Boost Creep:
Internally gated 14b's, and 16g's especially, are known for boost creep. There are 2 major factors to this: the wastegate (WG) passage design and how far the wastegate actuator (WGA) moves the flapper; both restrict the flow of exhaust gas around the turbine. This works fine for a stock vehicle when the exhaust is a huge limiting factor in boost anyway, so creep isn't an issue. Once you throw on a less restrictive exhaust and/or take out the cat, boost tends to rise uncontrollably in the upper rpm range where large amounts of gases must be bypassed in order to maintain a steady boost pressure.
In the past, there were a few solutions to this.
1. Port the turbine housing for creep.
-This directs some of the exhaust flow into the WG passage; flowing through much more freely when the flapper opens. It has been brought up whether or not this has a significant impact on turbine efficiency.
2. Switch to an 02 dump (non-rerouted o2 housing).
-This allows the WG to open directly to the atmosphere, reducing backpressure and allowing more flow out the WG passage. It is also incredibly loud (often annoying IMHO) when the WG is open. This often has a minimal effect since the exhaust path is less restrictive in the first place, and why creep started to begin with. Completely depends on the setup though, hit or miss.
3. Re-install the restrictive exhaust and/or catalytic converter.
-This sacrifices performance. Boost creep won
4. Go external.
-By installing an external wastegate (a WG that isn't incorporated into the turbine housing itself), there is often a much larger passage and valve, allowing more flow/exhaust to bypass the turbine. It is usually open to the atmosphere as well. Price is the main concern, and for a turbo as small as a 14b or 16g it shouldn't be necessary unless you are having troubles with the flapper blowing open, the exact opposite of boost creep.
5. Deal with it.
-Have enough modifications to support and tune for the higher boost pressures.
6. Get an upgraded 34mm flapper.
-This allows a larger WG passage but also increases the chance of the flapper blowing open under high boost. This limits the amount of boost you can run. It is debatable whether the larger flapper "shrouds" the exhaust flow inside the small o2 housing passage, hurting rather than helping.
Or...
Extend the range of the stock (seen below) WGA.
Fully "open" with a stock WGA. Compare this to the MWGA video at the bottom of the 2nd post.
Many people know that the flapper only opens about 1/3 of its total travel (~30*) due to the limited range of the stock WGA. This means the flapper is severely obstructing the path of the exhaust gases, even when "fully" open.
...So why not extend the range? It's not as intuitive or easy to explain as porting, but here's why I believe it is worth the time spent:
-Unlike most of the options above, it doesn't have a serious drawback. You still get to keep it recirculated, no need to take off the turbo/turbine housing (so no gaskets to replace), you don't have to settle for more backpressure, not very costly, doesn't require multiple modifications to accommodate, and it doesn't sacrifice the ability to run higher psi later down the road- denial is often the first step to admitting you have an addiction.
This single thing isn't always the end all to boost creep. You must first pinpoint the bottleneck in your individual setup. There are 3 major factors to boost creep in a stock wastegate setup:
Stock turbine housing
-Has an abrupt 90* bend leading to the wastegate hole
Flapper/WGA combination
-WGA only moves ~3/8" to open the flapper 30* obstructing the exhaust flow out of the WG.
Path behind the WG
-The exhaust exiting the wastegate must travel through the o2 housing passage then make a transition back into the main exhaust flow. The EvoIII o2 housing has a much better WG passage and transition design than the (nearly identical) 1g and 2g o2 housings.
Fix the bottleneck in the system, and increase the possible flow through the WG; helping eliminate boost creep.
-----------------------------------------------
Important: Boost creep test -Will it work for me?
There is a test to see if modifying the wastegate to open the flapper all the way will help. Take the cotter pin that is on the WG flapper lever out and remove the WGA arm completely from the lever; letting the flapper open and close freely. Now is a good time to check if it actually does open and close freely, without feeling like it gets caught in certain positions (common with new eBay 16gs). This is mush easier to do when the car is cold so you don't burn yourself.
