single or dual mufflers on the BP5?

[overl0ad]

ok, i'm sure that a few of you here know that i have a pair of STi Genomes on my NA BP5 .(no comments about going to a GT please, i can't afford an extra USD$16K)

there's nothing more there except of the mufflers.

i've recently been thinking about doing something with the whole system (in phases) and i think the i'm gonna work forwards from the rear. right now, focusing on cat back only.

so the question comes up, do i ditch the duals and go for a single?

some tell me that duals only affect the amount of sound produced,

some tell me that i will get more power out of a single.

how i'm thinking about setting them up is:

single: 2.5 inch all the way
duals: 2.5inch, then 2.25inch from the splits.

any experience or advice will be much appreciated.

[Huffer]

It's not really about dual or single - if the pre-muffler system is appropriately designed, it's about flow.

Is there an "H" crossover pipe in the system somewhere?

You might save on weight (and thus generate more real world HP/TQ) if you go to a lightweight single system.

Your biggest restriction will be the cat, followed by pipe diameter, IMHO.

[overl0ad]

A high flow metal cat is definitely going to go in, just a question of when.

As far as I know, I don’t think I will be using a H cross in the header section as I’m leaning towards a 4 into 1 equal length.

[Reason]

I like the dual set up on the BP's, but if you can save some weight and gain a little power with the single go for it.

[overl0ad]

agreed, but question is will i actually gain any power by going single?

...

[rougeben83]

keep the 2.5" straight to your headers, and the quasi-dual that you have right now. Not really worth the trouble converting it to a single - moreover it would look bad with the 2nd exhaust cutout being empty. In other words, you can't justify the loss in aesthetics with a significant boost in power (function > form approach) since it's an NA anyway.

[overl0ad]

the exhaust cutout doesn't really bother me...

black car, black tape. :P

nah, i gotta get the bumper resprayed anyways, not much more to get the guys to plug it up.

there's no real trouble as i need to get the cat back done, so i just need to decide.

can you guys advise if noise emissions will go up with a single?

[Huffer]

Noise-wise, that would depend entirely on the canister used, resonators, length of pipe etc.

I've heard some loud BP's before, and some really quiet ones.

If anything, you'll get a gain based on the weight reduction going from dual canister to single canister. Straighter pipe, fewer bends, better flow.

That alone would be worth it to me.

[gil_ong81]

the single most impt thing to me would be cost. how much power are you gonna gain or how much weight are you going to lose at what price?

did you hear mum screwed up the side of the van?

[rougeben83]

Yeah, plugging up that 2nd cutout can get pricey depending on the body shop.

Like I said, you won't be gaining anything by switch to either one; enough to justify the cost and labor to do it anyway.

Depending on the muffler you choose, the weight reduction won't even tip more than 20lbs or so.

Those STi genomes are relatively quiet from what I read over on Legacygt.com (granted these were turbo cars). If you go with one, it may be slightly louder, but not honda-fartcan loud.

I would be concerned with resonance in the cabin though; given you have a wagon.

[omahasubaru]

reroute it as best you can with new piping... go single, save weight, go faster.

[Huffer]

I would be concerned with resonance in the cabin though; given you have a wagon.

overload has a sedan.

[Reason]

It comes down to do you have the money and want to spend the money. If you want a bit more power and want a different sound re route it and do some research on different mufflers. If spending money is something you really don't want to do keep the set up you have now.

[overl0ad]

i was talking to someone last night and they recon about to 5KW at the wheels...

currently leaning towards a magnaflow as it comes quite highly reccomended. but i'm open to suggestions.

[rougeben83]

6-7hp at the wheels? That's...optimistic. More like 3-5hp at the *crank*

Sorry to say, but exhaust upgrades don't give such big gains on any NA car (yes, even hondas).