Columbia river and Ace race are where i get all my exhaust materials

Exhaust tubing should be arriving next Tuesday. Does Columbia ALWAYS take this long?

Anyway, reassembly has been delayed because I managed to crack the old Kia thermostat cover while tightening it down on the spacer for the coolant re-route on the back of the head. I've NEVER had that occur before, EVER so now I'm paranoid about it happening again since there are no Kia's in any of the local pick-n-pulls, the dealers have told me that the part isn't available anywhere in Georgia, and the online order (which arrives today) took a week. Does anyone have the recommended torque setting for that cover so I don't repeat this fiasco.

Yes. Columbia is running on a skeleton crew. I think they almost closed up shop sometime in the past year or two. They are also moving into a new building and not producing new bends until sometime in the new year.

I used Mandrel Bending Solutions out of MD fir majority of my pipe needs now.

PS - 14-19 ft lbs

Okay folks. Things are going to start getting stupid 'round here (as promised). The engine is rebuilt, and resting comfortably back in the chassis. It hasn't been started yet, but that's soon to come. But the most important thin (as it related to THIS thread) is that the first "stuff" has come in to begin cobbling together an exhaust system. But before getting to the action, here's a brief explanation of what I'm going to be doing...

(Preparing flame-suit for action)

What I'm starting with is 80% of a 2.5 inch stainless steel system from a Flyin Miata VooDoo kit purchased many moons ago. It's been a stalwart performer over all of these years, but it currently suffers from a few problems; first, it's 2.5 inches. Second, it uses several slip joints that have been prone to leaking, Third, the FM muffler bit the dust a few years ago so was replaced by a cobbled-together set of pipes comprised of a sawed-off section from a stock muffler from the axle-back flange, poorly welded to a 1.5" to 2.5" coupler, welded to an Autozone muffler. Yes, it's a hot mess, but it has served me well.

What I intend to do is to use my shiny new 5-bolt to 3" vband exhaust flange and 3" DP into a custom made (by me) 3" pipe, going into a flex pipe, then to a 3" to 2.5" reducer. This will feed back into the 2.5" FM exhaust, to the axle-back flange. From there, I'll replace the abortion between the axle-back flange and the AZ muffler with another custom-made (by me again) section to round out the system.

Now, you may be asking (perhaps, screaming) the question; "Why keep that 2.5 in, FM relic in your system?" Well, there are 3 reasons; cost, cost and a lack of welding skills/proper equipment.
- Cost #1; That FM section has two key pieces that I can't afford to toss into the shitcan at the current time - the cat and the resonator. Since I still have 5 more years of GA emissions tests to suffer through, I still need a convertor in the mix and I just can't swing a new one of those right now (having blown a wad on the rebuild).
- Cost #2; As much as I want to get a badass Magnaflow muffler, again I can't cut that cost right now. So I will keep the AZ muffler but ditch that cobbled-together, restrictive crap that is in front of it.
- Inexperience/bad equipment; I still have my POS HF welder and it just can't cut it welding SS, so the stuff I'm making will all be aluminized mild steel. Where there are junctions between that and SS, there will either be a vband, or a flange. Only one slip joint will remain and I'll have to live with that for the short-term.

Once I get through this project, and I feel a bit more assured of my "skills" (and replenish my wallet), I'll ditch that "FM section" and build a full 3" system front to back with a new cat, resonator and muffler. So, in the meantime...DON'T HATE!

PS - Here's a shitty, hand-drawn picture that I'm using as my build-guide.
https://cimg5.ibsrv.net/gimg/www.mia...ef56f9de33.jpg

(removing flame-suit)

I did some test fitting this evening and the results are encouraging (after a bit of a scare).It looks like I'll be able to make my plan work. The "scare" was that, at first glance, the very pretty, low-profile 90-degree vband fitting - intended to take me from the 5-bolt flange on the turbo, to the exhaust pipe, was going to be too long. The 90* from the FM kit is about 2-3 inches shorter than the new 3" 90*. It was looking like I would not be able to "turn the corner" and get a 3" pipe to fit in the gap between the trans and the subframe. I was thinking that I might have to take a chunk out of the new 90* in order to make it work, and that would mean taking that to a shop to have it done since I don't trust that HF rig to properly weld stainless steel.

Anyway, just for grins I tried the 90* - 3" pipe in the space just to see how bad it was, and IT FIT! There might be some clearance problems, but nothing some "massaging" with a hammer wouldn't fix. So, I think I can make it work. Here's a picture that might help visualize what I'm talking about. For some perspective, you're looking down at the ass-end of the downpipe into the abyss between the trans (at the top right) and what remains of the shelf above the steering shaft, The -AN fittings are for the water lines that feed the heater core;

https://cimg5.ibsrv.net/gimg/www.mia...a6d5fc1445.png
So, the next step is to get the car on the lift and tack this together and see where I land. Maybe tomorrow?

