I installed an external wastegate and when I WOT the car it sticks at 5psi for a long time then builds boost very slow. I removed the vacuum source to the Tial and it built boost very fast but of course hit boost cut. What would be causing this?

My setup:
D16y7
Greddy 15g 9psi
Tial 35mm
TurboXS MBC

 

bump

 

Where do you have the line for the wastegate getting its boost signal from?

 

Vacuum box on the firewall. The box gets it's vacuum from the big hose that goes from the intake manifold to the brake booster.

 

Can you move the boost signal line closer to the wastegate? Like directly off the turbo housing?

Mike

 

Yes, I will try this. Why would this do anything different?

 

Shortest possible line to the wastegate seems to work best. The boost signal off the compressor housing is right there and accurate.

Mike

 

It sounds like the waste gate isnt closed all the way. Or theres a leak.check to see if the wastegate is leaking or take off ur dump tube and see if its closed all the way

 

I changed the vac source to the compressor housing and it did not change anything. It must be a boost leak somewhere.

 

How can there be a boost leak if when u take the vac line off it hits ur boost cut? Check the waste gate

 

Or maybe ur exhaust housing is cracked. Did ur turbo have a flapper before?

 

Was the TiAL wastegate new? Even if it was, did you even bother inspecting it internally to make sure the valve, diaphram, etc. are in fine working condition?

The excess vacuum line from back at the manifold to the wastegate has the potential to slow spool down a bit, but not how you describe, and it will account for any boost that is lost between the compressor housing back to the throttle body. Running the line from the compressor housing, the wastegate will still see 9 psi, but that doesn't always mean that's what is present in the intake manifold. Just food for thought for you.

 

Do a boost leak on the car

 

Yes, my tuner weld it shut.

 

Tial was used. Yes, my tuner and I took it apart and inspected it.

 

I would take it apart and recheck it..

 

did you install the fire ring on the wastegate?

 

Have you changed your downpipe since you installed the external WG? I installed my turbo setup and I didn't run a downpipe and it took forever to build boost. Once I had one fabricated it hit the desired boost level much faster. Make sure that you have a properly sealed downpipe.

Good luck,

Blaze

 

what spring is in the wastegate? it kind of sounds like it has a 5psi spring in it and then the additional boost that starts coming slowly might just be boost creep.

 

thats what it is i bet... my car spooled really fast with a 14lb spring... i put a 7.5 psi spring in it and it spools slower b/c it opens up quicker

 

It is a 4psi spring. Should i get an 8psi spring?

 

Bump

 

It is a 4psi spring. Should i get an 8psi spring?

 

yes. but only if that is the lowest target boost that you will want to see.

 

Thanks you.