Boost creep on small 16g

[kruel]

Hello Again,

I am still learning more and more about my recently aquired DSM. I talked a little more with my friend who has had a few of them. And we discovered that the car is actually running a Small 16G turbo, no the stock 14b like I had previously thought. Which may explain the boost creep issues I am having.

So the setup (to the best of my knowledge) is as follows :

Small 16G Turbo (Ported, manifold ported to match)
Full 3" Exhaust
Stock wastegate
Fuel pump (However, the heavier gauge wire mod has been done)
Stock BCS is disconnected, and there is not boost controller attached right now, all appropriate vacuum lines have been capped. So I should be sitting around 8PSI (which is does hold at first)

I did some research of my own, and I gather that part of my problems may be that the wastegate cannot dump enought pressure.

I spool pretty quickly, once I get to second it will hold around 8psi (as it I want it too for now) , but when I get to about 4500RPM though, the boost creeps exponentially to just about 18 or 19 PSI. This is pretty much the standard for 3rd and sometimes 4th as well.

I have done my best to check for leaks, and I have been able to eliminate the ones I found by replacing vacuum hoses (old and cracked ) The car holds good vacuum, -18/-20hg in idle, and about -28/-30 when decellerating.

I am unable to move the wastegate actuator arm by hand, but I don't know if I should be able too.

So the best idea I can come up with, is my wastgate cannot dump pressure fast enough, or is not opening all the way and is allowing the boost to creep.

What can I do to further test this out, and make sure the wastgate actuator and what not is working fine?


Additionally, how hard would it be to install an external wastegate, and would there be any benifits for me in that case?

Thank you in advance!

 

[robs90tsi]

Small ported 16G, ported manifold, ???? 02 Housing ????, you need to port your wastegate, or upgrade to one with a larger flapper, and port your 02 Housing if you dont already have one. To install an external wastegate, you have many different options as to where to run it, off your exhaust manifold which would require a new manifold, or off your 02 housing, which would require a different 02 housing, and you would have to remove the stock wastegate and immobilize the stock flapper.

 

[zippyshoe]

Also check that your wastegate flapper is able to open fully (90 degrees). If not, then port away the area that is preventing the flapper from opening a full 90 degrees.

 

[seajay2525]

I don't want to repeat the above posts, but I do want to agree with them.

 

[jonk00000]

you need to get a boost controller. also get a boost guage, didnt seem like you are to sure on your boost levels.
porting your o2 housing is a cheaper way to help a little with boost creep. switching to an external wastegate is a little more expensive but a much more efficient way to eliminate boost creep

 

[kruel]

Thank you everyone so far, I do have an after market boost gauge hooked up, that is how I got the numbers, they just vary a little depending on how open the throttle is and when I get to scared of how high it is creeping and let off. I am waiting for my boost controller to come in. I will look into weither the O2 housing is already ported, and I will check to make sure the wastegate is opening 90 degrees or not.

 

[kenamond]

If you disconnect the wastegate actuator arm from the turbine housing, you should be able to turn the flapper on the housing with your fingers to see if it opens and closes freely. The wastegate actuator spring is pretty stiff, so unless you can get a good grip on the actuator link, you might not be able to move it - removing the link lets you turn the flapper without any problem.

While you have the arm disconnected, you can check for creep by doing a test drive and monitoring your boost gauge. If it boosts more than a few psi, then not enough exhaust is getting out of the wastegate passage and is choosing instead to go through the turbine and generating boost as a result.

As robs90tsi has pointed out in many previous threads, when you buy a ported turbo, they usually focus on improving flow between the exhaust manifold and turbine inlet, but not necessarily on the entrance to the wastegate passage inside the turbine housing. Porting this passage (on the inlet side of the wastegate) gives the exhaust gasses an easier way out and is one recommended fix. Another is to use an external wastegate.