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YOUR RESEARCHCatalytic Converter Options - Looking for Input
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Performed · outcome unconfirmed · Original poster
I haven�t checked the code, but I�d guess it�s the O2 sensor picking up the failed cat.
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It sounds like it�s filled with gravel when you shake it.
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I also installed 4 new Bosch O2 sensors at the same time.
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Performed · outcome unconfirmed
They are beautifully made, nice welds, very light weight, and installed easily.
Install these same topgear cats back in january of 2020
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I bought and installed these same TopGear Cats back in January of 2020.
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In the process of doing the Fister mod + Agency Power headers, I discovered that one of my original catalytic converters is on the way out. It sounds like it�s filled with gravel when you shake it.
So I�m considering options. Find a used set? Find an OEM replacement? Go with a lower restriction 200 cell cat? Straight pipes???
Here in MN, there�s no risk of emissions controls, so I�m free to do as I please in that regard. (Sorry Cali)
I�ve had cars in the past with a bypass pipe, straight pipe, whatever you want to call it. I know there�s performance to gain, but man, did those cars put out some exhaust!
Also, this is not a track car, but I�m always pleased to add performance upgrades when replacing parts.
Sound off with your experience on this. What have you installed and did you like or dislike? How did it affect the sound? Any actual noticeable butt-dyno results? Was it worth the dollars vs stock?
2003 C2
PS - I broke exactly ONE exhaust manifold bolt on removal and OMFG is it a nightmare trying to get it to turn. Still at a standstill on that thing. No welder here. I�m ready to take it to a shop to get it removed by the pros.
de Jeeper - I know you offered your bolt removal jig and I never got back to you. This is the penalty. I just decided to go for it. Oops.
Currently out of stock, but I'm running the 200 cell cats from Top Gear UK. You can get 10% off using code 911UK.
https://www.topgear.co.uk/porsche-91...ll-sports-cats
Too bad you don't have a welder. That looks like an excellent candidate with al the thread left there. You could try and put more penetrating oil and heat into (MAP/Propane) it for a couple days and use a pair of vice grips. That's otherwise an easy one for the pros.
Since the threads look intact, and you have quite a bit of stick out, it may be worth trying to get a nut and jamb nut on there so you can use a wrench to break free. If you can't get the jamb nut tight enough, staking the nut on may work as well.
Wow, only one broken bolt? Seems like a great outcome considering some of the other results I've seen. I don't have the top gear cats but I do have the mufflers and the fitment was good so their cats might not be a bad option.
I�ve done all of that. Jam nut against a larger nut, vice grips, a slot across the end of the threads into the nut with a screwdriver holding them together while turning the jam nut combo, lots of mapp gas heat, a whole can on PB Blaster, etc.
It won�t give with what I have available.
Yep.
I think my mistake was to loosen the rest before that one. They all came out so easily, I got the rest of them too loose, which can change the tension on the remaining bolts. The right way is to loosen them one and at time, then snug them up again before moving to the next one. When they are all broken free, THEN it�s ok to pull them out.
My car had FOUR broken header bolts when I bought it (sure would have been nice to know that before buying but I guess that's what I get for forgoing a PPI). I had AutoEdge remove them for me. As far as cats are concerned I'd never run a catless car on the street. The tradeoffs and environmental effects are not worth the marginal power gain. I'd hop on a 200 cell x-pipe and never look back.
Just to relay my experience... I bought and installed these same TopGear Cats back in January of 2020. They are beautifully made, nice welds, very light weight, and installed easily. I also installed 4 new Bosch O2 sensors at the same time.
They say that they don't throw CEL, but within 30 miles, and continually after that, I got Cat efficiency codes for both bank 1 and bank 2. Used Durametric to monitor voltages, and the sensors are good, the Cats just don't do enough. I tried to contact TopGear asking what they generally recommended, but I could never get them to reply. I had to install O2 spacers onto my after-Cat sensors. Finally got to that about 5 months after Cat installation, and the code was finally cleared and gone.
You can search the forums, some people haven't had an issue, but some have. If you DO have a Cat issue now, my recommendation would be to either:
1) Be honest about it and just use a straight/test pipe and O2 spacers. The TopGear Cats really aren't doing much anyway.
2) Pay more for better Cats.
Thanks! That�s great real world feedback. It�s a shame they didn�t either advise on how to correct the CEL or re-engineer the cat to not throw codes.
