Single 2.5 inch exhaust vs dual 2.5 inch exhaust

[batemada]

My V6 S2 VY exhaust requires replacement. Which of these combinations would breathe better then my standard 2.25 inch setup yet still have enough back pressure not to stuff up my fuel economy.

Option 1: single pipe 2.5inch setup
option 2: dual pipe 2.5 inch setup from a VY SS.

any sugetions would be welcome.

[one_and_only2004]

back pressure....
Get the SS setup

[batemada]

Thanks for that, i forgot to mention im replacing from after the cats.
My VY is running a factory dual cat system that is one for each side after the extractors before they join up.

[Cobez]

Twin 2.5" zorst on a V6? Isn't that a bit excessive? You would lose more power than anything.

[danja]

I'd ask a reputable exhaust shop mate.

[Bax]

back pressure....
Get the SS setup

Back pressure? You need it.

Get the single 2.5.

[Cobez]

Single pipe 2.5 set up would be fine.

A twin 2.5" set up can be too excessive even on a 304. Anything bigger than a single 2.5" set up is a bit of a waste on a V6, as they don't need that much pipe to breath, you just end up losing power.

[batemada]

Thanks for the replys guys. You have confirmed what i suspected with the dual 2.5 being a bit over the top for V6. Will have to keep looking for a reasonably priced single pipe 2.5 setup.

Here in NZ the cheapest i have found is arround the $600 NZ mark.
Holden want arround $1300 NZ for a stock from behind the cats 2.25 inch setup. (must be gold plated)

[Cobez]

Don't buy ANYTHING from Holden mate, you would have to have rocks in your head to do that. They are only good for minor spare parts.

And $600 is a bit much for a single 2.5" mate, jump on ebay, look up 2.5" exhausts, i picked up a brand new single 3" for my Senator for $370, it's a cat back. It would cost you less than $600 maybe to have it shipped over to NZ, then fit it yourself. It's one of the easiest things you can do. So straight forward it isn't funny.

[Macka21]

my mate bought an 2.5" of ebay for his falcon and it shit itself after 2 months started to get holes in it. so be careful wat u pick.
im getting an exhaust done tomoro for my car twin pipes into single pipe for $500 including an aftermarket tip. will post pics if interested tomoro

[Cobez]

Nah i got mine off Egay via an exhaust shop down in Pakenham. Good stuff too!

What size pipe is yours merging into? If it's going into a single 3", look forward to a little power loss. V6's don't need that much flow, nor do they benefit from it unless they have F/I.

But hey, each to their own

[Macka21]

nah its staying th esame size all the way bro 2.5" tip

[Cobez]

Ahhh yeah, that mightn't be too bad then!!

[one_and_only2004]

You don't need back pressure.
Back pressure = resistance
after a certain threshold when you go bigger you actually increase the resistance of your pipe.

[Bax]

Yes you do need back pressure.

By going bigger you increase the resistance? I'll give you a chance to explain how. Think of a hose with the same amount of water in it, if you change from a 1" pipe to a 10" pipe, how is it going to have more resistance?

[Nanos]

to a certain point no back pressure is good. for example if your runing huge cam etc... but on a stock engine you need a degree of back pressure or you will loose all your low down torque.

most of us at one point have driven a car with no exhaust on it. yes it revs free and up high in the rev range you will notice a difference but down low you will notice a loss. if your floggint he guts out you wont, but sit low in the revs with the engineunder load and you will see a loss.

i dont have any articles or dyno sheets at hand but i have seen this test done on dyno's and if you speak to any engine tuner you need a degree of back pressure. agiain though im no proffesor on this topic just going by what i have read and seen

[Cobez]

That's a good way of explaining it Bax!!

[one_and_only2004]

By going bigger you actually slow the flow of the exhaust gases. Your 1" pipe would have a lot more flow pressure compared to the 10" pipe, but air velocity would be lost. Probably just better if you read this


The myth of exhaust backpressure - My Pro Street

IV. So how did this myth come to be?

I often wonder how the myth "Hondas need backpressure" came to be. Mostly I believe it is a misunderstanding of what is going on with the exhaust stream as pipe diameters change. For instance, someone with a civic decides he's going to uprade his exhaust with a 3" diameter piping. Once it's installed the owner notices that he seems to have lost a good bit of power throughout the powerband. He makes the connections in the following manner: "My wider exhaust eliminated all backpressure but I lost power, therefore the motor must need some backpressure in order to make power." What he did not realize is that he killed off all his flow velocity by using such a ridiculously wide pipe. It would have been possible for him to achieve close to zero backpressure with a much narrower pipe - in that way he would not have lost all his flow velocity.

[Grennan]

All you need is a single 2.5incher. Anything over that is overkill. You will start loosing torque if you go to much bigger.

[Nanos]

not to mention how bad it will sound. a stock v6 with large pipes sound like crap

[Cobez]

Hahaha ain't that the truth. Then when people put hot dogs on their V6 exhausts, they sound even worse. Way too tinny and 4 banger like. Argh.

[one_and_only2004]

i've found that no matter what you do with the ecotec you can never really get an awesome note out of them, just something that doesn't annoy the general population as much as an excel...

[one_and_only2004]

Don't know why i even bother trying to help people around here especially when they're know-it-alls that pretty much say a restriction is good in your exhaust. If back pressure's such a keeper then why do we bother swapping the exhausts off from stock? Excuse me while i go and weld a steel plate over the ends of my exhausts so i net some gains.
Thanks for the cowardly anonymous negative rep too

[Bax]

Wasn't me, you can help out mate, but I guess in a way we're helping you out by saying that back pressure is needed.

By swapping the exhaust from stock you're taking away some of the restriction and allowing it to flow further. But once you go too far you're losing out on all back pressure and as people have said above it's no good at all.

[stocky]

Don't know why i even bother trying to help people around here especially when they're know-it-alls that pretty much say a restriction is good in your exhaust. If back pressure's such a keeper then why do we bother swapping the exhausts off from stock? Excuse me while i go and weld a steel plate over the ends of my exhausts so i net some gains.
Thanks for the cowardly anonymous negative rep too

you dont think its odd at all that NOONE is agreeing with you? 2.5 is a good size for a v6. 3 inch max. anything else, you lose torque.

twin 2.25 inch exhaust is bigger than a 3 inch.
twin 2.5 inch is like having a 4 inch catback on a v6. what a stupid idea