has been steady at 17 PSI from about 3200 RPM or so.

 

[97 gst turbooo]

i had this same problem with my fully ported sbr evo iii 16g and ported manifold. i could not spool less that 22psi with or without a boost controller. upgraded to a tial 38mm off the manifold and no problems since then. stock wastegate opening couldnt control the boost.