Not hitting boost target, need advice.

Mental · 12-17-2012, 09:50 AM

I will be able to post logs later if necessary; currently at work.

2005 WRX w approx 130k miles. Applicable mods include catless up and TBE, MBC/EBCS in a hybrid setup, K&N short intake, JDM v8STI TMIC, Cobb AP.

I'm in the process of being re e-tuned by a reputable tuner. Car was making 17+ PSI every day no problem (except boost spikes, which is why I added MBC and figured if I'm paying for a retune I may as well add intake and TMIC too) on a previous TBE/up/EBCS e-tune by same tuner. In the process of getting retuned for the MBC, K&N, and TMIC something has gone wrong.

We were zeroing in on boost target of 18ish PSI by adjusting the Grimmspeed MBC 4 clicks at a time (which should = ~1psi) on a single map revision, I did not change maps or reset ECU when this problem occured. I was at around 17psi, so I turned it 4 more clicks, did a pull, and was barely able to hit 15psi. Further adjustment of the MBC makes no discernable difference (I tried 24 more clicks and still barely hit 16psi).

I inspected and tightened every hose, nothing appears to be leaking. I'm thinking I could tighten the WG arm, but it's strange to me how I was making boost fine and now suddenly won't make past 15psi and the MBC adjustment makes NO difference. The humidity went up to 100% as well around here RIGHT when this problem started, but I'm not sure that I would be a full 3psi below target with the MBC set at like 20+ psi.

At full throttle the MBC is basically completely in control of regulating boost, so my tuner explained that it must be something mechanical.

Anyone run into a similar issue?

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Mental · 12-17-2012, 01:21 PM

Solved. I just kept turning the MBC tighter and tighter. Maybe the spring loosened up slightly after break in. No idea. Yay!

12-17-2012, 09:50 AM	#1
Mental Scooby Newbie Member#: 321773 Join Date: May 2012 Location: Exton, PA Vehicle: 2005 WRX Aspen White	Not hitting boost target, need advice. I will be able to post logs later if necessary; currently at work. 2005 WRX w approx 130k miles. Applicable mods include catless up and TBE, MBC/EBCS in a hybrid setup, K&N short intake, JDM v8STI TMIC, Cobb AP. I'm in the process of being re e-tuned by a reputable tuner. Car was making 17+ PSI every day no problem (except boost spikes, which is why I added MBC and figured if I'm paying for a retune I may as well add intake and TMIC too) on a previous TBE/up/EBCS e-tune by same tuner. In the process of getting retuned for the MBC, K&N, and TMIC something has gone wrong. We were zeroing in on boost target of 18ish PSI by adjusting the Grimmspeed MBC 4 clicks at a time (which should = ~1psi) on a single map revision, I did not change maps or reset ECU when this problem occured. I was at around 17psi, so I turned it 4 more clicks, did a pull, and was barely able to hit 15psi. Further adjustment of the MBC makes no discernable difference (I tried 24 more clicks and still barely hit 16psi). I inspected and tightened every hose, nothing appears to be leaking. I'm thinking I could tighten the WG arm, but it's strange to me how I was making boost fine and now suddenly won't make past 15psi and the MBC adjustment makes NO difference. The humidity went up to 100% as well around here RIGHT when this problem started, but I'm not sure that I would be a full 3psi below target with the MBC set at like 20+ psi. At full throttle the MBC is basically completely in control of regulating boost, so my tuner explained that it must be something mechanical. Anyone run into a similar issue? * Registered users of the site do not see these ads. Last edited by Mental; 12-17-2012 at 10:09 AM.

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12-17-2012, 01:21 PM	#2
Mental Scooby Newbie Member#: 321773 Join Date: May 2012 Location: Exton, PA Vehicle: 2005 WRX Aspen White	Solved. I just kept turning the MBC tighter and tighter. Maybe the spring loosened up slightly after break in. No idea. Yay!