cat back size ??

[geo41e]

ok guyz..l know this has been covered abit..however i'm still not finding what i really need

engine is a d16a8 in my civic...
l got headers and a muffler...however i wanna know my ORIGINAL size cat back....

i heard that 2" is better all round and 2.25" is better for top end...
now my question is....which is better:
2" MENDREL BEND OR
2.25" PRESS BEND ???

is there anything in between that?? what is the "best" diameter for all round performance ?

[Kit]

mate, despite what everyone else says, i think you should only go 2 inch mandrel bent and no more.

[wynode]

Original is around 1 3/4 or thereabouts if I remember correctly. But thats presed bent and i'm not sure how thick the stock piping is/was.

As for what's 'best' it depends on what you want.

[geo41e]

what i want is overall power increase...that is..without loosing low end, but still increasing top end ?

these obviously a certain diameter to get the best of both worlds...l'm thinking, in betweeen 2" - 2.25" ?? 2.10" - 2.20" ??

[Kit]

like i said, get 2 inch mandrel bent.

if you're asking about pipe diameters then obviously you are getting it custom made... I would recommend you goto somewhere like liverpool exhaust cos out of all the custom work I have seen, their work seems to be the best.....

but still the quality won't be as good as a jap exhaust though.

get a stainless steel straight through muffler, and don't bother with any mild steel mufflers. and dont forget to ask for a really big resonator in the middle, cos otherwise it will be really loud.

Chris

[geo41e]

cheers kit
seems like 2" mandrel bent seems the choice, and what u mean by straight through ? as in,. without bending at all ? that would make my ground clearence even lower coz my cars pretty low already.

is there a big diff if its madrel bent straight through, and mandrel bent while following the original path of the stock cat back ?

[Kit]

geo,
no, the exhaust will definately follow the original path of the stock cat back.
it would be impossible to have straight cat back exhaust due to ground clearance etc.

when I was talking about straight through, I was referring to the muffler.

there are mufflers that are baffled (i.e. they have lots of chambers inside it for muffling sound), these baffled muffers are bad for flow.

Straight through mufflers don't have any baffles, if you had a look, you can see straight through it, there are no chambers, hence the name: straight through muffler.

Chris

[wynode]

You could go underaxle :)

[bennjamin]

You could go underaxle :)

only if ur a crazy ass fecker with no sense for ur own hearing , those around you or any pot hole deeper than 3 cms :)


Does look dam hott tho :P

[geo41e]

lol..yonas has a underaxel ??? or i must of mistaken his car for another blue eg with and ART sticker

anyway..thanks chris..l'm prolly gonna get 2" mandrel bend...not..with the resonator...what does Obe run..the guy with the buddy club exhhust civic ? the black one? Does he even have a resonator ?

[Kit]

lol..yonas has a underaxel ??? or i must of mistaken his car for another blue eg with and ART sticker

anyway..thanks chris..l'm prolly gonna get 2" mandrel bend...not..with the resonator...what does Obe run..the guy with the buddy club exhhust civic ? the black one? Does he even have a resonator ?

you're not getting a resonator?
ok.. try it, and see how long you can last! :D

[joneblaze]

You're not getting a resonator Geoff? Errm... *oh Christ*... :)
Like 95% of exhaust systems you hear out and about have a resonator (or two) sitting somewhere along the line. You might wanna reconsider that one. AFAIK, having a hotdog/resonator fitted on your catback only loses you a fraction of "power", if any.


Here, I've cut and pasted this from Team-Integra.net , hope it helps in relation to muffler flow question -


=====>

[joneblaze]

Mufflers
Exhaust manufacturers can use a single method or combination of methods to manipulate exhaust noise with mufflers. The main muffler designs are chambered, straight-through, and twin-pass.

Chambered
http://www.team-integra.net/images/BAEC1978-D3A7-4405-AB2D-2761DC15A96D/articles/faq/exhaust_basics/exhaust6.jpg
This is mainly a combination of restriction and reflection methods. The dead end chambers like I mentioned earlier serve to keep sound waves from exiting the system. For sound waves that reach the end of the muffler, the majority are reflected back to destroy any sound waves that may be trying to get through. Very quiet but also somewhat restrictive.

Straight-through
http://www.team-integra.net/images/BAEC1978-D3A7-4405-AB2D-2761DC15A96D/articles/exhausts/exsound2.jpg
Absorption is the name of the game here. The size of the muffler is going to play the most important role in how the exhaust note will sound. A short thin muffler casing will ensure a louder higher pitched note while a long and fat muffler casing will give a deeper and quieter note. Also, exhausts like the Greddy EVO are designed so that the pipe enlarges when entering the muffler. This slows the pulses down and allows more sound to be absorbed. That's how a muffler that is relatively small like the EVO sounds much better than other mufflers it's size. So sometimes you also want to find out what the piping size INSIDE the muffler is, as that can also attribute to how the exhaust will sound.


