Stuck with Stock Exhaust?

[Smoove1010]

I may be days away from closing on my first Porsche, an 87 that's nearly box-stock. I've been reading this excellent forum relentlessly, and planning ahead on possible upgrades - the SSI heat exchanger install looks like a no-brainer, but I can't find references to any implementations that include cats. NYS/NYC metro-area rules say that if a car came with a cat originally, it must always have one to pass inspection. Am I stuck with a stock crossover-pipe configuration, or is there a bolt-on upgrade solution available? Thanks in advance - maybe my next post will have pictures of my new ride...

[Arne2]

I've never seen cats for the SSI systems. But then again, many people have said that SSIs aren't big enough for a 3.2 and tend to choke the top end. So especially if you need to retain your cat, I'd stay with the stock cross-over system. Possibly add a high-flow cat and then a different muffler.

[Ronnie's.930]

Originally Posted by Smoove1010

- the SSI heat exchanger install looks like a no-brainer

This might be a no-brainer with regard to that it is desireable, but, speaking from experience, it will likely be anything but a no-brainer when you go to make the swap! On my 1987 930 almost all of the stud nuts were so deteriorated that there wasn't really a flat side on them (the nuts looked like rust blobs). Initially I tried soaking the nuts in penetrant and using heat, but the studs snapped with very little force used! The rest had to be torched off and studs removed by welding nuts on to them (some had to be cut and drilled out) - all had to be timeserted!

[nkotselas]

Arne is right. There is some debate but the general consensus is that SSI heat exchangers are too small for the 3.2 motor. They will still give you a nice torque boost but not much top end.

Headers are likely the best option for power but because of smog it is common to see people go to a premuffler or cat bypass in place of the cat. Couple that with a good muffler and you will have nice sound and a decent power bump. This is definitely the best bang for the buck and not to hard to change back every year or two for the inspection.

[Quicksilver]

I switch my exhausts over to the stock configuration every 2 years to do the smog check. Because of a modification to the oil lines I can do it in less then an hour and it is rather painless.

[Arne2]

Since I'm in an area where there are no smog checks, I didn't think about changing back and forth for inspections, but that would work. I've got an M&K pre-muffler on mine, but still have the stock cat on the shelf in my garage. Probably wouldn't take longer than 30 minutes to change back, since the PO used stainless hardware to bolt it on. That and a couple of gaskets and you're ready for the test.

[MMiller]

Originally Posted by Arne2

I've never seen cats for the SSI systems. But then again, many people have said that SSIs aren't big enough for a 3.2 and tend to choke the top end. So especially if you need to retain your cat, I'd stay with the stock cross-over system. Possibly add a high-flow cat and then a different muffler.

+1 do this^^

I have SSI on my 3.2 and it's a lot of cost for the "reward".. Search Steve Wong I think he has dyno lots of combinations. Best I recall not much to be gained except as stated some low end torque. YMMV

[zimmer266]

Congratulations on the car. You'd likely be fine with a high flow cat and a sport muffler, and maybe a SW chip. This was a great improvement over stock for me, and the car has been easier to drive at partial throttle and low speeds as a side bonus.

I don't need to do inspections anymore as the car is over 25 years old, at least as I understand the local laws.

[CharlesJones]

I put SSI's on my 3.2 and it really wasn't worth the hassle. It was a big pain - you have the risk of broken exhaust studs, and then you have to tackle the plumbing for your heat (I deleted my engine bay fan) and you have to change a couple of oil pipes too, plus in your case you have the issues of where the cat is going to go. It is questionable whether there is any performance gain, although I am certain it doesn't choke the top-end on a stock motor.

Its just not worth the trouble and the cost, and I certainly wouldn't ever consider doing it again. I suggest you just change the muffler back-box - that would give all the benefits with 99% less hassle!

[Jack Olsen]

SSIs on a 3.2 are definitely not a no-brainer.

In your shoes, I'd keep the stock headers -- get a sport muffler and a Steve Wong chip.

[Josh D]

Craig-D did a very cool mod to adapt dual cats on SSI's on his SC. Search for it and check it out.

[darrin]

Personally, I'd keep it stock for the time being too. I thought that I'd do the same with my '86, but have been dissuaded by most that I discuss this with. Significantly, it's my understanding that the midrange torque boost one feels on the 3.2 is caused by the ssi's being MORE restrictive than the stock header arrangement. I also understand that there's not much HP to be gained from a sport muffler. My stock original exhaust system (headers>cat>muffler) is still working a-ok at 150k miles.

I'd suggest instead that you first invest the time and $$$ into getting the car completely sorted out (brake lines, fuel lines, suspension rubber, etc.) and get the engine dialed in (and get familiar with the car) before you start performing mods. The first mod I'd consider would be the aforementioned steve wong chip. My car really came to life after its top end overhaul, afm replacement and installation of a remapped chip.

Another thought on the SSIs is that Porsche didn't see them as worthwhile on the european versions of the carreras and instead used the same headers you have with a premuffler instead of the cat.

Finally, rarely8 has developed a nice header setup that appropriately sized for a 3.2 engine -- he's threatened to add cats (along with heater boxes) as options. I've been keeping an eye on these and would consider if/when I choose to hotrod my 3.2 into a dual plug 3.5.

