Trent540va

I'm about to purchase a set of headers for my z06 and was wondering how Nessecary it is to get cats along with them and if they make a huge difference?
Thanks



Think I'm going with the lg longtubes

ZZ06

You didn't specify as to difference in what? Sound, power, smell, installation.....

grantv

... legality...
Basically;
Sound = a bit louder without
Power = no noticeable change
Smell = some report smelling raw fuel without them
Install = $300 or so extra to buy & install
Laws = you may not be allowed to run without depending where you are

JeremyGSU

I'll rephrase some of this.

Basically;
Sound = a LOT louder without
Power = no noticeable change
Smell = my car stinks without them
Install = $300 or so extra to buy & install
Laws = you may not be allowed to run without depending where you are

I did not have them on my car in Florida and if I had to do it all over again I would. I could not drive it anywhere without coming home and throwing my clothes directly in the hamper. They would wreak. Especially if I had the windows down.

zeevette

I'll re-rephrase some of this:


Smell: no noticeable change with HF cats. I won't go back to catless because it's not worth the bother to uninstall them. A cam change made all the difference is smell level. A couple of degrees of negative overlap worked for me.

2003Evo

If your state allows you to run without them then dont bother installing cats. I dont know why people complain about the fuel smell because mine is barely noticeable. It is more noticeable in enclosed areas such as the garage, but out in the open no problems.

JeremyGSU

Must be your setup. I could not sit at a stop light with the windows down without it reeking of fuel smell. Even with the windows up and A/C on recirculate you could still smell it at stop lights.

zdeckich

I had LG high flow cats on mine. I ended up taking them off because I wanted it to be a tad louder. But like others said, sitting at a red light for a bit you can for sure smell fuel, but it does not bother me, wife hates it lol.

grantv

And how much louder did you perceive it after? Just curious. At idle and open...?

zdeckich

for sure noticeably louder but not crazy.

zeevette

In my experience, the cam overlap is much more of an issue that affects the smell. When I had my NA setup, with a +8 overlap, and no cats, it smelled bad anytime you stopped moving. I then added the HFCs, and could tell NO difference in smell level. It wasn't until I went supercharged, and changed to a -2 SC cam, that it lowered the bad smell considerably.

pavell

I went from Stainless works high flow cats to cat delete pipes.

at idle and to 3000rpm it sounds exactly the same.

3000rpm to Redline I would say its 15-20% louder...

grantv

Ahh... everything runs great and sounds great. Plus I installed them mostly for environmental reasons. Add the fact that our single attached garage is beside every bedroom (ours, 5 year old and 2 year old) and I leave 2 hours before they all wake up every morning... better leave it alone.

C5Dobie

I've run headers w/ and w/o cats - while not identical to a Z06, my G8 GT and LS1 04 GTO are very similar mechanically & both of those cars smelled when running catless headers, worse so in the summer, and worse in the GTO b/c I'm guessing the car was shorter & window placement/size allowed alot of exhaust smell into cabin.

Z06 has catted ARH headers - slightest egg smell on cold startup, goes away in 5 mins, overall exhaust smells a bit more in general but nothing like catless setups. Z06 would probably be even worse than G8 or GTO running catless b/c it has such a short free flowing exhaust to begin with...IMO no point in running w/o them unless you're running bigass power-adders and running competitively @ drag strip & need every last ounce of performance edge.

Sound - will sound louder w/o cats.....but not "better" IMO - particularly if you're running stock TI axleback.

Just run hi-flo cats...this is a corvette Z06 not a rustang or budget Camaro SS running 4" straight pipes trying to do your best nascar impersonation!!!

zdeckich

Me running at 1/2 mile with cam, bult ons, Lg super pro headers, catless X and Borla Atak

Ls2gtoowner

If you are running a supercharger just forget about them. Cats hate superchargers

Revolver ZSTi

are you serious?

C5Dobie

yes I am serious - running catless provides no noticeable power gain/performance inmprovement until you're talking bigger power adders like FI or big H/C

This has been shown many times.

And it stinks - your clothes stink, the interior stinks, people give you sh*tty looks sitting in traffic/stoplights around you, drawing more police attention to yourself than need be considering you're already driving a Vette to begin with.

Lastly - no idea what the cumulative harmful physical effects of inhaling those fumes are...but I'm positive it is worse than running cats - inhaling exhaust fumes is OBVIOUSLY a health hazard, and exhaust fumes with less filtering/absence of catalyst material has to be worse for you and those around you.

If you just track the car that's one thing, if its a very occasional use car and is a dyno queen and you HAVE to have the highest # possible but in reality barely drive it (you know you're out there) that's another, but if you DD or seasonally DD your car I think the "tradeoff" cats vs. no cats is just plain stupid and immature to run catless for the sake of it to have a louder exhaust, save a few hundred buck etc.

Am I serious? - yeah, serious.

zdeckich

I assume you have no personal experience in this running catted vs catless. Yes they can stink, but also depends on the cam and tune. Like I said I run catless and my clothes or interior don't stink. I also dont DD my car and i do use it to race. Now if i was going to DD it. I still would go catless. I personally like the way they sound and i want every little extra power i can get.

C5Dobie

To each his own - plenty of personal experience as follows:

'90 Grand Prix Turbo - cut out cats w/ angle grinder straight pipe welded in place - ghetto style, fun (and looking back RARE) cool little car that was my pride in highscool - stunk BAD especially on cold starts, probably wasnt running perfect, definitely made more sound/power w/o cats in that platform..but was a turbo

'04 GTO - used kooks LT's catless into custom H pipe/connection (didn't have mid-section) into more straight pipe into Sweet Thunder chambered mufflers - sounded like a dang nascar, LOUD LOUD LOUD, couldn't tell much of a difference in power (on dyno difference was +4whp but to be honest such a small diff who knows could be dyno error too), but smell was noticeable

'07 Silverado - dynamax headers w/ hi-flo cats into nagnaflow dual catback, more power, more sound, no smell (not dyno tuned just handheld)

'08 G8 GT - JBA LT's into custom straight pipes/magnaflow X pipe NO cats into magnaflow axleback - not as loud as GTO, actually had great tone once AFM was taken out and AFM delete cam added, smell got even worse & was worse than my GTO w/ tiny DOD delete cam, no cats. Everything in the car would smell for hours or even day after. gave me headache in stop and go traffic w/ windows down.

'03 C5 Z06 - gained like 25whp/tq across curve w/ ARH LT headers w/ hi-flo cats, slight change in smell - but nothing like my catless applications, Sound is a little meatier/deeper @ idle and meaner wail/scream @ WOT

So - while actually it appears I have PLENTY of experience w/ both catted and catless exhaust setups it appears you admittedly have NONE when it comes to having either setup on a DD type car. All the vehicles I mentioned were DD or nice-weather DD's - while I have already stated & agree that in a weekend warrior or track day only setup going after every inch of performance you can make a case to go catless, I feel obligated to give my own opinion on this subject to inform other forum members prior to making a fairly significant purchase/modification since I DO have experience both ways.