mbc problem

[talontsi98]

I have a joe p pro z mbc. I have it turned all the way down and I still get 18 psi when im trying to set it at 15. I believe I have it hooked up correctly. What can cause this?

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[architechnik]

MBC's should be loose for the least amount of pressure. The more down it is the more air it lets out and effectively reduces the pressure on the wastegate actuator. Try turning the other direction and make sure there aren't any leaks in the lines you've run.

 

[talontsi98]

I do have a crack on exhaust manifold between turbo bolts.(waiting for manifold) Would this cause high boost?

 

[98GSXtreme07]

Usually counter-clockwise is the way to turn down the boost. This of course is on most, if not all MBC's.

 

[RC_slow_dsm]

I do have a crack on exhaust manifold between turbo bolts.(waiting for manifold) Would this cause high boost?

If anything, that would cause low boost and late turbo spool. The air that should be going to the turbo is escaping through the crack. is this on an external or internal wastegate?

 

[talontsi98]

Internal wastegate

 

[kanderson]

If you adjust it for more pressure does it respond to that?

Try run a hose straight from your boost nipple to your wastegate actuator. This will cause you to run wastegate pressure, so for example if your wastegate opens at 11 psi you will run 11 psi boost.

If you do this and it still doesn't open until 18 psi it means that your wastegate is sticky or the spring is too hard. If it does lower the boost pressure than you know your problem lies with the MBC or its hookup.

 

[talontsi98]

Ran hose directly from turbo nipple to wg actuator and it still goes to 18 psi. I don't think the wastegate is sticking because the pressure rises steadily.(doesn't jump to 18 psi)

 

[kanderson]

Sounds like your wastegate spring is too stiff

 

[talontsi98]

Just called hahn and they said to switch to a 8-10 psi spring rather than the 15-17 psi spring that is in the actuator now.