Boost gauge needle fluttering

[dynoman]

While chasing a knock retard problem I noticed that the boost gauge flutters ( vibrates rapidly) 2-3 psi at max boost. It rises steady and smooth until I believe the wastegate opens , then it flutters . It dosen't matter if the boost is set for 22 psi or 18 psi . I don't remember ever seeing this with my first GN. What would cause this and could this be part of my knock problem? Sam

 

[Slow91z]

I'm gonna go out on a limb and say you have a RJC boost controller or similar.

What you need to do is turn down the RJC controller and then add some tension to the wastegate...You have the controller turned up high enough that it's trying to overcome the wastegate (which it can't do) and you are seeing the oscillation that's in the ball and spring type of controller all the time...Normally the spring tension keeps it from bouncing all over.

Doubt it's related to your knock problem unless it's bouncing higher than what you want your boost to be (so turn it down).

 

[dynoman]

I have a manual adjustable flow control valve that goes to atmosphere after the stock Y connector from the turbo (RJC style ?). I have that almost closed off to lower boost (while chasing knock retard) but the wastegate rod is loose. Do I need to have tension on the rod ? If so how much?
Thanks Sam

 

[Slow91z]

I have a manual adjustable flow control valve that goes to atmosphere after the stock Y connector from the turbo (RJC style ?). I have that almost closed off to lower boost (while chasing knock retard) but the wastegate rod is loose. Do I need to have tension on the rod ? If so how much?
Thanks Sam

Hmmm I wouldn't think that style would do it.

You don't have a boost leak do you? Like a hose that leaks only over 18 psi, or anything like that?

 

[dynoman]

I'll check for a leak cause I just replaced a head gasket and don't recall it being like that before. Should the wastegate arm be pulled tight , right now it's loose over the wastgate post ? Sam

 

[Slow91z]

I'll check for a leak cause I just replaced a head gasket and don't recall it being like that before. Should the wastegate arm be pulled tight , right now it's loose over the wastgate post ? Sam

Yes you should start with at least a little bit of tension...unhook the rod, and hold the wastegate closed with one hand and screw the rod down until you have to pull it approx. half a hole to pull it on.

 

[toomanymodz]

Wastegate rod should be tight. I like to have mine about 1/8 inch short so I have to pull it slightly to place it onto the post. With your air valve closed, you should have only 18psi with an H/D actuator. If you want lower boost, you'll have to switch to a standard actuator instead.

 

[shifty6]

boost flutter

Wastegate solonoid(s) ok...?

 

[dynoman]

I tightened up the rod and the flutter went away @ 18psi but it fluttered when I opened up the valve for ~22psi . It's getting harder to test with our fall weather. Sam

 

[Slow91z]

I tightened up the rod and the flutter went away @ 18psi but it fluttered when I opened up the valve for ~22psi . It's getting harder to test with our fall weather. Sam

Yep, gonna have to tighten up the rod some more...Think of the spring in the wastegate like a dampener it smooths out any fluctuations in the pressure pushing the wastegate open.

 

[dynoman]

Better weather on the way , so I can give it a try . Thanks Sam

 

[WSLN 6]

You might want to check the "weld my heads on" thread...... That is exactly what happen to my boost gauge when compression is escaping back into my rad. Just another option for you, chek the level on your resevoir to confirm.

 

[dynoman]

Thanks , just one more thing to check. Sam