The time has come... I want to remove my OEM cats and replace them with something more free flowing. I will have SS headers installed and eventually a high end SS exhaust system.



At this point I have two options, but can't really decide. I need your help. My car is and always will be a daily driver.

1. Test pipes with "RESONATORS" and the SES solution posted by Zivman.
https://my350z.com/forum/showthread....8&page=1&pp=20

2. What I know to be "carb legal" high flow cats. See illustration for my choices. I'd like to stay under $500 bucks.



I don't want a lot of rasp if I go with the TP w/resonators...do I really have a choice around this matter?
If I go with the carb legal high flow cats can I expect a vast improvement over OEM? Is it worth it the price tag?

Thanks to everyone,
Zquicksilver

 

I have resonted test pipes and honestly that is the only mod i really felt the power from and with all my other mods combined the car pulls pretty hard now

as for rasp i think all test pipes resontors or not with be alil raspy but just have another resonator welded in somehwre else in the exhaust piping and problem solved

my car is also daily driven and it is a toch too loud for me (i thought the stock exhaust was a perfect volume so loud to me is different from loud to others) so im probably going to sell mine if your interested shoot me a pm

but for power i would definatly go with test pipes but if you go High flows crawford or kinetix has my vote

hope this helps any other questions let me know

 

TP/w res. louder than stock tone at times...good to know

thanks for your input...

ps at this point i'm partial towards the beautiful HELIX downpipes if i go HF cats

 

the one thing i like alot about resonated test pipes is that as crusing speed they are as quiet as stock but like i said when u step on the gas its a touch to loud for me.

 

I have heard this "rasp" on a couple of 350z's... ya, it kinda reminds you that you aren't driving a mustang or Z28 or some other big V8. But in all honesty I wouldn't say it sounds bad, it really sounds exotic, similar to what the Italian super cars sound like (similar, not same). Anyway, I like it. I don't wanna sound like a 3800 lb "muscle car" that runs 15 second 1/4 at 89 mph (stock Mustang GT's before 2005). I bought a 350z for high-tech horsepower in a car that handles. I like the fact that my n/a V6 with leather heated seats blows away your loud echoey POS sounding "muscle car". ya

 

Why do you want to stay carb legal if you live in Chicago? You won't be carb legal if you run Test Pipes, but if you don't have emissions testing, that shouldn't be an issue.

If it were my car, I would get the labree resonated test pipes (I actually have these) and pair them up with an exhaust like the greddy evo2 or HKS ti-dual exhaust. The rasp that you are worried about is more of a factor of the catback than the testpipes themselves. As long as the exhaust has decent resonators and mufflers, the rasp will stay to a minimum.

Replacing the cats in any form is basically illegal unless they are replaced due to defect or damage and in which case, they should be replaced by a cat that peforms the same. That said, unless you're in a state that has regular emissions testing (I don't know if IL does) you might as well get test pipes rather than HFCs.

If you do run HFCs, you won't have issues with SES lights, but with testpipes you most likely will if you are running an 04.5 or 05 model yr car. Though, with the link you have above, the light is EASILY taken care of.

I would start looking into what catback you want to run and let that determine if you should go HFC or test pipes.

I run topspeed headers and labree resonated test pipes into the evo2 exhaust, the exhaust is definitly noticable, but it is easily tolerable for an everyday driver

 

Thanks for the analogy...xephiron...but I'm not sure I want people to assume I'm getting on it when the car is hardly accelerating and they hear the rasp at 3-4k.
It's more like... hey, look at me, I'm trying really hard to get your attention because my car is not worth the looks or prestige...aka 92 honda accord


Zivman,

The angel side of me says be environmentally responsible and stay kinda carb legal because it's a high mileage commuting car, but the little devil in me wants more power and could give two sh*ts about how much a 3.5L car pollutes. So...with that being said it comes down to a couple of other things.

1. What you stated about emission testing...The US government is getting more strict with their emission laws and it's only going to get worse/ or better IMO. What I mean is I'm all for it, at least for the average JOE and his 7.2L SUV. I looked into the IL. laws the other day and found after a car is 4yrs old it must under go testing every 2yrs after. So, I'm not 100% if I want to get under the car every 2yrs and swap out the catless with the OEM. That could get very annoying.

