Right now I have a 60mm exhaust on my car. I plan to go allmotor and want optimal flow. I see how everybody recomends a 2.5 inch exhaust as opposed to a 60mm exhaust, but does that 1/8inch and 3.1xx millimeters make that much of a difference?

I am looking at headers also and see that many JDM companies have 60mm outlets while US based companies have 2.5 inch outlets. Would running a 60mm outlet header w/ 60mm piping be just as optimal as running a 2.5 inch header w/ 2.5 inch piping? As long as the flow is uninterupted with no bottle necks wouldn't they both perform basically the same?

Thanks, here is a pic just so the thread is attractive

 

i guess it would depend on how highly your car is modified, and keeping that in mind i would say yes every bit matters when you tune it. I personally upgraded to 2.5 all the way through and i think its a worthy upgrade.

 

bump

 

Considering someone is making close to 200hp. Is running 2.5 piping to a straight thru muffler more efficient compared to running open header with a 2.5 collector?

 

bump

 

Internal area jumps about 12-13% when going from 60mm to 2-1/2". Most JDM headers are 65mm (2-9/16") not 60mm.

2-1/2" exhausts are worth it.

 

if SMSP says its good, then its good

 

BUT, a 2.5 inch exhaust is not going to flow as well as a 60mm exhaust if it is crush bent. The problem here is that there are not alot of commercially available 2.5 inch exhausts. ESPECIALLY for 1988-1991 Civics/CRXs. So if you want a 2.5 inch exhaust, you are likely going to have to go custom. And shops that do mandrel bends are quite rare. If you don't go mandrel bent on a 2.5 inch system, you are better off just sticking with a 60mm mandrel bent system.

 

yea, thats what i was talking about, a 60mm exhaust w/ no interuptions in flow compared to a 2.5 inch exhaust w/ no interuptions. I see how any exhaust w/o good flow characteristic could be a hinder on the hole system.

Question two if anybody knows the answer, do japanese tuners with NA hondas run 60mm exhausts or bigger? (70mm?)

I found a pretty good deal on a JDM apexi header. It has a 54mm collector according to apex, so would stepping the 54mm collector to a bigger size piping hinder the system in any way? or would an exhaust system that keeps a maximum size the whole way through be optimal?

 

i did my mandrel-bent 2.5 inch exhaust, with my 2.5 header(that i made, so its the same size, i used the same tubing) and it sounds great(under full throttle) but kinda buzzy at under-3k. it has a flowtech worlock on the rear, so i can take the plug out and make it 2.5 open exhaust......it seems to make a little more power then, i'll dyno tune soon and hopefully post some numbers. i would highly recomend keeping the whole system the same size after the collector. crush bent is NOT the way to go for anything, unless you need an exhaust for your mom's grocery getter.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by StorminMatt &raquo;</TD></TR><TR><TD CLASS="quote">BUT, a 2.5 inch exhaust is not going to flow as well as a 60mm exhaust if it is crush bent. The problem here is that there are not alot of commercially available 2.5 inch exhausts. ESPECIALLY for 1988-1991 Civics/CRXs. So if you want a 2.5 inch exhaust, you are likely going to have to go custom. And shops that do mandrel bends are quite rare. If you don't go mandrel bent on a 2.5 inch system, you are better off just sticking with a 60mm mandrel bent system.</TD></TR></TABLE>

http://www.accordinglydone.com...id=64

in case local shops can't do mandrel bends.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by kommon_sense &raquo;</TD></TR><TR><TD CLASS="quote">

http://www.accordinglydone.com...id=64

in case local shops can't do mandrel bends.</TD></TR></TABLE>

nice...then all you would need, is a high flow cat or test pipe and a muffler.

 

HAHAHA, CONDORITO

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Bolivianstrtwpn &raquo;</TD></TR><TR><TD CLASS="quote">
I found a pretty good deal on a JDM apexi header. It has a 54mm collector according to apex, so would stepping the 54mm collector to a bigger size piping hinder the system in any way? or would an exhaust system that keeps a maximum size the whole way through be optimal?</TD></TR></TABLE>

I was under the impression that Apexi used a 45mm primary, 50mm secondary, and 60mm collector.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by BlueTeg &raquo;</TD></TR><TR><TD CLASS="quote">

I was under the impression that Apexi used a 45mm primary, 50mm secondary, and 60mm collector.</TD></TR></TABLE>

This is their headers specs according to their 2003 catalog
186-H001 / GT Manifold 96-00 Civic Type R JAPAN MODEL ONLY / 45mm-50.8mm-60.5mm
186-H002 / GT Manifold 96-97 Integra Type R JAPAN MODEL ONLY / 42.7mm-50.8mm-54mm
186-H004 / GT Manifold 98-00 Integra Type R JAPAN MODEL ONLY / 42.7mm-50.8mm-54mm

all are listed at $599.00

the CTR header is beefier than the ITR headers, why? I wish somebody could explain to me

I wanted to buy the header, but inlinefour only sells the ITR spec headers