Okay, I did a thing today;
Vband onto 3" downpipe;
https://cimg5.ibsrv.net/gimg/www.mia...07f438ed82.jpg

Flex pipe onto 3"exhaust tube (w/ store-bought 3" to 2.5" reducer)
https://cimg6.ibsrv.net/gimg/www.mia...53fe5dde7e.jpg

The whole monstrosity in it's entirety;
https://cimg7.ibsrv.net/gimg/www.mia...3f13cdf270.jpg

This will v-band onto the FM midpipe.

Tomorrow's task...re-do the axle-back abortion! My welds are ugly AF. I don't know if they are gas-tight (yet). On the plus side, I didn't blow through the tubing, not once!

PS - this will be a tight fit, it may contact the front subframe and rattle like hell. But I'll cross that bridge when I get there.

Looks good for the first time, I can't do that, so props to you! Just doing, not talking, I like that

Progress!

I did something else today;

The Axle-back "abortion" is gone! It is now a proper 2.5" into the muffler. PS - please don't laugh at my Autozone mini-muffler. I'll get a REAL muffler when all of this gets swapped out for a full 3-inch system.
https://cimg9.ibsrv.net/gimg/www.mia...d210a51d79.jpg

Per my hand-drawn schematic earlier, this is the transition from the 3" downpipe, into a 3" - 2.5" reducer, then into the FM system. The ONLY reason for doing this is the FM system has a cat and a resonator. Cost is prohibiting me (now) from replacing all of that. Also, there are bungs for the WBO2 sensor, and the two stock NBO2 sensors in the FM system. I didn't want to tax my (marginal) welding skills trying to put a bung into the 3" piping - I'll save that for later. Is it ugly? Yes. Are there too many v-bands? Yes. Will it work? We'll see.

https://cimg8.ibsrv.net/gimg/www.mia...05b5382f21.jpg

Tomorrow's "adventure" will be to fab some hangars (right now, it's all held in place with tie-wraps). My car is 50% tie-wraps...

PS - Yes, the lower two bolts mating the trans to the engine are missing. I'll get that done soon.

PPS - All of the mild steel pieces will get a coat of VHT to delay any rusting. I just wanted to mock it all up.

I'm baaaack!

I've been running with the above "hybrid exhaust" for the past few months without issues. Now it's time to finish the job...which is to have a complete 3-inch exhaust all the way to the exhaust tip. To that end, I've assembled;
- Some 3" straight tubing
- Some assorted 3" mandrel bends (a 45* and a "U-J" bend to fabricate the axle-back)
- A generic resonator
- An O2 sensor bung
- Assorted v-band clamps and flanges
- A teeny-tiny Flowmaster (pseudo) muffler

Why not the MT-approved Magnaflow? Because I want "loud and deep", but not "fart-can obnoxious". I'm designing this so that I can swap in different mufflers until I get the sound that I want. I might end up with something that drones and rattles, but that'll match the rest of FrankenMiata to a tee.

Cutting and welding commences on Saturday.

Out with the old...
https://cimg0.ibsrv.net/gimg/www.mia...a0cd6a3431.jpg
and in with the new...
https://cimg6.ibsrv.net/gimg/www.mia...f2f3d53e2e.jpg
https://cimg7.ibsrv.net/gimg/www.mia...7eabf01391.jpg

3" stainless from stem to stern. There are a few touch-up's I need to take care of, but that's it for now.

So I’m in a similar predicament to you. I currently have everything to build a 2.5” exhaust, am I going to regret not just going to 3”?

My sage advice is, "It depends".

If you're running an El Cheapo Chinese turbo like I am, 2.5" is probably good enough. In that instance, the turbo itself is most likely more flow-limited than the rest of the exhaust system. If, however, you are running a "Big Boy Turbo" then a 3" exhaust might be the better option.

Of course non of this is based on scientific theory, or rigorous testing - it's just my opinion, so take it for what it's worth. I went wit a full 3" system because I'll be ditching the churbo for an EFR in the very near future.

I have what is probably one of the least likely to spool well setups and a 2" exhaust is still doing well and a total blast. 1.6, Kraken TD04 manifold, 2.5" kraken downpipe to a 2" test pipe that just changes at the flange, then a 2" ebay cat back that came on the car. Makes 175kpa at 3300rpm and spools up in first gear while trying to pull into trafic (that's "fun" if you aren't ready for it).

Build the 2.5 and send it.

kind of what I figured. I have an entire 2.5” diy exhaust kit I bought for another project that never got finished but have yet to own anything to use it on until now.