Disadvantage on 2.5inch all the way exhaust?

[Evok]

Hi i found myself a offer for a 2.5inch exhaust system with headers for a DC2 integra.

Wondering the disadvantages and advantages of it? Loss? Powergains? Lose torque? Mid or high end power? Etc

Thanks

[NightKids]

Chuck it on, back pressure is a myth

[dougie_504]

2.5 is fine mate, put one on my brother's DC4, goes well.

[migoreng]

2.5 inch catback on my h22a.. more midrange after tune...

[Symphorced]

If it's a 2.5" straight through exhaust (making assumption from thread title) it'll be loud as hell. Need more details... is it an off-the-shelf exhaust or custom? Hi flow cat? What sort of headers?

[GSi_PSi]

advantages > more hp/tq
disadvantages > noise

[kyzz]

loud as fk, put on a cannon bro it will sound mad

[TheSaint]

im running stainless 2.5" on my DD - didnt notice a difference between this and the previous mild steel 2.25" lol

[IV73CI]

your intake will generate the sound - Ram Pod = louder / CAI = quiter.

Then your headers/extractors will then flow the noise to your 2.5 system.

If you dont have a resonator then the noise will still continue to travel to the muffler.

depending on your muffler - cannon = loud as hell or twinloop = nice quite sound.

Saying that - a resonator depending on size/quality should be able to shut the fhukker up but yet again a str8 thru cannon will definately make the incabin noise annoying.

Power vs sound = what is it that your after?

2.5 will give you abit of lag from 0-80 but after that it should flow nicely as the engine is working harder.

for a daily - i would recommend 2.25 rather than a 2.5..

but this will depend again on what bolt on mods you have.

[bennjamin]

2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.


IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system

Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.

IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.

[Jccck]

2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.


IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system

Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.

IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.

Back pressure is not real, and by smaller engines you're talking 4stroke dirtbikes.
Some sort of flow velocity must be kept however, and if you can't move the gas through the pipe as fast as you should.. Then you're got nothing left to gain out of that oversize piping.

[rhys.l]

Taken from an article by an engineer at Garret:

"N/A cars: As most of you know, the design of turbo exhaust systems runs counter to
exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure)
in the collector to aid in scavenging other cylinders during the blowdown process. It
just so happens that to get the appropriate velocity, you have to squeeze down the
diameter of the discharge of the collector (aka the exhaust), which also induces
backpressure. The backpressure is an undesirable byproduct of the desire to have a
certain degree of exhaust velocity. Go too big, and you lose velocity and its
associated beneficial scavenging effect. Too small and the backpressure skyrockets,
more than offsetting any gain made by scavenging. There is a happy medium here."

[TheSaint]

2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.


IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system

Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.

IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.

i on my D15b7 have ebay 4-2-1 headers, magnaflow cat and 2.5" stainless catback with one resonator and an xforce 2.5" s12 twinloop
runs great - i was a true beleiver of the whole 2.25 over 2.5 for n/a honda - but after i got that system put on the car i was like ... eh almost no difference between that and 2.25
the header collector size is still the same - it than bottlenecks OUT to the cat after a bit of piping - perhaps this is why

[dougie_504]

So do we agree that the happy medium is.....2.25"? I'd have put 2.5" on my brother's dc4 but unfortunately nobody really makes that size, only 2.5. Seems to work fine though and we can probably use it when he goes turbo. But I always thought 3" was best for F/I.

[rhys.l]

I'm not sure if you can group all 2.25 or 2.5" systems into the same boat. The piping diameter in some systems ( such as spoon?) steps down at the axle back flange (like with the stock dc2r system), and this is designed to create some back pressure (which another 'straight through' 2.25 or 2.5" system wouldn't)

[Evok]

Hey guys, great info. So im guessing i should just go for it...its just custom exhaust with custom headers. 2.5inch piping with stock cat. asking cause i got a good offer.....i mite have to mod it later cause i think its guna be too loud ...the engine has no work to it at the moment to clear things up... so should i still go for it?

[MWAKU]

lol

1. dont mod for the sake of modding it
2. lol my vote is no. whats the point, go buy a hi flow cat. comes out of headers, then gets restricted again. if its going to be too loud. dont get it, just for the sake of it, unless its something u plan on really wanting. if u can do without it, do without it. sometimes its better to just save that money even if its cheap, rather than bolting on shitty loud exhausts
3. 60mm is what most jap branded exhausts use for their piping, this would probably be the best?

[bennjamin]

Another variable is the piping design itself - whether it's mandrel bent ( same sized ID at straights and bends) or crush bent ( tapers slightly in bends).
Also most bolt on Japanese cat backs have tapered restrictions at every joint !

