Turbo Boost Creep Creeping T25 14B 16G [Merged]

[kenamond]

Wow, looks nice. Do you think it will make much of a difference if I dont polish my turbine housing like that? I'll still go to town on it with some hand sanding but it will never be that smooth.

Or should I keep searching for a flapper wheel to use.

And OP sorry for jacking your thread. I hope this is useful to you anyways

I got the 80 grit flapper wheels for $5 each or something at my local hardware store. Find a place with a dremel section. The flapper wheel does A LOT with the burr marks and can actually take off metal, though much more slowly. Then I spent a couple of hours with 120, 200, 400, 600 grit or something like that and finished up with wet 600. You could do the flapper wheel then 120 and 200 aluminum oxide to get it "good enough". It'll look pretty damned shiney even after those. I honestly doubt the mirror finish lasts more than a few days before it is covered with soot, but I was fascinated with my first metal polishing experience.

My T25 housing looks kinda like yours except I opened up the WG entrance more.

 

[kenamond]

I was wondering about that, how much is safe to remove? If you want to do me a big favor you could trace it out in mspaint for me.

I'm just worried I;m gonna go through somewheres and make a hole I cant plug up with a mig welder.

He's talking about the divider between the WG and turbine outlet passages. If you're having creep issues, it's related to flow problems in the WG outlet. Any way to decrease backpressure in the O2 housing will help. I still think you want to have a divider that tapers off like what you have, but you could move the divider back into the housing. That part of the housing is all on the inside, so there's no way to open up a hole to the outside.

Here's where Bruce comes in, tells me I'm all wrong, and embarrasses me (again).

 

[IslandTSI]

I figured it would be good to keep a bit of a divider there as well. I'll do some more work in it tomorrow and see how much more I can take out. Porting the o2 housing has been the biggest pain in the ass ever. It's taken so long compared to the turbine housing and manifold. I almost just said screw it and orderd a tubular, but I will run this for the season and see how it goes.

I promised myself I woulden't spend any more money on part to support the t25. Not worth it. I'm just going to get everything ready and jump to a gt35r variant.

 

[oldman]

Here's where Bruce comes in, tells me I'm all wrong, and embarrasses me (again).

You're all wrong, I was talking about the O2 housing outlet , I would never advocate destroying turbine effeciency (undivided housing) to solve boost creep, might as well put on a cat.

It hits a bout 16 in 2nd and goes to 17 then drops down slowly, in 4th gear it does the same thing but to like 18 psi. I think I turned my boost controller all the way down and in second now It didnt go to 17.

I would focus on the boost leak test and resolve your 17psi fuel cut first so we can determine the true degree of your boost creep.

I was wondering about that, how much is safe to remove? If you want to do me a big favor you could trace it out in mspaint for me.

 

[IslandTSI]

Cool thanks a lot. I'll get back at it tomorrow

 

[kenamond]

You're all wrong, I was talking about the O2 housing outlet , I would never advocate destroying turbine effeciency (undivided housing) to solve boost creep, might as well put on a cat.

Bruce, you ninny! I was talking about the O2 housing outlet (as in the part depicted in his 3rd image)!

HA!

I'm not at all a proponent of divided turbine housing mod.

However, I don't know if cutting that much of the O2 housing divider () out wouldn't enable the turbine exit flow to pinch off the WG outlet flow since you're taking out the material that makes the turbine exit flow turn the corner toward the road.

Here's where Bruce tells me how he fixed his boost creep problem by making this single change and embarrasses me (again).

 

[IslandTSI]

How much does the turbulence effect the flow of the gases out of the o2 housing? Does anyone actually know or is it mostly assumptions?

Like I said I thought about a tubular, and was looking at the punishement 2.5 inch recirc but the angle that the wastegate tube angled back in seemed like it would disturb the gas from the turbine.

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It seems like it would be detrimental to flow. Although I'm no expert in fluid dynamics.

The SSS housing seemed a little better to me, although it costs a lot more

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Any thoughts?

And this isn't a dig at punishment. I have heard nothing but good things about them. Just a question

 

[oldman]

Damn and I thought I got you again, oh well next time.

 

[kenamond]

How much does the turbulence effect the flow of the gases out of the o2 housing? Does anyone actually know or is it mostly assumptions?

Like I said I thought about a tubular, and was looking at the punishement 2.5 inch recirc but the angle that the wastegate tube angled back in seemed like it would disturb the gas from the turbine.

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It seems like it would be detrimental to flow. Although I'm no expert in fluid dynamics.

The SSS housing seemed a little better to me, although it costs a lot more

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Any thoughts?

And this isn't a dig at punishment. I have heard nothing but good things about them. Just a question

I'm thinking about it like you are. I have no idea how big of a deal it will be, but I know that reintroducing WG flow perpendicular to turbine exit flow is worse than merging it in gently (worse for flow in both pipes), so I agree with your assessment of the two O2 housings depicted. However, if folks say good things about the cheaper housing, that's what matters. It may be worse than the SSS housing, but how much worse?

But look at the diameters of the WG pipes on both models compared to the stocker. That's probably why the merge angle doesn't matter too much.

 

[DSM4me44]

You can test the wastegate actuator. I connected a rubber line to the nipple on it and shoved the other end into a tire valve stem. I used a little air compresser and shot a little bit of air into the valve stem. I watched the flapper move and when you unhook the hose from the valve stem, the flapper shuts. I found out my flapper was only opening not even half what it should.

 

[TURB0]

An update: I actually did just that, I rigged a bike pump to the actuator and pumped it a few times to test the actuator. The wastegate started opening and closing after letting air get pushed through it. After that....boost holds steady!

