Plus sized SSIs
 

These showed up the other day:

http://forums.pelicanparts.com/uploa...1650544923.jpg

http://forums.pelicanparts.com/uploa...1650544923.jpg

http://forums.pelicanparts.com/uploa...1650545158.jpg

http://forums.pelicanparts.com/uploa...1650545158.jpg

http://forums.pelicanparts.com/uploa...1650545158.jpg

The SSis look so good!

They are pretty nice!!!

http://forums.pelicanparts.com/uploa...1650545292.jpg

http://forums.pelicanparts.com/uploa...1650545292.jpg

http://forums.pelicanparts.com/uploa...1650545292.jpg

http://forums.pelicanparts.com/uploa...1650545292.jpg

http://forums.pelicanparts.com/uploa...1650545292.jpg

http://forums.pelicanparts.com/uploa...1650545292.jpg

Eagle eyed readers may note the DHL shipping label with the origin "BRU".

According to Dansk these aren't available in North America at this time which completely mystifies me. They are being built in limited quantities so that might be the reason, I got in on the second batch after missing out on the first.

I would prefer the 1mm bigger 42mm Eisenmann's which are every bit as nice, but the pricing on them has gone through the roof. Although to be fair the 41mm SSI's are close to %50 more than the 38mm version.

http://forums.pelicanparts.com/uploa...1650546056.jpg

Stunning looking. My question.....the "larger" 41mm SSI's.....are for up to what horsepower engine? Or maybe what capacity (3.0, 3.2, 3.4, 3.6, etc)??

i got mine of craigslist many years ago. now i want to go measure them as i have no idea what i have on my car .. but they sound nice :)

Here's the theoretical flow into each pipe for 2.7 thru 3.8
http://forums.pelicanparts.com/uploa...1650550468.gif

the original SSI's that I had back in the day were 35mm ID w/ 47.6mm collectors, I've used them on 3.0 thru 3.6, they were fine for the 3.0 Carrera 3.0 and a nice improvement over stock

on a 964 3.6 they were fine around town at lower rpm but lost ~20hp at 6500 on the dyno

So it depends on use, displacement and the rest of the engines design, generally for stockish 3.2 and up 39mm ID(42mm OD) is much preferred

stock 964 use 41.275" ID and stock 993 uses 39mm ID but w/ a more efficient design than 964
factory race 3.0(SC/RS & RSR) used 42mm ID, 993 race used 42mm ID

I've used stock 993 and custom 42mm ID on 3.6 and 3.8 RS and don't se a difference on a dyno or seat of the pants

Very nice!

Thanks for the very helpful empiricle data Bill.

They will be 38mm OD. These bigger ones are only recently available.

Like Bill says..... it depends. But in general these should be a benefit over the 38mm version to 3.2L and up and maybe even a highly tuned 3.0.

The choice of 1-1/2", 1-5/8", and 1-3/4" primary diameter has been debated and covered many times. Headers in these sizes have been readily available for some time, if you're willing to go without heat. Of course there are a few aftermarket heat choices but IMO none quite as elegant as a factory style heat exchanger like the Eisenmann or SSI.

Thank you Bill and Jonny. I agree 100% with both of you in that "it depends" on many factors, on one hand.

On the other...Bill said it best. "On the 964 3.6 they were fine around town at lower rpm but lost ~20hp at 6500 on the dyno." That's not a light switch, that at 6,400RPM they lost no HP vs better solutions, and at 6,500 they suddenly lost 20. I am not even sure if they lost 20 to the stock setup, or something better like B&B headers and a good muffler either. Regardless it's a sliding scale that probably started back at around 5,000RPM, and probably really kicked in at 5,500 when the intake flap opens. My particular car is my 1975 rat rod, so its light and SSI's would fit the look/feel of the car aesthetically. The car doesn't need any more power than it already either, its plenty quick. That said it's all personal, and for me I would not want to put headers on my street car that "cost me" power, and certainly not 20HP near redline.

I just keep hoping for the unobtainium of SSI's that are sized properly for a mild 3.6. I also think its just about impossible to do because the packaging required for SSI's shape etc vs the tubing size required for proper flow for a 3.6 don't mix. But hope springs eternal! :eek:;)

And again beautiful headers! Should be an amazing setup for the OP.

Well, I'm putting then on a 3.4, albeit a 10.5:1 twin plug with ITB's and relatively aggressive cams. Horsepower will probably be similar to a mild 3.6.

These would probably work well for you. Any bigger and you're getting into pretty rarified territory, mostly reserved for race cars where low RPM driveability isn't a concern.

Just checking, you know that Bill was referring to the smaller sized SSIs, right? The 41mm version hot off the presses in Denmark have considerable more flow capacity.

I've been waiting for something like this for my relatively high hp 3.6. Sure would like to have heat.

Never expected to see GG Allin on a Porsche forum talking about headers

ah thanks

For you guys with bigger motors and deep pockets who decide you absolutely need that 1 extra mm of flow in the primaries (it DOES calculate to be 5% more pipe area) the Eisenmann 42mm HE's are pretty nice.

