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  1. #1
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    4 out of 4 members liked this post. Yes Reputation No

    New Custom Exhaust for my 335d

    First let me say that Joe and Brian at Benchmade Proper in Elkridge, MD did a phenomenal job fabricating this exhaust system for my 335d. It’s 100% stainless steel and tig welded throughout. They offer a lifetime guarantee which speaks volumes to the quality of their work. They were VERY accommodating and true professionals and I don’t say that lightly, since I can be a pain in the ass sometimes.

    The exhaust looks absolutely fantastic from any angle, I couldn’t be happier. Since I was the first here in the US (that I’m aware of) to install a custom exhaust on a d, I wanted to get this right the first time, so I did a lot of research to help me in deciding pipe diameter and how they relate to exhaust gas flow rates (CFM’s), high flow mufflers vs. free flowing resonators etc. I had multiple goals in mind when I decided to take on this “experiment.” First, knowing that by their very nature a diesel engine’s exhaust note is usually much quieter than a gasoline engine even before mufflers and pipes are added. Therefore, I wanted to try and improve the sound quality of the 335d’s exhaust, since there was virtually no sound being emanated from the back of my car while at idle or when revved. Secondly, after closely examining the OEM exhaust we noticed how crushed many of the pipes bends were, not to mention some of the crazy angles BMW took to route the piping, which lead me to believe that exhaust flow could be dramatically improved, thereby reducing backpressure as well as reducing EGT’s just by intalling mandrel bent pipes. In addition, the mufflers were HUGE and I could barely feel any air flow coming from the tailpipe while at idle or when the engine was revved. So I suspected that the mufflers were not only heavy but also very restrictive. In a nut-shell I was looking to improve the exhaust note, reduce backpressure, egt’s and weight, and at the same time perhaps pick up a few extra ponies in the process.

    That said, with some guidance from Joe at Benchmade I decided to go with 2.5” mandrel bent stainless steel piping connected to Vibrant free flowing resonators. Thought being unlike the i’s true dual pipe exhaust system (from headers back), the d has a single pipe coming off the header which then branches out to a split pipe system after the mid cat. The single pipe coming off the header which is oval in shape appeared to be approx 3.5” – 4” in diameter, which then narrows down to a approx 2.25” split pipe system, which is then crushed down to under 2” in diameter in some places. In theory two 2.25” diameter pipes coming off a single 4” pipe should provide adequate flow assuming of course the 2.25” OEM pipes’ had minimal bends and the diameter was consistent throughout the run – that wasn’t the case. Considering my car is tuned I decided to increase the pipe diameter by .25” and to maintain a consistent diameter throughout the run with minimal bends. Reason being two 2.5” pipes are equivalent to a 6”+ diameter single pipe (if memory serves me right), which is good for up to something like 500+ hp, so going any larger would not be accretive.

    I decided on the high-flow resonators since they virtually offer NO restriction as opposed to a traditional muffler. I also thought that they would allow a bit more sound through then a traditional muffler since I suspected that getting sound from this system was going to be a challenge.
    Well my suspicions proved right. While the exhaust note improved somewhat, more specifically there's actually some sound coming out of the tailpipes now and it is deeper in tone, the improvement I would consider marginal, so it was a little disappointing in that regard. Don’t get me wrong I am still happy that I am actually getting some sound now, but I was optimistic I was going to get a few more decibels. What we discovered going through this process is that the cats appear to be suppressing A LOT of the sound, as I imagine the DPF is as well. To give you an idea, when the twin OEM pipes/mufflers after the cat were removed and before the new system was installed, the car was started the exhaust note was still very quiet (will post some video of that too), not sure why BMW even installed such large/heavy mufflers – they actually look identical to the i’s.

    That being said, I am very happy with the quality of the system/install, it simply looks fantastic! The system is also significantly lighter than OEM (+/- 25lbs). I also feel A LOT more air flow from the tailpipes at idle and when the engine is revved, which supports my belief that in addition to the DPF and cats, the rear pipes and mufflers were/are very restrictive. Before the install and aside from zero sound, I felt hardly any airflow from the tailpipes. I would like to believe now that I've been able to improve the airflow/reduce the back pressure that there would be some performance gains, not to mention perhaps some benefit in terms of reducing EGT's. It could be false perception, weather or whatever, but my car feels like it’s pulling harder. I plan to take the car back to the dyno later in the month.

    While this was somewhat of an experiment for us US diesel owners I consider this a stepping stone of things to come for the US BMW diesel. While I am not brave enough (yet) to try removing the cats and to tinker around with coding for NO2 sensors, DEF system etc, perhaps another daring owner will be willing to advance the cause and take this process to the next level!

    In summary I am happy with my decision and purchase.
    Benchmade stated they would make this system available for purchase/shipped to anyone that is interested. You can custom tailor it if you like e.g. different resonator/muffler or straight through exhaust, bigger or smaller tips etc. Give Joe a call for pricing and information.

    (410) 540-9990 they also have a website benchmadeproper .com

    I will post up some video later.
    Attached Images Attached Images         
    Last edited by cssnms; 11-08-2011 at 12:28 PM.

  2. #2
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    Sound clip?

  3. #3
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    This is a freaking awesome thread!!!

    Nicely done man, nicely done!

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    @cssnms I spoke to Joe and he gave me as estimated price range between $800 to $900 dollars, he told me he is waiting for you to bring the car back for follow up and production, BTW its me Axel61 from 'fest. I hope your dyno produces some HP/TQ numbers unlike the M3 exhaust system that cost $4k and only gives out 2hp LOL. Next weekned LANDo bound for RENNtech ECU flash!!! Whoopee, will give you guys before and after dynos, problem is its feraking raining down here in Puerto Rico this week so I have to have it done next week hopefully before I leave!!

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    Click here to enlarge Originally Posted by Puerto Rican 335d Click here to enlarge
    Whoopee, will give you guys before and after dynos
    Looking forward to those.

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    Chris, nice job on this.

    I have a little somethin somethin for you guys coming in the next 2 to 3 weeks...stay tuned. Click here to enlarge
    Click here to enlarge

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    Click here to enlarge Originally Posted by Ronin Click here to enlarge
    I have a little somethin somethin for you guys coming in the next 2 to 3 weeks...stay tuned.
    Exhaust?

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    Yup, but not the same deal as what Chris has going up there (which is awesome, btw).

    Also...Chris, still waiting for that sound bite. Click here to enlarge
    Last edited by Ronin; 11-12-2011 at 07:23 PM.
    Click here to enlarge

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    Nice exhaust. Need sound clips.
    Some people live long, meaningful lives.

    Other people eat shit and die.

    I'm not racist, I hate everybody equally; especially fat people.


    Click here to enlarge

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    1 out of 1 members liked this post. Yes Reputation No
    Thanks guys.

    Ronin, yes I know I still need to get those sound clips up, but it's probably going to be another week or so, dropping the car off at the body shop tonight, since someone ran into the back of me Click here to enlarge Damage isn't bad but will need the bumper cover replaced - going m-sport/performance bumper now. Looking forward to see what you have coming. It just takes a few of us daring owners to move this endevour forward.

    As for the sound don't want to get everyone's hopes up that it is something that it is not. As said the sound improvemen is marginal, but noticeable to the discerning ear. I suspect the video sample will not be able to capture that difference, but nevertheless I will post it up and let you all decide.

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    Click here to enlarge Originally Posted by cssnms Click here to enlarge
    As for the sound don't want to get everyone's hopes up that it is something that it is not. As said the sound improvemen is marginal, but noticeable to the discerning ear. I suspect the video sample will not be able to capture that difference, but nevertheless I will post it up and let you all decide.
    Thank you.

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    Amigo Chris whats the latest on the exhaust system, let us know when you do the DYNO runs and get HP/TQ numbers and BTW show Pics of how to get the Torque Readings so I can get these knuckle heads down here to do mines correctly since they have never done a DIESEL before ok!! Gracias

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    Yes, update please.

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    Chris, chris WHERE are UUUUUUUUUUUUU? Santa didnt bring anything LOL

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    Looking good
    Sveinbjörn Hrafnsson

    E30 CABRIO S3 8B38
    ALPINA B10 BITURBO 346 @ 507

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    As an addendum to mine, here's some email correspondence today regarding what I'm looking at (schedules have prohibited me and the fabricator from meeting up):

    Basically I am going to map the enitre exhaust and see what connections go where, and then see where it can be improved. I would not cut into anything without your approval and a very accurate breakdown of what we would be doing to it. I want to be able to do a full midpipe and new muffler, and I like the idea of meth injection for the D's also
    Click here to enlarge

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    Yes @Ronin thanks for stepping up, Chris is MIAClick here to enlarge

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    1 out of 1 members liked this post. Yes Reputation No
    Here is some video, sorry for the delay.


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    1 out of 1 members liked this post. Yes Reputation No
    Follow-up dyno up next...
    Attached Images Attached Images  

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    1 out of 1 members liked this post. Yes Reputation No
    I posted this up elsewhere too, but for anyone that is interested in a comparison between a turbo-back (no dpf w/cats) exhaust and a dpf back exhaust w/all catalysts in place, the link below will take to a test conducted by Diesel Power Magazine.

    It is interesting to note that while the dpf does supress sound it is not as restrictive as many thought.

    http://www.dieselpowermag.com/tech/d...s/viewall.html

  21. #21
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    Looking forward to the dyno but you got a baseline right?

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

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    Click here to enlarge Originally Posted by Sticky Click here to enlarge
    Looking forward to the dyno but you got a baseline right?
    Yes

  23. #23
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    Click here to enlarge Originally Posted by cssnms Click here to enlarge
    Yes
    Click here to enlarge

    Stage 2 or 2.5 E9X M3 S65 V8 supercharger kit for sale
    : http://www.boostaddict.com/showthrea...r-kit-for-sale

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    I finally heard or should better say could not hear the exhaust tone, I thought it would of been louder but if it gives more hp/tq then i guess its allright

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    Click here to enlarge Originally Posted by Puerto Rican 335d Click here to enlarge
    I finally heard or should better say could not hear the exhaust tone, I thought it would of been louder but if it gives more hp/tq then i guess its allright
    And what would have made you think it would have been louder? Would it be from where I said the sound improvement was marginal?

    The fact that there is now some sound coming out of these pipes is an improvement. The tone is def deeper. Removing the cats and dpf are going to be only way to really get an appreciable sound improvement from a diesel.

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