ARH / Kooks w/ H-Pipe

[JGT]

Is anyone here running ARH or Kooks longtube headers with an H-pipe? If so, how did you go about doing it?

I was all set on the ARH headers system that included an H-pipe, but they apparently do not offer that anymore, only an X-pipe.

I've currently got a 3" Magnaflow catback with the 2.5" MRT H-pipe. I was hoping to eliminate the 2.5" bottleneck and go 3" pipe all the way back, but can't find an easy solution that won't involve some custom fabrication from an exhaust shop, which I would prefer to minimize. And I'm not sure which of the ARH offerings would get me there the easiest. Kooks apparently only offers a system that necks down to the factory 2.5".

But really, how much HP would I be leaving on the table if I just get one of the systems that connect to either a factory or aftermarket 2.5" H-Pipe? I'm not planning to go forced induction.

And if I stick with the 2.5" bottleneck, would I be better of with the 1 3/4 or 1 7/8" headers?

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[18 Smoke]

I am running Kooks 1 7/8 with Magnaflow X & competition cat back. 3” all the way through. Kooks offers 3” adapter pipes that I used with stainless ID couplers I bought off amazon. Not that tough. An exhaust shop could handle it easily. I’m sure it work with an H pipe the same way

 

[AZ18yote]

Running ARH catted 1 7/8 with direct connection to corsa which feeds to double x. 3 in all the way. I'm sure there is an H with similar dimensions of where it connects. Keeping the 3in especially important if you are ever planning on going FI.

 

[Guard5.0]

Full ARH with an H-pipe here at 1 7/8 albeit in a 2015. Odd they don’t offer the H anymore. Mine is catless. I’d go 1 7/8 just in case I got the itch for FI In the future. The H really removes the raspiness inherent in the Coyote but the full system like I have is LOUD due in part to the lack of cats. Adding the cats or a resonator calms it down a bit but then you’re back to some customization.

 

[MustangPP1]

Im running Kooks catted 1 7/8 with MRT 2.5 H pipe and Corsa Sport mufflers. You should for sure still go with 1 7/8 headers, you would not gain much more power at all going to a 3 inch H pipe. Very minimal difference.

 

[Chad11491]

i called ARH and emailed Kooks about the 1 3/4 - 17/8 difference. Both recommended 1 3/4" for N/A applications, saying it would feel torquier and more fun to drive around town. I went 1 3/4" catted ARH with the x bottleneck kit with the ARH catback ( i really wanted to keep an H, but i don't mind the X after getting used to it), and put down 439/408 SAE, so i don't think 1 3/4 loses much up top as that seems ballpark what other 15-17 put down with a CAI/Headers/93 tune. I picked up ~ 40wtq below 2500 rpm, and 30 at 3500rpm. that's definitely noticeable seat of the pants driving around, while still picking up 40 peak hp and tons through the curve.

 

[MustangPP1]

i called ARH and emailed Kooks about the 1 3/4 - 17/8 difference. Both recommended 1 3/4" for N/A applications, saying it would feel torquier and more fun to drive around town. I went 1 3/4" catted ARH with the x bottleneck kit with the ARH catback ( i really wanted to keep an H, but i don't mind the X after getting used to it), and put down 439/408 SAE, so i don't think 1 3/4 loses much up top as that seems ballpark what other 15-17 put down with a CAI/Headers/93 tune. I picked up ~ 40wtq below 2500 rpm, and 30 at 3500rpm. that's definitely noticeable seat of the pants driving around, while still picking up 40 peak hp and tons through the curve.

Wow thats really good. I also asked them as well as American Muscle and many other people and all recommended 1 3/4, but I still went with 1 7/8 just because its so common and what everyone is doing. Even the ones that recommended me 1 3/4 have 1 7/8 on their own N/A cars.

 

[watisthis]

Have 1 3/4 with FI. Was recommended it by a local shop who have 1k+ hp cars getting tuned all the time who haven't seen a huge difference between 3/4 and 7/8 so I just saved a few $s.

However, I do want to replace my double corsa X with a 3in H.

 

[ManBearPig]

I’d like to see real data about 1-3/4 vs 1-7/8 primaries on an NA coyote. I have read various opinions supporting both. I’ve also seen NA LS cars make more powers everywhere with larger primaries but that may not apply to our cars. FWIW the area I get was most improved after my 1-7/8 longtubes was the area under the curve. It’s hard to feel a 15hp peak gain but I sure feel it around 3k rpm. I also like the way the headers sound paired with an H pipe and straight through style mufflers. Its a much deeper, cleaner sound than the more common x pipe with chambered mufflers. YMMV

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