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Thread: E23 735i exhaust help

  1. #1
    Join Date
    Apr 2018
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    CA
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    2
    My Cars
    1985 BMW 735i

    E23 735i exhaust help

    I recently acquired a 225k mile 1985 735i that had been sitting for a year or two and have been refreshing components as needed. One thing I’ve come across is a muffler crack on the forward side where the exhaust tube joins to the muffler itself, and so I’ve been looking into replacing the muffler or getting a new catback system. I have basically no experience with this sort of thing, so I figured I’d ask for some advice here.

    Ideally, I’d like to keep the car somewhat quiet, so a nice rumble a bit louder than the stock system would be perfect.

  2. #2
    Join Date
    Jun 2002
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    Aberdeen, NC (yes, again)
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    E39M5, E500 4WD
    Welcome to the forum, AirBoss.

    It's going to be very difficult, if not impossible, to find a quality supplier of a pre-made performance system for an E23. If it were an E32 7 series, I'd send you right over to the E32 forum, and Shogun and the other fine people there could point the way. I'm sure the E23 forum has excellent people too....but I'm not hopeful for your finding a good aftermarket exhaust for this car.

    Which leaves me to suggest that a custom system might well be your best choice. There are excellent Magnaflow mufflers, even free-flowing cats, which can be easily made to fit the spaces formerly occupied by your stock, less technologically advanced parts. Summit Racing is a great source for these items, but you're going to need a custom exhaust shop to put them together in a quality arrangement for you. I find it hard to imagine that you'll have emissions trouble on an '85 car, but, well, you do live in California, so you should check that first, if you change the cat.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  3. #3
    Join Date
    Jan 2005
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    Japan
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    11/88 E32 750iL+98 E36M3
    Thanks, Chris, will move it to the E23 forum
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    Jun 2010
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    TX
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    1983/84/85 745i

    Thumbs up

    Quote Originally Posted by bmwdirtracer View Post
    I'm sure the E23 forum has excellent people too.


    We try.



    B&B are obnoxiously loud to me. Been there, done that on these cars. ANSA is just a misspelled four letter word describing defecation. Really, your best bet is OE unless you like the extra noise. Attempting to quell the resonation/drone when using aftermarket parts is quite difficult.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  5. #5
    Join Date
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    E39M5, E500 4WD
    Thank you, Hit Man. I'm just unfamiliar with the E23 forum, although I love the car. I know Shogun well, and the E32 and E38 forums are exceptionally well informed, so I probably should have expected that of the E23 forum as well. As you'll know, if you've explored some of the OTHER model-specific forums, good information isn't always easy to find. It's wonderful to know that the E23 forum has the same excellent care as the next 2 generations ! I'll not hesitate in sending people directly to your care!

    AirBoss, please take the word of Hit Man, above, and get yourself an OE system. They've already done the math, so there's no point in trying to reinvent what's already available and proven.

    Chris Powell
    Racer and Instructor since, well. decades, ok?
    Master Auto Tech, owner of German Motors of Aberdeen
    BMWCCA 274412
    German Motors is hiring ! https://www.bimmerforums.com/forum/s...1#post30831471

  6. #6
    Join Date
    Jul 2010
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    Leland, NC
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    85 €735i 08 550i/6
    Im dealing with the aftermarket drone syndrome. He's right, I'm going back to a stock muffler and resonator asap.

    Sent from my LGLS755 using Tapatalk

  7. #7
    Join Date
    Mar 2013
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    USA
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    E21/early e23/e34
    I've done a custom exhaust on my '79 and have zero drone and it sounds great and made a difference the way the car drives. I'm not running a cat as the car was originally a catalyst delete, I used the following;
    M30b35 exhaust manifolds with e32 downpipes into a single 2.5 single exhaust, Magnaflow muffler, a center resonator and a Vibrant rear muffler.
    Sounds great, car definitely drives better- savings were about 150+ lbs in weight and it cost much much less that a factory replacement, assuming you could find one.
    Will it last 40 years like the original did? Dunno, don't really care-
    Last edited by kojo96; 12-05-2018 at 02:36 AM.