Let the car get up to operating temperature; you may notice the exhaust is louder, this is normal since the exhaust can bypass the turbine all the time. Make a WOT pull in 2nd or 3rd gear to redline or the highest rpm your car sees. The higher the gear the better since creep is more likely in higher gears, but speed is an issue. Keep an eye on the boost gauge (aftermarket, not the inaccurate stock one) and see what it creeps to. What usually happens is the car will jump to 0 psi, and hold it until ~5k when it will start slowly creeping to 5-10 psi near redline. This sees how prone the car is to boost creep with the flapper fully open, testing how well the wastegate passage flows. It is also a good indication of the lowest psi a modified WGA could hold without creeping, since it should open the flapper the full 90*. Keep in mind that the wastegate spring still determines the lowest amount of boost you can run and that boost creep is unrelated to this.
If you still creep past your desired psi, then porting may be needed in conjunction with a modified wastegate actuator. It's a good idea to first port for boost creep and see if that cures it before modifying your WGA. I haven't personally seen an instance where porting (improving the turbine housing flow into the WG) didn't help, or where the MWGA didn't help. Combined they work VERY well together.
Modifying a TD05H WGA:
Disclaimer:
DO NOT attempt this is you aren't mechanically inclined or don't have decent fabrication skills. Look over the entire process and be confident you can complete it before cutting into your WGA. It is important to understand how boost control and internal wastegates work before doing this.
If you aren't careful, there is a possibility of puncturing the diaphragm or melting it while welding. Attempt at your own risk.
Note: Another alternative is to fit a Garret style WGA, which tend to have a longer throw. The mounting bracket and arm will need to be swapped with MHI parts to work. A T25 WGA has a weaker spring so in my eyes isn't a very good candidate, even though they are common among DSMers. 1" of travel is just about right to get the flapper 90*.
This works for an eBay 16g WGA as well, but some of the steps may be slightly different. They did a pretty good job duplicating the MHI unit.
Tools:
Here are the tools I used, but you may be able to get away with less:
Welder
Bench grinder and grinder with cut-off wheels etc
Sandblaster
Drill press/drill bits
Vise
Measuring tape/ruler
Center punch
Tap for your choice of threaded rod-if adjustable
Materials:
Exhaust piping that matches the diameter of the WGA body that you are extending.
~1/4" Threaded rod if you make it adjustable, and whatever else you want to make it adjustable with, I used 1/8" thick and ½" wide flat stock along with some 5/16" brake line for the threaded rod to slide into.
Process:
This will take me 4-5 hours on average, with jigs for welding the adjustable arm etc.
Here's what you'll be starting with. This WGA in particular is from an Evo3 16g. If you don't plan on making it adjustable, be sure to measure how long the arm is from the body of the WGA to the hole for the flapper. Modifying it WILL change the length. I highly recommend making the arm adjustable.
Now, grind off the "ears" on the arm near its base, and cut the arm about where I did (~1/2 from the bend). You'll probably need to use a cut-off wheel since its hardened metal. Don't worry about the half-finished cut into the WGA body in this pic; I was getting ahead of myself
Clamp the WGA into a vise but be careful not to crush the body. Use a hacksaw to cut AROUND the body. Try to get as close as possible to where I cut and keep your cut as straight as you can, you will thank yourself later when you need to weld it back together. What I found works well is to score a mark around the WGA with the hacksaw before you begin cutting all the way through (be careful once you do, it will want to spring apart).
WGA body after it has been taken apart. Notice the metal flakes on the diaphragm; flush them out with water or with compressed air. If using compressed air, protect your eyes.
Take out the spring and other misc. pieces then cut off the nipple flush with the WGA body. It will be relocated later. Keep track of everything you've taken off.
Here is everything you should have so far. Keep tabs on how everything goes back together.
Cut off the back of the WGA body just like you did in the front. Try to cut as close to the end as possible so it's easier to weld back together and also to keep heat away from the diaphragm while welding. Keep cuts as straight and even as possible. Again, remove any metal chips to avoid damage to the diaphragm.
Remove the nut on the back and disassemble.
Put this piece into a vice and crush it so it looks like this:
Doing this lets the spring compress a little farther once assembled.
Cut the larger cup about 3/8" from where it clamps around the diaphragm. I found it easier to have it assembled with the other cup while cutting it. Cut as evenly as possible.
Take the smaller cup that was behind the diaphragm and remove the lip as shown in the picture. This keeps it from getting hung up on the insides of the WGA body, particularly one the welds when you get it back together. Not completely necessary, but I like to do it just in case.
