I decided to take the BMW for a complete dual 2.5" ss exhaust system. The car still had the original exhaust system except for the cats. Cans were rotting so it was time to replace exhaust now that I have the car on the road.
I must have stopped in or contacted at least six shops around my city and I found a small place where the owner does all of the work. Shop does excellent work and they started on the car Friday and should have it finished tomorrow. I am using 18" Vibrant resonators and one-into-two 2.5" Magnaflow cans at the back. Shop is fabricating the dual downtubes, Y-adapters, X pipe, and the rest of system using mandrel bent 304 ss tubing.
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Last edited by JDP530; 04-02-2018 at 09:52 PM.
That’s pretty. I have an eisenman exhaust on mine and have been considering removing the resonator. I know it’ll sound good I just don’t want it to drone. Interested to know how yours sounds when it’s done.
Me too!
Hurt
Current project working on the E31 rebuild.
1992 BMW 850i, 1995 E31 840ci, 2008 E90 M3, 2008 750Li
Great looking work so far. You may want to tell Tim that the actual jacking points are under the rockers, and not where he is lifting the car. That floor brace is not string enough and will deform.
Desecrator of all things Sacred
I was concerned about location of lift arms, but for some reason he could not get the arms adjusted to fit under the rockers.
That’s the frame. Nothing wrong with lifting it there. It’s probably more sturdy there than anywhere else really.
I am suppose to pick up the car this evening. Will be curious to see if I notice any change in engine power. Some people believe this engine needs more back pressure and I dont have enough experience to know any better, but, I always had the notion that less back pressure equals more power. And, this engine was available in Europe without cats so leaded fuel could be used. I can always add in high flow cats if needed. The fella at this shop does have a chassis dyno so maybe I should put it on there one day. He also suggested running a stand-alone ECU!
The old back pressure myth ) What you need is an exhaust system that keeps the exhaust flowing at its highest velocity without causing too much back pressure. Too large (zero back pressure) a pipe will cause exhaust gases to slow, too small and they will also be too slow. There is a calculation based on engine size you can use, BMW had it pretty much spot on. The only thing overly restrictive on the system is a section of the header where it's welded and the Cats.
No performance benefit for an X pipe on a V12, that's purely for killing annoying sounds at certain RPMs.
Factory ECUs can be tuned easily and are ultra reliable.
Last edited by Omega man 1969; 03-26-2018 at 06:28 PM.
Back pressure is never good for any engine.
I picked up the car last night and it is a little loud at idle and up to about 1500 rpm or about 20 mph. But at higher speeds is pretty darn quiet just cruising along. I will try to capture some audio files this weekend but I still having issues with engine going into trans fail-safe mode.
We used Magnaflow cans and 18" Vibrant resonators and a Summit 2.5" tubing kit plus some extra bends, tips, and clamps. Total cost of kit was about $900 and he charged me 12 hours labor.
Good looking work at a decent price IMHO. I am soon to be in Whitney, and it might be worth the drive to San Antonio to see this gentleman.
Desecrator of all things Sacred
Last edited by JDP530; 04-02-2018 at 09:54 PM.
Thanks for the link. He's less than an hour from me, I'll be paying him a visit.
Here's a pretty good and accurate audio clip of new exhaust while sitting in driveway. Phone did not record it well so I used a GoPro but it was sitting on a metal stool so you hear a bit of vibration from camera on stool. Exhaust note is much, much quieter on the road at 2000rpm and higher. I did not have my remote microphone here at the house but I will retrieve it from my race car this weekend and get some audio while driving around. Stool was about five feet behind car sitting about 18" off the ground.
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Last edited by JDP530; 03-29-2018 at 08:29 PM.
That’s a pretty exhaust but I’m convinced there’s no way to make these V12s sound good lol
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