N1 Straight-through
http://www.apexi-usa.com/graphics/pImgLeft_exhausts_n11.jpg
A more extreme design of the straight-through systems are the "N1" style mufflers. As you can see, there's little to no sound absorption going on here. Muffler is short and very small. Insulation material is kept at a minimum. This flows no better than a regular large muffler straight through however will sound much louder and high pitched. Couple this type of muffler with no resonator and you'll turn your Honda automobile into a Honda weed trimmer. "Hey my weed trimmer sounds tiiite yo!"



Twin-pass
http://www.team-integra.net/images/BAEC1978-D3A7-4405-AB2D-2761DC15A96D/articles/surferx/hytechm2.jpg
The method used with this muffler to reduce noise is mainly absorption. The pulses have to travel through the muffler twice, which basically makes the muffler twice as long with twice the sound killing power. Also some acoustical tuning goes into making a muffler like this as well. With brass wind instruments, you change the note by selecting different length tubes for the air to travel. Longer tubes will give a deeper note while shorter tubes give a higher note. This type of muffler basically lengthens the tube, allowing sound waves to spread out and emit a deeper tone once exiting the system. The twin-pass design flows as well as a straight-through but will sound much quieter.


Info taken from www.team-integra.net :)

[VTEChnique]

I had Cat-back exhaust fitted on tuesday.. I had the same dillema..

My current D16Y1 SOHC VTEC will hopefully soon be replaced by DOHC VTEC and I didnt want to get exh system done twice so I opted for mandrel 2.5" in anticipation of the DOHC.

I also went UNDER-AXLE but am amazed by how high the exhaust shop (Genie) managed to keep the system.. it follows the path of the OEM exhaust - AROUND the fuel tank, then ducks under the rear axle and up to the OEM mount points.

so IMO it is much better to go AROUND the fuel tank than UNDER it as yes, you WILL get clearance problems.

FYI, the 2.5" with 1 x hot-dog resonator is FKN loud !!!
Power delivery in low end seems laggy in terms of 'spinning-up' but seems to make good power all the same.. mid and top end is completely different beast, smoothing out my power curve rather than the usual VTEC spike with top end making traction an issue in these damp roads..

The SOHC VTEC's do NOT have VTEC on the Exhaust valves, so I figure any help to get the spent gasses out of the cyllinder would be a great help..

wouold have been VERY interesting to do a before and after dyno comparison on this system.

Basically i'd reccomend 2.25" mandrel for SOHC's..

[Civic Type R]

why did you get 2.5" on a SOHC bede ? thats too big !

[Kit]

I had Cat-back exhaust fitted on tuesday.. I had the same dillema..

My current D16Y1 SOHC VTEC will hopefully soon be replaced by DOHC VTEC and I didnt want to get exh system done twice so I opted for mandrel 2.5" in anticipation of the DOHC.

I also went UNDER-AXLE but am amazed by how high the exhaust shop (Genie) managed to keep the system.. it follows the path of the OEM exhaust - AROUND the fuel tank, then ducks under the rear axle and up to the OEM mount points.

so IMO it is much better to go AROUND the fuel tank than UNDER it as yes, you WILL get clearance problems.

FYI, the 2.5" with 1 x hot-dog resonator is FKN loud !!!
Power delivery in low end seems laggy in terms of 'spinning-up' but seems to make good power all the same.. mid and top end is completely different beast, smoothing out my power curve rather than the usual VTEC spike with top end making traction an issue in these damp roads..

The SOHC VTEC's do NOT have VTEC on the Exhaust valves, so I figure any help to get the spent gasses out of the cyllinder would be a great help..

wouold have been VERY interesting to do a before and after dyno comparison on this system.

Basically i'd reccomend 2.25" mandrel for SOHC's..

It would be good to get a dyno reading for your exhaust, my guess is that you're losing more down low than you think, and not gaining as much up top as you think.

also, the 2.25 and 2.5 exhausts will drone more at cruising speeds

[Civic Type R]

2.5"on a D16y would be detrimental to your backpressure and you WILL lose power and torque.

Please refer to my exhaust write up.

Civic gets exhausted
http://www.dohc-vtec.com.au/pages/linked/civic-gets-exhausted.htm

[Kit]

2.5"on a D16y would be detrimental to your backpressure and you WILL lose power and torque.

Please refer to my exhaust write up.

Civic gets exhausted
http://www.dohc-vtec.com.au/pages/linked/civic-gets-exhausted.htm

hmmm here we go with that nasty "B" word again :D

I explained it in another post (can't remember which) but its nothing to do with backpressure, which is actually bad for power production, but rather its to do with scavanging.
:)

Chris

[Civic Type R]

how could it have nothing to do with backpressure ?

