I have a IX with a few mods and am having toubles controlling boost. I have 3" tb, AMS licp and ic, UNOS, HKS 272 ex. cam, k&n drop-in, and just installed a jet-coated o2 housing.

After the o2 install, my boost is spiking wildly. As rpm's increase, boost increases until it hits fuel cut. Wierdly enough, I had the problem when I tried installing an open element k&n cone filter. When I went back to stock airbox, everything was fine, 20 psi with a slight taper near redline. Now its doing the same thing. What a strange coincidence huh?

Anyone have any ideas? Has this happened to any of you? Any help will be appreciated. Thanks.

-Dave

 

Did you grease the ball in the mbc?

 

Yes, similar things have happened to others. You would know that with a quick search. You would also have seen the solutions to those issues, but since yours sounds a little different to me, let me give it a shot:

1) Do you have all those mods without a tune? I assume you have a flash - there's no way you have all that other stuff installed without a flash, right?

2) Which spring are you using?

3) Did it spike like that before the o2 switch? You said it started after the o2 switch, so did anything get changed/touched/moved/uninstalled/reinstalled related to the boost? Did you modify/change/adjust/mess-up the WGA? Did you put the boost lines back how they were before? If you have them backwards (wga/turbo nipples), it will spike uncontrollably.

4) Which spring are you using? I assume the stiff spring. Did you take the UNOS apart to ensure that the bottom coils of the spring are FULLY SEATED ON THE NIPPLE inside the bottom half of the MBC?

5) Have you applied fully synthetic grease to the ball and spring as prescribed by Forge and others in the other threads mentioning similar spiking issues?

6) Have you ensured that the small bleed hole on the MBC is cleaned out and free of any debris from the anodizing process as per the instructions of Dynoflash Al in the thread he posted regarding this situation?

 

Thanks Warrtalon, I was hoping you would reply. Answers:

1. I am actually getting tuned at AMS this Thursday

2. Stiff spring, because I was running alcohol in my VIII and I never changed it

3. No change to actuator. I was spiking before the o2 install only for 1 day, that was when I installed an open element k&n cone filter just for the day. The only thing I did today was the o2. So I was running a steady 20 psi for atleast a month.

4. Yes, I have opened the MBC and the STIFF spring is seated correctly.

5. Yes, I have applied fully syntec ball grease to the ball, but I didn't lube the spring.

6. I will have to again check to see if the bleed hole is clean and free of debris.

So, what is wierd is that I was having no issues with the stock airbox. I had the same problem before only after I tried an open element intake.

BTW, I did do a search, but didn't feel like reading and sifting for hours.

Thanks.

-Dave Rush

 

I just swapped UNOS's with my brother and figured out it is not the problem. I just don't understand why or how an o2 housing can make my boost so erratic. Anyone?

 

ttt for a little help. Boost increasing as rpm increasing!?

 

the watsgate arm is prob not correctly adjusted

 

I have yet to install my boost controller, but I experience a very similar scenario whenever it is extremely cold out, and I too just have an open element conical K&N filter... My only other mod is a 3" tbe, and I assume this is why I get a boost spike of around 25-26 lbs, but it qucikly settles, so I don't worry... However, on ocassion in 3rd or 4th gear I experience a boost CREEP much like you refer to, which continues until the car hits fuel cut... Mind you this never happened on my VIII just the IX...

 

your car is also flowing a great amount of air now too from the o2 back... Try a Halman MBC... On my VIII it held a rock steady 20lbs alll the way to redline..You also say the problem is a spike but a spike is when the boost spikes and quickly settles... This is not a problem.... you have boost creep, where the boost continues to rise until the car hits fuel cut.....

 

I actually havn't touched the arm of my wastegate. But I did take a look at it yesterday to make sure I didn't hit or mess up anything when installing the o2 housing. Thanks Al.

 

I understand what you are saying, and thanks for the term correction, but just slapping on an o2 housing should not make that big of difference on boost. Yes, it will make a difererence with exhaust flow, but that only will normally make a pound or two of boost change. Not the way in act entirely. This is too wierd, and frustrating. Thanks for your help though talontid.

 

A freer flowing exhaust system is more likely to induce boost creep. I'm not saying that's necessarily what's happening, but it's not inconsistent with the information provided so far.

 

Wouldn't be the other way round? A restrictive exhaust would prevent the WG from bypassing enough exhaust hence creating too much boost?

Giving this a bit more thought, is your point a freer flowing exhaust would allow more boost to be created because the wastegate cannot keep up with the added efficiency of the compressor since everything flows better?

-Brian

 

Less backpressure, more flow, more boost, and then the wastegate cannot keep up and divert enough exhaust away from the turbine. This phenomenon is certainly well documented on lots of turbo cars that come with inadequate internal wastegates (STi VF39 comes to mind as poster boy case). They may be OK at stock airflow levels, but increase airflow and you trigger boost creep. The solution is to port the wastegate or run external :-)

However, I have no hard evidence yet that the big 16G in the IX suffers from this problem, but then again I can't rule it out completely yet either.

 

You are right, there is too much flow from the exhaust. The wastegate actuator just can't keep up. I'm going to AMS tomorrow for an Ecutek dyno tuning, they said they can take care of that. Thanks.