CAT bypass on 84 Targa; good idea or not?

[JCoop]

Does anyone have any recommendations regarding the wisdom of a CAT bypass ? Does it appreciably increase horsepower ? Is it easy to remove for a smog ?

[bornrich]

I use a cat bypass on my 81 and it does affect the performance not by a whole lot but it does help also it gives the exhaust note a deeper tone.

[Oh Haha]

It will help the exhaust note but you probably won't notice much of a power increase.

Now, do the bypass along with a sport muffler(M+K, hint hint)and you WILL feel an increase.

You could keep your stock setup for smog certification time. You will most likely have to adjust the air/fuel mixture when switching between the 2 setups.

[gtc]

Removing the rusty bolts holding it on will probably be the hardest part.
If I were in CA, I would just leave the exhaust intact and buy a chip from Steve Wong.

[450knotOffice]

Remove the Cat and buy a Steve Wong chip and you WILL feel a difference. BTDT.

[jlynch1960]

I just put the cat back onto my 84 Targa. PO had gone to a bypass and sport muffler. The model year is exempt from emissions inspection in NY, but I couldn't justify the added pollution. I didn't notice a bit of difference, except in the exhaust tone.

With the cat off the emissions just go through the roof. Is an extra couple of hp at most worth adding all that junk to the air? I live next door to 10 million people and for me it wasn't.

[s5uewf]

Not to get too far off thread, but cats are not perfect. They also contribute to environmental harm...the U.S. EPA has stated catalytic converters are a significant and growing cause of global warming, because of their release of nitrous oxide (N2O), a greenhouse gas over three hundred times more potent than carbon dioxide.

I think if you remove your cat and get tuned, you'll notice an improvement in power. Likely not too much.

[pmason]

Initially I removed the cat and put in the fabspeed bypass and the M&K 1in1out, also had Steve's chip, but dyno seemed like it gave a few more hp. Sense then I have switched to headers and M&K 2in2out and have Steve reflash the chip, sounds even better.

[Icemaster]

Originally Posted by 450knotOffice

Remove the Cat and buy a Steve Wong chip and you WILL feel a difference. BTDT.

...AND add the M&K - you got a winner. You wont regret it.

[Joe Bob]

Spend a few bucks on GOOD fasteners and they will spin off easily. You can then run leaded fuel if you run hi octane race gas for a DE.

Chip, bypass and sporty muff will be a good improvement. SSIs....the word is...not a big help as with the 3.0.

[Wil Ferch]

For bolts....here's what I say in another thread.....

I've also found that I can use US-thread muffler bolts ( stainless 5/16" x 18 pitch x 1.5" long, along with Silicon-Bronze hex nuts) are *very* close to the stock 8 mm x40 mm steel units that rust up real bad. The Stainless /SiBr combo doesn't gall ( as stainless bolts with nuts might)...and has the added benefit of having a 1/2" head..so standard metric 13 mm tools can be used. This allows easy cat addition / removal during those pesky emissions inspections...and easily allows you to go back to pre-muffler....a serious advantage that SSI's don't enjoy.

[Shaun @ Tru6]

it's a very good idea, but only when matched with a SW chip and an M&K muffler.

[Swoboda]

Is a stock muffler too restrictive compared to a M&K? Is sound the only difference?

[hcoles]

one aspect that might be considered when running without a cat, it saves the cat from wear and tear, it can then be installed for testing if needed in your state or location - I would never consider doing that but it occurred to me.

[rusnak]

And a cat bypass can have a second testing bung installed for an O2 sensor. Do that to the cat, and all of a sudden it's illegal.

[DRACO A5OG]

My 2 cents, I feel the upper end performance, not much at low RPMs.

A side effect may be some back fires on decel, liken to a race car

I've installed the M&K Pre Muff (Cat By-Pass) on stock 1 in1 out & SW Chip.

Sound is much more throatier.

Jim

[lynn911]

I replaced my cat with a bypass and SW chip noticed some small gains , I am running a quite open exhaust Straight pipe with a 24" cherry so the noise was an issue, I did not change the mixture.Can some one describe a little better how to adjust the mixture . or is this a Porsche shop job?
I have since gone back to cat till I can work out better noise reduction.
Has any one used the car chemistry baffle plate systems?
Cheers

[Autoban]

I have a stock '86 cab and would like to switch to a cat bypass with a sport exhaust. I live in Virginia. Does anyone know if an '86 Carrera with the 3.2 L needs to pass any emission testing?

[vash]

i have a bypass i would love to get out of my garage.

[Arne2]

Originally Posted by DRACO A5OG

A side effect may be some back fires on decel, liken to a race car

I've installed the M&K Pre Muff (Cat By-Pass) on stock 1 in1 out & SW Chip.

Sound is much more throatier.

Same exact setup on my '84. I bought mine that way, so I can't speak for the "before" and "after" changes. But it does run great and sounds pretty good. Some people complain about exhaust smell w/o the cat, I haven't found that to be too bad. No backfires on mine.