[Kit]

In a nutshell:

basically, its a common misconception that backpressure is good for low end power production in an NA car.

In reality, backpressure is bad for power production.
you want to be able to get max air in and max air out of the engine for it to produce its optimal power.

So why doesn't everyone just whack 3 inch exhausts (which would have very low restriction and backpressure) on their NA civics?

cos with the large pipe diameter, the small displacement NA engine isn't able to produce enough exhaust gases at low to mid (or even high) rpm for it to scavange effectively, so in effect it won't be able to have the exhaust gases exit at a speed at which it possibly can.

Chris

[denaro]

Uh...he said he put on the 2.5 inch exhaust as he was going to go for a DOHC engine, I presume a B16 or B18....

Even though it's still a bit big, at least he thought ahead for his engine swap ;)

[KB]

IMO anything over stock will be an improvment in power.

What kit says is absolutly true, having back pressure is bad, because if a cylinder can't get all the exhaust out then on the next stroke, the cylinder will only get partial amounts of fresh air in, because there is still crap exhaust gasses in there taking up space.

Although Adam has a point too having a masive exhuast like 3 inch on a civic is bad because exhaust gasses wont travel smoothly through out.

For example, put a straw in your mouth and blow, notice the air comes rushing out the the other end fast.
Now sick you head inside a massive pipe and blow notice the air doesn't rush out the other end, because there isn't enough air inside the pipe to create enough pressure to make it flow, and it just pools in one place.

So ultimatly the trick is finding a size where there is still sufficent back pressure to make exhaust flow, but not so much that it becomes restrictive.

IMO

1.5L SOHC = 2.00 inch cat back
1.6L SOHC = 2.00 inch cat back
1.6L DOHC = 2.25 inch cat back
1.8L DOHC = 2.50 inch cat back


btw Adam, Bede is planning on putting a B18C engine is his hatch, so he was just thinking into the future. But **** it sounds nice though :D

[VTEChnique]

Uh...he said he put on the 2.5 inch exhaust as he was going to go for a DOHC engine, I presume a B16 or B18....

Even though it's still a bit big, at least he thought ahead for his engine swap ;)

thankyou that was my exact point - but has made big gain over stock 1.75" pipes !! Did I not say that IMO 2.5" is too big for SOHC - or I recomended 2.25" for SOHC.

Like I said, it feels to not be losing power, but the ability to get through the revs up till 1,500 RPM.. from then on it's GREAT. but tell me since when do you race with Low RPM ??

is a bit too loud though, but the tone is very nice IMO.. remember I still retain the stock cast exhaust manifold, so basically the stock restrictive header is still there for low-down ; )

yeah I have B18C or worked B16A on the way.. now I just have to weld on the flange at the cat end when I swap.

My car seems to pull better than before - hey Kyle.. if Kyle's NEW civic is a little faster than his old one.. I am pulling harder on kyle's civic than his old one which I could oly JUST beat..

[Jus-10]

2inch mandrel will give you the best all-round performance, no doubt!

Anything bigger than 2" and you will be sacrificing low end for slightly improved top end.

My BC3 system on my Jazz (remember 1.5) had a diameter of 2.38"! It suffered majorly down low, but absolutely hammered up high. All fine and dandy if you are racing and keeping the revs up all day, but on the street, it could be a b*tch at times...

Don't go 2.25". You said you want all-round performance and 2" will give you just that!

[VTEChnique]

2.38" ?? you are measuring the inner diameter ?

I was measuring the inlet on my mufler which was "2.5" but the inner diameter of the pipe was 2.385 or something..

2.38" is actually the 2.5" - but they go off the outer diameter which is pretty dumb..

[mo]

2.38" ?? you are measuring the inner diameter ?

I was measuring the inlet on my mufler which was "2.5" but the inner diameter of the pipe was 2.385 or something..

2.38" is actually the 2.5" - but they go off the outer diameter which is pretty dumb..

Most Jap N/A exhausts are 60mm in diameter which reads out at about 2.38. Not sure if it's the inner diameter or not.

[sze5]

Hi there. Installed a fujitsubo power getter RS 2.5" for 97 vti D16Y coupe with a high flow recently as well. LOUD AS HELL(For my family and gf)

Will be getting it road tune with the VAFC soon, hopefully would maximise the overall performance again. Correct me if i am wrong.

Header is changed to xforce 4-2-1. My question is, with the 2.5" fuji, will it perform better at mid to high rev as compared to the stock system?

[LatinoHatchCrap]

i dont know much about x-force headers. do you know the collector size? (the last part of the header before it connects to the cat)
As long as you have a contant flow from collector through to muffler you should see decent gains.

[geo41e]

2" mandrel bend is prolly the way to go

is it possible to get 2.15" ???

