3” Dual Exhaust Build w/ X Pipe

I’ve been thinking about fabricating a catback exhaust for my RCSB. Currently running 1-3/4” American Racing long tubes and 3” midpipes with the TRD catback. I’m also supercharged with other mods, tuned. Making ~590hp/540tq onnlast dyno.

I was wondering if I should go with 2.5” or go up to 3” true duals? Would also be adding an X-pipe. Not sure about mufflers or resonators at this point.
One thing about the ARH midpipes is that the OD necks down from 3” to 2.5” right at the catback flange. Not sure why they did this, but imagine it needed to be compatible with other catbacks beside their own.
I’m really after something a little more aggressive than the TRD catback. Some more power wouldn’t hurt either.
I already have some 304ss adapter flanges, so I can do 3” or 2.5” at this point.

 

With the kind of money you have already laid out there is no reason to go cheap now. 3 inch stainless

 

agreed. sounds like a sick setup. What other mods do you have surrounding your boost?

 

Custom fuel system (pump/injectors/rails) custom intake, built trans etc.
it’s not about being cheap (although I am) but more about setting the right system up.

 

I hear that. I saw you had the Auburn LSD, how has that been for you? Would you recommend it? I have a 2012 Crewmax, I do a fair bit of off road/forest service roads, camping, etc. What is the "window conversion"?

 

3" stainless with X pipe... talk with Keith @dirtydeeds about the best muffler & resonators.

 

Auburn has been great. No issues in the 8+ years it’s been installed. always lays two black stripes.

Window conversion details here. Grab a beer: https://www.tundratalk.net/threads/crewmax-glass-conversion-on-rcsb.153393/

 

just made it through the glass conversion. Pretty sick. he did a great dob on that. Kuddos to you to for taking that on.
Good to know about the LSD. Definitely looking to pick one up soon.

 

I want to go with Auburn if I do install an LSD. It's the path less traveled lol

 

Thanks man. That was probably the wildest body mod I’ve taken on. Nobody has done one before so there was not a go by to reference. Fortunately it worked out and has been flawless over the last 7 years.

 

You're damn near famous bud lol

 

Agreed. His products are amazing.

 

can't recall, does adding the x make it louder or quieter? I have the factory TRD dual with no X.

 

Believe slightly quieter as it helps with scavenging and smoothing out the exhaust pulses. I’m sure there’s a far more scientific explanation or possibly a contradiction to what I just said.

 

To quickly amend my statement above, it would only be quieter if all other components remain constant. Adding an x pipe to the system I want to build would not be quieter than what I currently have.

 

I have been thinking this over and have an rough draft of how I want to set this up.
I’ve procured some adapter flanges that are 2.5” DIA at the flange and quickly flare to 3”DIA. This is to adapt to the ARH midpipe flange that tapers from 3” to 2.5” at the catback connection. Another option would be to cutoff the adapter flange for the ARH mids and weld on a true 3” flange, but I’m not quite ready to permanently modify these yet.
I’m also procuring some UJL 3” mandrel bend pieces that should give all the variants of bends I’ll need to connect the system.
Next I’ll need an XPipe. Still researching the best options, but I’ve pretty much ruled out the stamped section ones as I cannot find any details of the chamber geometry where welded pipes are known.
For mufflers, I’m looking to do dual 3” in/out. For cost sake, I’m trying to stay under $100/muffler and I want to be stainless since the piece I’m building is all 304SS. I’m looking at either carven or Kooks oval at this point as they meet the criteria. I can’t find much info about the kooks design, so I’m going to call them tomorrow to find out. It’s also strange that they have 2 models of oval mufflers with nearly identical (but limited) specs on their website. But one is $80 and the other is nearly $300. I’ll find out what that’s all about tomorrow.
Lastly, I intend to reconnect this new piece to my TRD tailpipes. Seems kind of counter intuitive to do this, but my thought is 1.) it’s less pieces I have to fabricate for now 2.) hopefully the exhaust has cooled enough at that point where the narrower ID does not affect performance. 3.) the tailpipes look good and have resonators in them to hopefully mitigate drone.
In all I’m sure this approach would probably seem not so well thought out, but i do appreciate any feedback. Also I enjoy fabrication and doing this as a hobby. That’s also why I do not want to permanently modify anything at this point. Worst case scenario is that I put the TRD muffler section back in and sell the mufflers/ x-pipe.

 

Do you think you'll have much drone?

 

I’d like to avoid that if possible. I’m thinking the x pipe will smooth the flow and the tailpipe resonators will help. Guess I’ll find out!!

 

Resonator at the ready lol

 

Been playing around with this design in my head for a while. I’m just going for it. If it sucks I’ll take it out. Nobody makes a proper x-pipe in the dimensions I want, so I’m making my own. I do my own work out of my tiny garage so unfortunately I don’t have every tool I want at my disposal. Sometimes you just have to make it work.
I purchased some pre bent mandrel 180’s from Squirrelly. I needed a jig to make accurate miters, so I made one.

 

The proper tool for this job in 98% of cases is a bandsaw. Well I don’t have one. Don’t have the space for it. I do have a table saw, however I cannot recommend to anyone to do this even though it works really well. While I labored for days thinking about how to make accurate miters in stainless, I just could not justify or accommodate the expense of a bandsaw. Much to my surprise, a 10” metal blade comes with the same arbor size as a wood cutting blade. So for $5, I outfitted my table saw to cut metal.
Disclaimer: this is incredibly unsafe and I cannot recommend this. The blade rotates and throws sparks at the user, so PPE is mandatory. Stay out of the line of fire.
As long as you take your sweet time and let the tool do the work, it comes out really nice. Note that the cut depth is not sufficient to go through the 3” pipe, so each cut must be flipped over for completion. This is why the jig is a must have item.

 

Also worth noting that while the squirrelly mandrel bends are the cheapest out there, they are not top quality like stainless bro’s are. I ordered 2 180 bends, but they are more like 167 degree bends. They are very dirty and have tooling marks. If that matters to you then prob don’t order them.

 

The final cut in these is the mating faces of the “x”. I’m sure there is some research out there on the optimum scientific profile, but I can’t find it. Obviously you want to create a scavenging effect, so the converging pipe area must not create a choke point. I am targeting a 6.5” center to center measurement to mate to the TRD dual tails. That translated to roughly a 30% cut off of the 90’s to form the mating faces for my “x”. It also translates to exactly 2x the cross section area so this seems ideal in my head.

 

A bit of hand cleanup and a mock up of the X pipe. Everything fits really nice and I’m at exactly 6.5” center to center. I’m pooped so welding will have to wait.

 

Working with what you’ve got. Respect. X-pipe turned out great. Good job!

 

Great job ! You are definitely doing it right as a fellow DYI'er

You planning to Tig or Mig it ?

 

I only have a MIG welder, but have welded some 409 in the past with good results

 

Got everything tacked in place. I have a buddy who is going to TIG weld it for me, so this is all the welding I’m going to do for now. Nice tight joints. Not too bad.

Until I mocked it up and realized I could buy a few extra inches if I point one of the legs at the driver side midpipe. This will allow me to move it up and give some more freedom on muffler selection and placement. So I cut it off and rewelded that leg.

 

Making some progress here. The x pipe is fully tig welded. And the post showed up with a pair of beautifully polished Kooks mufflers. Still need a few more pipe pieces, but this should be nearing completion soon.

 

Those mufflers look really good, looking fwd to a sound clip.

I'm shopping 3in for my RCSB currently so staying close to this thread.