Cats or No Cats???

[Billy Mild]

I'm debating between getting some high flow race cats or to go sans cats altogether. I have heard without cats the interior of the car will always smell bad after driving the car. I would prefer not to have this smell. For the small HP loss I don't see a reason not to run cats. They only will take away 5 HP.

The cats I am looking are: Random Tech 100 cell, Magnaflow Spun Cats, and MBS High Flow cats. Another option I saw someone on here do is run C6z06 Cats on their car. Is one better than the others?

http://www.summitracing.com/parts/mpe-59959/overview/

http://mandrelbendingsolutions.com/mbs-4-100-cell-cpsi-high-flow-race-converter/

http://www.randomtechnology.com/products.html

[WARP TEN]

I currently run without cats as Illinois does not require emissions testing. I have SW headers, a stock 95 exhaust system and electric cutouts just before the mufflers (some pix in my albums). Another reason I did not want cats if that with the length of the SW headers I would have had to cut up the front part of my stock exhaust system and I did not want to do that. When I had my Corsa on the car I did use I believe Random Tech cats. You are correct that without cats your car exhaust will smell a bit--kind of like they did in the 60s and 70s. Not too bad and usually just on cold start up. The biggest advantage to cats (other than for the environment) is that they soften exhaust noise. I would say cats can reduce exhaust sound by as much as 20%. Yet they only cost a couple of horsepower. --Bob

[efnfast]

the only people that smell my car without cats are the people behind me.

[RussMcB]

I've never heard of non-cat cars getting smells into the interior of a car. Is there an explanation of how and why?

My initial gut feeling is there must be an exhaust leak for that to happen.

Or maybe it's because gasoline is formulated differently now? Still not sure how straight pipes in place of cats would cause a smell (much less going into the car's interior).

[secondchance]

I have heard without cats the interior of the car will always smell bad after driving the car.

Smells bad?! To me it "smells like VICTORY!".

[mike100]

The making your car smell comment is what I take to be when you stop at a light with your windows down and you choke on your own hydrocarbons...

I ran the Z06 cats because:
1) I already had some laying around.
2) they are fairly compact for a 3" catalyst.
3) you know they have a lot more precious metal content and do a better job of converting the pollutants than some universal hi-flow mini cat.
4) oem cats don't usually clog and break apart at the slightest hint of rich running or minor impacts with speed bumps. I thought it was the best catalyst for the application regardless of cost (which happened to be cheap since I had a pair).

I also had some LS2/LS3 catalysts too, but they are flat shaped and I thought it would be a challenge to fit those in the C4 tunnel. People have been giving them away since the LS2 came out.

[batchman]

Cats are a cheap technology that works. One thing for a competition car but for the street, no question for me - cats.

In fact I even run cats on my event car, doing otherwise would stink up the grid too much. You can tell the cars that don't run them, if you're next to one within moments your eyes water...

Cheers,
- Jeff

[PhillipsLT5]

Random Tech

[Billy Mild]

The headers I have are stainless works headers that have a 4" collector. I will have to run a reducer regardless.

My current exhaust situation is stock manifolds/cats into the stock exhaust with the center resonator deleted and Borla Axle Back.

My thought was to run SW Headers with 4" collectors reducer to Z06 cats back to an x-pipe then out to the borla mufflers.

Bad idea?

[edram454]

I love cats but not on my car. no cats.. less restriction. I had randon tech performance cats on my c5 and during a dyno pull it blew the guts of the cats out the exhaust pipes and i picked up 10 horsepower. no cats on my car. I got two beautiful cats at home.

ed ramos #3028

[WARP TEN]

I've never heard of non-cat cars getting smells into the interior of a car. Is there an explanation of how and why?

My initial gut feeling is there must be an exhaust leak for that to happen.

Or maybe it's because gasoline is formulated differently now? Still not sure how straight pipes in place of cats would cause a smell (much less going into the car's interior).

No exhaust leak, Russ. Just an excess of hydrocarbons that the cats usually eliminate. If the car is just standing on a windless day or there is a slight tailwind, it is noticeable in the car. Or if you are just standing nearby or behind it. As noted before, I only notice it on a cold startup, and usually in my garage when I back out. And if I am driving my car it usually means the windows are open.-Bob

[GOLDCYLON]

Random Tech

Both Phil and I are running RTs. Its the right thing to do. 2nd choice is magnaflows

[KILLSHOTS]

I went with no cats when I installed my headers. After a 5-minute ride, I'd return to the house with my clothes stinking of exhaust, and this was after Boudreau had datalogged my car and worked with Marc the get the calibration correct.

It's not worth 5HP. If you go without cats, you'll most likely be sorry. Good luck.

[Billy Mild]

I went with no cats when I installed my headers. After a 5-minute ride, I'd return to the house with my clothes stinking of exhaust, and this was after Boudreau had datalogged my car and worked with Marc the get the calibration correct.

It's not worth 5HP. If you go without cats, you'll most likely be sorry. Good luck.

This was my issue.

[RICKYRJ1]

I have had no cats for 5 years now with no issues, smell or other :proud:

[FU]

The 441 is cat-less. After 4 set's of various cats , we decided to X them. The 441 inch engine just blows them out. Some cats did last a little longer than others.
Recent tuning minimizes the "gag" to the point where it is just about non existent.

[Billy Mild]

The 441 is cat-less. After 4 set's of various cats , we decided to X them. The 441 inch engine just blows them out. Some cats did last a little longer than others.
Recent tuning minimizes the "gag" to the point where it is just about non existent.

The most mods I will do are longtubes, ported plenum and injector housings, and tune. Other than that my car will stay mostly stock since I have a limited fun car budget. haha. Too many toys not enough budget for them all.