Should I bother installing SSI's?
 

Hi

As the topic says, should I?

My reason for asking this, is that I already have gotten rid of my cat, and replaced it for a pre-muffler. Also, it has a big sports muffler on the back. So I guess I have some HP gain already, although, I do have the stock heat exchangers still.
I should explain that my engine was rebuilt this summer, and have 964 cams, and pistons with 9,8:1 CR. So that will probably make changes to the exhaust more apparent, right...?

So, what do you think?

Absolutely. Go with a 2-in/2-out muffler. Check out M&K exhaust. These changes should really open up your motor!

On what engine?

Sounds like a 3.0 based on his upgrades....

Thanks, but how much REAL difference will it make? 10 HP?

It is a '79 911 SC, 3 litre engine. As previously mentioned, it has 9,8:1 CR, 964 cams, Fabspeed pre-muffler, sports exhaust, but stock heat exchanger.

Hard to say what the actual figure will be. Seat of the pants should feel much better, though. You should also get better power throughout the RPM band

OK...
I guess the real gain is made from the headers, that will give less resistance...?
Hence "free flow"....?

SSI's would balance better but you would probably not notice much improvement unless you go straight out with a 2in/2out muffler but.......................
All 2in/2out mufflers have a very bad drone/resonnance between 2-3k that will drive you nuts.

I've tried M&K, Dansk etc..............and it's just disgusting.

2in/2out are great for the track but not for street-driving.

With 9.8 CR, concentrate on mixture, timing and octane to prevent detonation!
What is the curve on your distributor?
Is it a Bosch 0 237 306 001 or 0 237 301 007 or 0 237 301 009 ??
What plugs are you using?
Bosch ???

My easy fix for this is to flex the right foot more and you pass through that rev band before you know it. I just had SSI's and a 2 in 2 out M&K sport muffler installed and love the combination. Cheers, John

Better heat from SSIs too.

Do it....nothing out there better with heat....except maybe early OEM equal length HEs.

We just installed a set of SSIs on an '89 Cab and a Cat Bipass Pipe on an '89 Coupe. They both drove identically when stock and now the Cab edges out the Coupe in seat of the pants torque.

OK...
"Seat of pants", you tell me!
But is there any hard figures to back it up?

As I mentioned, I got a "free flow exhaust", except from the heat exchangers....
So... What would I gain, realistically speaking..?
I now have a great car, but I'd like some more!
(It's addictive)
I'm not gonna spend $1500 for a few HP, unless I get 10 - 15 HP more...
What do YOU think!?

Then buy a 3.6, swap it in, sell the 3.0.....it's a smog engine that has antiquated FI and exhaust. Geeez, what ya expect? It isn't a Chevy where you can add an Edelbrock double pumper carb and headers and get 100HP.

Next you'll be asking how to get the 915 to shift faster.....

I don't know anything else than that the dizzy is stock... The plugs? dunno...
They came along with a service bundle parts shipment...
I have adjusted the mix to 3,5% CO at idle (at 950 RPM and 5 deg BTDC)

Ok... ...Relax!
I'm NOT stupid! I know about the 915 problems, and will be doing some work with that this winter...
Anyway:
This is why I ask this question here!
Because I am not made of cash, I'd like to know, if what I'm going to do to my car, is really worth while...
(I already spent a few bucks)

All opinions are welcome!

I'm T O T A L L Y relaxed.....but you have to realize that the 3.0 and 3.2 have limitations that are built in. One is the cams, next is the FI and the other is the exhaust.

Doing the upgrades is not cheap and neither are the parts. Unless you do the labor yourself you will price the upgrades up to the level of Steve Wilkerson and the Gold Plated Porsche fame.

The Fuel Injection cam is limiting due to smog restrictions...simply putting carbs on it usually just pissezzs off the engine. It sounds nice but you lose MPG and get minimal HP gains....doing the exhaust helps....going with 964 cams was my best upgrade.

Then I just sold it all and crammed a 3.6 in my SC except for trashing the 915 due to increased torque and my heavy foot on launches, it's been a blast.

How fast do ya wanna go and how much $$$ do ya have to spend.....

Alright..
My plan is to make the most of my engine as it is... (NA)
BUT I'm not gonna spend a lot of bucks on an upgrade, that I won't really feel... 1500$ is not cheap!

I've test driven a '84 carrera with a 3,6 with 915, and I gotta say, although it went better than mine, I'm not way off...

Sounds like you've had some fun with your car..!

But you have to understand, that I'm not getting rid of my engine for another... I just rebuilt it, and will keep it as long as it is-, or I am -still alive...

You sound like you're in the prime Eram demographic. Add in a Cool Collar to keep it together, maybe a K&N filter, and you're good to go.

I might address the intake before doing SSIs - it is surely easier to bolt on a set of SSIs first tho.

See if Steve Weiner posts -- then your only question is whether you want to pay for it.

Since you plan on keeping the car...the good thing about SSIs is that they will likely outlive you and the car...they have great sound, provide better heat and look great...and most agree that there is a decent increase in horsepower over stock...probably 10 or more. Since you already do not have a stock setup, you may experience less improvement. Pesonally, I waited until I needed to replace my exhaust to move up to SSIs...to make it a bit less painful.

OK, maybe the butt dyno isn't all it's cracked up to be (pun intended) :D

The second best thing to SSIs are stock pre-74 heat exchangers. These sell on the used market for about 1/3 of the cost of SSIs for a decent set. If you plan to keep the car a long time then that is money wasted. Stock rusts which is why they are replaced with SSIs.

The difference in HP between SSIs vs stock H/E and a pre-muffler is not so much. The difference in torque is significant. $1500 worth of significant? That's up to you. NOTHING you do to a 3.0L for less than $1500 is going to make much difference. I tricked one out a few years ago resulting in 190WHP. Felt good but not much bang for the buck.

So given all that, I'd camp out on e-bay and pick up a set of stock pre-74 exchangers for $200-$300 if you can and try them out. If you don't like them you've lost nothing and can sell them. If you do like them then start saving your change for a set of SSIs that will last longer than your car.

good advice... but he's in Norway

the few that once existed there are surely long gone back to soil amendments...

Spend the money or don't, you can't ask somebody else their value system.

YES the SSI's totally wake up the power 4000-6000 rpm.......just like your 964 cams, they cost money, did you feel the bang for the buck.........

I spent the money, and it totally changed the car......enough said, and yeah I have the dyno charts. Yes it's spending money, and no they don't go down in value, so you can always sell them.

First, the HP improvement from the "free flow" exhaust is questionable as far as I'm concerned. The real improvement comes from the balanced SSI's.

You want hard proof. There's a related thread on the site right now. In it I linked to an old thread I posted several years back. I actually ran some before and after tests using a G-tech pro. The results are shown. They were not scientific and I didn't spend thousands of dollars insuring that all the parameters were equal but I did try to keep the before and after tests as consistent as possible. I also used a sound meter and recorded the difference in dB levels if that is of any interest.

Also, I had two dyno tests done right after I installed the SSI's. The results were within 1 HP of each other as far as peak HP. Let's just say the car dyno'd with more HP at the rear wheels than Porsche publishes as the stock crank HP. So yes, I got at least 15 HP improvement. But as others have said the butt-o-meter also reflects the improvement.

http://forums.pelicanparts.com/porsche-911-technical-forum/394868-performance-upgrades-911sc-3-0-a.html

Great!
That's all I need to know!
Thanks guys!

Otto:
I am getting worried about you. :)

You have a nice engine with 9.8 CR and 964-cams.
With high CR, you'll need to pay attention to detonation.
Search for comments by Steve Weiner and Henry Schmidt.
If you want maximum performance without the possibility of detonation, concentrate on the distributor-curve and plugs, not SSI's.
Adding SSI's vs. your current set-up will not make a great difference IMHO.

I also have 9.8 CR and 964-cams and I've tried different distributors.
Steve Weiner (Rennsport Systems) re-curved one of mine to run without vacuum specific to my engine.

Please, pay attention to the issue of curve and plugs.
I assume that the Euro distributor has vacuum advance?
Was the distributor serviced/re-curved along with the engine-rebuild?
Take one plug out and tell us what type.
Bosch W6DC or NGK6BPS ??
Or ??

