I've only found archived info on porting the JDM exhaust manifold. I was looking at my downpipe the other day and noticed that there's an anti-reversion chamber (is that what it is?) inside that's very very narrow. It might not have been so bad if with the stock catalytic, but I finally got around to installing my SMSP 2.25" cat and the difference is very big.

Would cutting out the chamber and attempting to port match the downpipe to the cat be better, or does the chamber serve any purpose? I haven't had a look at the exhaust manifold at the cylinder head end, but is there room to port there too?

edit: there's that bump/ridge that I've seen at the top of the downpipe on all the Hondas I've looked at too. Could that be another area for cleaning up or is it possible that serves a purpose too?


Modified by B18C5 at 9:06 AM 5/26/2003

 

I think you might benefit more by just getting the JDM ITR manifold.

I don't know how much more you can improve the stock manifold...

 

Yeah I wouldn't even think its worth wasting your time with it

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by py1188 &raquo;</TD></TR><TR><TD CLASS="quote">Yeah I wouldn't even think its worth wasting your time with it</TD></TR></TABLE>

i was taking a look at this the otherday...

even if you ported it to paper thin quality...the restriction would still be there.

imho if you are concerned about the powerloss, go with aftermarket, or custom 2.5" ID mandrel bent tig welded goodness

 

Well, I can't justify spending any money on a header, especially since it's not legal in my class. I can modify or change the downpipe, but I can't add a header. What I was thinking about doing was cleaning up the funny looking ridges in here:


The part I was thinking about cutting out was this:


Before I go cutting and cleaning I'm wondering if any of these ridges or chambers do anything, or if I should take them out.

 

I would imagine you'd want it to match the port on the cat.