N75-WG Line 6mm ID... Is this okay?

[agentsmith988]

I've been having problems trying to track down some high RPM boost surging and am trying to figure out if my N75 control lines are too big. When I swapped my turbo out, I also changed the original lines with ones that had a 6mm ID. I can't remember how big the original lines were...

While I'm in there poking around today, I'm going to be changing all of my check valves (found a few that were bypassing) and changing my pre-cat O2 sensor (It's 160k miles old). Just want to know if I should change my N75 lines out too.

[MetalMan]

6mm seems a little large for the nipple on the wastegate actuator. The stock WG lines are tapered to accomodate for this.

The "best" way to determine if 6mm is too large is to perform a boost leak test... this will tell you if air is leaking between the line and WG actuator nipple.
Also a boost leak test will tell you if you have any boost leaks contributing to you boost issue, and if any check valves are bad.

[agentsmith988]

No leaks with a boost leak test. Replaced all the check valves and now my idle sits at a solid -21 inHg (used to sit between -19 and -20).

So as long as I'm not leaking from the WG lines they should be alright? The slightly larger ID lines shouldn't cause boost control issues?

[old guy]

No it should not matter. The wastgate is controlled by pressure, not volume.

[agentsmith988]

No it should not matter. The wastgate is controlled by pressure, not volume.

Sounds good! I was only thinking along the lines of a hydraulic system... use a line that is too large and you can end up with excessive pressure drops when the system is under load. Got me thinking that it might be contributing to my overboost condition. Overthinking it!