2.75" - 3" Headers?
 

Are there any headers that are 2.75" - 3" out there?

I searched a couple catless + UEL headers, but most of them don't provide the size for some reason.

I am getting a 2.75 DP/FP combo to a 3" cat back. I'd like them to be similar sizes, but I am having a hard time finding a header larger than 2.5.

Question is why??? 2.5 inch exhaust will be sufficient until you reach the 500hp area.

The Nameless header is 3 inch from the Merge Collector to the flange that meets the overpipe. There is a knock-off of the Nameless also, PLM I believe it is called?

Nameless, also sold via Cosworth. If you're patient and dig through the development thread you'll even seen that 3" through appears to help... YMMV, tune required, etc.

Yes, there's a knock-off... don't.

Also, be prepared for loud. It can be tempered, but... well, let's just say I'm tempted sometimes to sell the whole setup and get something different that still delivers power where I need it (now that there's another viable looking option...)

not true
there are gains to be had even with NA on a 3" system over 2.5"
the gains are small, about 3-4bhp on 230bhp so they will be more appreciable at higher power levels

fair enough.

The Cosworth option is now discontinued and only 2.75 because of RHD and less room for the overpipe

Thanks all!

I bought the Ultimate Racing 3" single exit cat back. I wanted to get their Front pipe and Downpipe too. The FP/DP is 2.75".

I was trying to make it more uniform from start to finish is why. I currently have the Tomei knock off (I think?) Gruppe-S header, which is 60mm or 2.3" iirc.

Part of the reason I bought the UA Catback is because it didn't sound insanely loud, and I am hoping it isn't as loud as the N1 (knock off) was.

I figured it is time to get quality parts now, haha. The knock-offs were to hold me off and give me some sound.

I figure if it's 3" and single exit (also why I wanted bigger FP/DP) that would hopefully be about the same flow as 2.5" dual exits, but this is just a guess. Any insight on that?

Let me know what you think? Preferably not the negative unless it's constructive.

Bigger does not necessarily translate in better, especially on the header pipe size. There should be a fine balance between say the physical parameters like the length, diameter and the wall thickness of the tubing, how the pipes are routed, are header pipes equal length, the type of collector, the length of the collector, the material the headers are made from, and how they are welded together AND the dynamics of it like temperature, pressure, and sonic energy. Ultimately what you want is extracting gases out of the engine at a higher rate and help create a lower atmospheric pressure in the cylinder before the intake valve opens.
Not going to go into too much details but, like I said, there is a reason why some headers or majority of them have the 2.5/2.75" exit pipe and different size of the actual runners. What follows after the header is much less important! You can go 3" (start saving now for an internal ear implant) or less!
If you are pushing big power, then a bigger size pipes might benefit, however for NA, there is no point!

With a 2.3" set of headers and this new exhaust, it is almost silent. I am considering buying a secondary mid pipe without a resonator.
Do you think 2.75" or bigger would be significantly louder? It's a quality exhaust, so I am guessing it wouldn't get much louder.

If you understand it better than me, may I ask what you would suggest? I now have 2.75" downpipe, and front pipe. The cat back is 3." It is all the same brand/company. Would it be worth while to get a 2.75" header, or would you stick with 2.3"? I feel like 2.3 -> 2.75 is too much of a difference. I am not super familiar with auto air flow, but I was an HVAC tech for a good 10 years, so I am familiar with air flow in general.

Also, the cat back is single exit, which was why I was ok with 3". I eliminated a whole 2.5" run with this exhaust. I figure a bigger header would be better in this case.

So you basically changing the size for sound? or is there a plan further down the track to turbo/SC? Also i am assuming you refer to the 2.3/2.7" header more about the size of the actual exit after collectors/etc.
LIke I said before, provided the header is of quality (both execution and design) you want to extract the gases out at the highest velocity. What follows after the header is least important. 2.5/2.7 for over pipe and front pipe is ok.

Sound, uniformity, and because I went single exit. I'd imagine overall there is less airflow by reducing my tips by one. I wanted to increase in size to make up for the lost piping.

I do plan to install a turbo in time. It will be another 6 months at least, though. I am in no rush. With an exhaust and tune, the car is more enjoyable than stock.

You haven't responded directly to the single exit stuff. Does it not matter at all that I got rid of a bit piping in your opinion?

See my answer in red. :)

You dont really have a true dual exit exhaust! From the engine down to the back of the car it goes in one pipe then it splits in two. A true one would have a separate exhaust for each engine bank.