  8. #8
    Join Date
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    1983/84/85 745i

    Thumbs up

    I used to have an E32 V12 for years, parted it when it started consuming oil on the passenger bank. Too bad, it was a great cruiser...and over 4lbs of R12 in the HVAC



    Finally, I did get my 10/84 745i quiet with a pair of glass packs side-by-side up front to mimic the front muffler. Factory center resonator. Factory rear muff. I wish I was able to hear the turbocharger, but I can drive my other vehicles for that.

    I think the key is the use of three mufflers, or two mufflers and the factory size catalyst with of course proper pipe sizing. Any pics of your setup, David? Or did you post them, I viewed them, and have forgotten?



    If you want a B&B a pal of mine I think has one he may sell, I can ask him. He is parting the vehicle is why selling. It was the same one that was on my 10/84...then went to an L7 that was totaled. Then his 732i.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  9. #9
    Join Date
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    E21/early e23/e34
    It's in an old thread, nothing really fancy- kept the original orientation which left my drive line fully exposed which was nice as it really makes it easy to work on the car, ie; CSB, driveshaft, pull trans...

  10. #10
    Join Date
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    85 €735i 08 550i/6
    Quote Originally Posted by kojo96 View Post
    I've done a custom exhaust on my '79 and have zero drone and it sounds great and made a difference the way the car drives. I'm not running a cat as the car was originally a catalyst delete, I used the following;
    M30b35 exhaust manifolds with e32 downpipes into a single 2.5 single exhaust, Magnaflow muffler, a center resonator and a Vibrant rear muffler.
    Sounds great, car definitely drives better- savings were about 150+ lbs in weight and it cost much much less that a factory replacement, assuming you could find one.
    Will it last 40 years like the original did? Dunno, don't really care-
    I've Been contemplateing doing the single 2.5" myself with a magnaflow muffler and glasspack. Maybe 2 glasspacks and a muffler, or 1 glasspack with 2 mufflers?

  11. #11
    Join Date
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    E21/early e23/e34
    Use the B35 manifolds! They do flow more air, and you'll need the down tubes/pipes as the mounts are different, you'll need them at least for the connectors.

  12. #12
    Join Date
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    E36 Compact,Coupe,E30
    Supersprint will make most anything in their catalog. May take few months minimum but they will. Turner/ECS is their only NA distributor. It appears they only make headers for your at but using borla/vibrant or used SS parts you could probably make something.

    https://www.supersprint.com/ww-en/bm...-steel.aspx#!/

    Price isn’t accurate either. Least for what I’ve ordered


    Sent from my iPhone using Tapatalk Pro
    S52 E36 Compact
    E36 325is Coronaproject
    08 Saab 9-3 in Oxford Green

  13. #13
    Join Date
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    1983/84/85 745i

    Thumbs up

    B35 manifolds also fit the later cars, I too used E32 downpipes. I had them on my 05/85 735i.



    Three mufflers or one cat and two mufflers is the key to me, so is proper pipe sizing for scavenging. 10/84 745i has factory center resonator (it is a Helmholtz if you care) and factory rear muffler, since the front muff on them is expensive I just did two side by side stainless glasspacks from Heartthrob. Probably should have a used a tiny Magnaflow muffler that is dual 2" and dual 2" out. Front muffler on them looks like a Magnaflow inside, so does the rear.

    BUT

    The car is silent at cruise with no drone. I just cannot stand excessive noise anymore. When I was 16, I thought it was cool.
    I make E23 parts.
    09/1983 745i (stolen spring '13 around Houston, TX Achatgruen on nutria buffalo. 8481080)
    10/1984 745i
    11/1984 745i
    11/1984 735i (10:1-265/6)
    Ford, MB, and GM round out the pack.



  14. #14
    Join Date
    Jul 2010
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    Leland, NC
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    85 €735i 08 550i/6
    I'm in the same boat. My car is too loud.

    Sent from my LGLS755 using Tapatalk

  15. #15
    Join Date
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    1985 BMW 735i
    Thanks for the tips, everyone! Looks like I’ll be sticking with factory. An M60 swap may be in this car’s distant future, but for now, stock rocks.

  16. #16
    Join Date
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    85 €735i 08 550i/6
    I just put in a y pipe going to a single 2.5". Jones 20" resonator to a dynomax turbo muffler. No interior drone, but still a deep sound outside the car. Sounds a million times better.

    Sent from my LGLS755 using Tapatalk
    Last edited by motohunter4; 01-23-2019 at 04:01 PM.

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