Sport Cat Installation w/ Fister Mufflers on '99 C4

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5chn3ll
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Sport Cat Installation w/ Fister Mufflers on '99 C4

Post by 5chn3ll » Thu Jun 21, 2018 10:40 am

These are the sport cats I purchased from another user on Rennlist (dammit) ...time to finally install 'em!

01.jpg

To get started, remove the airbox.

First, pop the oil filler free from its clip.

01A.jpg

Use a socket, nut driver, or screw driver to loosen the airbox hose clamps and the single large bolt holding the airbox to its mount.

03A.jpg
02.jpg
03.jpg
03B.jpg

At this point, push the release on the back side of the MAF and remove it from the airbox assembly.

If the MAF housing cracks like mine did, give it the bird.
04.jpg
Then rotate the MAF toward you and use your security Torx bit to remove the MAF from the airbox assembly...I'll deal with the busted sensor later.

04A.jpg

Once the MAF is out of the way, finish removing the airbox.

You can now see the O2 sensor connectors on both sides of the engine bay.

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08.jpg

Next, label both ends of the oxygen sensor connectors to simplify reassembly later.

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To disconnect the O2 sensor connectors, push the exposed part of the sliding clip in toward the body of the connector.

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Disconnect the O2 sensor wires from their clips. Make sure the wires are as free as possible so they don't get caught when you're removing the cats.

12.jpg

Now it's time to get under the car...

Remove the three nuts that hold the cats onto the headers.

You may notice that my cats are held on with nuts and bolts instead of the factory studs...after breaking a couple of studs the first time I pulled the cats off, I paid my exhaust guy a couple of six-packs to torch the studs out of the headers and switched to stainless steel hardware.

13.jpg

Use a 17mm wrench to loosen the clamps that hold the cats to the mufflers.

14.jpg

Carefully rotate each cat after it is loose and remove it from the vehicle.

Here's what my car looks like with the passenger-side cat removed.

15.jpg

TO BE CONTINUED...

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Re: Catalytic Converter Removal/Replacement

Post by 5chn3ll » Thu Jun 21, 2018 10:43 am

Looks kinda empty without all those crusty 20-year-old cats...

06During.jpg

A little extra effort put into keeping track of parts coming off will make life suck less when putting stuff back on.

01parts.jpg

Lay the new cats out next to the old cats to ensure you understand the oxygen sensor configuration...

02matching.jpg

Labeling now ensures winning later.

03NoShame.jpg

Once you're sure you know which bungs go with which holes (heh), remove the sensors from the old cats and install into your sport cats.

As I mentioned, I hate the lone oxygen sensor removal tool AutoZone carries. IF the sensor comes out at all, chances are good it will get bound up in the socket.

04HateIt.jpg

This crowfoot wrench from Home Depot - intended for tightening faucet supply lines in cramped situations - is my go-to for removing oxygen sensors.

05Crowfoot.jpg

I have not ruined a single oxygen sensor since I started using this tool...

Finally...a lousy "after" picture featuring the sport cats.

07After.jpg

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32wildbilly
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Re: Catalytic Converter Removal/Replacement

Post by 32wildbilly » Thu Jun 21, 2018 11:08 am

5chn3ll wrote:
Thu Jun 21, 2018 10:40 am
These are the sport cats I purchased from another user on Rennlist...time to finally install 'em!

If the MAF hosing cracks like mine did, give it the bird.

04.jpg

TO BE CONTINUED...
Just for my notes to refer to in the future, does the bird given have to be left handed or would a right handed bird also be acceptable?

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Re: Catalytic Converter Removal/Replacement

Post by 5chn3ll » Thu Jun 21, 2018 12:49 pm

Typically, this would be performed using the dominant hand. In this case, the left hand was used; the photographer needed the dexterity of the right.

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Re: Catalytic Converter Removal/Replacement

Post by sweet victory » Thu Jun 21, 2018 1:14 pm

THOSE DON'T LOOK CARB LEGAL. I'M TELLING
2001 996 C2 Aero

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Re: Catalytic Converter Removal/Replacement

Post by 32wildbilly » Thu Jun 21, 2018 3:00 pm

5chn3ll wrote:
Thu Jun 21, 2018 12:49 pm
Typically, this would be performed using the dominant hand. In this case, the left hand was used; the photographer needed the dexterity of the right.
bird flashing at broken MAF: use dominant hand...got it. Thanks!

