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09 Subaru Outback SE PZEV
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Discussion Starter #1
So, I've done some browsing around about the famous "Subaru rumble", as I'd heard said sound is usually created by the exhaust manifold design. I've got an N/A 09 2.5, and recently replaced the manifold, as the cat inside was going bad. While browsing around both here and the LegacyGT forum, I've seen people calling the headers on my specific vehicle, equal length.

Now this did somewhat confuse me, as every time I look for equal headers, to compare to stock ones, they always look different. The ones I put on, looks as if one side is just a bit shorter. Am I just missing something? Or are these headers a weird half and half between UEL and EL?

Example of the headers in question. Just nabbed from Amazon.

495004

495005
 

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2008 OB Limited 2.5i, Portland OR USA
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6,110 Posts
Equal length doesn't necessarily mean symmetric (or mirror-image symmetric). It only means the centerline length is equal up to the common collection point.
 

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2010 Outback 3.6R 2014 Legacy 2.5i 2003 Legacy L special edition (retired to backup)
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and it means you are going to get the best performance possible as the pulses are properly timed and work to scavenge each other
 

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09 Subaru Outback SE PZEV
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Discussion Starter #4
and it means you are going to get the best performance possible as the pulses are properly timed and work to scavenge each other
So, the equal length manifold lends to better performance, than the same vehicle with an unequal length manifold? Guess that makes sense.
 

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2008 OB Limited 2.5i, Portland OR USA
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So, the equal length manifold lends to better performance, than the same vehicle with an unequal length manifold? Guess that makes sense.
"Better performance" can be ill-defined when it comes to headers, as the effect that @YeuEmMaiMai speaks of will be specific to a narrow RPM range.

There's a whole science around header design and the engine tuning that goes with it, and whole books have been written and careers dedicated to the subject. I'm not that much into them, but I can say one thing for certain that I'll offer to you for consideration: an eleven year old Gen 3 H4 EJ253 NA engine is not the engine to be trying such mods on, as they will not pay you back with much performance improvement.
 

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09 Subaru Outback SE PZEV
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Discussion Starter #6
H4 EJ253 NA engine is not the engine to be trying such mods on, as they will not pay you back with much performance improvement.
Wasn't really planning on throwing such a mod on it in the first place. I assumed it really wouldn't be worth the cost to get them, as most I've looked at are in the ballpark of 700 or so. I wouldn't wanna impact the performance I do have just for a different exhaust sound
 
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