When the last Supersprint groupbuy started up, I contemplated the idea of getting the best cats (HJS) so that I would no longer have to swap headers/sect 1 every 2 years for CA SMOG. I also contemplated just having some cheap cats welded into my straight pipes, but I wanted top quality and HJS cats barely lose any power. The retail price of the HJS is eye watering, but the GB discount was hefty enough, I pulled the trigger.
Despite the groupbuy taking a while, and issues with QC both in the manufacture and shipping of items, mine arrived in perfect condition, just in time for me to swap them in for my smog test that was due in a few weeks.
Beauts
Car up - I had noticed the giubo (OE, replaced in 2014-40k ago) had some new cracks forming, so I bought a new one (FCP warranty) ahead of time since you have to drop sect 1/2 to access D/S.
SS "S" pipes out
One of my other goals on this job, was to extend my muffler out a it more, especially (mostly) on the right side, to even the tips out. You can see how uneven it was, below. Yes, my tips are adjustable, but the factory metal piping that my tips attach to, are very short and there's no more room for me to bring the tips out further. (Only an issue with CSL diffuser)
Next, dropped v-brace and sect 2
Need to drop heatshield in order to reach CSB. Have to loosen CSB to push D/S back enough to get giubo out. You can access giubo without dropping sect 2 and heatshield, but then you're stuck.
You can see cracks on the giubo. Made it almost 40k of hard driving.
Giubo removed. Inspected the shift linkage. I had done it all recently enough, though, so still well lubed and everything looking as it should. (pictured is UUC DSSR & RE tranny bushes)
40k giubo vs. new. You can buy the cheaper Febi brand, and in the package will be a factory SGF. Save yourself like $100. (also pictured is a factory corteco centering bush that wasn't actually needed [don't waste your time/$])
Don't forget to push the CSB forward when torqueing, before you finish up.
Put copper paste on the new SS hardware and the O2s. O2s (post-cat) were replaced like 7 years ago for when I was passing smog with the euro headers/cat setup. Didn't use them with my v1s, so these are still pretty new.
New pipes ready to go in:
New gaskets:
Before installing the sect 1, I routed the O2 plugs through a hole in the heatshield (made when I had euro cats) and run along the tunnel, driver side
Hello
Once the pipes are installed, I pulled the O2 plus as far forward as possible, to meet the harnesses that need to be run behind the airbox and down tranny/clutch line area (already done in 2014). They'll reach a bit past the tranny brace. It's actually a good area for them to meet the harnesses as there are already some clips for the wiring of the tranny sensors.
Before removal, I had marked (sharpie) where the S pipes settle on the header outlets. I wanted to install the new pipes about 3/16-1/4" further back:
I also shimmed the passenger side hanger with some rubber blocks. This helped push this side out a little more.
Here's the end result:
For me, this is perfect. While I miss having some more exhaust noise sometimes, I don't think I'll touch this setup now that I have it exactly how I want. I'll put a muffler on my other M3 to enjoy those sounds.
In the wild:
Impressions: Shit, the cats eliminated all the drone and rasp 😭 Bright side - the airbox is even "louder." Power-wise, I've always noticed an increase in responsiveness when going catless, then a bit less when I would swap back. I have to say, these HJS are incredible. No perceivable loss at all, and zero smell, I mean zero. Seems like even less than stock, from memory.
Overall, the engine/exhaust sound is a little too calm for my tastes (I like a little drone and overall raspy nature). The airbox is the shining star, and that makes up for it.
in a perfect world, I'd have an electronically controlled "dump" installed at the end of sect 2, and open it up as desired. Maybe one day.
Next up is swapping the airbox back to stock, stock tune, and getting a smog test. We'll see if the cat/o2 monitors go green 🤞
Despite the groupbuy taking a while, and issues with QC both in the manufacture and shipping of items, mine arrived in perfect condition, just in time for me to swap them in for my smog test that was due in a few weeks.
Beauts
Car up - I had noticed the giubo (OE, replaced in 2014-40k ago) had some new cracks forming, so I bought a new one (FCP warranty) ahead of time since you have to drop sect 1/2 to access D/S.
SS "S" pipes out
One of my other goals on this job, was to extend my muffler out a it more, especially (mostly) on the right side, to even the tips out. You can see how uneven it was, below. Yes, my tips are adjustable, but the factory metal piping that my tips attach to, are very short and there's no more room for me to bring the tips out further. (Only an issue with CSL diffuser)
Next, dropped v-brace and sect 2
Need to drop heatshield in order to reach CSB. Have to loosen CSB to push D/S back enough to get giubo out. You can access giubo without dropping sect 2 and heatshield, but then you're stuck.
You can see cracks on the giubo. Made it almost 40k of hard driving.
Giubo removed. Inspected the shift linkage. I had done it all recently enough, though, so still well lubed and everything looking as it should. (pictured is UUC DSSR & RE tranny bushes)
40k giubo vs. new. You can buy the cheaper Febi brand, and in the package will be a factory SGF. Save yourself like $100. (also pictured is a factory corteco centering bush that wasn't actually needed [don't waste your time/$])
Don't forget to push the CSB forward when torqueing, before you finish up.
Put copper paste on the new SS hardware and the O2s. O2s (post-cat) were replaced like 7 years ago for when I was passing smog with the euro headers/cat setup. Didn't use them with my v1s, so these are still pretty new.
New pipes ready to go in:
New gaskets:
Before installing the sect 1, I routed the O2 plugs through a hole in the heatshield (made when I had euro cats) and run along the tunnel, driver side
Hello
Once the pipes are installed, I pulled the O2 plus as far forward as possible, to meet the harnesses that need to be run behind the airbox and down tranny/clutch line area (already done in 2014). They'll reach a bit past the tranny brace. It's actually a good area for them to meet the harnesses as there are already some clips for the wiring of the tranny sensors.
Before removal, I had marked (sharpie) where the S pipes settle on the header outlets. I wanted to install the new pipes about 3/16-1/4" further back:
I also shimmed the passenger side hanger with some rubber blocks. This helped push this side out a little more.
Here's the end result:
For me, this is perfect. While I miss having some more exhaust noise sometimes, I don't think I'll touch this setup now that I have it exactly how I want. I'll put a muffler on my other M3 to enjoy those sounds.
In the wild:
Impressions: Shit, the cats eliminated all the drone and rasp 😭 Bright side - the airbox is even "louder." Power-wise, I've always noticed an increase in responsiveness when going catless, then a bit less when I would swap back. I have to say, these HJS are incredible. No perceivable loss at all, and zero smell, I mean zero. Seems like even less than stock, from memory.
Overall, the engine/exhaust sound is a little too calm for my tastes (I like a little drone and overall raspy nature). The airbox is the shining star, and that makes up for it.
in a perfect world, I'd have an electronically controlled "dump" installed at the end of sect 2, and open it up as desired. Maybe one day.
Next up is swapping the airbox back to stock, stock tune, and getting a smog test. We'll see if the cat/o2 monitors go green 🤞
But, I still have so many questions, mostly related to the actual wrenching, as I am always so nervous I'll mess up 5 things to work on one 
This is my favorite thread, thank you for all the hard work and effort!
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