 

[xdsmlaser93x]

we all know that the 16G has boost creep issues, so my problem has been seen plenty of times. i have a few questions, what is the best way to keep the turbo from just boosting over what has been set by the MBC? i mean i have the screw set so loose that it is only in there a few threads, under acceleration at about half throttle in 1'st gear its fine it hits 15 an hangs there, same with 2nd gear, one you grab third it hits 15 stays for a split second and then starts going up, i let off before it goes pat 20 because from what i've heard you cant go much past 20 on stock head bolts, and a regular non MLS head gasket, it has a stock exhaust system on it for now, gonna go 3" really soon, but will that help or hurt the boost creep issue? should i port the o2 housing where the wasgate runner is? and/ or should i port out the waste gate passage in the turbo? ive also seen people grind out the divider between the waste gate flapper and the turbine outlet... so i dont really know where to go with this. anything would be grealty appreciated

 

[EclipseGSX012]

port your exhaust manifold, o2 housing, this should help you out with boost creep but i have seen people porting turbo also to reduce boost spike.

 

[justin_5585]

Is your mods list current? Do you still have stock exhaust? Either a tubular o2 housing or an external dump will definitely help cut back boost creep. I picked mine up from punishment racing, and for the price you can't beat it. They are a site sponsor, so look in the list of vendors. If that doesn't do it, you can break out the old die grinder and do a little work on the hot side. Check out the how to section of the forums or vfaq for the full rundown. Good luck,

-justin

 

[dspecv]

I have a question to add to this, since I'm also getting creep. I've pretty much read what I need to do to resolve, but had a question. I currently have a 2g exhaust manifold and 02 sensor housing to put on the car. I figured I'd probably port those out also before putting them on, which should help with the creep. What I couldn't find by searching is which manifold gasket to use. Should I just get my 1g gasket again, or a 2g gasket? I currently have a k&n drop in, and buschur 3inch turbo back exhaust.

 

[No_Skillz]

Boost creep happens when your internal gate can't flow enough to get rid of excess exhaust gasses that make excess boost. As a result, porting your exhaust manifold will not help this issue (although it does increase performance). Getting a 3" turboback exhaust will make the issue worse, since these upgrades tend to favor the flow of exhaust way over the flow of the wastegate. The best solution I've seen is to port the wastegate passage on the turbo itself and to make sure the flapper opens without restriction. With a propery ported turbo you should be able to run all sorts of upgraded exhaust manifolds and exhausts without any boost creep.

Another solution popular with many is running at 20psi, high enough so that there isn't any more creep.

As for manifold gasket, you should use whichever gaskets fits the bigger runners.

 

[romeen]

Another solution popular with many is running at 20psi, high enough so that there isn't any more creep.

I strongly believe that this is the best solution. Porting around the wastegate passage has been shown to work but I feel that this significant change to the contours of the turbine inlet will adversely affect performance. BTW Mike, I'm not directing this at you but generally to anyone who is considering porting.

 

[xdsmlaser93x]

i thought you could run 20 psi on the stock head bolts and a plain old head gasket?

 

[romeen]

i thought you could run 20 psi on the stock head bolts and a plain old head gasket?

Every car is different but more than likely you can. I have although not for extended periods.

The stock composite HG when used with ARP head studs has worked very well for guys running boost into the mid 20's.

 

[xdsmlaser93x]

Its not so much that im worried about the head gasket as much i am the head bolts i have yet to get the head studs... dumb me... i just dont know if 20 psi would be too much for them to hold.

 

[cmjdskates]

First, regarding your over boosting. You said that your mbc screw is almost all the way OUT. Maybe you have a different type of mbc that I've never seen but out is usually for increasing boost. Try screwing it all the way back in. If that doesn't work try removing the mbc from the system. Connect your boost source directly to the wastegate actuator.

If you're still creeping then it's time to make some changes. Porting the wastegate passage worked for me when I was creeping with a 16G but I didn't have a fmic at the time. You can just crank up the boost to wherever eliminates creeping (I had my 16G set to 25lbs for almost a year with a stock 7bolt long block and my compression is still spot on) and tune with your afc. If it's not a wideband you're using to tune then just watch for knock or go to a shop or a friend with a wideband and tune it right.

Good luck.

 

[xdsmlaser93x]

I know i have the MBC set to work how it is designed. correct me if i am worng though, the boost pressure enters the controller head on with the spring and ball-bearing, then exits the nipple 90 degrees from that , the tighter you make the bolt against the spring the longer the wastegate stays closed.

 

[cmjdskates]

I know i have the MBC set to work how it is designed. correct me if i am worng though, the boost pressure enters the controller head on with the spring and ball-bearing, then exits the nipple 90 degrees from that , the tighter you make the bolt against the spring the longer the wastegate stays closed.

I think the way a mbc works is by relieving boost pressure. When the bolt is tight the relief port (where the boost pressure escapes to atmosphere) is blocked. As you loosen the bolt the port becomes exposed and some of the boost is vented off. This fakes the actuator on the turbo into thinking there is less boost pressure so it stays closed longer. I could very easily be wrong here but it's easy enough for you to check. Just tighten the mbc all the way down. If things don't get better you should really try removing it and connecting a boost source directly to the actuator. See if you still creep when you do that.

 

[xdsmlaser93x]

check this out and you'll see what im talking about

http://www.dsmtuners.com/forums/showthread.php?t=237982

 

[cmjdskates]

That's a nice little write up. Besides mixing up Vertical and Horizontal, it all makes sense. First time I've see that type of boost controller although I'm sure it's quite common. But considering your symptoms and if you refer to what oldman said about bleeder mbc, you might consider humoring my ignorance for just a little while and try what I suggested. Porting takes a long time and is very expensive if you pay for it. What I'm suggesting is free.
You seem to have a firm grasp on the concepts so I'll leave this alone now. Good luck man, let us know what you find out.