over boosting

'06 LGT

 

Finally got the motor back together with a bunch of new parts, having a few issues.

 

-SixStarSpeed SS-30XR (11psi spring)

-Cobb CAI

-Cobb BPV

-Perrin Inlet

-Grimmspeed TMIC/EBCS

-TGV Top Feed deletes

-ID 1000

-more

 

I'm in the middle of tuning with Dave @Cryo, with the break in tune complete and some miles on the motor, we moved on towards the power tune. First real pull and I hit 20psi. Dave wants 0psi.

 

I pull the waste gate actuator arm and move the flapper to make sure there is no obstruction. It moves freely.

 

Used a bike pump to test the actuator and it opens easily at around 12psi, Hook it back up to the waste gate valve and it takes 20+psi to open. Hmm.

 

There was a lot of preload on the actuator spring and it was hard getting it off the flapper valve, I thought maybe with a big preload the wastage valve would take more pressure to open.

 

I adjusted the actuator so it would open at around 12 psi.

 

Instead of over boosting to 20+ psi now I hit 15 psi. Still over boosting.

 

Check my vac lines by blowing through ports 2 and 3, no restrictions. Can't blow anything through port 1. Seems normal.

 

Re-route the vac lines on top of intake runners incase they were getting pinched under boost. No change.

 

Replace vac lines. No change.

 

Looking for a fresh set of eyes to help me out.

Size of restrictor pill in wastegate hose?

No pill, 3 port EBCS.

 

I bypassed the Grimmspeed EBCS and routed the pressure line off the turbo directly to the wastegate actuator, I also adjusted the arm so there is minimal preload on the spring.

 

2nd gear pull I hit 11.84psi. Cool.

3rd gear partial pull I hit 20+psi. Not cool.

 

Ugh.

Rig your wastegate wide open with some safety wire or something? Then you can at least rule out the wastegate being undersized.

No pill, 3 port EBCS.

 

I bypassed the Grimmspeed EBCS and routed the pressure line off the turbo directly to the wastegate actuator, I also adjusted the arm so there is minimal preload on the spring.

 

2nd gear pull I hit 11.84psi. Cool.

3rd gear partial pull I hit 20+psi. Not cool.

 

Ugh.

 

Straight from turbo housing to WG should be at WG pressure. Right?

Rig your wastegate wide open with some safety wire or something? Then you can at least rule out the wastegate being undersized.

 

I did hit wastegate pressure in 2nd gear? Maybe the actuator closed up some? I'll try that when the weather gets warmer.

 

Straight from turbo housing to WG should be at WG pressure. Right?

 

Correct.

 

The actuator has an 11psi spring, so the 11.84psi I hit in 2nd gear seems fine.

 

The 20+psi in 3rd gear with the same set up is worrisome. It was 25º outside? Maybe boost creep?

Bad actuator?

Bad actuator?

 

Not sure?

 

Turbo/actuator are new. Less than 1K miles.

 

I am starting to think the actuator is fine, I did hit wastegate pressure in 2nd gear when bypassing EBCS. Its the more flow in 3rd gear thing that I am worried about.

 

Anybody dealt with boost creep?

 

Maybe the divorced wastegate, catless, 3" downpipe is too free flowing? Choke the thing up a little with a bellmouth catted downpipe?

I know many people with catless DP have dealt with boost creep.

 

That turbo isn't very common and I'd hate to spring for a catted DP and end up in the same place.

 

Dave would be the ideal person to help you with this. What has he said?

I know many people with catless DP have dealt with boost creep.

 

That turbo isn't very common and I'd hate to spring for a catted DP and end up in the same place.

 

Dave would be the ideal person to help you with this. What has he said?

 

Too bad nobody makes a restriction piece to test that. Like a 3" to 1" cone to put at the end of the DP. Hey! Better yet, make a plate with a small hole in it where the DP to mid-pipe gasket goes for back pressure? Just an idea.

I know its not the same turbo but I had boost creep issues with my old VF52 paired with a GS CAI, CNT catted DP and catback exhaust. With OEM airbox I was fine.

 

My solution was to port/smooth the wastegate edges in the hotside housing.

Rig your wastegate wide open with some safety wire or something? Then you can at least rule out the wastegate being undersized.

 

I like that idea.

 

I know many people with catless DP have dealt with boost creep.

 

That turbo isn't very common and I'd hate to spring for a catted DP and end up in the same place.

 

Dave would be the ideal person to help you with this. What has he said?

 

Dave is thinking its the wastegate, Im' gonna use Captainlvsac idea and run it with the wastegate wide open and see if it builds boost.

 

Really don't want to pull the turbo in 25º weather.

Wired the wastegate fully open (which is farther than actuator travels) and was able to boost 10psi before I let off. It was super laggy, then the boost came on super quick.

 

Plan forward is to have a shop port the wastegate cause I've never done that and it I'd bet it would get too much portin'.

 

At the same time put on a bellmouth catted downpipe, been wanting to do that anyway.

 

My goal is to increase flow through the wastegate and give the exhaust a little back pressure.

Might be cheaper and more effective to go EWG?

 

I would assume any porting is kinda trial and error.

Not sure I want to go in that direction, trying to keep this car somewhat civil. >_<

 

EWG sound horrid to me.