2. If I do go catless and decide on a true split catback like the Stillen version, will it be annoying with RASP even though it has two separate muffling CANS for each back pipe?

3. If I go with a HF cat like the HELIX, can I really be sure that it will pass the test in 4yrs. as the test get more stringent? HELIX says the design passes the most stringent CALI test to date and they are moderately priced, besides just being damn beautiful.

4. Loose a little power and stay Carb Legal or at least just get under the wire and make sure "they" don't start sniffing around? Or save about $325 and go with TP/w resonators, gain power and be annoyed with having to swap them out for each test? Just being a little lazy up front But at least I'll pass considering the OEM cats will be almost brand spanking new!! mmmmmwhaahhhaaaaa!


Opinions...

 

screw the environment. get the labree. I have about 3000 miles on mine and love them. I had rt cats before which collapsed and were more raspy than my labree tp's. Its louder but you get used to it. When i am cruising i dont notice the sound. THe good thing about the sound they produce when you step on it is that other drivers can hear when they need to get the h3ll out of the way.

 

emissions testing is a joke. The only reason we have cats on cars is because Americans are lazy. We don't do the proper maintenance on our vehicles. Not only that, most cars run rich from the factory, so the cats help in this area as well. Cats IMO are a joke since they trade one harmful emission for another. Heck, those big deisel trucks don't even have cats.

IMO, HFC won't last the life of the vehicle, so you would be under the car in a few years anyways. Heck, my '98 protege's OEM cat went out this past fall with 83K on the odometer. Do you think I replaced it? Heck no, I ordered up a $10 MIL eliminator to get rid of the SES light and I was good to go. You're first emissions test will be in 4 yrs and then every two yrs after that. Some emissions tests only include a hook up to an code reader and if you have no codes, you are on your way.

MN doesn't have emissions testing thanks to good 'ol Jesse Ventura. When we did, it was a joke - a waste of time an money IMO. I read a few studies that the emissions testing had no impact on pollution levels, so why is it needed? Those CA emissions people are nuts. They have warnings and standards and what-not for just about everything.

I used to work for a major retailer and I was involved in a dept that sold lead crystal. Well in CA, they have a deal called "Proposition 65" ever heard of it? Well, it requires that these big "bi-hazard" type signs be displayed along side the Vases, candle holders and what ever else contained lead that was being sold. I couldn't beleive it, since it would require you to eat like 10 of the bowls or vases for you to ever be exposed to any potentially dangerous levels of lead.

 

I agree with you, but I also feel vehicles contribute to about 3% of air pollution. It's the factories, powerplants and other who contribute the most. I was thumbing thru National Geographic the other day and they had a satillite snapshot of the N. Pole 15yrs ago and today...a little scary to be honest.

Anyway, back on topic

So some say the HF Cats like Random Tech. will just collapse over time...that's freakin great! $720 down the tube, literally! Did you happen to drive under extreme conditions constantly, like autocross every weekend??

If I do go with TP w/res. and don't want to spend $500 for a ECU reflash do I take the chance at running lean?

I'm learning here thru experience

 

Yes, you may run lean with cats or tp.

You mentioned the ecu flash.

One of the best things i ever did for my car. The 7100 rpm redline is hot, tq is better throughout the rpms and it just plain runs better.

I sent my ecu off about three weeks ago and i am really wondering why i did not do it sooner.

My rt cats collapsed after about 20k miles. I have 44k on the car.

 

You won't run lean enough for it to be a concern. The ECU does a decent job adapting to the increased flow and will keep you in a safe A/F ratio - especially the 04.5 and 05 ECUs. You would need the flash as much with a HFC setup as you would a test pipe setup.

IMO, most HFC will fail in a relatively short time. The cats crawford uses (based on the looks of them) what seem to be carsound HFC made by magnaflow. In my personal experience with these cats(carsound- which are only about $50 each), they could burn up in a matter of 10K miles depending on the A/F ratio. I burnt up one in 5K miles. There is post of a guy that just ate up his Crawford cats. The R/T cats have a history of collapsing, and Kinetix....well, let's just say I have read a few posts about issues with them.

 

Damn...

So it's kinda a no win situation

TP/resonated = possible rasp, running lean unless you spend $500 for ECU, failing emission test(with my luck) if you don't swap with OEM every two years...

