Ok, so everything is finished up. In the end there was an issue which led to a not-entirely-to-my-liking result, but I don't want to spoil the ending...

First thing I did was cut the st-res pipe to length [HF has a bandsaw sale for June):


I deburred the inside of the pipe with a round hand file. If you are performance minded, this is akin to polishing your valve ports, but given where this is in the exhaust, it more just a helpful thing to keep metal splinters down. The shavings are also a prime spot for rust to start, but I would understand if someone elected to skip this step:


I used the bandsaw to cut out the cat flange from the 1/4 steel plate after I grew frustrated with the plasma cutter. I ground down the edges to be sure everything was the correct size (the bandsaw blade kept coming loose when I tried to freehand the curves--grrrr...)


I was extremely fortunate to have a 2 1/4" bimetal hole saw bit to cut out the inside on hand, as the plasma cutter was the only other method to cut out the center section. Unfortunately the flange was wider than my drill press vice (4" vice). I had to tack weld the flange to the vice, then drill it out:


This is where I digured out that the DX stock exhaust piping is 1 7/8" and the EX aftermarket exhaust is 2 1/4". The adapter I procured is from ROI Exhaust, part # 12-8564-2, and goes from 1 7/8" OD (perfect fit over the st-res pipe) to 2 1/4" ID (If you find one going to 2 3/8" instead, I would pick that one). There were two other big numbers on the laber, a 548 and 509 which can be barely seen in the picture. I resized the length of the pipe to the zip-tied exhaust tand welded it in place. [If only I knew the zip ties were going to be my undoing...]

 

Next came drilling out the bolt holes. I will tell you 3/8" is too small. Unfortunately my metric titanium nitride bits have "letters" and not a number in mm, so I can't tell you the size I finally used to get the holes correct as I lost the conversion chart, other than it was metric and bigger than 3/8"


Finished cat flange. The nubbly bottom edge is where my plasma cutter (or, more likely, my lack of skill with it) was pissing me off


Check against the gasket. Looks good!


Back to the car. The flange where the st-res pipe was going to be reattached was rusty, so I took a wire wheel to it

Before:


After:


When I went back out to mark the rotation amount needed for the flange to mate with the catback exhaust I discovered my exhaust did NOTmesh. I replaced all the zip ties with the rubber bushings and fully tightened all the all the pipe flanges with their gaskets and it still looked bad:

 

Well, crap. I decided to push ahead. It looked like some force could allow the pipes to be joined, and there was a lot of sag in the rear (in the elbow where the pipe takes a 90 deg turn to go from the center of the car to the passenger's side).

I welded the flange on, and this created the final configuration on the DX-EX connector from the st-res pipe:


Since the Honda OEM pipes have a coating on the inside to protect them from corrosion, and the coating was not on the flange I created, nor on the adapter, and had been scorched off where I welded the adapter to the st-res pipe I coated all reworked areas in exhaust manifold enamel to help prevent corrosion:


I did manage to get everything installed, though it took two clamps to get the spring bolts back in place. There is still a bit of an angle where the down tube meets my customized adapter pipe, but it seems to be holding for now. I may have to cram some high temp RTV in and around the joint to make sure there are no leaks, but I haven't heard much so far

Finished product, installed:



Test Drive

The sound is deeper, which I don't personally care for but is typically the target of these exhausts. I find the car cruises at 65 more easily, but there isn't much noticeable differences in power other than that. As I said before, this is a commuting car for me only, so I doubt I have the requisite ability to tell differences in power across the whole power band.

If I had to do it over again:

-Go ahead and install the whole exhaust system with the real hangers after you remove the old system, use that for sizing up where everything has to be located

-It may be worth while to use the bent section of the st-res pipe, cutting off the flange area are re-welding it closer to the bend in the pipe. Then cut off the final straight section of the st-res pipe as needed to fit. I think this is the reason why my measurements were off.

-You can make a rough guesstimate of where the st-res pipe needs to be cut and adjust +/- 1.5" with the adapter

-Get a 1 7/8" OD to 2 3/8" ID adapter, if possible

-don't futz with the plasma cutter unless you know what you are doing

 

looks good! thanks for coming through with pics. I feel like I learned a lot. I hope to eventually get a welder and learn how to use it.

 

I was never formally taught to weld. It one of those things where if you do in enough and have a reasonable ability to be critical of yourself you can pick it up. Exhaust is easy welding work because it's not ultra thick (suspension), specialty metals (blocks, drive shafts), or ultra thin (bodywork). All the welding I did above was done with a 120V MIG welder using flux core wire all from Home Despot. Such items can be had for cheaper, such as HF. If you're reluctant to use Harbor Freight, Northern Tool has some cost conscious items of better quality.

I'm sure if someone competent saw my welds they would laugh. Fortunately, while not pretty, they're good enough to get the job done!

 

thanks for the info on the welder. My dad and brother have always wanted to learn how to weld also. If/when I get a welder, I was thinking about paying a professional to give us a 1-2 hour crash course.

 

The exhaust so far has been holding. The misalignment that causes the pipe elbows in the rear to sag down is annoying at humps, bumps, and inclined driveways as the drag & grind is a constant reminder, but on the whole it works. It also passed safety inspection, which was the big thing.

Mileage is close to normal (possibly down 1-3 MPG, was near 40mpg), but there may be other factors.