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View Full Version : Why did I put a cat on?


DevoBuzz
10-17-2012, 04:10 PM
So when I did my 3 inch exhaust, I decided to put on a cat. Rather reduce emissions for the small HP loss. Anyway I am running +20s with the 86/87 GLHS Stage2 cal and whenever I get into it, the exhaust smells horrible. Guess it's dumping too much fuel in. Any way I can get rid of the smelll with some gas additive or something? Preferably a one time fix!
Reaper1
10-17-2012, 04:38 PM
If it's dumping too much fuel it can hurt the cat. Get a wideband on it and see where it is. If it's off the charts fat, call FWD and tell them what's up to get a tweaked cal. If the cat is shot, it'll usually smell like rotten eggs from what I've always read and been told.
DevoBuzz
10-17-2012, 04:54 PM
Actually I dont care if it hurts the cat at this point. No emissions test on a classic car. Just looking for a way to get rid of the smell without having to remove the cat.
Reaper1
10-17-2012, 05:03 PM
Does the exhaust extend past the car, or does it dump under it? What does it smell like?
DevoBuzz
10-17-2012, 05:17 PM
It exits past the car. Not really the rotten egg smell but similar. Did it since new about 1K miles so far. And only when I get into WOT. So I am assuming the fuel tables are too rich for +20's.
turbovanmanČ
10-17-2012, 06:28 PM
Rotten egg smell is your running rich. When the smell stops, your either lean or you killed the cat, :p

Get a wideband on there and see what's going on, you shouldn't smell anything until your at WOT, where its supposed to go rich.
DevoBuzz
10-17-2012, 06:37 PM
Right - I dont smell anything until WOT. I thought they sold some sort of additive to prevent the rotten egg smell...lemme look around online.
turbovanmanČ
10-17-2012, 06:39 PM
Right - I dont smell anything until WOT. I thought they sold some sort of additive to prevent the rotten egg smell...lemme look around online.

That is normal to some point, so check the routing of your exhaust so your not getting inside the car.
RoadWarrior222
10-17-2012, 07:12 PM
I thought it was normal for them to be a bit eggy for a day or two when new, 1000 miles sounds like a longish time though.
GLHNSLHT2
10-17-2012, 08:06 PM
Just ditch the cat :)
tryingbe
10-17-2012, 08:12 PM
Or put stock injectors back on. Stock injectors are what 86/87 GLHS Stage2 cal is written for. Really no point to use bigger injectors, unless you have a ported head, bigger turbo, or etc..
turbovanmanČ
10-17-2012, 08:12 PM
I thought it was normal for them to be a bit eggy for a day or two when new, 1000 miles sounds like a longish time though.

Nope, new cats have a different smell but sulphur smell is too much fuel.
2.216VTurbo
10-18-2012, 01:34 AM
Actually I dont care if it hurts the cat at this point. No emissions test on a classic car. Just looking for a way to get rid of the smell without having to remove the cat.

May not care about the cat but you will when it melts down the substrate,completely blocks the exhaust path and leaves you stranded with a no start condition. I had to punch a window in the front of my cat with a hammer and a dull cold chisel during a roadside repair just to drive my GLHS home a few years ago...
bgbmxer
10-18-2012, 05:34 AM
May not care about the cat but you will when it melts down the substrate,completely blocks the exhaust path and leaves you stranded with a no start condition. I had to punch a window in the front of my cat with a hammer and a dull cold chisel during a roadside repair just to drive my GLHS home a few years ago...

I do This before install to all my cats. It makes them supper efficient and get better emissions haha. Then I sleeve it with a pipe.