Internally gated 14b's, and 16g's especially, are known for boost creep. There are 2 major factors to this: the wastegate (WG) passage design and how far the wastegate actuator (WGA) moves the flapper; both restrict the flow of exhaust gas around the turbine. This works fine for a stock vehicle when the exhaust is a huge limiting factor in boost anyway, so creep isn't an issue. Once you throw on a less restrictive exhaust and/or take out the cat, boost tends to rise uncontrollably in the upper rpm range where large amounts of gases must be bypassed in order to maintain a steady boost pressure.
In the past, there were a few solutions to this.
1. Port the turbine housing for creep.
-This directs some of the exhaust flow into the WG passage; flowing through much more freely when the flapper opens. It has been brought up whether or not this has a significant impact on turbine efficiency.
2. Switch to an 02 dump (non-rerouted o2 housing).
-This allows the WG to open directly to the atmosphere, reducing backpressure and allowing more flow out the WG passage. It is also incredibly loud (often annoying IMHO) when the WG is open. This often has a minimal effect since the exhaust path is less restrictive in the first place, and why creep started to begin with. Completely depends on the setup though, hit or miss.
3. Re-install the restrictive exhaust and/or catalytic converter.
-This sacrifices performance. Boost creep won
4. Go external.
-By installing an external wastegate (a WG that isn't incorporated into the turbine housing itself), there is often a much larger passage and valve, allowing more flow/exhaust to bypass the turbine. It is usually open to the atmosphere as well. Price is the main concern, and for a turbo as small as a 14b or 16g it shouldn't be necessary unless you are having troubles with the flapper blowing open, the exact opposite of boost creep.
5. Deal with it.
-Have enough modifications to support and tune for the higher boost pressures.
6. Get an upgraded 34mm flapper.
-This allows a larger WG passage but also increases the chance of the flapper blowing open under high boost. This limits the amount of boost you can run. It is debatable whether the larger flapper "shrouds" the exhaust flow inside the small o2 housing passage, hurting rather than helping.
Or...
Extend the range of the stock (seen below) WGA.
You must be logged in to view this image or video.
Fully "open" with a stock WGA. Compare this to the MWGA video at the bottom of the 2nd post.
Many people know that the flapper only opens about 1/3 of its total travel (~30*) due to the limited range of the stock WGA. This means the flapper is severely obstructing the path of the exhaust gases, even when "fully" open.
...So why not extend the range? It's not as intuitive or easy to explain as porting, but here's why I believe it is worth the time spent:
-Unlike most of the options above, it doesn't have a serious drawback. You still get to keep it recirculated, no need to take off the turbo/turbine housing (so no gaskets to replace), you don't have to settle for more backpressure, not very costly, doesn't require multiple modifications to accommodate, and it doesn't sacrifice the ability to run higher psi later down the road- denial is often the first step to admitting you have an addiction.
This single thing isn't always the end all to boost creep. You must first pinpoint the bottleneck in your individual setup. There are 3 major factors to boost creep in a stock wastegate setup:
Stock turbine housing
-Has an abrupt 90* bend leading to the wastegate hole
Flapper/WGA combination
-WGA only moves ~3/8" to open the flapper 30* obstructing the exhaust flow out of the WG.
Path behind the WG
-The exhaust exiting the wastegate must travel through the o2 housing passage then make a transition back into the main exhaust flow. The EvoIII o2 housing has a much better WG passage and transition design than the (nearly identical) 1g and 2g o2 housings.
Fix the bottleneck in the system, and increase the possible flow through the WG; helping eliminate boost creep.
-----------------------------------------------
Important: Boost creep test -Will it work for me?
There is a test to see if modifying the wastegate to open the flapper all the way will help. Take the cotter pin that is on the WG flapper lever out and remove the WGA arm completely from the lever; letting the flapper open and close freely. Now is a good time to check if it actually does open and close freely, without feeling like it gets caught in certain positions (common with new eBay 16gs). This is mush easier to do when the car is cold so you don't burn yourself.
Let the car get up to operating temperature; you may notice the exhaust is louder, this is normal since the exhaust can bypass the turbine all the time. Make a WOT pull in 2nd or 3rd gear to redline or the highest rpm your car sees. The higher the gear the better since creep is more likely in higher gears, but speed is an issue. Keep an eye on the boost gauge (aftermarket, not the inaccurate stock one) and see what it creeps to. What usually happens is the car will jump to 0 psi, and hold it until ~5k when it will start slowly creeping to 5-10 psi near redline. This sees how prone the car is to boost creep with the flapper fully open, testing how well the wastegate passage flows. It is also a good indication of the lowest psi a modified WGA could hold without creeping, since it should open the flapper the full 90*. Keep in mind that the wastegate spring still determines the lowest amount of boost you can run and that boost creep is unrelated to this.
