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  1. #1
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    High flow secondary cats

    A couple of months ago, I bought a slightly used ets exhaust system for my e92 335i. Its a dual 2.5 inch system with an x pipe, and separate mufflers/exits. I was running the factory e92 335i catback before with stock secondary cats in place + catless downpipes. Now that I am fully catless, the more freeflowing exhaust has def provided a nice midrange gain....and it actually idles around the same sound level as the stock exhaust did, only maybe a tad bit louder.

    Thing is, at first I was alright with the fuel smell, and I kind of still don't mind. The interior pieces of the car do tend to make noise/rattle at a certain rpm due to drone, mainly the center console. I rode in a friends rb turbo 335i yesterday who had a custom dual 2.5 inch exhaust to an x pipe, to bastuck muffler, with some 300 or 400 cell cats welded in the midpipes. Not a peep as far as noise is concerned from the interior pieces of the car. No drone. Before, without the cats, he said his car droned horribly.

    Question is, I found some 100 and 200 cell race cats from mbs. I want to restrict flow as little as possible, but am unsure of which cats I should order that would help eliminate some of the drone/interior rattling. Any ideas or experiences?! Thoughts? Thanks!

    http://www.mandrelbendingsolutions.c...High%2C/Detail
    Last edited by Stucks; 11-22-2013 at 07:48 AM.
    2008 e92 335i: JB4 G5 ISO/BMS back end flash, fbo, e85, inlets, Rb turbos, level 10 valve body + converter, water/methanol.....and a lot more....

  2. #2
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    they should certainly help your situation.. i may add these to my exhaust
    09 6AT 335i Coupe M-Sport - SOLD
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    Looking for a n54 project e90/e82

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    Why not just use resonators? Isn't their purpose of resonators to eliminate drone with as little restriction as possible? This should be less expensive with more products to choose from.

    While the cats may reduce drone that is not their purpose.

    A resonator should flow better than a cat from my understanding.
    E92 Bren Tune / E90 PTF Tune / E70 Twin Turbo Diesel JBD

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  4. #4
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    resonators will help rasp more than drone but theyll help drone...

    I am going to use them for getting rid of the smell... its either throw them in my aftermarket or go back to stock... Dont want my child breathing in fumes
    09 6AT 335i Coupe M-Sport - SOLD
    Current - 16 Jeep Wrangler - Few Mods
    Looking for a n54 project e90/e82

  5. #5
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    Click here to enlarge Originally Posted by ChuckD05 Click here to enlarge
    resonators will help rasp more than drone but theyll help drone...

    I am going to use them for getting rid of the smell...
    +1. They don't really do much for drone. may affect it a little bit, but the main use for resonators is cancelling out raspy sound. As I stated, Im ok with the smell, but if I can put some 100 or 200 cell race cats in without affecting flow too much while getting rid of the smell and drone, ill do it lol.
    2008 e92 335i: JB4 G5 ISO/BMS back end flash, fbo, e85, inlets, Rb turbos, level 10 valve body + converter, water/methanol.....and a lot more....

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    Click here to enlarge Originally Posted by Stucks Click here to enlarge
    +1. They don't really do much for drone. may affect it a little bit, but the main use for resonators is cancelling out raspy sound. As I stated, Im ok with the smell, but if I can put some 100 or 200 cell race cats in without affecting flow too much while getting rid of the smell and drone, ill do it lol.
    I am going to have to respectfully disagree with you regarding resonators:

    http://mkiv.supras.org.nz/articles/exhaust_drone.htm

    http://bit.ly/I86vMC

    http://g35driver.com/forums/v36-engi...esonators.html
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    E92 Bren Tune / E90 PTF Tune / E70 Twin Turbo Diesel JBD

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  7. #7
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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    those harmonitz or whatever they are called resonators are amazing... theyll work sure..

    but not your $50 ebay resonator 90% will buy... I have tried to find those in the past and have no been successful and i don't think theyd fit easily in our cars without pulling the exhaust off etc..

    but they are still not doing anything for smell which is why I personally want to add hi-flow cats , its easier and cheaper to just get some 100 or 200 cell 4" diameter by 11" long hfc... if your going balls to the wall for power i dont think one would care about sound or smell... HFC is for balance
    09 6AT 335i Coupe M-Sport - SOLD
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    1 out of 1 members liked this post. Yes Reputation No
    Click here to enlarge Originally Posted by ChuckD05 Click here to enlarge
    those harmonitz or whatever they are called resonators are amazing... theyll work sure..

    but not your $50 ebay resonator 90% will buy... I have tried to find those in the past and have no been successful and i don't think theyd fit easily in our cars without pulling the exhaust off etc..

    but they are still not doing anything for smell which is why I personally want to add hi-flow cats , its easier and cheaper to just get some 100 or 200 cell 4" diameter by 11" long hfc... if your going balls to the wall for power i dont think one would care about sound or smell... HFC is for balance
    +1 I was referring to the bottle style resonators. hemholtz resonators just move the drone out of cruising range and into another rpm range.
    2008 e92 335i: JB4 G5 ISO/BMS back end flash, fbo, e85, inlets, Rb turbos, level 10 valve body + converter, water/methanol.....and a lot more....

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    i have 100 cell race cats from HJS. perfect. i pass emissions and sound is good no drone.
    Edit QUOTE
    07 335i AT - MOTIV 750 - MHD BMS E85 - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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    Click here to enlarge Originally Posted by enrita Click here to enlarge
    i have 100 cell race cats from HJS. perfect. i pass emissions and sound is good no drone.
    Edit QUOTE
    hows she smell ? Click here to enlarge
    09 6AT 335i Coupe M-Sport - SOLD
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    I replaced my secondary cats with vibrant resonators and replaced the stock mufflers with magnaflow mufflers. I did notice a nice gain in low/mid HP/TQ. The car was actually too quiet and droned too much. I'm not sure if it was the mufflers that made the drone or what but I wasn't very happy with the performance of the exhaust. I spent about $500 with parts and labor and though really that i should have just bought an aftermarket exhaust instead.
    2011 335is DCT, JB4 + MHD BEF, stage 2 LPFP, e50 + 50/50 meth, FBO, MT ET Streets when needed


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    i ordered those 100 cell 4 inch diameter cats today lol. well see how they do. if the drone is still there i guess ill cut them out and put the 200 cell ones in their place and sell the 100 cells cats.
    2008 e92 335i: JB4 G5 ISO/BMS back end flash, fbo, e85, inlets, Rb turbos, level 10 valve body + converter, water/methanol.....and a lot more....

  13. #13
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    Click here to enlarge Originally Posted by Stucks Click here to enlarge
    i ordered those 100 cell 4 inch diameter cats today lol. well see how they do. if the drone is still there i guess ill cut them out and put the 200 cell ones in their place and sell the 100 cells cats.
    Please report back. I'm thinking about exhaust and high flow secondary cat too. Thanks!
    08 535i 6MT - JB4 G5 ISO - Luke performance flash - E40 & BMS 100% Meth - AR design catless DP - ETS 5" intercooler - BMS DCI - BMS OCC - ER chargepipe - HKS BOV - K-sport coilovers - UUC evo SSK - CDV deleted - ACS spoiler - Click here to enlarge

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    No smell, maybe a bit at cold start.
    07 335i AT - MOTIV 750 - MHD BMS E85 - BMS PI - JB4G5 - Okada Coils - NGK 5992 Plugs - Helix IC - Stett CP - Custom midpipes with 100 HJS Cats - Bastuck Quad - PSS10 - QUAIFE LSD - BMS OCC - Forge DVs - AR OC - ALCON BBK - M3 Chassi - Dinan CP - Velocity M rear Toe arms - Advan RZ-DF - LUX H8 - Level 10 AT upgrade
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  15. #15
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    Click here to enlarge Originally Posted by Stucks Click here to enlarge
    i ordered those 100 cell 4 inch diameter cats today lol. well see how they do. if the drone is still there i guess ill cut them out and put the 200 cell ones in their place and sell the 100 cells cats.

    link?
    E92 Bren Tune / E90 PTF Tune / E70 Twin Turbo Diesel JBD

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  16. #16
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    Click here to enlarge Originally Posted by Torgus Click here to enlarge
    link?
    Its at the bottom of the first post.
    2008 e92 335i: JB4 G5 ISO/BMS back end flash, fbo, e85, inlets, Rb turbos, level 10 valve body + converter, water/methanol.....and a lot more....

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