Those are beautiful. :)

there's absolutely nothing wrong with a nice set of 38s .....

someone want to remind me what we were talking about again ???

oh yeah ...

https://i.imgur.com/mrHRU0y.jpg

I have considered these for my 3.0 hotrod build. Larger might be a good thing. I calculated 40.5mm would be ideal for my airflow and peak torque rpm values.

Curious if that would be inner or outer diameter? Also IIRC correctly you have pretty torquey cams?

Yes. I have basically about a 964 exhaust side cam. I wanted area under the whole curve for my build.

My calculations are based on 5800 rpm peak torque. That is about right based on fuel delivery curves and seat of pants. Also consistent with using these on a small engine vs 3.6 and not having the same intake resonance and restrictions of a typical 3.6 installation.

I calculate 43mm with the same cam and your 3.4 displacement.

I do admit that sometimes these "numbers" are far from perfect. Lots of other considerations of cam timing, overlap, etc that can shift the requirements. Plus there is no consensus for ideal EGT and Exhaust gas velocity. Basically, Pick the harmonic you want, size them and weld them. If they are near equal length they will be better than any stock system.

Thanks, Jamie! So these calcs would be ID, then?

I figured the 41mm (OD) are a little on the small side but it's probably better than being too large. I chose the cams (DC43-106) to provide good mid to high range torque, 4 degrees more lobe separation than the project car. Just to push the peak power down a bit for Auto-X and drivability.

Yes. I am calculating ID.

In general, The tubing ID will increase with larger engine capacity and higher rpm volumetric airflow driven by higher power requirements. The tubing lengths are adjusted based on the resonance peak rpm requirements and matching harmonics. I am modeling a half wave initial primary and a quarter wave stepped secondary.

I really wish I had a dyno I could regularly use so I could test and refine the calculations.

The challenge is that you may calculate for a peak number but that's not what you want because it is too large for normal driving where you are not at peak torque. These are not all track cars that spend time in the rpm range that matches the exhaust build.

Many years ago (15?) I did an EFI 3.2SS with SSI and ITBs. I used a DC40-108. Loved the power band. I am considering swapping my cams in the current engine back to this cam but my intake/exhaust ports are not large enough to support. Right now, my engine is very well matched all the way through.

I am sure your 3.4 will end up the same. The difference in a 43mm and 41.5mm ID is only 400 rpm in a calculated peak torque. The advantage of going smaller is that the torque curve levels off and flattens as it limits airflow. This is way better than going too large and not having any velocity at low rpm to provide torque. The engine ends up being peaky instead of drivable. Fine for a race car. Not as much fun on the street.

Of course, YMMV.

If anything I'm worried that the Carrera heads with the 41mm (more like 42mm in actuality) ports are a little bigger than the motor really calls for - but sometimes you need to work with what you have. The 46mm PMOs have a 42mm manifold outlet so in all it should be a reasonably balanced system.

You will be fine with 3.2 heads. No one ever complained about that engine not having torque across the rev range. Just have comfort knowing that they will flow enough when it needs to breath.

Only thing I would do is to smooth the casting around the valve guide boss and then some coatings.

While length and width are factors the more critical one is muffled or non

The effect of the desired reflected acoustic signal depends on the transitions from one cross sectional area to another, By far the largest such transition, which generates the strongest reflection, is the the one to atmosphere, which is totally muted by a muffler but would be enhanced by a long open expanding taper from the collector. A reverse cone added to the end of the taper smears the signal a bit and broadens the torque curve. The valve overlap the more effective the signal will be.

for an SC w/ stock smog cams there is little to no TDC overlap
an RSR w/ open header profits greatly,

Here's an RSR the pulses are shown side by side due to pulse duration
http://forums.pelicanparts.com/uploa...1650665137.gif

an SC not so much

here's an SC/Carrera w/ inline pulse because little to no tdc overlap and little to no exhaust gas pulse duration overlap
http://forums.pelicanparts.com/uploa...1650665137.gif


The gases leave the exhaust port at ~120m/s but slow to ~100mps @ the collector and then into the 40-50mps range or lower depending on the design in a muffler

Thanks for the update Jonny.

It's good that we have another option for our 3.4's if we want heat exchangers and 1 5/8" primaries.

The price of the 42mm Eisenmann's scared me off too along with having to cobble up the hot air ducting.

Consequently I went with the generic 911 headers from BBE with 1 5/8" primaries specified (FPOR - 0401) and also allows for the use of the generic 2 in muffler. These were good as the standard 3.2 hot air duct was easy to modify to make it work without making it look Frankenstein!

https://i.imgur.com/CAiWeDS.jpg?2

https://i.imgur.com/0V1nHrv.jpg?1

I look forward to seeing how you rig up your hot air ducting.

Those look like a great solution - especially if you want to keep that crossover duct for the air! I had already backdated the heat ducting to eliminate the top mounted blower motor and add back the second air duct, but I also wanted to ditch the AC compressor.

Does anyone know if these new 41mm SSIs will work on an '84-'89 ?

https://www.youtube.com/watch?v=r-Mb5DsSUv8

The engine will have RSR sized MFI. The S cams and custom MFI fuel pump space cam will probably seem more like an E in this 3.2SS engine.