Cant blame you there. It garners too much attention for my taste too. Maybe if I was 15 years younger....

 

Can it not be plumbed in such a way that it isn't audible?

 

So that turbo is a six star housing with a Garret cartridge? So six star undersized the wastegate?

So that turbo is a six star housing with a Garret cartridge? So six star undersized the wastegate?

 

Yep, the turbo has the 3071 ball bearing center with the MHI housing. I wanted to keep the TMIC set up and this seemed like a good option at the time.

 

http://www.6starspeed.com/ssghybabetu0.html

Couple things to try...

 

Run the boost line directly to the actuator from the turbo housing (bypass the three port). Run some data logs and see what your max boost is and how it tapers. This will give you an idea if you have boost creep or something else.

 

Put the boost lines under target boost pressure(up to what you are max boost level is) then soap each connection and watch for bubbles. I had a similar problem on mine where I would overboost and couldn't figure out why. I did a boost check on it in the garage up to about 18psi and could not find a problem. I finally checked it at 22 PSI (my target boost level) and found the leak with soap. It was an easy five minute fix that took me two months and lots of needless disassembly and reassembly of various components. (My hose was leaking at my EWG connection)

Here is where I'm at now:

 

• Unhooked WG and made sure it doesn't hit the divorced downpipe.

 

• Tested the wastegate actuator(still unhooked) and it opens around 10-12 psi.

 

• Tested the wastegate actuator (hooked up) and it opened around 20psi. Adjusted the preload 4 turns till it opened around 15psi.

 

• Then I bypassed EBCS and ran the pressure line to the actuator.

 

• Finally, I tie-wired the WG open. 2nd gear seemed good at first, but 3rd gear started to build boost. Tried to repeat the results and then even in 2nd gear it started to build boost.

 

Local Subie shop did a boost check and said everything was good, I'll ask what pressure they went up to.

 

I think I have a case of the creeps.

 

EDIT:

• Replaced vac lines with new

• Pulled NPT fittings and installed pipe dope.

Plan forward is to port the WG and install a Bellmouth Cobb catted downpipe.

After reading the entire thread, I apologize for my repeat suggestion...

 

Boost creep tends to be more creep. That is, you will go to target boost, then it will creep slowly upwards as the RPMs climb. Is that how you are achieving the 20psi in third gear or is it spiking to 20psi then tapering?

 

What downpipe are you using? I didn't see that in the thread, but as noted above, I don't read so well...

 

Have you talked to the people that built the turbo? I wouldn't think they would sell a turbo that would creep. They should have some test data on other cars?

 

 

I know it was mentioned above, but have you thought about an EWG with the dump plumbed back into the downpipe? If I had to do it all over again, that's the route I would go, hands down. Best boost control you can get(IMHO) and quiet!

No worries about suggestions, I need to re-read things anyway.

 

The boost depends on throttle input, I can hang out @0psi and partial throttle but when I mash the gas it will build up to 20psi or until I let off the gas. 2nd gear (less load?) went to 15psi. No tapering as its pretty steady, I should look at the logs again.

 

Downpipe right now is Invidia Catless divorced wastgate that goes into a SPT V2.

 

Can't get a hold of Jonathan @SixStarSpeed, yet.

 

Haven't thought too much about going EWG as the only ones I been around have been obnoxious. Never heard one plumbed back into the downpipe?

 

I'm 46 years old, got a wife and kid, and I drive a wagon It needs to be somewhat quiet.

Post the logs up if you can. I'm curious.

 

I know others have struggled with the Invidia. Not saying it's definitely your problem, but could be? I loved my Cobb DP. It was incredible build quality and worked well. I had a Grimmspeed up pipe with a Tial 38mm EWG that vented to atmosphere. I won't lie, it was obnoxious, so I know exactly what you mean. I had always wanted to plumb it back into the downpipe to get rid of the noise, but never took the plunge.

However... You may want to look into a Grimmspeed downpipe. They were not available when I built my car.

I had talked to them once about using their UP and DP and building a setup that had the EWG plumbed back into the DP through a Tial EWG. Given their cat converter is located lower in the pipe, this is easily done! It could be worth a shot! They seemed receptive to it a couple of years ago.

 

Otherwise, if they wont (they are busy folks), I would seriously look at using a Grimmspeed UP with a 38mm EWG setup, and then plumb it back into a Cobb DP. The Cobb also has the cat converter lower in the pipe. It could be mocked on the bench with a turbo and welded up. You'd have to disassemble it to install it, but would be pretty straight forward with the V-Band clamps on the EWG. It would be pricey, but damn it would be nice! It would also be as quiet as your current setup since you are dumping into the exhaust system. The SPT is the perfect balance of performance and noise. I had the same one and loved it!

I can vouch for the GS DP. Ceramic coated black it is a beautiful part.

 

I believe Cobb has now moved the cat to after the bung and that has caused complaints.

I can vouch for the GS DP. Ceramic coated black it is a beautiful part.

 

I believe Cobb has now moved the cat to after the bung and that has caused complaints.

GrimmSpeed has made that change on both auto and manual. As of a couple months ago, Cobb has done it to the auto only. Boo to both of them for doing it at all.