Did those TG cats improve the sound at all?
Oh man! That sucks! I have an appt in the morning to get help from a shop to extract that one bolt. I just couldn�t enjoy the ride knowing there�s a broken bolt back there.
Not that I�d ever advocate for just leaving it. But I wonder what�s the harm in one broken bolt? Did you get any error codes from exhaust escaping or air coming into the system? Could you hear a leak?
They did make the exhaust a louder, with a nice throaty sound. When I pulled out after installation, my neighbor immediately asked if I redid the exhaust. I have PSE, and now definitely keep it quiet in the neighborhood. But opening it up once out on the road sounds great, so no regrets there.
Yeah - that would be great! Mine is a 3.6L 2003 C2.
For now, I reinstalled the cats as-is. 20 mins later and a CEL popped up. I haven�t checked the code, but I�d guess it�s the O2 sensor picking up the failed cat. So I�ll have to solve this problem sooner or later.
Wow! $2500! That�s ambitious.
For about $300, I�d rather have this, or something like it:
https://www.autohausaz.com/pn/DC-99711303605
Or something like this:
https://www.vividracing.com/-p-153388674.html
I have fister mufflers and a FVD x pipe. It sounds amazing and no drone. It certainly isn�t quiet though. Nothing like a muffler delete, but it�s pretty aggressive outside the car. You will need spacers on the o2 sensors.
You Tube
With the stock cats:
You Tube
Basically just turned the volume up a few notches with the FVD pipe.
Yup. A big difference. I�m definitely not sneaking up on anyone. A big weight difference, although I�d be lying if I felt any difference while driving. I definitely feel a power difference. Not huge, but it pulls better than before.
I have the topgear 200 cell x-pipe and have never thrown a code with them. They sound unbelievable. I do get a little exhaust smell but not nearly what bypass pipes have. Overall I am completely satisfied with the top gear 200 cell x-pipe product.
I have Design 911 200 cell cats and have been pretty happy with them. Seem well made and I�m happy to to have something that�s not straight piped. I think design 911 Cats are the same as Top Gear from what I can tell.
I've heard topgear after sales service in non existent, very prompt in getting your order through but after that you're on your own.
I asked a simple question on my topgear mufflers 2 months ago via email, got zip zilch response
Update to this thread. I did indeed end up grabbing those stock cats from Mr
ltusler last week. It was great to meet another enthusiast and get a peek at his sweet collection, including a 996 track toy and a classic Porsche tractor. Thanks again for the good deal!
I had to drive a couple of times before then, so I ran with my original cats. And sure enough, a code came up. The replacement took care of that problem!
After wrestling with that broken bolt for far too long, I had the same shop that welded my Fister mod on the mufflers put the car up on a hoist and extract the offending bolt.
So I ended up with an all new exhaust!
Agency Power Headers
Replacement original cats
Fister modded mufflers
I put on a few miles over the weekend, and I gotta say, I�m VERY happy with the result! It sounds amazing!
I also run the FVD cat bypass and can attest to the increase in top end but the mid range is noticeably reduced. A tune helped but did not eliminate it. It is reflected on the dyno sheet, there is a flat spot in the torque curve from 2-4k RPM. Over 4K though the car pulls like a freight train and sounds incredible. 3.6L car and it made 291rwhp with a cat delete and stock gundo mufflers.
Curious if you got a off-the-shelf retune or custom with catless? I have the same setup (catless + gundo) and am really bothered by the hesitation <2k rpm under heavy load, the flat torque not as much. Agree that after 4k rpm the car has a big bump in power.
a little of both I guess, it�s an EvoMS tune that they apparently have �perfected� for my mods that they supposedly have a lot of experience with. Worst $895 I ever spent. I should have just gone directly to a shop and had a custom tune done for my car. I know better but so many people sang their praises I was confident it was what I was looking for. They were also supposed to raise my limiter to 7500 which didn�t happen even after they sent me a new tune which was specifically modified just to increase the limiter.
Good to know! I'm convinced an OTS tune like evoms won't do it for me without the supporting mods, not mention I'm in Canada and the environment is very different VS Arizona. Going to give the local custom tune a try to see if I can get rid of the hesitation. At this point it's annoying enough that I'm considering ditching the x-pipe or adding cats. The loss in torque is a non-issue, but having to ease the car in slow traffic is frustating. For what it's worth the PO had the FVD tune added and it still hesitated, or perhaps has contributed to it.
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