OBX Shorty Header Size Question

Forest Green 2k · Post by **Forest Green 2k** » Fri Feb 19, 2010 9:27 pm

I'm having a tough time trying to find out what size downpipe/testpipe I need to bolt up to my OBX shorty header. If anyone could point me in the right direction or help me out I'd greatly appreciate it.

Thanks.

Post by **occasional demons** » Fri Feb 19, 2010 9:46 pm

2.5 is what is out there, pre made.

Some neck down to 2.25" at the end.

Just search "down pipe neon" on ebay, and you will get a variety of them to choose from.

Forest Green 2k · Post by **Forest Green 2k** » Fri Feb 19, 2010 9:57 pm

Do you think I'll lose power with the header + test-pipe? I'm having trouble finding a 2.5 inlet for a 2g.

Neon4Life · Post by **Neon4Life** » Fri Feb 19, 2010 9:58 pm

its called a downpipe.

and no you shouldnt really loose power. youll get better flow because you are eliminating the cat and that is restricting flow a little.

Forest Green 2k · Post by **Forest Green 2k** » Fri Feb 19, 2010 10:01 pm

Will the codes from removing the cats hurt performance?

I think I found one that will work, what do you think guys?

http://cgi.ebay.com/ebaymotors/00-01-02 ... 2eaaba0feb

"2.5", 2.25" diameter opening (measurements are from the outside)"

Hopefully it means an 2.5 inlet because I'm having a tough time finding the right one.

Post by **occasional demons** » Fri Feb 19, 2010 10:15 pm

Not really. The down stream o2 cel doesn't put the PCM into limp mode, or at least it shouldn't. Not on an '00 pcm anyways.

You could try the non fouler trick. Just search "non fouler" for details.

By inlet did you mean the midpipe that attaches to the pictured down pipe? Because the down pipe is 2.5 inlet/2.25 outlet. It is made to bolt up to a late '01 and up exhaust system. If you are keeping you oem pipes, you will need another adapter, as '00/early '01 is 2.00"

www.trubendz.com sells 2.5" cat back piping, if you want 2.5" all the way out.

Forest Green 2k · Post by **Forest Green 2k** » Fri Feb 19, 2010 10:24 pm

occasional demons wrote:By inlet did you mean the midpipe that attaches to the pictured down pipe? Because the down pipe is 2.5 inlet/2.25 outlet. It is made to bolt up to a late '01 and up exhaust system. If you are keeping you oem pipes, you will need another adapter, as '00/early '01 is 2.00"

I just want to make sure that downpipe will fit my OBX header, I can just get an adapter to make it fit the midpipe. I don't want to go too big since I'm n/a but if the 2.25 or 2.5 midpipe won't hurt maybe I'll get that instead.

Post by **occasional demons** » Fri Feb 19, 2010 10:33 pm

The 2" will do you fine, until it rusts off. With P&P head, and R/T cam, a 2.25" prolly wouldn't hurt. But I can understand not spending until it is necessary. I really didn't feel too much seat of the pants gain going to 2.25" on mine, but my head isn't too aggressively ported. More like a basic cleanup. And that was going from the stock muffler/2" to a dual outlet Camaro muffler/2.25". PPL really don't give the oem system it's due.

Forest Green 2k · Post by **Forest Green 2k** » Fri Feb 19, 2010 10:47 pm

Right now the header is already installed but it's ghetto rigged and I need a whole new mid section. I have a temporary cherrybomb turbo muffler so it's not too restrictive but I'm getting a downstream o2 code and I think the stock cat is clogged.

Post by **occasional demons** » Fri Feb 19, 2010 10:55 pm

Well, if you have a leak between the header and cat?, that may cause the downstream code/CEL.

How do you mean ghetto rigged? The oem cat should bolt directly to the shorty header, unless it is a 1gn header.

Forest Green 2k · Post by **Forest Green 2k** » Sat Feb 20, 2010 3:24 am

They butchered the midpipe to install the header (the kid I bought the header from didnt have the downpipe) and only used C clamps to put it back together. I could def hear a leak and it feels like my cars power is being choked. I took her off the road for the winter and when it gets warmer I'm fixing everything.

Caraudioholic24 · Post by **Caraudioholic24** » Sat Feb 20, 2010 10:07 am

Curios if keeping the stock with the obx midpipe......will it still help at all? Not expecting to burn tires off but will it increase exhaust flow or should I manipulate a cat into my downpipe as well. I just dont want to put up with emissions and cel etc. I really just wanted to get a better exhaust note with my kaminari dual rear exhaust.

Jeepin' · Post by **Jeepin'** » Sun Feb 21, 2010 1:50 pm

Is 2.5 too big for our cars? Is it a common size for the 2.0? I was always leary of it robbing power from loss of back pressure, mind you I'm basically a stock motor.

Forest Green 2k · Post by **Forest Green 2k** » Sun Feb 21, 2010 2:30 pm

Jeepin' wrote:Is 2.5 too big for our cars? Is it a common size for the 2.0? I was always leary of it robbing power from loss of back pressure, mind you I'm basically a stock motor.

I feel the same way, that's why I'm either keeping the 2.0 or 2.25. I don't want sound, I want power. Every year Neon came with 2.25 except the 2000's which was only 2.0.

Post by **occasional demons** » Sun Feb 21, 2010 8:27 pm

This pertains to N/A 2.0

2.5" would be fine if you had a heavily ported DOHC/ Magnum Head with aggressive cam(s) where the power band doesn't kick in 'till 3800 rpm or so. For a mild DD, 2.25" will be plenty adequate. The volume of air for normal DD cars is not enough to maintain velocity in a 2.5, or larger pipe. Not enough velocity, and you are having to push the excess air in the pipe. This is almost as bad as back pressure. And in a sense, it is BP.

Edit:

Now if you want to run 12" of 2.5" pipe to a cut out, then do 2.25" for the rest, that would be fine, since there isn't enough length there to really make a big impact.

Jeepin' · Post by **Jeepin'** » Mon Feb 22, 2010 7:36 pm

^^

And this is why you sir, are the man.

Forest Green 2k · Post by **Forest Green 2k** » Wed Feb 24, 2010 3:06 pm

Just ordered this, $55 bucks w/free shipping: