Yes
Interesting stuff this is. There was a certain evolution to this project and it started over a year ago. The system I had on my car was in poor shape with a lot of sub standard work to say the least. Plus one of my down pipes had a serious ding....weird as it appeared to be done on purpose, but for why? No idea.
I was considering different systems and talking to all that would answer my questions. The boys at "CoupeKing" at that time did not want to split anything up on their systems and would not ship to Canada…. OK....now I am on my own. Judy Stahl was very helpful for specification as well as Carl Bennett at Korman. Lots of ways to go with exhaust and many differing opinions. Not much in the way of support here where I live shy of Budget Muffler. So research required . I also felt that a nice system could be built for reasonable $$$. I pre-paid and hoped a good used set of post 1988 down pipes for the 635 CSi to show at O2 salvage (thanks Marshall) This took nearly a year, they are rare. These are 2 inch and fit the two bolt style manifold. In the mean time, I bought a set of 1987 635i spec. down pipes with cat from a Canadian supplier, Bosal. They were cheap, so to speak, $240. The test fit was no good to the stock manifolds. So I preceded to cut and weld to make good. This we refer to as "Pipes 1.0" Basically 1 3/4 down pipes to a merge...1 3/4 to 2 1/4 with the bung just past the junction. This is as BMW designed as the proper position for the O2 sensor on the 1988-89 635i. Meanwhile, again, some headers showed up on 'da Bay....I bought these and had them ceramic coated. The so called "headers of mystery" Nicad has a set as well and I still have no idea as to the fabricator.
I can weld mild, no stainless...gotta learn.
Prior to install of the headers I did some testing and comparison, measurements as to have a base line. Please keep in mind that at the end of the day it is velocity of the exhaust gasses that is important and not necessarily the elimination of back pressure. I measured back pressure from the bung with a water manometer.
In conversation with Sven, I asked " why do you figure those '87 pipes did not fit? Seems to me the "clocking" of the bolt pattern may be different. Did they use a different manifold in 1987?" He says "I dunno....I thought all were same until the two bolt....let me find out" Turns out my intuition was correct.These are #808 286 808 here after referred to as the "808". Stock on my car was 603 250 603 or the 603. The two bolt is #816 286 816. There was in 1987 a change for some 8 months only, until they made the change to the two bolt ball and cone. Sven found two sets of the 808's on the 'Bay. Says "you buy one set I buy the other" " "Get a set of the Magnaflow #23556 and lets see" This was the "skunk works" exhaust and we did not want to share if the deal was no good.The trouble arose as these pipes I believe were designed for the sedan. Also that their jigs are a little off. Sven made the corrections as required. I validated off the test engine as to fit.
Volume for the three cast manifolds as followed :
816....425 cc
808....350 cc
603....300 cc
As you see there is volume differences as to the cast manifolds. Air in and spent gases out. The normally aspirated engine needs a balance. Finding the right combination without benefit of 'dyno is a chore. Trial and error.
It is my opinion that these 808's are very nice. Even cast and porting vs the others. What Sven has done is the correct combination of the 1 3/4 to 2 1/2 system using the 808 manifold applicable to the stock 3.5.
I did no back pressure testing for the 816.
The headers work for my car using 2 1/4 pipes and mufflers, 3.3 and stock cam. These have 1/1/2 tubes and "short" style. I did a reduction to 1 3/8'' prior to the merge to the 2 1/4 pipe. The manometer readings showed that "pipes 1.0" were "spiky" for lack of a better term. The headers were a gradual climb and the result was a little more back pressure at WOT. This leads me to believe that the headers were "tuned".... back in the day. Much as we did with motorcycle pipes, balanced for better flow. Similar to carb tuning to the bubble. The headers are more quiet than 1.0. Nice torque curve by my seat of the pants. Burble....certainly I will get questions as to why I choked it down a bit....that is another story and again, much research on the subject. My way and others will not agree. Too bad. As you can see I used band clamps, same as the "CoupeKing" The V-bands are much more elegant and provide positive sealing.
A few still make new headers. Judy can supply from 1 3/8 to 1 5/8'' *Mild to wild as it were. These are long tube design.
These are what they sell to deep pocket customers at Korman, cheaper you get from Judy. Ireland builds to 1 5/8 spec. and short tube, I dunno. The Dane's have the 1 5/8 and short tube....could work.
Be careful not to "over pipe" is my opinion.
My friend in Alberta has the 2 inch pipes from this project and will test further with the 'hypo 3.5. Let me share some of the photos as the project developed on my shade tree island end of the show.
http://s552.photobucket.com/albums/jj325/allenpinc/Bimmer exhaust/
http://s552.photobucket.com/albums/jj325/allenpinc/635 exhaust/Headers of Mystery/
http://s552.photobucket.com/albums/jj325/allenpinc/635 exhaust/
In these...pipes 1.0, the header fit. test fit of the 2 inch.... experiments
