3.3t Turbo manifold research

October 13, 2026

10/6/24

I purchased a 3.3tt turbo manifold to research the possibility of "Porting" the inside to allow for more flow and less back pressure. My thoughts are that this would benefit oem turbos and Stuffed turbo users.

My initial findings are that the manifold is...

-Cast stainless steel
- Has very thick walls

From my research cast stainless steel is very easy to weld. I of course tried to weld it and I was successful with my first attempt. My next objective is to flow test the oem manifold and then cut it in a strategic spot so that I am able to take a die grinder to it and widen the choke point and entrance to the waste gate area. After this is complete I will weld the manifold back together and flow test it again.

If anyone has a better idea for opening up this manifold please comment.

Attached are photos of the manifold, a quick weld and my ideal cut path.

12/12/24

There are plenty of stock dyno whp examples on this forum. I don’t think Kia/Hyundai designed these with the thought of people pushing 500whp in mind. I believe they designed them for fast response and great reliability.

A tight restriction has nothing to do with the turbo spool besides slowing it down. The ar. Controls the turbo spool. So likely after my modifications the turbos will spool better, the engine will pull harder up top and the exhaust will sound better

Time will tell. I reached out to a cylinder head porting company to see if the will flow test the manifold.

12/13/24

Exactly, this is my thought process. I hope to be able to make this a service.

Anyway the company I wanted to get it flow bench tested with is swamped with work so no flow bench testing. I’m going to make the cut tonight and we’ll have to be happy with before and after results via caliper measurements and dyno measurements (later on)

Okay good news and bad news.

I cut open the manifold and it’s larger than 1 quarter and doesn’t neck down at all around the bend ( maybe a tiny bit at the end) honestly it’s a good design just small.

I measured the opening around the bend at 32mm.

The thickness of the manifold material is 5mm at the thinnest point.

Porting the manifold by cutting it open like I did and removing 2mm uniformly would gain us 36mm

The waste gate opening is 20mm and that’s extremely small.

The waste gate door is 30mm. I will port the wastegate door as large as I can get it. This will lower back pressure and increase hp between the 2 manifolds.

I’m afraid my research on this topic won’t net much gains for the amount of work involved. Maybe 20-40whp max

Attached are my photos.

Doesn’t neck down until after the wastegate opening and at that point is “ar.”

12/14/24

I have a die grinder. Which the right head it wouldn’t touch the sealing face. The waste gate doesn’t seal directly over the waste gate hole it’s shifted over so a step bit may actually ruin the turbo because it can’t help but be centered. Tonight I may grind out the wastegate hole and upload photos

12/15/24

26-27mm from 20mm

12/21/24

So great news. This (photo below) is ported out to 26mm (relatively circle).

Notice the unported flat surface I expect that if the wastegate flapper was modified to cover that portion it would be able to be ported out to 28mm. But that would require some custom machining and welding which I can do.

12/21/24

That’s great ! You’ll need to grind the wastegate flapper to remove it. It’ll give you more access. Stainless filler wire is needed to put it back together. You don’t need to cut the manifold because these no porting that needs to be done except for the wastegate

Do a water leak test before putting it back together. Should only slowly leak the water out. A air tight perfect seal isn’t 100% necessary

12/23/24

Waste gate opened to 28mm. A 95% increase in area !

180% between both turbos.

Before and after.