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Old 05-27-2008, 05:38 AM   #1
samb
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2012 Mustang

Default Boost Oscillation *Almost* Gone

Gentlemen and ladies, I have been struggling to solve a boost oscillation problem that I have been having since I bought the car a few months ago. I bought it bone stock, unmolested except for a set of wheels and tires. I noticed after a week of driving it that the boost would oscillate between .05MPa and .1MPa in all gears. There was a noticeable drop in acceleration each time this oscillation occurred.

I tried replacing the vacuum lines on the T-connector, I tried cleaning out the BCS, I replaced the IC hoses, reset the ECU and none of that worked. This weekend I just went stage 2 with a TBE and Cobb AP reflash, and the oscillations were even worse. I looked at the map notes and converted the target boost of 15.8psi into MPa, which is about .11MPa. I realized that I was exceeding target boost by about .01-.02MPa as I was hitting .12-.13 on my stock boost gauge. I was not spiking though.

So I read up on exceeding target boost as well as on the article Cobb has on boost control (actually I have been reading that article all month). I have been skeptical of doing anything with the waste gate because I hear everywhere that I shouldn't touch it and that it should be tuned out. I have had a suspicion though that there was too much pre-load on the spring which is causing premature boost rise. Well tonight I said F-it and I loosened the actuator arm half a turn, PROBLEM SOLVED!!!! Boost builds right up to just below .11MPa which is target boost for Cobb stage 2, holds there and then gradually tapers to about .09MPa. Awesome!!

I have been referencing Corky Bell's Maximum Boost as well as Cobb's article on factory boost control and I must say I have learned a lot from those two sources. You guys should check them out if you haven't already.

Cliffs notes: Been having oscillation since stock due to exceeding boost targets, tried everything except adjusting waste gate actuator arm. See post #7 for solution.

I have had no luck so far on this site searching for anyone who has solved their issue, because there are never follow up posts. So I figured this might be helpful to someone. I'm not saying this is the solution for everyone but this is what did it for me. I am very happy, now I have to finish an 8 page paper due tomorrow. Good night Nasioc.
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Last edited by samb; 09-30-2009 at 08:20 PM.
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Old 05-27-2008, 07:02 AM   #2
samb
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Default

To adjust the waste gate actuator arm, pull the turbo heat shield off to access the adjustable end. Spray some penetrating oil on the lock nut to loosen it up and then unscrew that a few turns to get it away from the connector.

Then pry off the C-clip that is holding the connector on (I put a plastic bag underneath it so that if it shot off it would shoot into the bag). Once you have this done pull the connector off the post, you may have to pull the rod away from the actuator a little bit to do this.

Once you have it off you can loosen or tighten the arm depending on the direction you turn the connector. Counter clockwise will loosen it and clockwise will tighten, you want to loosen if you are having oscillations don't turn too much I don't did a half a turn. Reconnect everything and test it out.

Remember though that this may not fix the problem as these symptoms can be caused by a few different things.
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Old 05-27-2008, 01:23 PM   #3
tabrad
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Gotta love the feeling of being able to fix something yourself
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Old 05-27-2008, 01:48 PM   #4
Defiant Autospeed
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Quote:
Originally Posted by samb View Post

Then pry off the C-clip that is holding the connector on (I put a plastic bag underneath it so that if it shot off it would shoot into the bag).
To add to this, be SO careful when prying that clip off. There is a reason why they refer to them as "damnits" and "bastard clips"
I like to refer to them as "craaaaapp, where did it go" clips
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Old 05-27-2008, 05:13 PM   #5
samb
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Post #7 for solution.

Last edited by samb; 09-30-2009 at 08:21 PM.
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Old 07-23-2008, 12:24 PM   #6
TeamUnique05
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Hey I had the same problem! But mine started when I couldn't reach proper boost while being stage 2. I turned the wategate arm tighter to achieve proper boost. I turned it a total of 5 complete turns! Then went out and bought a new T hose setup by the turbo and then the car was over boosting. So I had to turn my wastegate arm back out 3 or 4 complete turns. That seemed to do the trick for a couple days. But then the other day it was spiking/oscillating really bad! My stock boost gage was jumping way up to .12/.13 then down to .09 then back up to .12. But it would only really do that once. It would rise like normal, but it wouldn't stop until .12/.13 then drop then rise again.

I turned my wastegate arm back out another full turn, and seemed to help for now. But does any know the cause of this? I think I am going in the right direction to solve this problem...
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Old 12-22-2008, 03:21 PM   #7
samb
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New update: Got bored a while ago and decided to spin the arm at least 4 turns. After a few test runs and more loosening I finally got the oscillations to go away completely. I'm still +/- 1psi of target boost. I think it took about 6 turns past where it was when I bought the car.
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Old 12-22-2008, 04:33 PM   #8
Hyelude
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I had the same problem. I played with the actuator arm up and down, replaced all hoses with new oem ones and nothing seemed to work. Finally, I took out the restrictor pill from the hose that goes to the turbo and replaced the hose with smaller diameter and my oscillating overboost went away. go figure!
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Old 12-22-2008, 05:11 PM   #9
Badler
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FWIW you might have just band aided the problem. Did this happen with the change in weather? If it really was stock turning that arm could cause other boost problems in the future. I would have someone/a tuner that is knowledgable(sp?) look at it.
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Old 09-30-2009, 08:17 PM   #10
samb
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It has been almost a year now and not one instance of oscillation after adjusting that arm, boost pressure builds and holds steady at target PSI.
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Old 09-22-2010, 09:30 PM   #11
burnside
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Thanks, samb.

This post was very helpful. For a pictorial representation:

WRX Wastegate Actuator Adjustment
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Old 01-15-2014, 02:10 AM   #12
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