exhaust without cats

[Anniv88]

Marc H. did all my work. Top end package, headers, Borla, no cats, and
tune. Never any smell.

[efnfast]

Originally Posted by efnfast

I have a 90, so no exaust valve seals, headers, no cats and Marc's chip. You can definately smell the unburned fuel- makes me horny, if you're into that kinda thing.

On that note, my daughter was behind me today getting on the highway. I punched it in second and rowed up to forth. She called me on the two way redio's we had and told me how much I offended her nose. Of course she new nothing of this post. Her windows were up, and the air was on. -Steve

[PhillipsLT5]

you already answered your ?

[Corbusa]

Has anyone not used the fake cats in the OBX system and replaced them with real cats? and will everything still bolt up to the original exhaust pipes / H pipe.? Also if all I'm going to lose is 1% hp I might as well have them on.

[WARP TEN]

Originally Posted by Anniv88

Marc H. did all my work. Top end package, headers, Borla, no cats, and
tune. Never any smell.

Good to know--Thanks

[Daniel_Mc]

Not cats on our 91 LT's with a stock system a bit raspy and not a smell that I ever noticed. Now LT's with B&B with X pipe no real smell either but still not loud enough for me

-Daniel

[WARP TEN]

Originally Posted by VetteVet

The PID (Proportional/Integral/Differential) control system is always going to swing lean and rich above and below stoichiometric ratio. The cats absorb the unburned hydrocarbons during the rich swings and burns them off in the cats when the excess oxygen is present during the lean swings. When cats are eliminated, there is nothing to catalyze the unburned hydrocarbons produced during the closed loop rich swings. Unless you are willing to run open loop full time or are willing to tweak the O2 crossover point so that you always run on the lean side, a car without cats will always have an unburned fuel smell that is obvious to all other vehicles in your vicinity (think old school pickup trucks thats you have pulled up behind in traffic that have carb problems, you know, the ones that burn your eyes.) The latest technology cats will clean up your emissions with minimal (think 1%) HP loss. Rant over! Jep

Hey Jep--
Not a rant--you are correct based on my general experience although as others note the smell can be mitigated by a bit of tuning. Of course I come from the days when we used to tune cars based on the color of the spark plugs and the smoke from the exhaust!--Bob

[BigJohn]

Smoke?
Like a blown headgasket?
Like bad valve seals?


In the old old old days the inside of your tail pipe was white not black.

There I go again, anyway I forgot!

[DennisC]

Hows is that legal David because of age of vehicle?

[ZZZZZR1]

Originally Posted by DennisC

Hows is that legal David because of age of vehicle?

In 20 years we get historic tags in Maryland



David