Boost is uncontrollable....help

[whiteflash]

So i just put on a ported 14b turbine housing and an o2 dump and now it's boosting around 20psi in third and a little past 16psi in second. fourth and fifth gear are 14psi solid where it should be. i didn't touch my mbc before i did the swap, but i'm gonna try and turn it down to see if that helps. Any suggestions?

 

[whiteflash]

Are you sure that you're not seeing boost spikes in the lower gears? You could try brake-boosting in 2nd to see what the boost stabilizes at, but don't let it sit at 20psi.

I saw 17 psi in second, whenever i see it go past 15 pounds i let off so i don't damage anything...

Not sure why you'd have more creep after porting unless you did it in such a way that the flow to the WG is worse than before. Below is a picture of my FP B28 port job, but I still have the stock exhaust (anyone wanna give me $500 for a 3" Megan turboback exhaust?).

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My port job is nowhere near yours. wanna give me your turbine housing?

I'd still check the WGA to see where the actuation pressure is and that it is functioning properly. If you pressurize the WGA to ~12psi, the arm should be fully extended, and you can check how much the lever/flapper is being rotated as a result. Maybe the flapper is opening even less now than before for some reason (clocked the housing a bit off? Arm is hitting the heat shield?).

Do you have any preturbo exhaust leaks?
I'm running out of ideas.

I positive i didn't clock the housing and i don't have a lower heatshield. but i was looking at the housing i took of the car, and i was playing with the flapper and it can't open fully because it hits the side of the flapper chamber. I was looking at the v faq on porting and it said to port this chamber to allow the flapper to open fully. wouldn't that stop most of the creep? (On the porting vfaq, it's the 8th picture down). I think i should just take the turbine housing out and port it out more. I still don't understand how you ported yours so good, i spent 8 hours and i still didn't get the step ground down all the way. but im getting full spool at 2,500rpms.....
thanks for the help...

 

[emoguitarboy]

I positive i didn't clock the housing and i don't have a lower heatshield.

You may want to reinstall it or heat wrap yout turbo...cause your alternator will fry.

I was looking at the v faq on porting and it said to port this chamber to allow the flapper to open fully. wouldn't that stop most of the creep?

It should help stop the boost creep.

I still don't understand how you ported yours so good, i spent 8 hours and i still didn't get the step ground down all the way.

FP normally does porting before they send teh turbo out, so it was rither done by a pro or a computer.

 

[kenamond]

FP normally does porting before they send teh turbo out, so it was rither done by a pro or a computer.

Here's what they shipped me:

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The other image I posted previously is what it looked like after I got done with it.

The porting that FP and others do is usually just to match a 7cm^2 gasket and doesn't do contouring around the WG entrance...atleast that's what I've read.

The vfaq section talking about getting the flapper to open 90° doesn't help if the throw on the WGA only turns the lever 45°. I'm not sure about the 14b WGA, but the evo3b16g WGA doesn't have much throw and is one of the main culprits of creep on that turbo.

If the OP tests the throw on the WGA, he'll find out if that extra bit of porting is going to help him at all.

 

[turbolover10]

Well obviously it seems you need to test the arm, if that checks out I bet properly porting the wastegate passage would solve you creep issues.

It took me forever with my cheap compressor to get that divider down too, until I realized that was the problem then went to my uncles where it took us about 2hrs to port the turbine and the exhaust manifold with his monster air compressor.

 

[kenamond]

Well obviously it seems you need to test the arm, if that checks out I bet properly porting the wastegate passage would solve you creep issues.

It took me forever with my cheap compressor to get that divider down too, until I realized that was the problem then went to my uncles where it took us about 2hrs to port the turbine and the exhaust manifold with his monster air compressor.

Did you grind the divider between the WG outlet and turbine outlet? Or did you just contour it a bit so the exhaust "splashing" off of the WG flapper would hit a divider that sent it toward the O2 housing rather than a flat "wall"?

There is a debate about whether or not you should remove the divider altogether, and I'm in the camp that is against it.

 

[whiteflash]

Did you grind the divider between the WG outlet and turbine outlet? Or did you just contour it a bit so the exhaust "splashing" off of the WG flapper would hit a divider that sent it toward the O2 housing rather than a flat "wall"?

There is a debate about whether or not you should remove the divider altogether, and I'm in the camp that is against it.

I just contoured the wall and rounding it off basically, but i didn't take out the whole wall.

