Ad0911

So it won't fit because of the curvatures of the pipes, not because of the flanges also after cutting off the 3rd hole. The other holes seem to lign up with the 2 studs of the 16-V engine. Am I right?

Mike Simard

16V heads have 2 bolts per port, 32V has those same 2 but they are moved downward slightly and a new one added up top.
Devek made flanges with both hole patterns, the lower 2 looked like a figure eight because of the difference in position.
The Devek idea was the installer to cut off the top part of the flange for use on 16Vs.
I didn't want to do that since a 32V was going in there eventually so I made spacers that kept that top flange from hitting so I had no need to cut anything.

The other 16v-32v difference is the ports are centered at each cylinder in the 32v but offset to one side in the 16v because of the nature of 2v heads having an intake and exhaust next to each other.
That means that the collectors will be forward on one side and rearward on the other.
That difference makes the piping that bolts to the collectors be in different positions from 16v to 32v but I found that everything else cleared around the steering etc.

BTW, in theory you could open up the lower 2 holes and use stock manifolds from 16v to 32v and vice versa but in reality the holes would break out making this impossible. Only the Devek flanges have enough material for both sets of holes.

17prospective buyer

OBX is pretty big in the rice burner, excuse me, "import" crew... they make a bunch of stuff. I've heard it's hit or miss though.

The Fixer

I emailed the seller the question of whether these would fit my '83S

His response was Pls read this link for the answer to that question.
http://forums.pelicanparts.com/porsc...all-month.html

ROG100

I just bought a set for an overseas customer so we will see what they are like next week

ROG100

These are not free shipping as the description seems to indicate.
Seller was very responsive and has a link to this thread so be nice y'all.

MjRocket

Here's a full description of them.....

1.6" OD primaries
3.0" OD collector
2.3" OD outlet
0.4" CNC machined flange perfect fitment
16 gauge (1.5mm) runner wall
304 stainless steel mirror polished finish
Mandrel bend smoother flow
Individual port increase output and efficiency
Great throttle response with great sound
Dual Tig welded for durability
Accessories on the photo is included
Acutal photo of what will be send out
See disclaimer on the bottom of this page
OBX backed lifetime warranty against manufacturer defects

PorKen

You're not from around here, are you...




Third link - OBX Header Exhaust Porsche 928 USA / European Euro 32V-GT

MjRocket

LMFAO

FredR

An interesting thread but a simple question- do these things make any notable difference?

Now before folks start getting all hairy arsed let me explain. Several folks have offered this spec of headers [assuming it is the MSDS design] and yet I have never seen a before and after dyno comparison specifically for the 32V variant. I have read positive things when fitted to 16V motors. The Devek headers definitely do wonders - I have seen the evidence but they have bigger primaries and therein lies the trick or so I understand.

I have no position on this- just looking for hard evidence here. Even the Devek header design has or had some potential issues with heat if I remember correctly.

Regards

Fred R

928mac

Ducman, i like your T-rex

simos

Fred, I think I can explain this...

http://www.epi-eng.com/piston_engine...technology.htm

The effect of a straight collector is generally a very peaky tuning, in which the lengths of the primaries can be varied to produce a 'rocking' effect of the torque curve around its peak. Lengthening the tubes raises the portion of the curve below peak and reduces the portion above peak torque; shortening them has the reverse effect. Various strategies have been devised to spread the effect of exhaust tune over a wider RPM band. These strategies typically involve generating additional waves of smaller amplitude (additional, smaller steps, for example) or attempts to increase the width (duration) of the pulse at the expense of pulse amplitude by using a tapered section to extend the area change over a longer period of time.

The Pipemax says me that MSDS collectors are way too short to give peak torque under 6000rpm. Therefore no torque increase for stock 32V engine.
That was perhaps done for catlysator fitment reasons for 32V, the OB headers and colletors are longer.

The primaries are 1,6" which is good for from stock to around 500hp. The lenght of primaries gives the pulse tuning effect something after 5500rpm. This is too high for stock cams as they stop producing more flow around 6000rpm. Even the primaries are varying sizes, they are quite close to pulse harmonics to each other to work just fine(not perfect, but remember the price...).

The solution for getting torque is to replace the old style straight collectors with conical or full merge collectors. I don't know who made the headers sold by Mark K. but if you look them, they do not have straight collectors like MSDS.https://rennlist.com/forums/928-foru...-for-sale.html

I removed the straight collector from my MSDS headers and welded conical 4-1 collectors with bullets in place. http://www.coneeng.com/exhaust_system_kits.html

They gave me nice broad torque boost for my S4 with Colins stage II cams. I also sent email to Martin Schneider, but he newer answered to my questions and ideas. i didn't take any dyno numbers as my project is still ongoing, but I was happy with my assometer findings.

Why not you guys ask OBX to make one with similar collectors for testing. They will then be wery interesting product also for stock 32V owners

The Fixer

Within the link i was told to read to answer my ? re fitment to a MY '83, is states; All 928 models are covered from the 1978 up thru the latest GT 32 valve.
The MSDS product in the link i was given to answer my question, looks to have different flanges than the OBX product.

Just as many questions as when i started.

Is there another manufacturer still making a good tested header for an early 16V motor like mine?

FredR

Good post- confirms my suspicions have some merit. Trouble with exhaust mods generally is that a gain somewhere results in a loss somewhere else. I agree that the S4 cams feel "done for" at 6k rpm, not so sure I would agree that is the case for GT cams but there is more to be had overall.

I like the idea of trying to get an optimal custom design.

Regards

Fred

17prospective buyer

HEY, simos, i'm the one who bought Marks headers! Sweet! I feel special, here i thought i was just getting MSDS headers... lol.