dumping WG back into exhaust and boost creep

[BMuu]

Hey Im having a problem with severe boost creep, if my boost gauge is accureate im getting as high as 14psi boost with a 6lb spring.

Im running a Gt35r and a Tial 38mm wg with 1.5" piping, I know 6psi is really low for a 35r but i would like to run at least as low as 8 while im still doing tuning just to be safe. I know my wg is hooked up correctly, and its hooked to a barbed fitting that I tapped into the back of the manifold, and I dont beleive there are any kinks in the vaccum line running to it. I think it could possibly bc the way its ran back into the exhaust.

Any thoughts?

here is a pic of how it is now

Yes I know the welds on the return arent my best, but I did it while it was on the car, it doesn't leak there at the bottom where it looks like i missed a spot.

[ebydrc]

i hardly read your thread but how far back is the dump ?

BTW, holy god awful welds batman

[BMuu]

probably a good 1' away if not a little more.

[BMuu]

i hardly read your thread but how far back is the dump ?

BTW, holy god awful welds batman

Im going to blame that on me not being able to look while doing most of it since the car wasnt high enough for me to fit my head under it with a welding helment on, I need to get a better jack.

[ebydrc]

probably a good 1' away if not a little more.

i pm'd you reguarding the subject

[CosmoE36]

i pm'd you reguarding the subject

id like to know too could be helpful when i redo my WG this weekend.

[jfdmas]

you ever here of the venturi affect??? well, you have the wastegate pipe coming into the exhaust at a straight 90deg. This isnt the most optimal design for flow considering the exhuast is going to be pressurizing the pipe rather then allowing it to flow.(Backpressure)

you need to merge into the exhaust at a 45deg angle causing the venturi affect and the flow of the exhuast will create a vacuum sucking the wastegate pressure out.

I hope this helps your prob.

oh, and your gunn need to add somelength to that dump, or just run it to atnosphere and solve your problems

[dredder]

[QUOTE=BMuu;8275728]I know my wg is hooked up correctly, and its hooked to a barbed fitting that I tapped into the back of the manifold, QUOTE]


Im trying to visualize this. If you tap the manifold to feed your wastegate, how does the wastegate see boost so the gate will open? If your using exhaust fumes, I dont think it has boost? anyone correct me if im wrong. Doesnt the wasgate need a feed from the compressor side of the turbo (boost)?

[95RogueM3]

Im trying to visualize this. If you tap the manifold to feed your wastegate, how does the wastegate see boost so the gate will open? If your using exhaust fumes, I dont think it has boost? anyone correct me if im wrong. Doesnt the wasgate need a feed from the compressor side of the turbo (boost)?

Intake Manifold

[BMuu]

id like to know too could be helpful when i redo my WG this weekend.

He just told me to get an electronic boost controller.

I am going to route the WG dump back into the exhaust at a better angle this weekend and hope that helps. I tested my WG with some compressed air and it is opening like it should.

[rt turbo]

Hey Im having a problem with severe boost creep, if my boost gauge is accureate im getting as high as 14psi boost with a 6lb spring.

Im running a Gt35r and a Tial 38mm wg with 1.5" piping, I know 6psi is really low for a 35r but i would like to run at least as low as 8 while im still doing tuning just to be safe. I know my wg is hooked up correctly, and its hooked to a barbed fitting that I tapped into the back of the manifold, and I dont beleive there are any kinks in the vaccum line running to it. I think it could possibly bc the way its ran back into the exhaust.

Any thoughts?

here is a pic of how it is now

Yes I know the welds on the return arent my best, but I did it while it was on the car, it doesn't leak there at the bottom where it looks like i missed a spot.

woooah dude, that is a bad way to route your WG.... you need to eas it into the DP like a Freeway onramp if your going to do it. what i always do to my cars (or the ones i routed back into the exhaust) is i would increase the downpipe size to 3 &1/2 inch right where it enters, and step it back down to 3inch about a foot or so afterwards, again, easing it in at a low angle... This is the MOST OPTIMAL engineering to route a wastegate back into the exhaust, but not completely necessary... if you dont want to up the DP size where entry point is then make sure you make it enter at a low angle and at least 1.5 ft. away from the turbine exit.

what your WG dump is doing is creating ALOT of back pressure on the wastegate side and its having an effect that slows the gated gasses and creats higher pressures in the manifold going into the turbine housing and causing boost to surge, or creep. this is a no no with that turbo size . you are gonig to continue to have this problem until its corrected.

also, i would use a larger WG dump piping than 1.5" for a 38mm.

