Lo Cost 3.2 Muffler and Cat Mods - Little Help Please

[bento]

Well i've got the car running pretty well right now and am about to do smog. once i get done with the army of CA smog technicians, i plan on doing some mods on the exhaust end to free up some horsies and get some better sound out of the car. i just drilled out the airbox on my 88 Carrera and i have started to scheme on the cat bypass and a modified stock muffler or the ever popular flaumeister. i guess i have two questions:

1) should i use the superman broomstick technique on the cat and just bust it open and worry about the consequences later?
(Subset question: Any shot that the car passes smog next time with a bored out cat?)

2) should i modify my stock muffler as per directions i received from Paul Brewer (listed below) or go with the flaumeister. I would imagine that the flowmaster sounds great, but there is no denying the cost savings on modifying the stock 3.2 muff.

here are the directions, please feel free to comment on them or let me know if you have done anything similar to your own car.

Here's what Paul did.
There are a bunch of plug welds on the OE muffler that hold the perforated pipe and packing in place.
(1) Cut the muffler in the transverse direction in two places: right
behind the plug welds toward the inlet/outlet side of that muffler end and toward the opposite side of the opposite (domed) end.
(2) Now the muffler will be in 3 pieces and all of the plug welds will be in the center section. Cut out all of the plug welds. Now remove the pipe and packing (you will have to pound it out).
(3) Reach inside the inlet/outlet piece and cut back the outlet pipe all the way back to the shell.
(4) Make 2 baffles. One goes in the inlet/outlet end, the other in the opposite end. The inlet/outlet baffle has a big hole for the inlet pipe and 10-12, 1 inch diameter holes all around the inlet hole (area of the outlet holes should be 1.5 times the area of the inlet hole or slightly greater). Weld it all around.
(5) the opposite baffle has holes equal to 2 times the inlet pipe area.
Pack the end piece with coarse steel wool and tack weld the opposite baffle over it.
(6) Weld both ends to the center piece and enjoy the HP increase and flat
6 music.

thanks for all the feedback,

david

[JackT]

A cat by-pass is not that expensive and you may need your original cat at a later date. Catalytic converters are expensive.

[Chuck Moreland]

If your car is otherwise running well, it will pass the sniffer test.

But, the gains to had with this approach are limited. It will be louder though.

I realize you are trying to keep the cost down. The budget way to get a really good exhaust on the car is to get a set of early exchangers and suitable muffler, even the flaumeister.

You can usually get early exchangers in the $200-$300 range in decent shape.

The real problem with the Carrera exhaust is the lack of tuned pipes, it's not excessive backpressure. For a good primer on the topic IMHO read this "How Headers Work" topic.

I've experiment with free flowing exhaust using the stock exchangers on my Carrera as well as SSIs. So I know first hand the results of these changes.

[MIK911]

Tho' i don't have answers for you, it did raise a question re: Pauls muffler mod.
What's the reported sound quality and loudness with this muffler mod? I was considering some type of mod to my '86 muffler, but unsure how to proceed. Is this mod LOUD? What about sound quality? Burbling vs Raspy vs ?

I know it's difficult describing sounds, but i'm looking to get a more mechanical/raspy sound (more Ferrari-like than Mustang 5.0 like).

Thanks
Mike
'86 coupe

[kepperly]

Sounds like too much time on your hands!! Try a differant aproach
perhaps. watch ebay for a used cat bypass pipe. when you get it
send it to jet hot have it high temp coated ( much cheaper than
the Dansk ss job)and buy a carrera single in single out Bursch.
mellow and very good low end and doesn,t get load until 4500rpm
about $400.00 max and only 6 bolts and two gaskets. just my
humble cheap at heart opinion.
keith

[JDaniel]

Don't "bust out" your cat unless you are absolutlely certain it's clogged up and otherwise unuseable. Replacement cats are not cheap.!

Used bypass pipes pop up all the time in the $75-$100 range. New ones are only a bit more.

If you can find an old euro pre-muffler you can add an O2 bung for little $$ and actually gain a Hp (or 2).

[doug petty]

BENTO - ON MY RECENT 3.2 REBUILD I GUTTED MY CAT. IT LOOKED GOOD ON THE OUTLET SIDE BUT THE INLET WAS BURNED OUT SO I USED A PIECE OF 1" PIPE IN A GARBAGE CAN & LET IT RIP. EXHAUST IS A LITTLE LOUDER, NOT BY MUCH JUST AT IDLE.DECIDED TO RUN THE CAR WITH IT HALLOW, SEEMED TO SURGE AT AROUND 1600 TO 2200 RPM. NEXT STEP TO GET 18" PIECE OF 2 1/2" MUFFLER PIPE. CUT OFF THE INLET & DROP IT IN. GOTTA FLARE THE INLET SIDE A LITTLE TO MATCH THE CAT, BUT THE OUTLET STOPPED ABOUT 1/2" FROM FLANGE, JUST REACH IN THE END WITH WIRE-FEED WELD IT UP. NOW SOUNDS BETTER & NO STUTTERING FLAT SPOT.
DEFINITLY AN IMPROVEMENT. HAVENT GOT THE MOTOR BROKE IN YET, BUT UP TO 4000 IT PULLS GREAT. OH BY THE WAY IT STILL LOOKS STOCK, AFTER A FEW SPLASHES FROM STREET WATER YOU CANT SEE THE NEW WELDS.

[doug petty]

SORRY, LEFT OUT THE PART ABOUT O2 SENSOR, HAD TO CUT IT OUT & WELD TO 2 1/2" PIPE THEN WELD AROUND TO CAT BODY. ALL THIS IN ABOUT AN HOUR & 1/2 & 5.00 FOR PIPE AT MIDAS, NOT A BAD DEAL, JUST CHEAP LABOR.