[GSi_PSi]

sigh, this is why the US honda scene will always be ahead of us in terms of outright power.....

everything past the headers is a restriction anyway....2.5 vs 2.25 you will be making more hp overall..
you might lose a bit of torque downlow,

[Jccck]

sigh, this is why the US honda scene will always be ahead of us in terms of outright power.....

everything past the headers is a restriction anyway....2.5 vs 2.25 you will be making more hp overall..
you might lose a bit of torque downlow,

People seem scared to try the bigger size.
Plenty will say "But that's too big i'll lose power" or "No way that'll be too loud"
Nonsense, and use a better muffler.

But you're right, alot of the USA runs with the motto "Go big or go home" for most things.. Haha

[khoannaDA9]

yo i got a non vtec b18a stock and im running 4-2-1 header and 2.5 inch all the way through. from my personal experiences so far. its loud as hell when u gun it and u can feel the power when ur at high revs. so when mine hits about 5 - 6k revs, u can feel the car pull. but thats just my 2 cents. i also did a lot of research but i just went with the 2.5. goodluck with ur choice mate.

[curtis265]

I got 2.25 on my H22 and it gives me a fair bit more midrange (untuned)
I still reckon that I probably should have got a 2.5..

I'd probably recommend the same for an integra

[TheSaint]

lol

1. dont mod for the sake of modding it
2. lol my vote is no. whats the point, go buy a hi flow cat. comes out of headers, then gets restricted again. if its going to be too loud. dont get it, just for the sake of it, unless its something u plan on really wanting. if u can do without it, do without it. sometimes its better to just save that money even if its cheap, rather than bolting on shitty loud exhausts
3. 60mm is what most jap branded exhausts use for their piping, this would probably be the best?

thats some very good advice there - listen to the man


sigh, this is why the US honda scene will always be ahead of us in terms of outright power.....

everything past the headers is a restriction anyway....2.5 vs 2.25 you will be making more hp overall..
you might lose a bit of torque downlow,

this ^^
i had the same ifs and buts when i got a lightened flywheel
lost a teeny tiny bit down low - but the car builds revs so much better/quicker and revs a hell of a lot smoother now too
so at the end of the day - piping size 2.25 to 2.5 wont really matter - but i would suggest getting something quality with no bottle necks
and make sure u get a desent cat to go with the system as well

[rhys.l]

Depends what you want out the car. If it's outright dyno power, I'm sure 2.5" (or bigger) is the way to go. However, I spend 99% of my time below 4.5k rpm so I would prefer something that is a bit more responsive around this rev range. I'd say that is where a 2.25" system or even stock (if we are talking dc2r) would have the advantage.

[Evok]

Alot of info, thanks guys

I'm not modding it for the sake of it...actually want some more power out of the engine and all..on student funds too so i don't really want to spend all my money on the car else ill be struggling to even afford the car..

right now i think 2.5 from everyone views and opinion is a good go...althought i did want 2.25 from what most people was saying.
Its guna be really loud but i guess ill just change the muffler later on

Thanks guys!

[bennjamin]

Doesn't a dc2 ITR have 2.25 cat-back piping , and 14kw more peak power ? ( plus is tuned to it)

Just sayin'

[dougie_504]

^
This is why I recommend to some people that they get an ITR exhaust for their dc4/dc2 but I usually meet a lot of opposition. Mandrel bent too I believe.

[GSi_PSi]

Ben, I don't think the exhaust is contributing any power gains by being at 2.25 inch vs VTiR...
Things like bigger cams, bigger intake manifold ,throttle body ,mild port work on intake, 11:1 compression might have something to do with it though lol.

Anyways it doesn't really that much of a difference anyway, as said 2.5 tuned with a tunable ecu will give you more power , and you faggots that negged me in my post earlier show me one dyno on a b series motor where power was actually lost going bigger and I'll eat 10 hats.

It's even been proven 3 inch vs 2.25 inch on a b18c makes more power everywhere this guy has a b18cr motor With just cams , made 10hp extra only thing he did was change the exhaust .
http://hondaswap.com/attachments/15357d1304012242-honda2

[meatball]

^
This is why I recommend to some people that they get an ITR exhaust for their dc4/dc2 but I usually meet a lot of opposition. Mandrel bent too I believe.

and its stainless steel aswell i think.

[vaikis]

go for 2.5 if you whant not too loud or take 3 for great sound :)

[bennjamin]

Ben, I don't think the exhaust is contributing any power gains by being at 2.25 inch vs VTiR...
Things like bigger cams, bigger intake manifold ,throttle body ,mild port work on intake, 11:1 compression might have something to do with it though lol.

Anyways it doesn't really that much of a difference anyway, as said 2.5 tuned with a tunable ecu will give you more power , and you faggots that negged me in my post earlier show me one dyno on a b series motor where power was actually lost going bigger and I'll eat 10 hats.

