just about to buy a decat pipe for my 2000 civic si hatch , all i need to know what size the collector size is , 2.5 or 2.25 inches thanks yall

 

If you buy the normal one (not the "JDM" spec), it'll be 2.25"

 

would it help if i said it's a 4-1 type ,
it's not a jdm spec manifold , so it's defitnaly a 2.25inc sized collector then

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bright rider &raquo;</TD></TR><TR><TD CLASS="quote">would it help if i said it's a 4-1 type ,
it's not a jdm spec manifold , so it's defitnaly a 2.25inc sized collector then</TD></TR></TABLE>

Yeah, because the inlet on a 99-00 Si catalytic convert is 2.25"

 

There are no DC headers with 2.25" collectors. If it's not "JDM-spec", it has a 2" collector.

 

Not saying you're wrong (because I'm willing to bet I am, I don't know too much about DC Headers), but why are they 2" collectors? I know a lot of stock exhausts are 2" or less, but isn't the 99-00 Si 2.25" at the cat?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Eran &raquo;</TD></TR><TR><TD CLASS="quote">Not saying you're wrong (because I'm willing to bet I am, I don't know too much about DC Headers), but why are they 2" collectors? I know a lot of stock exhausts are 2" or less, but isn't the 99-00 Si 2.25" at the cat?</TD></TR></TABLE>

The "USDM" headers all have 2" collectors, to match up with the stock cat (since the stock exhaust manifold collectors are also 2" OD). Most headers with 2.25" collectors are custom pieces.

 

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

The "USDM" headers all have 2" collectors, to match up with the stock cat (since the stock exhaust manifold collectors are also 2" OD). Most headers with 2.25" collectors are custom pieces. </TD></TR></TABLE>

I imagine I measured my catalytic converter from the wrong opening then. I have a 99-00 Si catalytic converter on my swap, and I was sure it was 2.25, just like my exhaust.

 

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

I imagine I measured my catalytic converter from the wrong opening then. I have a 99-00 Si catalytic converter on my swap, and I was sure it was 2.25, just like my exhaust.</TD></TR></TABLE>

You may have measured it from edge to edge at the flare, not the actual inlet tubing (which is closer to 1-7/8").

 

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

You may have measured it from edge to edge at the flare, not the actual inlet tubing (which is closer to 1-7/8"). </TD></TR></TABLE>

Sounds about right. It was like 3am when we were cutting off flanges from the exhaust to shorten it and fabbing it back up. I was tired and bored and decided to measure my cat ..... guess I measured wrong.