Anybody tried this? Sec-1 with cats and resonators

[1000hp]

Couldn't stand the rasp or the smell with Megan headers and dual-resonated stock section-1, so I added HFCs.

The rasp is gone. The smell is gone. The power feels the same. Maybe even better?

Tight fit in there, but they fit with no contact and the stock heatshield in place. The cats are Flowmaster 200-cell (PN: 2000124).

Pretty happy with the results. Don't judge my welds.

[Vonbimmer]

I’ve been thinking about adding resonators to my SS catted section 1 to take the edge off the rasp so something like this has been on my mind too. Can you share what resonator you were able to fit in that setup?

[1000hp]

I’ve been thinking about adding resonators to my SS catted section 1 to take the edge off the rasp so something like this has been on my mind too. Can you share what resonator you were able to fit in that setup?

The cats in this one are up front, just after the header/sec-1 flanges. The resonators are back where the cats are in your SS sec-1.

If you were to install resonators up at the front end where I put my cats, you'd want something 4" or less in diameter, and probably 6" long bodies.

Something like this would be ideal:

https://www.jegs.com/i/AERO-Exhaust/889/TR251/10002/-1

[Vonbimmer]

Ah thank you, I thought that was the layout I saw on your setup. Appreciate the link!

[1000hp]

Ah thank you, I thought that was the layout I saw on your setup. Appreciate the link!

Your layout will probably make things easier, since there are more/smaller options available for resonators than for cats.

[Slideways]

CPI used to make these. Cats should be placed before resonators.

[1000hp]

CPI used to make these. Cats should be placed before resonators.

And as close to the engine as possible if you want them to be efficient.

But I have placed them farther back on other cars (C63 AMG) out of necessity, and they did the job on the smell.

[///M3RIC]

Are there drawbacks to having the cats closer to the headers?

[Mustafa564]

I placed an order for equal length catted section 1 with 2 (200 cell) cats from Bomiz. We will see how it goes. Anybody tried Bomiz?

[Mustafa564]

Couldn't stand the rasp or the smell with Megan headers and dual-resonated stock section-1, so I added HFCs.

The rasp is gone. The smell is gone. The power feels the same. Maybe even better?

Tight fit in there, but they fit with no contact and the stock heatshield in place. The cats are Flowmaster 200-cell (PN: 2000124).

Pretty happy with the results. Don't judge my welds.

Did you cut up the OEM section 1 and add aftermarket resonators?

[1000hp]

Are there drawbacks to having the cats closer to the headers?

Nope. The closer they are to the engine, the faster they reach their operating temperature and start doing their job. But I think part of the performance gain from the euro setup is moving them far enough away from the collector that they don't interfere with scavenging.

[1000hp]

Did you cut up the OEM section 1 and add aftermarket resonators?

Yeah, I started by adding a resonator to the stock section-1. That killed the rasp with the stock headers. But the rasp returned and was even more obnoxious when I installed the Megan headers - even with the extra resonator. Gone now with cats back in the system.

[Mustafa564]

Yeah, I started by adding a resonator to the stock section-1. That killed the rasp with the stock headers. But the rasp returned and was even more obnoxious when I installed the Megan headers - even with the extra resonator. Gone now with cats back in the system.

will be doing that myself. Thank you

[///M3RIC]

I’m curious why the stock euro setup positions them at the far end of section one. Flow dynamics, heat, spacing? I had to look up what scavenging is, that’s a good theory.

[1000hp]

I’m curious why the stock euro setup positions them at the far end of section one. Flow dynamics, heat, spacing? I had to look up what scavenging is, that’s a good theory.

I was curious about that myself. Maybe just packaging constraints. The stock euro cats won't fit up at the front end, and they may be the smallest ones that will met Euro emissions requirements.

Our emissions laws are a lot more stringent than most of the rest of the world. The US cats are built into the headers because they need to be that close to meet CAFE standards.