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Old 05-27-2008, 06:38 AM   #1
Scooby Specialist
Member#: 177235
Join Date: Apr 2008
Chapter/Region: SCIC
2016 Focus RS
2002 WRX Wagon

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.

Last edited by samb; 09-30-2009 at 09:20 PM.
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