[RWebb]

you will want to spend your money on safety items first - new rubber fuel & brake hoses, maybe new tires if less than 6 yrs old you can keep them

get all the fluids replaced & see if it needs any long term maintenance... plugs, wires?

next performance upgrade would be hi perf. tires

next, suspension bushings

only then will you want to do other things like a modified chip & etc. as per Jack's comment

the best way to go would be twin high flow cats but I dunno if anybody makes that setup for our classic cars...

[andyt11]

If you can seperate your cat without damaging it, (my whole exhaust system was joined together with barnacles that will never come apart without a torch), you could replace with a premuffler and then stick a stainless silencer on the end. Then just put the cat back in as needed for testing. Stainless hardware and anti-sieze should make it reasonabley quick.

Lots of reports on here that SSI's are not that great on 3.2's anyway, so could be best to save to $1100 you'll spend doing that for other jobs that will come up.

The other advantage to using the stock exchangers over the SSI's, is that with SSI's on your car, you'll have to dick around plumbing in the cabin air.

[Smoove1010]

Originally Posted by darrin

Personally, I'd keep it stock for the time being too. I thought that I'd do the same with my '86, but have been dissuaded by most that I discuss this with. Significantly, it's my understanding that the midrange torque boost one feels on the 3.2 is caused by the ssi's being MORE restrictive than the stock header arrangement. I also understand that there's not much HP to be gained from a sport muffler. My stock original exhaust system (headers>cat>muffler) is still working a-ok at 150k miles.

I'd suggest instead that you first invest the time and $$$ into getting the car completely sorted out (brake lines, fuel lines, suspension rubber, etc.) and get the engine dialed in (and get familiar with the car) before you start performing mods. The first mod I'd consider would be the aforementioned steve wong chip. My car really came to life after its top end overhaul, afm replacement and installation of a remapped chip..

Thanks for the collective wisdom - I'm glad I asked. This sounds like a better plan. The current owner says he thinks it has an exhaust leak, so I may be wrestling with rusted nuts anyway, but if there's not a big payoff for the dollars involved, I'll keep it stock for now and use the $$ elsewhere. Thanks again to all for the replies. GK

[intakexhaust]

Originally Posted by Panerai

+1 do this^^

I have SSI on my 3.2 and it's a lot of cost for the "reward".. Search Steve Wong I think he has dyno lots of combinations. Best I recall not much to be gained except as stated some low end torque. YMMV

I do the same and agreed.

[will hung]

Plumbing heat isn't as hard as others make it sound. The performance gain on a 3.2 is debatable. It's much more with a 3.0. I know on my car, the mid-range torque is significantly improved, so you don't have that noticeable step up in power as the car comes on cam, but it builds speed like a freight train now, is so much easier to drive in all situations, and the heat will make you sweat.

If you do end up with an exhaust leak, and the leak is at the exhaust manifold, replace it as soon as possible. When you use your heat, you'll be pumping exhaust fumes into your cabin.

Having said that, if you do end up having to replace your heat exchangers, I suggest going a different route than suggested. Watch for a set of used 993 heat exchangers, get the flanges flipped on the one side, and for considerably less than a set of SSI's, you'll get a true dual exhaust that was designed by Porsche in the 90's instead of the 60's.

If all you need is new hardware and gaskets to fix your exhaust, and the upgrade bug keeps biting, I suggest investing in wear items in the suspension. Elephant Racing sells a "stage 1" kit that basically replaces/updates the wear items. It will transform your car, making it the infinitely capable in all situations car that 911's are.

[WIL84911]

Originally Posted by darrin

.... Significantly, it's my understanding that the midrange torque boost one feels on the 3.2 is caused by the ssi's being MORE restrictive than the stock header arrangement. Another thought on the SSIs is that Porsche didn't see them as worthwhile on the european versions of the carreras and instead used the same headers you have with a premuffler instead of the cat.

I disagree. I had both premuffler and now SSI's. I love the way it drives and sound now with SSI's but of course coupled with Mr. Wong's chip. Might not be worthwhile but it is for me. But then again I may not go through the same trouble next time (sacrifice sound, low end torque?). It's a matter of personal choice IMO.

[will hung]

Originally Posted by darrin

...Another thought on the SSIs is that Porsche didn't see them as worthwhile on the european versions of the carreras and instead used the same headers you have with a premuffler instead of the cat...

That's not necessarily true. You have to remember that they are a mass manufacturer of cars. The cost to have a 100% different exhaust on a euro car vs. US cars would be so much more, that it was easier just to get the performance increase of the pre-muffler and manufacture all cars with the remainder of the exhaust and oiling system the same. If they didn't think equal length exhaust was a good thing, why did they install them on their race cars?

[hcoles]

Originally Posted by Smoove1010

Thanks for the collective wisdom - I'm glad I asked. This sounds like a better plan. The current owner says he thinks it has an exhaust leak, so I may be wrestling with rusted nuts anyway, but if there's not a big payoff for the dollars involved, I'll keep it stock for now and use the $$ elsewhere. Thanks again to all for the replies. GK

Now your thinking straight.