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Re: Catalytic Converter Removal/Replacement

Post by 5chn3ll » Sun Jun 24, 2018 12:10 pm

Update: The car went back together incredibly easily. The one tool I need to add to the DIY is a crowfoot wrench - I use this instead of an oxygen sensor socket. The socket deflects and digs into the sensor every time I've tried. The crowfoot is self-tightening but can't bind up - it makes the job easier and possibly cheaper (i.e. destroying and having to replace 2/4 oxygen sensors...thanks, socket).

After I garaged the car on Thursday evening, I fell asleep and woke up Friday with a bitch of a summer cold. I've been in bed with blankets over the window shades for 2.5 days. Today (Sunday) was the first time I felt up to putting some time in the car.

Good news! The world's shittiest sport cats (as described by the seller) did NOT ruin my car. In fact, idling up and down my cul-de-sac, it's only nominally burblier. At normal throttle (dammit, oil, heat up), it's got bark but doesn't drone or rattle. Resonant frequency seems to be at about 4250 RPM - if you're not into it, you probably won't notice. When you give it the beans, it sounds like a stock car...but at a very narrow RPM range that doesn't seem to coincide with highway cruise speed. Less than 100 miles, so some objectivity is probably still due, but no check engine lights.

I need to go back and check the Rennlist thread so I can post the proper name for these sport cats. Despite the previous owner's hilariously candid comments, I'm pleased with the modified exhaust note. I have no dyno sheets to back up any "butt dyno" opinions one way or the other - maybe after the exuberance from playing with the new cats subsides, I can more objectively opine if the car feels faster/slower/different. I do notice that throttle blips are less responsive than normal, like it's running slightly rich. I should probably disconnect the battery to reset fuel trims (?)...

I have no before dyno numbers, so I won't be guessing any HP numbers. If I positively ID the cats, I will list any claimed HP gains and see if it's consistent with my impressions...

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Re: Sport Cat Installation w/ Fister Mufflers on '99 C4

Post by sweet victory » Sun Jun 24, 2018 8:15 pm

Could you monitor fuel trim levels to see how the 02 sensors are reacting to the new cats? Something I've been curious about, but haven't found any data on.

Will you be smoging these cats, or do you have 'a guy?'
2001 996 C2 Aero

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5chn3ll
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Re: Sport Cat Installation w/ Fister Mufflers on '99 C4

Post by 5chn3ll » Mon Jun 25, 2018 8:16 am

I will grab some data on the O2 sensor output and dig up some stock data to compare it to. Good idea.

One of the reasons I had the studs torched out of the factory cats was to ensure that unbolting the cats would be as painless as possible.

Both of my "fun" cars have graduated into the STAR smog program, which is basically the old smog program but without the handy cheating. There's no way the new cats will pass visual inspection. As far as 'a guy' - those are a lot harder to come by than they were 10+ years ago. CARB will shut the station down and fine the balls off of all parties involved with cheating; I'd rather spend a day swapping the cats back out than ask my Yoda-like, seemingly-300-year-old Vietnamese smog guy to risk cheating for me.
sweet victory wrote:
Sun Jun 24, 2018 8:15 pm
Could you monitor fuel trim levels to see how the 02 sensors are reacting to the new cats? Something I've been curious about, but haven't found any data on.

Will you be smoging these cats, or do you have 'a guy?'

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Re: Sport Cat Installation w/ Fister Mufflers on '99 C4

Post by 5chn3ll » Tue Jun 26, 2018 8:30 am

Update: After a couple of days of in-town driving (50ish miles), no emissions-related OBD codes (or any at all, for that matter).

I haven't prepared the final opinion yet, but they're still far better than I was expecting based on the ad:

I used them for ~2K miles and found absolutely nothing to like about them & went back to the factory ones.

The Bad: When installed with factory mufflers they add an unpleasant metallic resonance to the exhaust sound. The sound might be more compatible with sport mufflers, but assume it won't be. They produced CELs a couple times during the time I had them installed - so, they're unlikely to pass an emissions test.

The Worse: You're probably not going to like them, either & have to swap back to something else.

The Good: They are made of stainless steel and lighter than the factory cats. May be an alternative to bypass pipes. Can't think of anything else positive.

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