3" Exhaust, cat-back. Prep for VQ35DE conversion

[HusseinHolland]

Since I had to cut off the exhaust to deal with all the rear suspension work, I decided to put together a 3" SS rear section, starting after the existing cat, then going to a 2.5" Stainless Works rear muffler (ran it on my X1/9 K24 swap for a few months). The 3" SS exhaust I put together  from a exhaust I had made years ago for my Volvo C30, before I converted it to AWD & had to make it all over again.

Forgot to take pic before I cut it up - this is what it was

Eyeball the general placement, then cut, & tape together to check clearance off the forward crossmember and lower control pivot & diff casing

tack welded, then recheck fit 

I'll be adding a 3" - 2.5" step from this into the muffler

looks pretty good 

step down & dogleg to attach to existing exhaust/cat. I'll rework the entire exhaust forward of the 2 bolt 3" flange when I do the VQ35DE

2"-2.5" - 2.5"- 3" steps

 

Edited July 14, 2023 by HusseinHolland

[Racer X]

What welding setup are you using? MIG? Stick?

[HusseinHolland]

9 minutes ago, Racer X said:

What welding setup are you using? MIG? Stick?

TIG for this  - it's all stainless. I could use my MIG I suppose, but I don't have stainless wire for it. TIG is cleaner for pipe anyway. Where I had good butt-joins, the welds are clean (enough, I'm not a professional). Where there was discrepancy/offset, so so much.

More work on the exhaust today. Got all the tacked seams welded, and figured out the muffler placement 

cut down the 3"-2.5" step for the available spacing

have to figure out the hanger here, have to make sure it pulls it slightly away from the spare well

like this maybe

or here, to push it away from the spare well. There is a hole in each corner of the gas tank, I could use this one, and add a smaller outward placed one to locate the strap from potential rotation 

maybe one set here

[HusseinHolland]

Made a bracket (from a Volvo dash support) to utilize the stock hanger point at the front end of the muffler

reinforced to make sure it can't flex. The lip at the top tucks over the frame bracket

muffler hanger attachment

in place. Drilled an inboard hole in the stock welded bracket to positively locate the new bracket.

With that figured out, I tack welded the hanger to the muffler

Removed & finished the seam welds for the muffler inlet & tailpipe section. Just have to weld on the Redtail exhaust tip when it gets here.

[HusseinHolland]

Change of plans - I removed the front pipe. One of the Datsun guys on Turbobricks said the 2-1 junction is a severe choke point.

His solution was to make a new 2-1 section in 2" pipe

I can't weld something like that, Dealing with welding those to the flange, and the collector are extremely awkward, from my experience with the first header on the K24, I'm not willing to risk it.

Stock front pipe.

Flange. Making 2" pipes fit the flange would be tricky. I thought about using a 1 7/8" holesaw to get it close, then grinder to get the rest. I don't have a spare DP, so just not worth it.

taper point, only about 1.5" ID in there

So, I cut off the upper section of the DP where it's approx 3" wide & modded another section of my old C30 3" exhaust to fit. after a bunch of back & forth, I tacked it here. To minimize the reduction in the stock collector I cut it so there is only about 1/8" tuck.

test fit - clears the heat shield (next to my finger) by the same amount as the stock pipe - just looks like there's no clearance

It was raining at this point, so I took it down & seam welded the joint. But.. it moved, so I had to cut the pipe & add a pie cut (to be welded later) to get the pipe pointed where it needed to go

New cat & used resonator from a Volvo S40 T5. 

Edited July 20, 2023 by HusseinHolland

[HusseinHolland]

Got the rest of the front section figured out. No room for the 3" resonator though.

Added a dogleg to get good alignment with the rest of the front section

added a straight section off that, into a 3" cat, then another 10" section into the mid connection 

good clearance all around

fitted the cat behind that

10" section between cat & dogleg into 3" flange 

removed again to tack rear mid section 

re-installed one more time to figure out the hanger off the transmission case, then removed. Now I have to seam weld all the junctions

 

Edited July 19, 2023 by HusseinHolland

[HusseinHolland]

Welded up all the seams, took almost 4 hours(!)

After that, I had to reinstall it to figure out the center mount.

I decided to make one that used the stock mounting points

Once I had that figured out, I tacked it in place & then removed the entire exhaust to finish the mount welds for this & the rear muffler hanger

Archie was hanging around me much of the day

I had forgotten about the trans mount / carrier bushings, so I did those now

put the exhaust back in (hopefully for the last time)

clearances still good

Hangers

Still waiting for the Redtail Performance tailpipe 😞

 

[HusseinHolland]

RedTail Perf. Exhaust tip finally arrived.

Nicely constructed pieces. This particular transaction with the company was a PITA though.

Anyway, to question would be how much to have it protrude relative to the skinny bumper install. Didn't have much luck finding pics online to refer to.

I can cut a couple inches off the tailpipe & set it like this:

 

 

Edited July 28, 2023 by HusseinHolland

[HusseinHolland]

Expanded the tailpipe to get a tight fit for the tip, set it close to the bumper depth, to hopefully avoid exhaust discoloration of the taillamp 

 

Edited July 29, 2023 by HusseinHolland

[HusseinHolland]

Youtube of exhaust note, during warmup

 

[HusseinHolland]

So, now that I'm driving it again, the exhaust is WAAAAYYYY to loud & drones terribly between 2-3K rpm. I will have to look at a different muffler, and perhaps a resonator that is smaller than the 3" Magnaflow I have, that was too long to fit after the cat in the straight section, which is only about 10".
 

[HusseinHolland]

3" OD, 9" long resonator came today, so I'll hopefully get that in tomorrow.  

In the middle of making bike carrier adapters to hold the Volvo/Thule load bars & bike carriers I have had since the early 90's. I added stake holders to the bed sides when I made the truck. When my kids were young, we would typically fit 4 bikes on the roof of whatever Volvo wagon I had at the time. Wife & I are going to go upstate NY & CT in a couple weeks to do some hiking & rail trail biking. my bike is almost as old as my pickup.