Boost creep issues, and which external wastegate to go with?

[JST A 6]

I just removed my stock intercooler and installed a Mark Jackson SLIC yesterday, and since then I'm having problems with boost creep. Before the intercooler changeout I was running about 16 pounds of boost (sometimes it would spike to 18 then ease back to 16) with no knock or any other issues. Now that I have this freer-flowing intercooler with no other changes I'm getting boost creep up to 23 psi. I now have my boost controller backed all the way out, and when I get into boost it starts out at around 7 psi then climbs to 23. A friend of mine suggested hogging out the wastegate hole on my turbine housing but many other friends of mine think it's a wastegate issue especially since I have a crappy Chinese wastegate now. I have had issues in the past with this wastegate so before I try anything else I'm ready to swap it out for something more reputable...the wastegate I have is a close knockoff of a TiAL F38 wastegate, and after viewing several technical drawings and taking measurements on the wastegate I have I've determined all the important dimensions to be the same as the real F38, the Turbonetics Deltagate Mk II and the Turbonetics Evolution wastegate. Based on real experience with these wastegates, which would you guys recommend?

Here's a link to the Evolution gate for those not familiar:

Turbonetics Inc. | Home | Products | Wastegates | Wastegate Kit, Evolution

It appears Turbonetics rates it a little higher than the Deltagate as far as how much power it can handle.

Thanks for your input...

 

[87turbot-type]

Your probably going to have to port the WG hole either way if you want to get ride of the creep.

 

[JST A 6]

Your probably going to have to port the WG hole either way if you want to get ride of the creep.

Not trying to refute your post but does it seem reasonable that the MJ intercooler is causing a problem with the WG hole being too small to surface, or do you suppose I'm having a wastegate issue (admittedly that would be a heck of a coincedence)? I have a somewhat fair amount of knowledge about how turbos and related components work but maybe I'm missing something about the side effects of allowing more (and cooler) airflow with less of a load on the turbo.

Thanks to anybody who can shed some light for me...

 

[87turbot-type]

Your right less load on the turbo, thus allowing it now to spin up quicker. Plus I am assuming your making a bit more power with the IC so your pushing a bit more exhaust.

Porting the WG hole will allow more air flow out of the turbo and kill your creep. Putting an external gate on isn't going to allow you to flow more air threw the hole. (It shouldn't)

At this point I would try porting the hole and see how it goes. You will see a ring where the puck is covering you can use that as a guide and just make sure you stay smaller.

 

[kingots2004]

i have a knock off wastegate also and with mine once i started to turn it up it would boost creep .i added a stiffer spring and it stopped it completely. now my boost is soild where ever i set it at

 

[SRGN]

Remember where your original boost reference point is, on the turbo outlet. When you removed the restriction downstream of that point, it also changed the boost signal being used by the controller. You may have to change the wategate spring as mentioned above to compensate for the pressure delta. However, I would try one spring lighter first so it is easier for the pressure to lift the valve off the seat. The WG hole enlargement is a wise idea regardless.

 

[JST A 6]

All good answers/advice; I understand now where you all are coming from. 87turbot-type, as stated in my 1st post in this thread I already have an external WG--it's just the cheap Chinese one from GN1 Performance. I realize now that you can't cut corners like that with these cars and go the cheap route as it often ends up being the more expensive way to go. Such is the case here with me having to replace the wastegate to avoid any more issues with it--when I first got it one of the banjo bolts protruded into the housing too far and pinched the diaphragm, causing it to get a hole punched in it. Not to mention it also had not been deburred after they drilled and tapped the banjo bolt holes so that also caused damage to the diaphragm. I took it apart last night and checked the diaphragm; no holes this time but I also want to get rid of this wastegate so I have different springs available and/or the preload adjustment like the Turbonetics Deltagate has. This leads me back to one of my original questions--which wastegate would you guys recommend from my first post in this thread?

As far as the wastegate hole in the turbine housing, I guess I'll be tearing into that here real soon, and also the adjoining hole in the downpipe since it was pretty much the same size and matched up to the hole in the turbo almost perfectly.

