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Old 10-01-2018, 12:49 AM   #1
brandobot
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Default Are tunes required for just catbacks?

Iím protuned for my stage 2 plus equal length header.

My car came with a cobb catback that is too loud for me. Iím considering going to stock or another quieter exhaust. Will this negatively affect my protune?
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Old 10-01-2018, 01:55 PM   #2
mrsaturn7085
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Yes, but not to the extent that I'd recommend doing anything about it unless you can tweak the tune yourself. It's likely been locked by the tuner.
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Old 10-03-2018, 07:54 PM   #3
brandobot
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Quote:
Originally Posted by mrsaturn7085 View Post
Yes, but not to the extent that I'd recommend doing anything about it unless you can tweak the tune yourself. It's likely been locked by the tuner.
Thanks. I don't mind if I lose some power, but am concerned about reliability of the engine.
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Old 10-03-2018, 10:25 PM   #4
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I would always log data and evaluate - make changes if you feel you need to.
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Old 10-04-2018, 02:17 PM   #5
Charlie-III
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I don't come in here much since I am not well versed on tuning.

Unless you had a major issue with the CATback on your original tune, then a new CATback should be about 95% fine on existing tune.

Just my thoughts.
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Old 10-04-2018, 03:09 PM   #6
SirBrass
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Unless the catback is restrictive enough to noticeably affect the flow characteristics at the turbo (factory cbe won't do that, btw), then it's too far downstream of the turbine outlet to affect backpressure and therefore affect tune by altering the performance of the turbo.
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Old 10-04-2018, 03:30 PM   #7
mrsaturn7085
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Though 5% is the limit of closed loop fueling in some cases

Seriously though, it'll be fine - much better than 95% okay!

Backpressure on the stock system is mainly caused by the wastegate being undersized for a 2.5 liter motor without a restrictive catalytic converter when the turbo was designed around a 2.0.
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Old 10-15-2018, 04:53 PM   #8
ragnar007
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Default J-pipe

Do you have a catted J-pipe?
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