If you still creep past your desired psi, then porting may be needed in conjunction with a modified wastegate actuator. It's a good idea to first port for boost creep and see if that cures it before modifying your WGA. I haven't personally seen an instance where porting (improving the turbine housing flow into the WG) didn't help, or where the MWGA didn't help. Combined they work VERY well together.
Modifying a TD05H WGA:
Disclaimer:
DO NOT attempt this is you aren't mechanically inclined or don't have decent fabrication skills. Look over the entire process and be confident you can complete it before cutting into your WGA. It is important to understand how boost control and internal wastegates work before doing this.
If you aren't careful, there is a possibility of puncturing the diaphragm or melting it while welding. Attempt at your own risk.
Note: Another alternative is to fit a Garret style WGA, which tend to have a longer throw. The mounting bracket and arm will need to be swapped with MHI parts to work. A T25 WGA has a weaker spring so in my eyes isn't a very good candidate, even though they are common among DSMers. 1" of travel is just about right to get the flapper 90*.
This works for an eBay 16g WGA as well, but some of the steps may be slightly different. They did a pretty good job duplicating the MHI unit.
Tools:
Here are the tools I used, but you may be able to get away with less:
Welder
Bench grinder and grinder with cut-off wheels etc
Sandblaster
Drill press/drill bits
Vise
Measuring tape/ruler
Center punch
Tap for your choice of threaded rod-if adjustable
Materials:
Exhaust piping that matches the diameter of the WGA body that you are extending.
~1/4" Threaded rod if you make it adjustable, and whatever else you want to make it adjustable with, I used 1/8" thick and ½" wide flat stock along with some 5/16" brake line for the threaded rod to slide into.
Process:
This will take me 4-5 hours on average, with jigs for welding the adjustable arm etc.
You must be logged in to view this image or video.
Here's what you'll be starting with. This WGA in particular is from an Evo3 16g. If you don't plan on making it adjustable, be sure to measure how long the arm is from the body of the WGA to the hole for the flapper. Modifying it WILL change the length. I highly recommend making the arm adjustable.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Now, grind off the "ears" on the arm near its base, and cut the arm about where I did (~1/2 from the bend). You'll probably need to use a cut-off wheel since its hardened metal. Don't worry about the half-finished cut into the WGA body in this pic; I was getting ahead of myself
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Clamp the WGA into a vise but be careful not to crush the body. Use a hacksaw to cut AROUND the body. Try to get as close as possible to where I cut and keep your cut as straight as you can, you will thank yourself later when you need to weld it back together. What I found works well is to score a mark around the WGA with the hacksaw before you begin cutting all the way through (be careful once you do, it will want to spring apart).
You must be logged in to view this image or video.
WGA body after it has been taken apart. Notice the metal flakes on the diaphragm; flush them out with water or with compressed air. If using compressed air, protect your eyes.
You must be logged in to view this image or video.
Take out the spring and other misc. pieces then cut off the nipple flush with the WGA body. It will be relocated later. Keep track of everything you've taken off.
You must be logged in to view this image or video.
Here is everything you should have so far. Keep tabs on how everything goes back together.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Cut off the back of the WGA body just like you did in the front. Try to cut as close to the end as possible so it's easier to weld back together and also to keep heat away from the diaphragm while welding. Keep cuts as straight and even as possible. Again, remove any metal chips to avoid damage to the diaphragm.
You must be logged in to view this image or video.
Remove the nut on the back and disassemble.
You must be logged in to view this image or video.
Put this piece into a vice and crush it so it looks like this:
You must be logged in to view this image or video.
Doing this lets the spring compress a little farther once assembled.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Cut the larger cup about 3/8" from where it clamps around the diaphragm. I found it easier to have it assembled with the other cup while cutting it. Cut as evenly as possible.
You must be logged in to view this image or video.
You must be logged in to view this image or video.
Take the smaller cup that was behind the diaphragm and remove the lip as shown in the picture. This keeps it from getting hung up on the insides of the WGA body, particularly one the welds when you get it back together. Not completely necessary, but I like to do it just in case.
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Make sure the adjustable parts or anything else doesn't hit the turbine or compressor housing in their travel. 
