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Discussion Starter · #1 ·
ive found aout after i put my exhaust on (3 inch turbo back) my boost guage reads just under 8psi. is it common for an exhaust to do that?
 

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Frozen Lake Driver
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Less restriction on the turbo allowing it to spin more efficiently hence making more boost.
 

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Destroyer of Turbos
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Less restriction on the turbo allowing it to spin more efficiently hence making more boost.
/\ this. its very common to gain a lb or 2 just by adding a less restrictive exhaust. enjoy the free power!


Boost creep
/\not this... completely different item
 

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I have a 3" electric cutout in a custom DP, I gain about 5psi when I open it. I would think you could gain more than 1-2psi with a turbo back. Did you replace the elbow behind the turbo too? Or just get a DP that bolts to the stock elbow (not a 3" turbo back).
 

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I'm hitting around 10 psi with a 3 inch exhaust/test pipe 3 inch divorced recirculated down pipe, 2.5" IC pipes, and spearco replica IC on a stock CT26 with nothing else, no wastegate mods..

spools up nearly instantly, too..
 

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ƒ=1/2π(√k/m)
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The wastegate is what regulates the turbine speed, and it's pressure dependent.
It's common for boost levels to rise with an open exhaust over stock.
 

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NO SOUP 4 U
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I know after i did my exhaust i was up there. Plus... ya gotta watch the throttle on those cold days.
 

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I know after i did my exhaust i was up there. Plus... ya gotta watch the throttle on those cold days.
Yep, I'm going to have to De-shim the wastegate after I got the 3" turbo back.

What would be the next smaller step in mods to keep from hitting fuel cut? I'm not thinking that fuel cut defender either. Would the Lexus AFM and 550injectors be the next small step forward?
 

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Discussion Starter · #10 ·
I have a 3" electric cutout in a custom DP, I gain about 5psi when I open it. I would think you could gain more than 1-2psi with a turbo back. Did you replace the elbow behind the turbo too? Or just get a DP that bolts to the stock elbow (not a 3" turbo back).
nope its a legit 3 inch turbo back it has a full 3 inch dp elbow built in to it test pipe from titan motorsport and catback from znex motorsport...... yay free boost!!!
 

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Yep, I'm going to have to De-shim the wastegate after I got the 3" turbo back.

What would be the next smaller step in mods to keep from hitting fuel cut? I'm not thinking that fuel cut defender either. Would the Lexus AFM and 550injectors be the next small step forward?
The next thing I would do is to get the LEX AFM with 550's. I'll tell you like I was told. If you do this you will need some way of tuning the fuel curve. Just slapping the AFM and 550's in probably won't do you much good without the proper tuning. That will raise fuel cut slightly as long as your air flow is freed up as well (exhaust and intake). I would also suggest getting a Walbro and Adjustable fuel Pressure Regulator while you're at it. No sense in half assing anything. That's just my $0.02
 

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i could probably hit 11.5 psi as well, but i'm on a W58 with a 4.3 rear end, so I never hit full boost before I have to shift..
 
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