It's even been proven 3 inch vs 2.25 inch on a b18c makes more power everywhere this guy has a b18cr motor With just cams , made 10hp extra only thing he did was change the exhaust .
http://hondaswap.com/attachments/15357d1304012242-honda2


Sam you just said the exhaust isn't contributing that much to power gains - and that it's more to the engine/tune which we can all agree. Why are you suggesting a 2.5 or 3 inch exhaust on a 1.8 with little or no modifications or tune ?
Saying its proven doesn't mean it's actually proven - US are known for inflating numbers and altering dyno readouts and software variables ( for the customers peice of mind and competition!)


A final answer to the OP - if it's a free or cheap exhaust system - go for it. It will be louder , and you will lose a little bottom end and throttle response. You will gain a few kw's in the upper range ( apparently important to most people in this thread !)
So go nuts ! It's your car dude

[Evok]

Thanks to more people contributing to my question!

Didn't realize how serious this has gotten from 2.25 to 3 INCH EXHAUST TALK!
Haha interesting though!

Yeah it seems i should just go for it. I might be a tune later and other mods later thought due to student funds!

Cheers!

[dougie_504]

If you're going to tune and do other mods later then I'd consider a 60mm (2.5") if I were you.

I have trouble deciding what to believe. I respect a lot of people in this thread so it's hard to decide - is back-pressure real? If yes, is it relevant? Blah blah blah.


All I can tell you is that I put a brand new XForce 4-2-1 header on my brother's DC4 GSI with B18B2. It has a 2" collector. Then we mated that to a 60mm used magnaflow high-flow cat (CEL unknown) which was already bolted to a 60mm Fujitsubo Power Getter. He firmly states (just asked him now) that the car feels better, pulls/picks up better and sounds better, and is therefore 100% happy. Obviously it will depend on who makes the exhaust - Fujitsubo and some other JDM brands just make very good products and most of them are 60mm.

But for me I'd still be wary of getting something like a 3". Again, I don't know the evidence backwards, but it just seems extreme. So if I were you I'd go 60mm. It seems to be the size of choice for JDM brands and especially if you want to do more mods later. I'll bet you don't regret it.

[dougie_504]

...


Bro thanks for the input, but are you sure that guy only has cams?

2.25" or 3", either one, it seems that the figures are quite high for such a simple setup in a B18C7. That's K-series power pretty much...

[TheSaint]

^
This is why I recommend to some people that they get an ITR exhaust for their dc4/dc2 but I usually meet a lot of opposition. Mandrel bent too I believe.

this ^^
i ordered a mugen catback from Japan for my Dc2 - cost like $1550 back in the day
in hindsight i think i should have just got a JDM ITR exhaust, a hi-flow cat and a good JDM brand set of headers
but meh that was years ago lol

[GSi_PSi]

andy- its usa dyno figures bro they always ready higher..

[rhys.l]

I think all the info in this thread can be summarised as follows:

-Daily driver, minor bolt on mods -> 2.25" or maybe 2.5" with bottlenecks

-Performance car, all usual bolt ons, cams, tune (or planned) -> 2.5", true 2.5"

-Serious enthusiast seeking big power with major supporting mods -> 2.5" + (up to 3"?)

Or that's what i think :p

[1900-hustler]

the disadvantages in my mind would be the extra attention due to the noise and potential grief from the cops..
as long as you can deal with that then go ahead and do it.

[Evok]

Ye i noticed that...mostly since i had to take the exhaust off to cause it wasnt connected properly. Thought i might go for a run without it...louder then a formula one car...

Anyways, in return! Good gains :) mostly at high rpm's its a good good gain! this is with a stock cat too.

[marquee]

the disadvantages in my mind would be the extra attention due to the noise and potential grief from the cops..
as long as you can deal with that then go ahead and do it.

Nothing resonators can't fix.

I have a 3" exhaust and it has been tested by the pea and it passed. Obviously there may be a loss of power but would be minute.

All exhausts can be quite if you want them too.

[1900-hustler]

Nothing resonators can't fix.

I have a 3" exhaust and it has been tested by the pea and it passed. Obviously there may be a loss of power but would be minute.

All exhausts can be quite if you want them too.


so basically there is no downside lol..

[marquee]

so basically there is no downside lol..

Well i have two resonators and scrape on speed humps because im low. Thats a downside

[marquee]

Another question that should be asked what are the advantages as you are paying more for a larger exhaust on a stock engine there probably wont be many gains from 2.5 to 3"

[androo]

Another question that should be asked what are the advantages as you are paying more for a larger exhaust on a stock engine there probably wont be many gains from 2.5 to 3"
No advantage, except future-proofing if major mods are planned. In most cases, no advantage.

[marquee]

Yer agreed unless you plan on major mod such as forced induction but your paying more for materials when its not needed

[HondaTurboVtec]

I personally think, 2.5" exhaust is good from little bolt on mods to engine internals (i.e cams, pistons etc).... <-- 3" & you will make more power in the high rev range & will lose some down low.
3" if you are going forced induction.