[KB]

Alright bede! ill get a 2" mandrel bent cat back exhaust, then we will have a run, and we will be able to see the results.

BTW the other night i was changing gears at 5000 rpm. ... ...

You thought we were racing? HAHAHAHAHA.

Only kidding.

[Kit]

Hi there. Installed a fujitsubo power getter RS 2.5" for 97 vti D16Y coupe with a high flow recently as well. LOUD AS HELL(For my family and gf)

Will be getting it road tune with the VAFC soon, hopefully would maximise the overall performance again. Correct me if i am wrong.

Header is changed to xforce 4-2-1. My question is, with the 2.5" fuji, will it perform better at mid to high rev as compared to the stock system?

sze,
are you sure that fuji powergetter is a 2.5 inch? thats HUGE. especially on your car: a VTi Civic. Are you sure it was for your car/engine?

in the fuji range of exhauts, the powergetter is supposed to be for top end power.

[Kit]

I just had a look at the fujitsubo site.
I can't seem to find a powergetter RS cat back exhaust for Civic.

there is an RM01A for EG6, EK9, DC2, DC5 though, and they are all 60mm diameter.

[sze5]

Hi there. Installed a fujitsubo power getter RS 2.5" for 97 vti D16Y coupe with a high flow recently as well. LOUD AS HELL(For my family and gf)

Will be getting it road tune with the VAFC soon, hopefully would maximise the overall performance again. Correct me if i am wrong.

Header is changed to xforce 4-2-1. My question is, with the 2.5" fuji, will it perform better at mid to high rev as compared to the stock system?

sze,
are you sure that fuji powergetter is a 2.5 inch? thats HUGE. especially on your car: a VTi Civic. Are you sure it was for your car/engine?

in the fuji range of exhauts, the powergetter is supposed to be for top end power.

Affirmative, the story is. I bough it off a guy with a Turbo charged VTIR civic ek hatch.

But with my 4-2-1 header which provides mid-top end power, it should complement to my 2.5" fuji powergetter RS, u think(At least better than the stock)?

[sze5]

Should i just replace the 2.5" fuji piping to the stock piping, and keep the high flow cat and the fuji muffler from rear axle back?

Many thanks.

[b13nx]

Wow you guys like running larger exhausts don't you? The max I'd ever go on my car is 2.25" mandrell bent. It's currently a 2" mandrell bent system and that's on a SR20! (n/a 2.0L DOHC)

I'm having no problems with top end power either. It was recently dyno'd at 89fwkw - 14 kw over a stock SSS's and even other SSS's with cat-back exhausts (though I'm not sure wat diameter piping they were running) - and yes it was the same day, same dyno.

Kit, I'm curious why you mentioned not to bother with mild steel exhausts? I went mild due to financial reasons and I can't see the justification of paying at least double the price for SS.

[sze5]

GUYS what should i do :?

Option 1: Just replace the 2.5" fuji piping to the stock piping, and keep the high flow cat and the fuji muffler from rear axle back.

Option 2: Keep the 2.5" fuji piping, keep the high flow car and the fuji muffler.

Option 3: PLEASE ADVISE.

Thanks.

[geo41e]

hey man..no jijackin threads lols
kit...u lock this ?
2" mandrel bend for overall performance..stock size is 1.3/4"

lock

[Kit]

Kit, I'm curious why you mentioned not to bother with mild steel exhausts? I went mild due to financial reasons and I can't see the justification of paying at least double the price for SS.

Hi Mate,
running mild steel piping is fine, cos in this respect, stainless is more for looks that anything else. But with the muffler, I would try and stay away from mild steel mufflers.

The muffler is the last to heat up and the first to cool down in an exhaust system, so it goes through a lot of temperature fluctuations. A Mild steel muffler just won't cut it over time.

Chris

[Kit]

GUYS what should i do :?

Option 1: Just replace the 2.5" fuji piping to the stock piping, and keep the high flow cat and the fuji muffler from rear axle back.

Option 2: Keep the 2.5" fuji piping, keep the high flow car and the fuji muffler.

Option 3: PLEASE ADVISE.

Thanks.

sze,

I can't see any 2.5inch fuji on their website, can you confirm that is was for a civic originally? or was it just a fuji rear muffler with custom piping? cos I find it extremely strange that you say the exhaust is really loud. Although, 2.5 inch will drone a lot more than a 2 inch simply due to its inner diameter.

its just a bit of a waste though to fit it and now take it back off or replace it right?

one of the things you can do I guess is to keep the high flow cat, and then run the stock piping between the cat and the muffler. It will be a lot quieter too. but then you have essentially wasted your fuji's middle section.

how about you start a new thread and we'll discuss it some more?

I'll lock this one cos its going a bit off track now.

Chris