HF Cats = replacing them in 15-20k, $500-800 down the drain, still running lean with out a $500 reflash... What's the general opinion on the HELIX HF cats before I just give up?


Ok, there has to be a way to partially get around this problem. What about the following setups for a Semi-High flowing system?

Option ONE
1. SS Headers
2. OEM cats
3. Stillen or Very high flow exhaust system

Option TWO
1. SS Headers
2. TP/ Resonators + $500 ECU reflash
3. OEM exhaust to cut down on rasp and compensate for ECU reflash


Thanks

 

You don't NEED the flash with either setup and unless you are doing intake and plenum along with the exhaust mods, you should save your $.

The OEM exhaust paired with test pipes will not cut down on rasp. A good aftermakert exhaust like the greddy or hks should keep the rasp undercontrol.

In all honesty, I feel you are overthinking the situation. save the $500 on the ECU flash, save a couple hundred and get good resonated test pipes, and put this money towards the greddy exhaust and you will be all set to go and have a smile on your face because of the increase power and awesome sounding exhaust.

 

I already have the intake and I'm getting ready to install the AAM spacer in two weeks. So...I will have to spend the $500 if I go either way. I didn't think about that, grrrr. And if I do go thru with all of this; SS HEADERS, TP/reson, SS exhaust, ECU reflash and ever decide to switch back to OEM cats for sound reasons or just out of laziness of swapping every 2yrs, I'm screwed with the A/F ratio, right? Damn I wish I was rich.

Thanks for the input on the OEM exhaust/sound issue.

And yes, I do overthink every situation... It's out of habit as a product designer. I have some thinking to do...at this point I'm leaning towards option ONE, I'll take my small loss of power over more money and headaches down the road. My logic tells me that that SS headers, OEM cats, and SS exhaust won't screw too much with my A/F ratio... Damn CATS!

Thanks guys

 

Well...I made a decision. It was not easy with all of the factors involved; options for different setups and different name brands unique to each individual's desires. Too many choices to be honest. You can see how I went crazy above...

I went with the Helix 200 Cell Hi-flow Cats.

"Helix DNA Series High-Flow catalytic converters provide an exceptional balance between maximum power and emission cleanliness. Our high-flow catted products features 200 cell Metal Substrate Catalysts for maximum performance and emissions reduction."

- 100% SUS304 Stainless Steel
- Robotic TIG Welding
- Thermal boundary heat-shield for rapid light-off and maximum catalyst efficiency
- Features: 200 Cell Metal Substrate High Flow Cat with Thermal Shield x 2
- Piping Diameter: 60mm X 2

I went with metal substrate internals out of fear of the ceramic ones collapsing on me in 15-20k. I'm not a 100%, but I think this is unique only to Power Enterprise cats and HELIX cats. If you want some extra info on metal substrates, here you go.
http://www.autocats.com/html/motorsport.htm

I hope they're worth the $445...? Should get them in about 10 days...

Thanks for everyone's input
Zquicksilver

 

Wanted to know if you received and installed the Helix Cats ???

Can you give us some feedback re sound / installation / perceived performance?

These look to be the best value (quality /price) and is my next purchase decision.

Thanks in advance

 

I did receive them...along with my TS Headers...both have been sent out to JETHOT for 2k coating I'll be installing them Memorial Day weekend. For the next year or so I will have the stock OEM exhaust...unless I get a nice raise, then it's between TD Borla or TD Stillen. So sound evaluation will be based on that setup...pls. don't give your opinion to exhaust in this thread. I'll create a nice little write-up after everythings installed.

Here's a pic of the pieces together They are so beautiful in person, welds, fitment, everything...!

Zquicksilver

 

Looks awesome - I could never wait that long but think that coating the headers is a good idea. Not too sure about the cats though...

Will you be doing the install yourself?

Hope it all turns out better then you expected.

Still anxious for feedback on Helix installs..



Good luck.

 

I decided to do the cats for an extra $100. I figure they sit half way into the engine bay, why not keep them a little cooler. It will probably pay off when I get stuck driving 3mph in Chicago traffic...and when I go in for emissions. The smog suckers will be like, looks dirty and black to me...must be stock

I'm usually patient and that weekend is the first available time slot I have with my buddies well equipped shop. My grandfather was mechanic, so I get it from him!

I hope it's worth the money too! Those two parts with the 2k coating...$970.