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Catless Downpipe on 2015 STi

29K views 17 replies 6 participants last post by  Andre Wee-Tom 
#1 ·
If I install a catless downpipe will that trigger my check engine light to come on?
 
#5 ·
If you use engine management like a Cobb AP or something similar all the CEL's from emissions sensors are generally disabled. If you've already done that then removing the cat won't give you a CEL. If you have a totally stock car though and you take out the CAT, the sensor will say the CAT is malfunctioning (ahem) and give you a check engine light.
 
#6 ·
Most modern performance Cats are super high flow anyway, Other than being less expensive is there a reason your thinking catless?

/hippy rant/ I know not everyone lives in LA but during the summer months there is a haze that hangs over our freeways. If everyone just ran a decent catalytic converter we could keep a lot of that garbage out of the air. /end hippy rant/

I love horsepower but unless your at the track the difference between a catted performance downpipe and a catless would yeild marginal gains at best and will piss off the ECU at worst. Just grrab a nice catted down-pipe and enjoy your passable exhaust fumes and less CELs.
 
#7 ·
This whole conversation in regards to CEL's is kind of moot. Changing that part of the exhaust (with a catless or catted repalcement) requires re-tuning. Re-tuning can easily adjust for changes (or removal) to the emissions related sensors.

That, and what arcticscythe said.
 
#9 ·
I am fully catless as well. I have no issues with emissions. Where are you located?

It is a restriction but unless your pushing some serious HP you wont really see a benefit from it as far as more power. And even then its really not much but it is something.
 
#16 ·
- Best is really in the eye of the beholder. Best Exhaust is like the "best oil" argument.

Intakes and Exhausts alone do not make more power, they require a performance tune to operate safely and deliver gains. As far as power is concerned at stage 1/2 power levels the intake has very little effect. Even with a great tune a WRX with an intake vs a WRX without will be very similar. Intakes are really just ear candy until you get up in the 350-400HP range. The Cobb SF intake for example will give you more air rushing intake noise and more BPV noise when you come off the throttle.

As far as brands are concerned I am most impressed with the weld quality of Nameless and Invidia parts. They both have fantastic quality control but their turbo back packages are a bit loud for my tastes. that said when I get around to swapping my down pipe and cat back I will be using Cobb parts. They use a 400 Cel High flow cat in their down pipe and their cat back exhaust hangs at stock height, Its also not much louder than stock and should not draw unwanted attention.

Hope that helps
 
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