[Rob 99 M3]

If your WG control source is the intake manifold after the TB, then you're using the incorrect source. The WG source should be on the charged side of turbo, before the TB (at least that's what the TIAL documentation that came with my WG shows and how I understand it should be done).

[BMuu]

If your WG control source is the intake manifold after the TB, then you're using the incorrect source. The WG source should be on the charged side of turbo, before the TB (at least that's what the TIAL documentation that came with my WG shows and how I understand it should be done).

Thanks, that makes sence, I dont see how it would overboost with the TB open though, but I see how it could help keep the WG open a little longer just before the BOV opens.

[rt turbo]

If your WG control source is the intake manifold after the TB, then you're using the incorrect source. The WG source should be on the charged side of turbo, before the TB (at least that's what the TIAL documentation that came with my WG shows and how I understand it should be done).

yes, this is true. the boost guage is to be used from the manifold because its showing pressure inside the motor. the WG should not see pressures after the TB because it differs when you let off the gas from inside the charge pipe (surge). i think your technically supposed to use a source just after the compressor and before the intercooler... i think thats because most ic's have a small pressure drop which would make before just a hair more accurate, or safer at least.

[BMuu]

I will definitly move it then, thanks for all the help guys. This is my first turbo build and I couldn't have done it without all the great advice given here.

I plan to fix these issues along with some other small things I need to change and I will let you guys know the results.

Good news is other than a few little small issues I am pretty happy with the car, its a blast to drive.

EDIT: would it be a bad idea to tap the turbo outlet and use that for my WG source, simular to some precision turbos I have seen? Im thinking of just tapping that since a copper plug would more liekly stay in and not leak vs tapping the thin piping right after the turbo.

[Darth Maul]

how's that blow through tune???

[BMuu]

how's that blow through tune???

Not complete. Wont be for a little while I suspect, since I have several little things here and there to fix before doing final tuning. Right now im just on a base map.

[Rob 99 M3]

EDIT: would it be a bad idea to tap the turbo outlet and use that for my WG source, simular to some precision turbos I have seen? Im thinking of just tapping that since a copper plug would more liekly stay in and not leak vs tapping the thin piping right after the turbo.

I would not tap the compressor housing or flange, but would have a bung added to the charge pipe that leads to the IC. That way if there is a problem, all you have to replace is a cheap pipe not the compressor housing.

[jfdmas]

im surprised your gt35r doenst have the vauum right off the housing?? Yea, if you dont wanna tap the housing there is a kit that alows you to tap into the silicone coupler right off the housing.

http://www.atpturbo.com/Merchant2/me...egory_Code=BCS

[ebydrc]

im surprised your gt35r doenst have the vauum right off the housing?? Yea, if you dont wanna tap the housing there is a kit that alows you to tap into the silicone coupler right off the housing.

http://www.atpturbo.com/Merchant2/me...egory_Code=BCS

ive dealt with some gt35r's in the past and have never seen one tapped from garrett

[Darth Maul]

but you are running blow through though correct, any pics of your piping or are you na still?

[jfdmas]

ive dealt with some gt35r's in the past and have never seen one tapped from garrett

yea, my buddy has a gt35r and he doesnt have one either. You think it would be standard.

[ebydrc]

yea, my buddy has a gt35r and he doesnt have one either. You think it would be standard.

i wouldnt. i plug mine, its not as accurate as one being after the cooler due to pressure drops.

[5mall5nail5]

i wouldnt. i plug mine, its not as accurate as one being after the cooler due to pressure drops.

And then you have a ginormously long line to the wastegate... effectively nullifying your theory.

[BMuu]

I just tapped the piping right after the turbo, my 2.5" piping is actually pretty thick so it worked out well. I also hooked up my boost controller while i was under there.

Here is a quick shot of my charge piping I have right now, I plan to change the 3" 90 that goes into the TB to a better one i orderd.