Exhaust/noob question - Subaru WRX Forum
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#1 Old 01-13-2013, 08:47 PM
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Exhaust/noob question

Hello all I'm new here and new to Subaru. I just recently bought my first wrx(09) and I really enjoy it. I'm wanting to put a exhaust system on it, full turbo back. I'm reading with a turbo back exhaust I'll need to do a tune. I understand and know why I'd need a tune with say a intake upgrade. But could someone shed light to as why the car would need a tune for a exhaust upgrade. I'm sorry for kicking a dead horse here. I couldn't anything to support why. Just that turbo back exhaust upgrades need a tune. Like I said I'm new to wrx's so please forgive my ignorance on the subject.
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#2 Old 01-14-2013, 05:42 AM
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Increase of fuel needed to support the extra flow.

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#3 Old 01-14-2013, 05:53 AM
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I'm not sure I understand. Why would the extra flow on the exhaust side require more fuel.

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#4 Old 01-14-2013, 08:23 AM
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If I were to go with a non cat down pipe and a mufflered exhaust or even stock exhaust would I still ned a tune? I'm just trying to get away from the stock down pipe (partially blocked waste gate).

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#5 Old 01-14-2013, 08:38 AM
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If you touch the downpipe you need to tune.

Cat-back only and you're fine.

You need to tune because aftermarket downpipes let the turbo breathe easier, and often causes the stock tune to somewhat lose control of boost causing the car to overboost. You tune to account for the change in flow, generally raising boost a few pounds and adjusting fueling to match.

-Chris
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#6 Old 01-14-2013, 08:52 AM
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Thanks I was just wanting a explanation other than, you just need one. Well is there a way can get away from the factory down pipe (plate style) without needing a tune?

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#7 Old 01-14-2013, 09:08 AM
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No. And why would you want to waste your money trying to?
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#8 Old 01-14-2013, 09:12 AM
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Seems that you don't understand.

There is no performance benefit to just slapping a downpipe on. You put the downpipe on so you can tune the car to run more boost. You get exactly zero safe horspower from putting a downpipe on the car.

Alternatively, you can just get what is generally called a "stage 1" tune. The car has to be completely stock mechanically, you just get tuned for a slight bump in boost and power.

-Chris
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#9 Old 01-14-2013, 09:55 AM
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I'm not looking for a performance gain. I'm looking to a less restricted flow off the turbo for better flow/lower egt's.

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#10 Old 01-14-2013, 11:10 AM
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So I guess a cat back exhaust is the way to go if I'm not wanting to do a tune.

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#11 Old 01-14-2013, 11:16 AM
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Since cat back exhausts don't substantially change the flow of the exhaust or create lower EGT's (to use your words), they don't require tuning.

Basically, if you want to create more power with a car you have to ignite more air. Flowrate helps get more air through your engine, but you still need the corresponding change in fuel delivery to ignite it correctly. Too much air without a fuel increase means lean conditions and engine destroying knock.

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#12 Old 01-14-2013, 01:24 PM
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Yeah I know all about air to fuel mixture from the intake side. I just wasn't sure or knew why a tune was needed from a change on the exhaust side of the turbo until now. I was wanting to get away from the factory down pipe and its restricted flow and add some sound via exhaust system. Since now knowing I can't without a tune and I don't want to do a tune since its under warranty and I just got the car. So it seems I'll just have to settle on a cat back exhaust and mess with the down pipe later, when I'm ready to tune it.

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#13 Old 01-14-2013, 01:55 PM
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#14 Old 01-14-2013, 02:18 PM
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Hahaha its that new anti gravity tune. The stupid thing every time I tried to load the picture up it loaded up side down. So I turned the original up side down thinking maybe it'd load the right way. Well it didn't so I'm rolling with the up side down wrx lol.

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#15 Old 01-14-2013, 02:28 PM
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I didn't even notice. NICE

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