I feel like I'm on here every week with a new problem, lol. Anyways, I have purchased a set of long tube headers that are 1 7/8" in size. I also have the axle-back exhaust system from borla that is2.5" into the muffler. The x-pipe that is supposed to come with the headers is on backorder for an incredibly long time, and I just did a cam swap so I need to get my car tuned.

I would hate to have to pay to get it to him twice, so I'm wondering if there are any x-pipes out there that are readily available that fit these two items?

Also, is it normal for this size discrepancy?

 

Tunes have nothing to do with exhaust flow. You do not need a tune, people just prefer them to shut off the cel fo lack of catalyst.

If you really want it tuned, just wait until the mid pipe is in place.

The sizing is all common sizing. No issues there. Everything is bolt on

 

Awesome, thank you. I feel like everywhere I've been looking, the mid pipe is unavailable or on back order, lol.

 

What brand headers did you get? As far as I know most headers use a specific X pipe etc for that header. I had to return a set of longtubes without x pipe because I couldn’t find an x pipe to fit it.

 

What's stopping you from using the old X-pipe? Or are the pipe Dia. different?

 

you can’t use short tube mid pipes with longtubes unless you heavily modify it

 

He will need a tune if he just did a cam swap too.

 

I was talking about exhaust, I didn’t see the cam.
Why would one want to drive the car without an exhaust to a tuner to tune?

either way, if he tunes on stock exhaust, the tune is not going to change with longtubes, so either way, it’s a non issue

 

What brand of headers did you buy OP? I have some kooks n arh options in stock.

 

Got it Thanks

 

Really?

Tom

 

absolutely.

 

Need and should are two completely different things. Especially considered catted vs not.

Do you NEED a tune after catted long tubes? No. Do you NEED a tune after non-catted long tubes? Probably.

SHOULD you tune after any set of long tubes? Absolutely.

Your short/long term fuel trim could probably make do with the current tune and perform the fueling corrections needed. You probably wouldn't pick up any timing with long tubes, so your ignition tables would likely stay the same.

But with that being said, your airflow out changes along with a slight change in efficiency at different points of the rev range due to the helmholtz effect. Optimum RPM directly correlates with runner diameter and length, and that goes for intake and exhaust. If you change either, you should at lease do some datalogging to check and make sure everything is still how you want it WITH YOUR FUEL TRIMS OFF. That way, if one of your injectors ever starts to spray less, or any other issue arises, your fuel trims can help account for them.

In response to the OP's question, I'd either find another x-pipe that fits, or have an exhaust shop make the headers fit up to the factory midpipe. Any midpipe will be close enough to whatever you ordered, you just need some length of pipe on there with a crossover between the two, even if it doesn't connect to the mufflers. Mufflers are pretty negligible.

 

Also, no tuner turns secondary catalyst measurements off anymore, if they get caught by the EPA, they're done for.

If you're in a place where you have to pass emissions, I've had good luck with O2 extenders in my last car with long tubes (s550 mustang), but have yet to do headers on my C6 GS.

 

How does every tuner turn off the cel them if they are not turning the sensors off? I can promise you they aren’t installing extenders.

 

Probably the same way shops pass dark tint during inspections and tune deleted diesels. Maybe they just run that risk or maybe the EPA backed down recently, I just remember two years ago no one would turn off rear o2's.

 

I am telling you they turn off the 02 feedback on the rear o2’s. Lol.
PS: window tint is not a safety check atleast in PA. It’s illegal, but it’s not a safety check that would get flagged for inspection.

This is probably another one of those internet myths things like tuning with headers.
Your fuel trims do not change due to lack of catalyst. If they did, it’s by such a minute amount, it’s not worth discussing.