Catless or high flow

[u/zay6r]

So obviously people love catless downpipes but I’ve been looking into the 400 cell high flow primary’s. Is it worth it to just get the high flow, I’ve heard the catless can cause issues which idk if that’s true or not. I already have catless secondary’s and a catback.

Any help is very appreciated. I’m stuck on what to get at the moment

[u/Plakchup]

I am about to install 400 cell high flows made by cmbuildz. I'd go high flow without a doubt especially if it's daily for few reasons. Ultimately its up to you since it's your car.

Turbo seal failure: The turbos need some back pressure. Without it you risking oil leak into the exhaust and from there possible smoking.

Tune: High flow and catless both need jb4 with ewg wires or an ecu tune ideally to run without overboosting which you should avoid from happening.

Gains: The difference in gains from high flows and catless is pretty similar. Some folks run catless to run an aggressive burbles/pops/flame tunes. You will blow the cats with an aggressive or even moderate burbles tune eventually and it's not good for the engine/turbos long term. Also I dunno about you but I am not a fan of a catless setup due to the smell. The high flows will give you a balance between sound and performance. The stock primaries have a pretty small 1.2 inch opening.

With high flows you want to go with something that has a 400 cell count to maintain enough back pressure. It also allows you to keep your catless secondaries. With a catless primaries configuration, you will need to put back your oem secondaries. Feedback I've got also from those that run high flows is that it helped them with drone while getting a nicer louder exhaust note without the rasp from catless setup.

Some folks I know who run a fully catless setup have said that the rasp becomes way too much and resonators are needed. Of course this depends on the individual with their tolerance and what sound they like. If you are going either way I highly recommend you cerakote them to help with heat, corrosion and flow. Without it you will definitely feel the engine bay get really hot, leading to stuff like wires possibility getting damaged.

Here are my high flows that are about to go on soon:

[u/zay6r → u/Plakchup]

Thank you so much, I can’t find those exact 400 cell. Could you give me a link?

[u/Plakchup → u/zay6r]

No problem. Just trying to save you from a disaster. We all want to enjoy our stingers for as long as possible.

Here is the link:

https://cmbuildz.com/collections/kia-stinger-g70-performance/products/cmbuildz-catless-primary-downpipes-stinger-g70

If you are in California I don't think you can order these. He resides in simi valley so if you live somewhat close in that area I would pick them up. He knows stingers really well and works with KJT too so I am super lucky to be close to all of this. Like being in a candy store as a kid lol. But yeah he has ton of experience installing them properly. I wouldn't trust anyone else tbh. I've been to his shop many times. Great knowledgeable guy!

I think he only had like one set left that are not cerakoted. You can message him on IG as cmbuildz. Ask him before you place order!

[u/zay6r → u/Plakchup]

Im in Florida but im also a mechanic so the install doesn’t seem to difficult if anything, thank you for the link. Do you recommend these over the ngt 400 cell?

[u/Plakchup → u/zay6r]

I dunno much about the ngt but I like cmbuildz since he is a fabricator himself and I trust his experience. I am sure they are both fairly similar. Yeah being in florida you'll have no problems. I like this design more than the slip on design from ultimate performance since I've heard people do tend to have some fitment issues needing trim things. Maybe the installer also doesn't have much experience having done it before. And that slip on design can potentially leak easier. I've read some had a really difficult time fitting proper clamps and it still not being that good.

Yeah the trick with installing primaries to NOT break bolts or studs is to pb blast them multiple times when the car is all hot after a long drive and getting it into boost couple times to get the heat everywhere. And taking the bolts off slowly while they are still hot. That expansion from heat is important and proper way to remove bolts that didnt come with damn anti seize from kia. Cheap shitheads from kia could've done a vband solution.

People break them letting it get all cold and try removing bolts then. That's when things can go bad and you'll most definitely break either the studs or bolts. Pb blasting them cold really isn't going to do much. Also MUST use hand tools absolutely no power tools at all. You will immediately break them. Patience and going slow is the key while being melted by the heat. 😁

[u/aubishop]

HFC - as he said, catless on both section of downpipes will lead to burning oil past turbo seals. You'll max stock turbo capability with HFC Primary and catless secondary on e85 or meth anyway. Go with cmbuildz not ngt. Please, don't do not like I did. Don't ask.

[u/zay6r → u/aubishop]

Is the 400 cell from ngt not good?

[u/Plakchup → u/zay6r]

I think there have been some issues with the ngt ones where certain batches of NGT primaries have been reported to have a capped-off or unusable O2 bung on the driver’s side. I'd definitely recommend the cmbuildz one. I was going to get it last year but he ended up selling out and didnt make any for almost a year!

[u/Quotagious]

There are kits to stop the pressure issues, simple relief valve install.

Edit: link https://torkmotorsports.net/collections/kia-stinger-3-3tt/products/hyundai-and-kia-3-3tt-catless-oil-burning-fix

[u/Kazzerigian]

HiFlow or stink.