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Low boost after exhaust install

5502 Views 17 Replies 10 Participants Last post by  DC85
Hey people i have a wierd issue. Got a cruze 2012 Eco, MT.
At first i intalled a boost gauge and i could see the car hitting 13-15 psi but after installing high flow dual output muffler and removing stock resonator, the car will only hit 8-9 psi,10 if your lucky.
Added a cherry bomb high flow resonator and same issue.
I have never seen this issue here and im looking for some light into it.
Tought it could be the gauge and bought a different one, and same issue.
Apart from that i have stock intake with cone filter instead of box, and bvp vaccum line connected dirrectly to vacuum source on intake manifold.
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I'm no turbo expert, but I'm thinking more exhaust volume with your new system translates into reduced velocity which translates into reduced turbo rpms and less boost...
I had a 2011 ECO 6MT - installed a Borla cat back. I had the trifecta tune - would hit boost in the 20+ psi range. Did notice in summer temps boost was higher by 2 or 3 psi then in winter. Has to do with air density. Did outside temps drop significantly after you installed the exhaust?
I'm no turbo expert, but I'm thinking more exhaust volume with your new system translates into reduced velocity which translates into reduced turbo rpms and less boost...
True, and check for leaks in what you installed as well, never know you might have thought something was tighten down and turns out it wasn't
I had a 2011 ECO 6MT - installed a Borla cat back. I had the trifecta tune - would hit boost in the 20+ psi range. Did notice in summer temps boost was higher by 2 or 3 psi then in winter. Has to do with air density. Did outside temps drop significantly after you installed the exhaust?
That's strange, colder air should have higher psi rather than warmer air..hmmmmm
These engines boost to a certian power number. It may be that with the exhaust and lower temps it is able to hit that number on a lower boost. Does the power feel the same or maybe a little better?
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Cherry Bomb!? Do they still sell those in the Pep boys "Euro" Isle along side the snap on race peddles!
Thanks for the replies
1. It feels the same just numbers dont match, guessing the torque management system maybe...dont know
2. Yes it been cold, not extremely but we get days of 60 being the high, some days 25-35 is the high.
3. Leaks i havent notice yet, will check again to make sure.
And they do, i like because they quiet down the car a little but still maintain the growl
@cruzinred92 yes i can feel the power and better acceleration, but not the same boost number. That makes sense what you said
i'm having a similar problem i have a 2011 eco mt and the welds broke for my resonator and i immediately went from 16-18psi to 6psi if im lucky and right now its in the 40s at night and 60s during the day no change either way i also have huge power loss i timed my 0-60 and it was 16 seconds lol no joke.
Thats why i added back the resonator, to see if that was the problem, guess im not the only one seeing this happen
Boost is a measure of restriction. Less restriction equals lower boost and more volume therefore more power. I do not know the turbo map of our cars but you do not want to lower the boost and end up outside the turbo compressor map.


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Boost is a measure of restriction. Less restriction equals lower boost and more volume therefore more power. I do not know the turbo map of our cars but you do not want to lower the boost and end up outside the turbo compressor map.


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What? Boost is measured on the compressor side not turbine side. I think its computer related since its a torque regulated vehicle. Also if you are making the same amount of power at a lower boost level than thats better. Heat accounts for 65% of turbo spool.
I agree that it is better to make the same power at lower boost but if the turbo is out of its map now, then the turbo is not running efficiently.


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Boost is a measure of restriction. Less restriction equals lower boost and more volume therefore more power.
Yes. The 2.5" SS/TC exhaust combined with the mid-length header and 2.5" downpipe on my Cobalt dropped me a couple psi - but the car is quicker/more powerful as a result.
I agree that it is better to make the same power at lower boost but if the turbo is out of its map now, then the turbo is not running efficiently.


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If he is making the same amount of power at lower boost level than that tells you his kpa is in line.
Thanks for all the replies, still checking and still same thing, will be adding the downpipe soon and will report back if any changes cone up
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