Straight pipe with Stock Muffler ?
 

Please do forgive me if these are stupid questions. What happens if i go to a local shop and ask them to make Full Straight 2.5" pipe, 1.625" 4-1 header, except with stock axle-back. How would it sound like ? and does it gain Less power than a full straight pipe ? how bad is the drone ?

You would sound like an out of tune 10 year old Civic would be my guess.
The power change would be minor.

Farty

FTFY

It'll sound quiet, like the stock axle back. I have catless header, OP, catless FP, and stock mid pipe and muffler on my car right now, sounds stock.

Without a resonator it will most likely be drony, maybe.

I take it the exhaust will be catless, cats knock out alot of sound.

Exhausts are a funny beast, either you like it, or don't.

You can always add a resonator at a later date.

As for power, you may lose some, you may gain some, where you lose or gain will depend on header design.

I ran Tomei UEL, Motiv OP, Berk HFC front pipe, and stock catback for like a week.

I sounded like a 90s Civics with a Pepboys muffler. Not good.

I'm confused about this ELH UELH debate, everyone with the UELH on a EJ25 STI or older WRX is getting ELH for torque and hp gains, everyone with A FA20 is going for UELH for torque and hp gains.

Surely the difference between EJ and FA for the headers and subsequent gains should be typical.

From my experience, UELH have issues with the exhaust flow pulse being not efficient.

Marketing??

UEL helps midrange TQ. EL has better top end power.

WRX/STi has a turbo and no torque dip like our engine. Since you still gain up top on our car with UEL it isn't as much of a trade off plus you get the subie rumble sound vs your typical NA 4 banger sound with the EL.

Edit: To clarify this is a generalization. Exact headers and tuning means ymmv

Wouldn't a header with shorter primaries, good collector and secondarys design help the midrange, without the inherent pulse problems of a UELH?

For all my years, ensuring you had EL and correct length/diameter of your primaries/secondarys for where you want your power was always the focal point during design and fabrication.

My uncle was always going on about fluid dynamics and how important header design was.

I have no idea tbh. I just know what I gathered from dyno graphs between here and NASIOC essentially. Every UEL has different length runners from the collector affecting performance it seems and results in different results. Tomei seems to be the most "uneven" but has some of the best top end results too.

And an EL with a proper tune should help eliminate most of the dip anyway. But some EL do this better then others for whatever reason (length, diameter, etc). I'm sure it all makes a difference so just a matter of doing proper research or knowing exactly what you are doing if going DIY. Though I imagine its cheaper to let someone else like Tomei, HKS, or ACE do the R&D and just buy theirs in the end

I'm sticking to my 2017 OEM headers for now, they have a couple of mm larger diameter primaries and secondarys than pre 17 headers.

Unless of course I go turbo, which, at this stage, isn't in the picture.

Anyways, the torque dip isn't worrying me, either I'm cruising around the streets, or, if I'm up it, it's never under the rpm where the dip is anyway.

Fluid dynamics is like black magic, only with more math.

Between the improved headers and shorter FD the MY17+ really doesn't need it as bad. When I test drove one it felt just as fast as my car with headers and tune.

Same here except my car sounds like shit. :iono: