79 911SC Exhaust Upgrade Suggestions

[jsedlock]

Hi All,

I'm finally getting around to spending the time and $$ to improve my 79 911 targa. The original exhaust is getting pretty tired so I'm embarking on a fairly full rebuild.

I am planning on the SSI heat exchangers, and probably a Dansk factory-style muffler.

Issues: The catalytic converter is very rusty and I'm sure ready to be replaced as well. I live in Washington State (Seattle) and after 25 years the cars are no longer subject to emissions testing so:

Question one: do i replace the catalytic converter with a straight pipe? How will that affect performance? Will the car need further modifications to air/fuel mixture? Does a straight pipe significantly change the sound? (I want to keep the car mostly stock.)

Question two: what other mufflers would people suggest?


Thank you!

[Flat Six]

Your as-planned SSIs attach directly to a 2-inlet muffler; no provision for retaining/bypassing cat. Moot question.

[Oh Haha]

Originally Posted by flat six

your as-planned ssis attach directly to a 2-inlet muffler; no provision for retaining/bypassing cat. Moot question.

+1

[kerthunk]

You kind of have an either/or thing here.

1. SSIs with a new 2-in 1-out muffler
2. Cat bypass pipe and current (or new) 1-in 1-out muffler

If you are changing to SSIs, you may need to tweak your AFR mix slightly but you should gain some HP. The cat bypass won't net you much gains unless your current cat is clogged up.

The Dansk Sports are a good choice as well as an M&K. Monty makes some nice ones as well but seem much harder to find.

I'm over on Bainbridge Island. Feel free to shoot me a PM if you want to get together and talk about car stuff.

[mb911]

vote for ssi's and M&K but biased

[kerthunk]

Originally Posted by mb911

vote for ssi's and M&K but biased

That's the choice that I made! Ben, you do some great work!

jsedlock, the SSI upgrade is definitely a good thing. But if you are planning on doing the swap yourself, there are a few potential gotchas like broken exhaust studs and such that can make the project much more daunting. Bolting in a new cat bypass is a walk in the park. Worst case is all your fasteners are rusted solid, just get a nut cracker and new stainless hardware.

[will hung]

As others have said, the SSI's into a 2-inlet muffler deletes the catalytic converter, as it is a stainless steel replica of the pre-75 (pre emissions) exhaust. Here is a pic of mine to demonstrate that there are no cats.



As for myself, I have a Dansk 2in/1out muffler factory replacement muffler, and highly recommend it. Secondly, I'd have an M&K 2in/1out as it is lighter than the Dansk and doesn't have the drone issues associated with dual outlet mufflers.

The exhaust upgrade is incredible. Not only does it sound incredible, but it looks fantastic (for those nerdy enough to look), the mid-range torque is vastly improved, the top end horsepower bump is great, and the improvement in cabin heat is much appreciated.

[81 SC Ray]

I agree with Will. Think long and hard before you go with a two out exhaust.....the sound is really awesome....for a few minutes. But, I do not track my car. So, for me, "the drone" is not a good thing - it is just annoying over time. But, the SSI's into a 2 in - 1 out muffler is the best of both worlds. You don't need your radio, car "guys" look to see what is making that cool sound and you can cruise on the highway with no regrets.

Ray

[Slider79SC]

If you are going to pull your exhaust to bolt on SSI's, start spraying your exhaust nuts daily for a week or so with something like Kroil or equivalent to saturate them and try to prevent breaking them during removal.

I did this and had no issues.

[jsedlock]

Fantastic responses. I'm feeling more confident than ever. I replaced a 70 corvette exhaust once and indeed, soaked the fasteners for a few weeks before proceeding.
Thanks to all for taking the time to reply.

[jsedlock]

Hi John,

Thanks for the reply. I'd like to talk to you about this: obviously if i thought I still needed a Cat I must have missed something in my research. I read several articles re: SSI exchangers and never did it say "scrap your cat." I'd be pleased to chat. I'm just getting back into putting my car back together. New passenger side window lift motor this weekend, now replacing the door speakers since it's apart (and the rear deck speakers, what the heck?) but the exhaust is looming. Also planning on doing my front wheel bearings soon (slight groan once in a while) and bleeding brakes.

fortunately the exhaust was off the car about 10 years ago (and probably 2000 miles only) so hoping the studs are cooperative. Let's chat!

[SCOTITUDE]

+1 on spraying ur nuts.
SSI's and monty 2in/2out. hard to find used. one out is an option but sounds different.
if u dont wanna wait to find a monty go M&K.

[PorscheNerd]

Fabspeed makes some seriously nice exhaust setups. All stainless...