Just curious here. I've heard and read lots about how the SSI exchangers increase HP, but there's a LOT of variance between each's opinions. Does anyone have definitive info on how much the SSIs (particularly on a CIS 3.0) bump HP/Torque. Lets assume a streetable exhaust and no serious engine mods that would skew the comparison. TIA!


Edward

 

Bruce Anderson in his 'Porsche 911 Performance Handbook" says the 3.0 gains range from 17-22 hp, depending on the year of engine and dynometer. He did get 13 hp on a 3.2L engine (I'll add the benefit of SSI's on the 3.2L engines is less than on a 3.0L engine, as the SSI pipes are starting to get on the small side for the 3.2L engines).

 

Any exhaust mod's performance is going to be highly dependant on the condition of the engine and it's other tuning parameters. There is not going to be a single definitive #

 

Thanks guys!

My 82SC has a healthy, rebuilt engine with stock CIS and modest Elgin SC cams. It's purely an academic question as the car runs absolutley fantastic, but I'm curious. ... how much HP the SSIs are adding to a fresh (12K old) engine. Is it easily discernable? How about those of you that have made the swap to SSIs only, with no other mod to cloud the comparison. I know what the lit says, but was interested in real-world feedback. Thanks!

Edward

 

I have a stock motor in my 78 SC and switched to SSI heat exchangers and a dual in dual out Dansk muffler. I also had the air conditioner and all of its assorted pluming removed at the same time. First of all the sound is intoxicating. It's very throaty at idle, especially when the engine is warming up on a cold day. As you feed in throttle, a higher pitched metallic tone introduced. It's very racy.

On the performance side, you will notice an improved throttle response at all rpm ranges. I had my mechanic retune the engine at the same time we did the exhaust work and I'm sure that also helped. I'm very happy with the swap as it is one of the few exhaust changes that you can make on a vehicle that actually makes a difference in its performance.

 

I fitted easrly '73 heat exchangers and a Triad 2 in 2 out exhaust to my 145,000 mile '78 SC. the sound is intoxicating and there is a noticeable increase in torque and a feeling that the engine has been 'freed up'.

 

EarlyApex states he has replaced exhaust with SSI's. Eric since you live in California have you been able to pass smog?

 

Eric,
Great pic

Indeed, the sound is nice with my SSIs and 2/1 Dansk...just a bit louder than stock, but deep and burbly at idle. And WOT is intoxicating! Smog in Cali....hmmm, trying to get around that corner now
Yeah Eric, is yours street legal? ...fess up the secrets.

The issue is that I haven't had the chance to try side-by-side, but my car definitely revvs freely up the tach toward redline. Since my SSI was installed by the PO, I just wanted to get some feedback from those who have done the swap themselves and get their impressions. Thanks for the responses, all!

Edward

 

as far as smog its not exactly legal without its air pump, or catalyst. but it has been my experiance that as of lately in CA all of us are getting test only slips, but usually the smog guy doesnt know what does/doesn't belong on the car and you can get an SC to burn clean enough to pass without the stuff if the motor is in good tune.

I had built a 930 3.4 with a hot set of cams, enrichment, headers, and a hybrid turbo that threw down almost 450hp, and I got it to pass without its thermal reactors or airpump so it can be done.

dirty smog shops are around. you just need to have the money to do it (usually a couple hundred) and a car to borrow (i.e. a smog legal SC with all its stuff) to put on the dyno in place of yours while your VIN gets run through the computer.

 

here is a pic....to bad the car is gold with chocolate interior, frighteningly fast though

 

Now that's a work of art.

I just got back from a very fun and tiring day at Laguna Seca in my SC. The stock motor with SSI's and Dansk muffler passed sound (92 db) all morning until the afternoon sessions when I registered 94.6 db (3rd gear and WOT). I spent the rest of the day shifting to 4th and keeping it under 4k RPM between turn 5 and 6 and did fine. I have a set of exhaust turnouts planned.

My mechanic has not had any problems getting SC's with SSI's pass smog. I've met several of his customers who attest to this so I'm not worried.

 

"My mechanic has not had any problems getting SC's with SSI's pass smog. I've met several of his customers who attest to this so I'm not worried."

It all depends, as posted, where you live, i.e. in a large major city, Good Luck!

 

Loren, your absolutely correct. You can't easily generalize what we have done locally. We use legal smog shops and my mechanic has a smog test machine that he uses in his shop to help him tune the cars for the test. I've got a little bit of time before I go to the tail pipe sniffers.

 

A bit OT here, but in response to the CA smog issue...

FWIW, I had my car at my friend's shop who has a sniffer to see if we could get it "cleaned up" enough to pass. No dice. My 3.0 runs very clean and tight, only has 12K on a well-documented rebuild, has only the ElginSC cam (which I'm told by a bona fide cam grinder is very modest and would not cause a smog fail), and I ran it HOT HOT HOT, we fiddled, still not close enough that he thought it would pass. Sure I could get someone to "pass" it, but a $275+ every two years, I'd rather not. While I'm sure there are those testers out there that ignore the "visual," I'm still curious how others have gotten theirs to pass the sniffer. My "solution" is I'm sourcing out an exhaust system w/ cat and figuring I'll do the PITA swap every two years. I figure it's a one-time $200 shot, and I will actually pass "legit." You fellow CA guys out there that can get yours to pass are really fortunate ...maybe it IS a "big city" thing.

Edward

 

Just my $.02 but I had a 79 SC with 3.2L max moritz pistons and cylinders, Carrera crank, CIS,SSI headers and B&B 4" dual exhaust, ran the car on the street & track for 19 years and never failed NJ state inspection once. Although she was a little loud she came in just under the max db level.

I will say that the SSI with the B&B was a great setup although it did drone abit at 3500rpm. I was running about 235FWHP prior to the SSI changeover and was closer to 270FWHP with the addition of the SSI and B&B. I also found a considrable increase in midrange and high end performance.