 

[turbolover10]

Did you grind the divider between the WG outlet and turbine outlet? Or did you just contour it a bit so the exhaust "splashing" off of the WG flapper would hit a divider that sent it toward the O2 housing rather than a flat "wall"?

There is a debate about whether or not you should remove the divider altogether, and I'm in the camp that is against it.

I was reffering to the lip/divider, or whatever you want to call it on the turbine housing that needs to be grinded down"like in your second pic."to allow exhaust to flow easier through the wastegate passage. However I did smooth the divider that I think your talking about between the w/g and turbine housing, "but I'm not really clear on the divider that your talking about." Have any pics of it grinded down completely

I did port behind the wastegate arm to allow it to open more, I think if I really wanted to hold 15psi without creep I would have to change the e3 wga at the least and maybe do some more porting around the wastegate passage. You can clearly see from your pics that I could port a lot more around that area, I was just paranoid..

Heres some pics of what happened to my first ported turbine housing.

Btw this was with 2.5" catback and absolutley no creep on my gst.
Before,

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After about 1,500 miles at most!

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See the crack??
Btw that came straight from jnz and they replaced the housing no questions asked!

 

[whiteflash]

ya so i think i'm gonna take it off again, and just port it out as much as i can.

 

[turbolover10]

First I would pressure check your WGA and make sure you don't have any boost leaks.
If that checks out then yea I think it will help.

 

[kenamond]

I was reffering to the lip/divider, or whatever you want to call it on the turbine housing that needs to be grinded down"like in your second pic."to allow exhaust to flow easier through the wastegate passage. However I did smooth the divider that I think your talking about between the w/g and turbine housing, "but I'm not really clear on the divider that your talking about." Have any pics of it grinded down completely

Here's what I was talking about (2nd picture):

http://www.dsmtuners.com/forums/50427715-post20.html

The thread that post is in talks a bit about the debate of whether or not this is a good idea.

 

[turbolover10]

Ahh...
I haven't gotten a chance to read through the thread and I don't want to get off topic but what are the cons of doing that?? I assume you would know cause of what you said earlier about being against it but we all know that proper porting of the w/g passage will solve most peoples creep. If not possibly a different wga like that thread I posted earlyer.

 

[kenamond]

Ahh...
I haven't gotten a chance to read through the thread and I don't want to get off topic but what are the cons of doing that?? I assume you would know cause of what you said earlier about being against it but we all know that proper porting of the w/g passage will solve most peoples creep. If not possibly a different wga like that thread I posted earlyer.

At full boost, there is quite a bit of exhaust flowing out the turbine and the WG (the WG is open, because your boost is no longer going up). If you have an internal WG or are redirecting the WG flow so that it merges with the turbine exhaust somewhere along the exhaust, this is usually done carefully; the paths merge gently. For example, the stock O2 housing has two passages that merge into one before going to the DP. This merger is done "gracefully" with a tapered divider.

If you remove the divider in the turbine housing, you've inserted a new junction where WG and turbine flow can be combined, but you don't have a graceful merger of WG and turbine flow. The WG gasses splatter off of the partially open WG flapper (which only opens maybe 30° to 45°) and are redirected into the flow of the turbine exit. This interrupts the gas flow trying to escape from the turbine. This increases backpressure in the turbine exit flow (the pressure between this violent merger and the turbine wheel would be higher than if you gracefully merged the two flows together).

Because the torque applied to the turbine wheel (and therefore the compressor wheel) is dependent on the pressure difference between the gas upwind and downwind of the turbine wheel, increasing the downwind pressure decreases the torque on the turbine wheel. In order to get the same torque, the backpressure in the ex. mani. (upwind of the turbine) has to go up.

If you increase the backpressure in the exhaust manifold, you pay for it. The pistons have to push against this pressure during the exhaust stroke. If you increase the backpressure, you're actually resisting the forward motion of the engine during the exhaust stroke: you're subtracting additional torque at the crank. The motor is already paying a similar price to drive the turbine in the first place, but you've just made it worse by "backing up" the exhaust with this ungraceful WG/turbine merger downwind of the turbine.

So you either back up the whole motor and drop torque or you decrease torque on the turbine by decreasing the pressure drop across the turbine...or a bit of both (decrease the pressure drop across the turbine a bit and increase the backpressure. However you slice it, you end up dropping the overall torque and hp at the crank.

That's my reasoning. YMMV.

 

[turbolover10]

Makes perfect sense, thanks!