45mm is for 3.6 to 3.8

flanges needed are a function of the stud length

studs were,
20mm on most 3.0
22mm on most 2.4
30mm on 3.2

there are a few oddball 25mm too

You can use thin flange on a long stud, there is just extra stud sticking through

Thanks guys.

Ben, I was also asking about my options the '74 911.

Ah gotcha.. In that case 1.5" or stock/ssi is the best bet..

Ben,
I think the stock 3.2's have 1 5/8" OD primaries and the pre 3.2's like the SC's all have 1 1/2" and this is the reason the stock 3.2 headers out perform SSI's at the top end.

For completeness we should also mention the nicely made Rarely8 headers with heat exchangers that are nicely matched with equally nicely made M&K mufflers which has to be another front running option for 3.2 owners to consider.

RarlyL8 Headers for Porsche 911

Thanks - so thick flanges were designed for 84-89 cars purely to accommodate longer studs - seems shorter studs would have been more cost effective at the factory.

I had 42mm OD Turbo Thomas headers (thin flange) on mine before and had collars made up to make up the difference in flange depth -headers worked well performance wise but heat was minimal.

My 3.4 has been stroked into a 3540 using a Gt3 crank, so I’m looking at options.

I see PMs have a B&B option with I believe is a bespoke primary length - anyone confirm how this differs to standard B&Bs?

http://www.patrickmotorsports.com/part/1-58-exhaust-manifold-headers-heat-exchanger-set/

Yes that is correct when I was referring to stock I meant stock 914-6 heat exchangers are 1.5" OD..sorry my bad for not clarifying

Shirish,

The Patrick Motorsport ones:

1 5/8" Exhaust Manifold Headers Heat Exchanger Set By Patrick Motorsports Porsche & Mid Engine Performance Specialists

are the same as the ones I linked above on the BBE website. However buying directly off BBE will save you around $800 when compared to Patricks. They both have the same part number.

As for the different flange thicknesses, there is only 1/8" difference between the thin flanged BBE's and the thick flanged ones. 3/8" vs 1/2"

Shirish,
You are correct that the Eisenmann's are only thin flanged but those that have posted have not reported problems with fitting these to the longer stud 3.2's.

Sorry my earlier statement was unintentionally general and misleading about the Eisenmann's

w/ bigger displacement and more revs a larger tube is indicated, the 45s are probably more appropriate for you

Honestly the flange thickness and the sleeves on some are not worth worrying about

Thank you Peter. Our systems were designed for track cars with heater boxes that are removable. In an off road excursion the heater boxes need to be sacrificial and able to be replaced when damaged or removed when not needed. All of our products are 321 stainless which is much more robust and heat tolerant than standard 304. We have turbo systems that have been in service on track cars for 10 years, no other competitor comes close to that type of durability. We also use F1 merge collectors that are polished internally, no stamped junk with slag on the inside or a big hole where the merge should be. The primary length is not optimized for street engines but these headers perform every bit as good on a stock Carrera as the best street headers out there at our price point.

Brian, your muffler alone made me want an SC just by the sound.

One of the best tones I've ever heard in a car, and I usually prefer V8 tones.

No probs at all, thought I was missing something :)

From Bills feedback doesn’t sound as though that it will be an issue.

Cargraphic do some bigger ssi too
http://www.cargraphicts.com/en/products/exhaust-systems/for-porsche/911-models/911/911-30sc-g-models/id40-heat-exchanger-based/

Be interesting to know what they are worth and to see some independent dyno verification of the "up to 20ps" claim.

Old wisdom, originally posted by Steve (Rennsport) from years of dyno testing:

http://forums.pelicanparts.com/uploa...1521118090.jpg

Nux,

That's actually from Steve Wong who as far back as 2011 posted that the table wasn't flawless:

Guys, thanks for the interest. Since that chart was originally created, there would be further changes I would make to it and would prefer that that one shown should be deleted for the sake of accuracy.

With regards to exhaust mods, in all honesty the stock exhaust is actually very good and the best bang for the buck is a euro style premuffler in place of the cat for additional power. SSIs/early style heat exchangers are small for the 3.2 motor and I don't think it will make any additional peak HP over the stock exhaust/premuffler combo. Stock primaries are 1 5/8" diameter and SSIs are 1.5". If you really want to make more power over the stock exhaust with headers, you need to go at least 1 5/8", which can be from European George, SCARGO, Fabspeed, B&B, Bursch, etc. What the smaller primaries will net you is a 10 hp/10 ft-lb torque gain at 3500 which increases the midrange throttle response giving the feel of more power.

Case in point: Several 3.4 and 3.5 conversions in the past couple of years built by some of California's best engine builders were put on a dyno and live mapped for maximum power. All pretty much had the same wammy mods including cams and ExtrudeHoning, etc. On the 3.4s with a completely stock exhaust including muffler but with either a M&K premuffler or sport cat, the engine delivered over 230 rwhp on a Dynojet. On the converse, the ones with SSIs struggled to get past 220 to 221 rwhp, even removing the muffler and putting on megaphones as a test. With each change a quick AFR remap was performed to ensure the differences was not from unmatched fueling. A 3.5 I recently mapped with all the cost no object tricks but with SSIs could only achieve 233 rwhp, yet others in the past with such as 1 5/8" European George headers achieved around 245-247 rwhp.

On a 3.2 with various mods and SSIs and the stock early Bischoff single out muffler, live mapped and optimized achieved a max of 208.5 rwhp. Removing the muffler and installing megaphones and remapping to optimum AFR achieved 210.5 rwhp. The only area of any notable gain was around 6700 rpm with a 8 hp gain from the megaphones. Very interesting as it tells you the stock early muffler is actually very good. All this was done on the same day on the same dyno for 91 octane California pump gas. Later the exhaust was replaced with SCARGO 1 5/8" headers and a muffler, and the same motor made on the same dyno 218-219 rwhp.

As I said earlier, it is so hard to get good data on 3.2 modifications!

Ah yes sorry, bad memory. So many cool Steve's out there :cool:

I think Wong's table is good for a rough overview. As you note above, the difference between SSI and premufler is perhaps negligible - which the table also shows.

There are many variables involved in determining what exhaust to use
Big factors are
engine displacement - typically 2.0 to 4.0 L
rev range - typically 4500 - 9000
muffled/non
stock smog cams/happy cams
gearing including wheel and tire effects

w/ a muffled, stock 3.2 which most users here use the data shows that a stock euro premuffler as the 930/10 SC or 930/20 Carrera 3.2 flows well enough to compete w/ more traditionally headers designs. The reason is 3 fold, 1) sizing is adequate, 2) stock cams don't allow exhaust tuning to work to full advantage 3) any muffled system is going to inhibit flow and exhaust tuning

Here's is an SC premufler
http://forums.pelicanparts.com/uploa...1521210125.jpg
And a later 3.2 Carrera prefmuffler
http://forums.pelicanparts.com/uploa...1521210125.jpg

Small things like the different taper angles, step, transitions and internal structure all affect flow, these factors also affect tube header design and efficiency but the muffler is still the biggest potential impediment to flow.

tube headers will never be able to reach their full potential for enhancing performance in any muffled system because the tuning waves are disrupted so much by the mere presence of a muffler, smog cams will always fail, to allow for the best scavenging efficiency that headers potentially provide. As a result flow is the name of the game in these systems.