I bought '94 Firehawk #148 last week. The former owner
lived in a non-emissions county. I moved the car
into Dallas county, so I had to get the pipe-sniffer rammed
up my tail

I failed the new IM 240 dyno test for all three parameters
they check. The numbers weren't way off... like you'd expect
with an empty cat-con, but they were too high for the government.

I cleaned the K&N filter and put a bottle of RXP in the tank.
It was closer, but still didn't pass.

This afternoon when I was changing the oil I noticed the
cat-con looked odd. I have the SLP exhaust. The
Y pipes are 2.5 inches, but the inlets on the cat-con are
2.25 inches... is that right?



The SLP tail pipe is 3-inches, but th eoutlet of the cat-con is
onl 2.5. That doesn't seem right.



Is the cat-con supposed to have an air tube hooked up
to it? Mine doesn't.



Maybe this cat-con is why I can't pass the sniff test.
What else could it be?

 

The air pump system only works on cold start-up for three minutes.You may need new O2 senser,and a compete tune up to pass.Good luck.That cat might be gutted too,Also welcome to the board

 

Just looking at the pictures, I'd say someone took an old dual-inlet catalytic convertor from a 3rd Gen F-Body, and welded it up to the custom Y-pipe. That definitely isn't a factory setup. The factory cat only has a single 2.5" inlet. And I'd be willing to bet that there is nothing inside the shell... it has been "gutted". I suspect the three things you failed on are CO, HC and NOx... and generally, you will only fail on either CO and HC (running rich) or only on NOx (running lean). Failing on all three would indicate the cat may be empty, or at least "dead".

There was also never an AIR connection on the stock 93 and up cat... they stopped that with the 1992 models. So, no, you aren't missing the AIR supply line. Is the AIR pump still hooked up (on the front of the engine under the drivers side head), and operating (only for 2 to 3 minutes on startup)?

 

That is the SLP exaust that was available in '94. I'm not at
all familiar with the F-body cars, but what I have read states
that SLP did not touch the cat-con.

But if the OE '94 cat-con doesn't have an A.I.R. tube, then this
probably is not an OE cat. I can't get anyone on the Firehawk
site to reply to my post, so I'm not sure what the Firehawk
exhaust looks like. Where does the Y pipe join in the stock
f-body exhaust?

Anyone know of a source for a dual 2.5 inlet, single 3.0 outlet
cat-con? I haven't found one, yet.

Yes, I do believe the original A.I.R pump is still on the car and
is hooked up.

 

That is not the OEM cat for your car. You could get a single in/single out Random tech or other cat and make a small y at the rear to fit to the pipes. Do you have twin pipes all the way to the muffler?

 

No. After the cat-con, there is a single 3-inch pipe that goes
over the axle.

From what I've read, the original SLP muffler was a single
3-inch inlet on the passenger side, and dual 2.5 inch outlets
on the driver's side. Both pipes exit on the driver's side.
Lovingly called the TODL [two on da left] setup.

The seutp on there now has a Flowmaster with a single
3-inch inlet on the passenger side, and a 2.5 inch outlet
on each side with a pipe on each side of the car.
The former owner put 2.25-inch tails on that 2.5-inch
muffler

 

I also have a 94 Firehawk. That is not what my cat looks like at all. I have 1 inlet and 1 outlet.

Also, my cat is enclosed in what looks like a screen( the holes are round.)

 

You should look into getting a small y fabricated and replacing the cat. I don't know of any dual in/single out catalytic converters. That will probably help you pass as long as your other emissions devices are intact.

FWIW, the effective cross-sectional area of 2 2.25" pipes is the same as a 3.18" pipe, so it's roughly equivalent to the 3" pipe into the muffler. It's not hurting you to have 2.25 outlets.