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Old 12-15-2010, 11:05 PM   #1
Yamahammer
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325i exhaust Questions

Car: 1990 325i

So I know this probably been asked a lot, so please to deusche comments. I have searched pretty well everywhere and found many threads on e30 exhaust options, but people never give any real clear conclusions. So...

I am going to be doing an exhaust soonish. Motor is stock. Future mods would only include injectors/w chip, and intake.

The exhaust I am doing purely to get the perfect sound, and I want to do this with no noticeable power loss. My first option is cut out the cat and muffler, replace cat with pipes and then run a magnaflow (14815) or borla at the end (I contacted B&B and they will not sell me the muffler they use in their catbacks, and im not paying 900$ for a catback...) So this option I think would sound good, but will running just a muffler lead to a large amount of power loss?

Second option. Replace current cat with high flow cat (I would have to get two y pipes, unless i somehow ran two separate cats?) and then a muffler at the end, or just have the cats with no muffler at the end.

So three options:

-Only muffler
-High flow cat, or cats with muffler
-High flow cat, or cats, with no muffler

Any information is greatly appreciated. Please only comment on power loss if your information is actually correct.

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Old 12-15-2010, 11:29 PM   #2
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Chopping mufflers and whatnot won't yield significant gains. Obviously a straight-through muffler like a Magnaflow will flow better, but not as bad as you would think compared to stock. The butt dyno found the most gains to be with headers + cat delete. Since you are just here for sound, my 2 cents would be just buy a nice dual in/dual out muffler and get it installed with stock piping and rock that. Stock M20s sound good with any muffler attached to them.

Back in '07, I rocked this setup for a bit: Headers+no cat+magnaflow... and it turned out to be very loud (almost too loud) for the street so keep that in mind. I put a stock muffler on, and haven't looked back since.
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Old 12-16-2010, 10:05 AM   #3
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Hmmm ya, but will I loose power if I do a cat delete? Everyone seems to use the 14815 magnaflow muffler, which is a single in and they just use a Y, does this cause any problems. My main concern is power loss.
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Old 12-16-2010, 10:33 AM   #4
El Gato Liso
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heres a magnaflow Y single in and single out on stock m20 and headers, and a huge ass cat.

now its sounds even more nasty with the m50

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Old 12-16-2010, 11:07 AM   #5
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lol @ squeekeey belts!
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Old 12-16-2010, 11:26 AM   #6
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LOL them noises at the front of the car don't sound so good!

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Originally Posted by Yamahammer View Post
Hmmm ya, but will I loose power if I do a cat delete? Everyone seems to use the 14815 magnaflow muffler, which is a single in and they just use a Y, does this cause any problems. My main concern is power loss.
Just Y it after the stock resonator. Run a single 2.5" back to the 14815 (lighter than two pipes). Everyone says its only a 2.25 inlet, but you can actually fit a 2.5 in front of it.
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Old 12-16-2010, 01:12 PM   #7
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I ran that muffler and it was too loud for my tastes. If I were doing it again on a stock motor, I'd get the Ireland Engineering cheap rear stainless muffler (also available on ebay for cheaper). I've heard one and it sounds great, proper great.

No reason to remove your cat at all, or replace it, unless it fails etest. If you fail with a bad cat, you'll fail with no cat.

For my magnaflow, I just bought some various muffler pipe size adapters from CT, bashed them into an oval and flux cored the ugliest Y pipe ever. But it worked.

I've since gone to 3" exhaust and the magnaflow is WAY too loud, so its sitting in my garage.
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Old 12-16-2010, 01:12 PM   #8
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There is a made to fit Magnaflow stainless cat-back... I think around $550.

http://www.carid.com/1987-bmw-3-seri...low-90472.html

Magnaflow #16535
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Old 12-16-2010, 01:22 PM   #9
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Oh cool, in all my searching years ago I never saw this.. is it new?

If anyone is going to buy Magnaflow products, check out hottexhaust.com.. I've got all my magnaflow stuff from them, they ship from Canada, usually have cheaper prices than anywhere and you can find coupon codes online for them.
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Old 12-16-2010, 02:01 PM   #10
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that naz_t noise was the water pump!!!!
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Old 12-16-2010, 02:48 PM   #11
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hmmm, alright so will I get any sound out of removing the cat?

I will probably run magnaflow because I want it to be loud, and thats also why I want to remove cat, but only if it will not cause significant power lose.

I checked out the hottexhaust place. Not bad, not much cheaper than ebay, haha.

Last edited by Yamahammer; 12-16-2010 at 02:54 PM.
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Old 12-16-2010, 03:19 PM   #12
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You'll hate your car pulling out the cat. The drone will send you over the edge.

+1 for high flow cat.
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Old 12-16-2010, 03:47 PM   #13
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WOW, magnaflow has a catback now? That's sick. Somebody buy it, I want to see what it looks like

Cam, I have run no cat in my car, and its not droney at all? If anything, it just got raspier and more rough sounding. Definitely noisey though when you haul on the loud pedal.

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Back in '07, I rocked this setup for a bit: Headers+no cat+magnaflow... and it turned out to be very loud (almost too loud) for the street so keep that in mind. I put a stock muffler on, and haven't looked back since.
Hot damn, look what I found:



Not the best quality, but gives you an idea of how loud it was if you could hear it that clearly over the wind noise.
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Last edited by craz azn; 12-16-2010 at 04:10 PM.
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Old 12-16-2010, 04:59 PM   #14
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alright so i think the sound im looking for is no cat, with a magnaflow haha. But still...does anybody know if i'll get power loss?
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Old 12-16-2010, 05:08 PM   #15
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No you won't.
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