Just installed my SSI's last night! Had to escape the family activities for a little while :)

Here are before and after pics. I have not driven it yet but I am amazed how different it sounds...much cleaner!!! BTW, this is on a 3.2L that already had old style exhaust.

Chris

http://forums.pelicanparts.com/uploa...1072377117.jpg

http://forums.pelicanparts.com/uploa...1072377129.jpg

Some of the problems of the later style exhaust lie much further up stream than the cat and the muffler. It is mainly the routing, crossing over all the exhaust from the right side to go into one cat. You will never take care of those restrictions by bypassing the cat and adding another muffler!

The SSI heat exchangers don't only backdate the routing to no bypass, straight out the back, but are much superior to the factory jobs that were available pre 74. E.g. the special wrench you need for that one nut when you use SSI? That is to avoid a kink in one of the header pipes that the factory had put to allow access to that stud throught the heat exchanger!

The SSI setup is very well designed and good people have tried to surpass it with their own custom headers without much success.

Note that any exhaust mod that makes the car louder may lead the driver into believing that the car has more power. It works for the ricers, right? ;)

I have seen dyno numbers, showing power increase with bypass and muffler mods, but it won't be as much as the SSI will do for you.

SSI is the way to go, IMHO, everything else is a hack job. I am all stock so far and will wait until I have the funds to do it right.

Cheers, George

PS: Another thing: Pulling the O2 sensor to richen the mixture? Does that really improve power throughout the band? I think if you simply disconnect the sensor, the brain will go with a default value. Can't you enrichen the mixture with the O2 sensosor functional, by using the mixture adjustment screw? That will offset the mixture througout the band, and not keep a safe default value for all scenarios! While I am no CIS expert, I think simply disconnecting the O2 sensor won't buy you anything. The car will run overly rich, in order to make sure it doesn't blow up. Rich isn't always good. There is an optimum a/f ratio for performance just as there is for economy. If you have too much fuel, it will kill peformance. Only an O2 sensor will be able to adjust things in situ, keeping the a/f ratio where you want it. I think if it comes to CIS mods, you are best off bringing the car in to a shop that knows what they are doing, enrichening the mixture for your with the right analyzer etc. Going to the next tree and pulling the O2 sensor in the shade won't do. :D

Aigel, there's nothing magical about CIS. Most shops these days are as afraid of it as you seem to be.

With the O2 sensor conneced, the K-lambda box will vary the fuel pressure in the fuel distributor to 14.7/1 A-F ratio no matter what the idle CO value is, which is good for economy/emmisions and bad for performance. Disconnecting the sensor, letting the frequency valve operate at open loop and setting the CO to 3.5% (yes, I did use an exhaust gas analyzer) will make the A-F ratio 12.5/1 which is better for performance. An additional benefit is that your car will idle more evenly.

As for the SSI's the exhaust path makes as many 90 degree bends as the stock system. Also, when using SSI's and a stock style muffler there is no crossover pipe to aid scavaging between the cylinder banks so you lose torque there too.

The biggest gain to lowering backpressure is to use a free-flowing muffler.

Some guys spend $$$ and think their car feels faster afterward too........

Unfortunately, I did not get around to it. I plan to buy a digital recorder fairly soon and if I can, I'll get off my lazy butt and get the recording made. If I do before you buy your Dansk, I'll get it to you.

I already bought it. I bought a set of used SSIs with the Dansk & a bolt in roll bar for $650. Won't have the exhaust system on for at least another month so I'll keep a watch for your post.

Not a bad deal eh? I've been looking for a set to endow my SC with, but not many people sell tjese (for obvious reasons).

My buddy is upgrading his race car to headers & a full cage, I hope he keeps upgrading.:D

Having driven one or two SCs with SSIs, the one thing I notice is they don't bog down under the 3,500 mark. They seem to pull really well from 2,000, which is kinda weird since with bigger (diameter) headers it's meant to improve the top end.

I've got a set in the garage to put on the car sometime when I get off my lazy arse.

19 months until my 78 will have it's last smog test here in California, then I will join in the exhaust reigndeer games.

And lets face it, anything that costs you over two grand has to be a more effective placebo even if you don't feel it in the seat of your pants, you will imagine it.

Guaranteed!

Joe

Joe:

Who quoted you 2k for the SSI? They are $450 a pop here at PP. Add a nice muffler, and you are at $1500. But the nice muffler, or a modified one at least is what the nay sayers use too. So, it's just the SSI and the oil lines that you will need on top of the muffler mod. Thats about a grand total.

George

Paul:

And it does that constantly? I need to do some reading on the CIS, that's for sure. Understand that I thought you just pulled the O2 sensor and did nothing else.

QUOTE]Originally posted by 911nut

As for the SSI's the exhaust path makes as many 90 degree bends as the stock system. Also, when using SSI's and a stock style muffler there is no crossover pipe to aid scavaging between the cylinder banks so you lose torque there too.
[/QUOTE]

That's not true. I went into detail explaining about one pretty big kink that's in the stock system, to allow direct access to a stud. That is not there on the SSI. The runners are also designed with equal lengths.

I doubt very much that you get a pressure equalizing effect from the crossover pipe that's half a mile long! How could the right bank see a difference being that far away from the junction? All it does is choke the right bank and make the exhaust paths very unequal length. And that's bad, we all know that!

I know where you are coming from with the scavenging and pressure equalizing: If you look at an exhaust system that utilizes an H or X pipe, the connection lengths are kept to a minimum / zero. You won't be able to run that on a flat six. Where the crossover would be, you are already in the muffler. The muffler does that job. I also doubt you need it as much on a flat six as you do on a 7.5l V8. There is less than half the volume, if you look at it as a simple air pump.

And of course you need a free flowing muffler whatever you do. We agree on that.

You can talk to anyone that knows the 911 better than any of us amateurs ever will and there is only one opinion about the benefits of the SSI. It is in everyones favor 100%. I have talked to folks that were building complicated custom headers and ended up with about 3 horse more on the dyno than the SSI. I bet that made that customer very happy. :D

George

George,

With shop rates over $90/hr here, the price can easily jump past the two grand mark. I already had my share of broken exhaust heads studs to leave it to my wrench.

Cheers,

Joe

Joe, you are right, I can see that if you have it done, 2k can be approached very quickly. And of course, you probably can't bring your inexpensively aquired Pelican parts to the wrench either. He'll want to sell you the SSI for $650 each, guaranteed!

What's 2k on a 911 anyway? :D

Cheers, George

Well...that's about what it will take to get my 911 out of hock at the body shop right now. Both front fenders, hood and bumper are getting stripped to metal for a respray.

Cheers,

Joe

Whats ANOTHER 2k on a 911 anyway? :D

Good Luck!

George