Otto, keep an eye open for stock pre -74 HEs. I found a pair of new HEs for 5000 swedish kronor on the used market. They aren't stainless but after 2 years there is no hint of rust.
On top of that I found a used OEM muffler for another 1000sek and then another 1500-2000 for new oil lines, so you can do the backdate on smaller budget.

How much heat do you need?
I have a plan to buy headers and weld on a small heater box on them, kind of like this:
http://forums.pelicanparts.com/uploa...1226253856.jpg

Supposedly it will give you enough heat to keep it comfortable on cold spring and autumn days and to fight of the mist from the windows.

I hear ya!;)
I guess this is something I have overlooked. I was told not to worry about this, but I guess I should have been more skeptical...:rolleyes:
The car is now in storage, so it's not easy access at the moment. So I can't tell you what plugs I have.
The dizzy is stock for the 8,5:1 CR. And it has vacuum advance. Nothing has been done to it, except cleaning. That's all I know. Also, there is no knock, and the engine runs great. But I guess there is some more to gain from a recurved dizzy...

I'll have to investigate this further. Does anyone have a chart for a optimum curve for my setup?

Safe: Thanks, I'll keep an eye out for some used ones on the Porsche club web pages.

How does the B&B stack up to the SSI's, if you already have them. Also, have a Autothority chip. Both from my wrench on a 3.2 rebuild 90,000 miles ago. It's loud for a street only car. Wondered how different it would be with SSI's and a Steve Wong chip? Not trying to steal this thread, there are options that would help me learn as well. I would love to hear that it would be quicker and worth the expense of replacing a functioning system. Thanks, Glenn

Hey
I don't have the SSI's, that's why I was asking.

Or buy a Turbo...

When I said I already have them I meant me. Trying also to decide whether to go to SSI's, I have B&B already. Sorry for not being clear.

just my 2 cents here. just got on a set (w/ M&K 2in 1 out) moving from a bypassed system. it's worth every penny in my opinion. might be a few HP gain but it certainly drives way better in all ranges specially on low rpms. if you like to feel and hear the power then I say go for it. I also think it adds value to the car. nothing like the real sound of power through headers.

If the distributor is for 8.5 CR and was only cleaned but not re-curved, it's not entirely right for 9.8 CR.
According to the Gurus like Steve Weiner, curves are set for CR, octane and general air temps.
You don't have knock sensors and you won't hear any detonation at high revs and that's the danger.
You can check the curve somewhat with a Strobelight yourself.
Make a white paint mark on the Z1 notch and another at 33 degrees.
Set the timing to the recommended specs, then have someone rev the engine to 2, 3, 4, 5000 RPM and watch the movement of the mark with the strobe and note the degree of advance for various RPM's.
Do one set with vac connected and one without.
You want to see a steady advance through the range and no full advance before ~5k.

Here is what I observed with/without vacuum on a '78 distributor:

900 = 5 deg BTDC
2k = 16-17 w/vac 10 w/o vac
3k = 26-28 20-22
4k = ~28 25-26
5k = 30 28
5.5k = 33 30

Of course, you can affect the range by changing the starting point meaning: If you set ignition at idle at 0 BTDC, everything moves by 5 degrees.

I would really like to know what plugs are in your engine. :)

So you are saying I should not have as much advance now, because of higher CR?
I took a look at the charts for the curves on a 78 diz, and compared it to the 80 and 81- diz charts. The 80- has higher CR, (9,3:1), but the advance is a little higher than the 78. So based on this, I'd say I'm in good shape... Right?

http://forums.pelicanparts.com/uploa...1226338210.gif

Add a Steve Wong chip before you do that. If you still need to spend more money and time then move on down the list :>

This chart was posted by SW a while back on a similar discussion.

being in norway, you would probably appreciate the improvement in heat. a lot of improvement.

LA-DEE-DA

He doesn't have a 3.2, he has a 3.0 with CIS; no possibility for a chip.
His concern is about cost vs. gaining a few horses over his current set-up.
SSI's are great, I love mine but ..............there is the cost. :)

Thanks for useful and tips! (As usual)
Actually, the heat issue is not important. I only use it above freezing temps. Mainly a summer car, put on storage now. Won't be driving it until late march/early april...:( -I welcome global warming...:D

Anyone on my last question..? (prev. post)