 

[Chuck Leeper]

What's the OEM w/g hole have to do with using an external gate??

 

[JST A 6]

Their line of thought is since the gases still flow through the same hole to get to the external WG it still has to be enlarged. Several of my local Buick buddies think the size of the hole doesn't have as much to do with boost creep issues with an external wastegate as with an internal wastegate since there is no longer a puck even partially blocking that hole. Personally I'd rather not have to pull my turbo and disassemble it to hog the hole out; which is why I'm thinking I'll replace my substandard external WG with a good name-brand external WG and play around with different springs as a starting point, then hog out the hole in the turbine housing if I have to. Do you have any recommendations as to which wastegate listed in the 1st post of this thread I should go with? Thanks...

 

[JST A 6]

I just made an interesting little discovery that I believe may be the cause of all my trouble--I took my wastegate and attached a regulated supply of compressed air to the bottom of the diaphragm, and starting from 0 psi I slowly turned the regulator in until the valve started to lift, and air was leaking from around the valve stem. I also have an unused spare wastegate, also from GN1, that I tried the same test on and it also leaked. Upon disassembling one of the wastegates, I found that there is no seal around the stem!!! This is further confirmation for me that I need to replace the wastegate with something better.

 

[87NAT]

I fought with boost creep with an old deltagate. Lots of issues with it that I wont bore you with. New Tial 38mm gate and solid boost at 23 psi...no creep.

 

[Chuck Leeper]

Same stuff w/ the TR gate... John Craig modded them in an attempt to make them reliable.. Not much luck. [Mine was a problem, even after the mods. It ate up the flange that the valve sealed on.] I took mine off, and went w/ a Innovative, and a digital Innovate controller. No more problems.
As far as the old puck hole.. that's irrelevant. The gate will relieve the pressure out of the main downpipe, if it's plumbed as my ATR dp was.
Ideally, the gate exhaust should be re-entered into the dp, as far from the turbo as possible.. 18" if you can do that.
The best scenario is atmosphere dump.. The cops will luv ya for that!

 

[JST A 6]

Same stuff w/ the TR gate... John Craig modded them in an attempt to make them reliable.. Not much luck. [Mine was a problem, even after the mods. It ate up the flange that the valve sealed on.] I took mine off, and went w/ a Innovative, and a digital Innovate controller. No more problems.
As far as the old puck hole.. that's irrelevant. The gate will relieve the pressure out of the main downpipe, if it's plumbed as my ATR dp was.
Ideally, the gate exhaust should be re-entered into the dp, as far from the turbo as possible.. 18" if you can do that.
The best scenario is atmosphere dump.. The cops will luv ya for that!

What's a TR gate? Turbonetics Racegate?

Below is a picture of my downpipe (the one on the top--the bottom one was what the car had when I bought it) so you know what I've got. As you can see, it's plumbed so the gases are taken from the same hole that was covered by the original WG puck.

 

[GNVYUS 1]

Look at the size of the tube feeding the wastegate, is the turbo exhaust hole that size, NO, so you'll have a spike issue until you can make the hole match the needed size to relieve pressure. Anyone who says to run a huge 44mm gate with this style of exhaust gate feeding is just trying to sell some parts as the exhaust housing hole is never going be able to feed a gate that size. Look at what the Imports have as a hole size on the header for a 44mm gate, it fricken huge. Actually look at the size the pipe on his 38mm, that's not the size of the exhaust housing hole on the turbo I'd bet.

I actually think the pictured gate style is an engineering afterthought and the only one worth it is right before the turbo on the main feed tube of the header.

 

[JST A 6]

Just an update--

I installed a brand-new TiAL 38 mm wastegate today that is equipped with the .9bar (13.5 psi) spring and it seemed to help the problem somewhat. There was one point where the boost spiked to about 25 psi but it may have done that before the WG changeout had I stayed in the throttle long enough. Looks like I'll be buying or borrowing an air grinder real soon for that WG hole in the turbine housing...