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      11-08-2011, 10:47 AM   #1
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335d New Custom Exhaust Installed - Review

Sorry for the delay had computer problems which required a total system restore and didn't correctly back-up photos and videos so I spent most of the weekend trying recover lost photos/videos.

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

www.benchmadeproper.com

I will post up some video later.
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      11-08-2011, 12:25 PM   #2
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For some reason, your post doesn't show up entirely on my screen and I got tired of scrolling so sorry if it is already answered:

Any check engine light or effect on the DEF/DPF parts?

Why did you decide on resonated (versus straight pipes) - does your state require emissions or decibel max?

Can you post the price - I'm sure there will be a lot of us asking?

Thanks for doing this - glad to see someone taking the initiative. If we can get both sound and performance, this will be my next upgrade. And because it looks like "cat-back", shouldn't have any warranty problems at the dealer.

Note: If I wasn't still under warranty, I would like to pull the whole emissions related parts out since we don't have testing here in Michigan. Did that with my S4 and had full catless exhaust with non-resonated Millteks - sounded great.
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      11-08-2011, 01:27 PM   #3
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Quote:
Originally Posted by EYE4SPEED View Post
For some reason, your post doesn't show up entirely on my screen and I got tired of scrolling so sorry if it is already answered:

Any check engine light or effect on the DEF/DPF parts?

Why did you decide on resonated (versus straight pipes) - does your state require emissions or decibel max?

Can you post the price - I'm sure there will be a lot of us asking?

Thanks for doing this - glad to see someone taking the initiative. If we can get both sound and performance, this will be my next upgrade. And because it looks like "cat-back", shouldn't have any warranty problems at the dealer.

Note: If I wasn't still under warranty, I would like to pull the whole emissions related parts out since we don't have testing here in Michigan. Did that with my S4 and had full catless exhaust with non-resonated Millteks - sounded great.
Sorry big pictures are causing the problem.

As for resonators, since I did not know exactly how loud it would be, I wanted to be play it safe, so I thought resonators would be a good compromise (straight pipe vs muffler) and without restricting airflow. It is possible if I removed them the sound would be a bit better, but as I stated above even with all pipes and mufflers off the exhaust sound is still very quiet. If you look at that big empty cavity after the resonators in the pics above, that's how BIG the stock mufflers were by comparison. They were HUGE.

This morning I was sitting in my truck in the garage and the d was parked in the driveway right behind me with the rear/exhaust facing me and when my wife went to start the car I heard a nice deep growl from inside my truck when she started it. Now mind you it wasn't loud, but I never heard that before. Put a smile on my face.

No check engine lights. I did not want to interfere with the emissions systems. Since the exhaust is cat back, the cats, NO2 sensors, DEF and DPF are all untouched and operate as they normally would.

I would love to pull the emissions system out, but the obvious obstacles are the DEF and DPF for which we will need coding to work around it. I think there is a lot of pent up power in our cars.

As for price, my system was a prototype, so I am not sure what the retail cost would be, but I am sure if someone is willing to call Joe and ask he would be happy to tell you.
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      11-08-2011, 02:27 PM   #4
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Wow, that looks great! The welding work looks to be top notch, and the fitment seems to be great.

I wonder if we could use an o2 simulator (similar to what the 335i guys use when they remove their cats) and remove the catalytic converter. Based on your pictures, it seems there's just one o2 sensor after the cat. For example:

http://store.bimmerworld.com/oxygen-...tors-p871.aspx

Last edited by neovb; 11-08-2011 at 03:16 PM.
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      11-08-2011, 10:09 PM   #5
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Nice, looks good. I was just under my D the other day and I was looking at doing something similar as long as I'm still under warranty.

btw two 2 1/2 pipes are not equivalent to a single 6"...

And get some videos up!!!
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      11-09-2011, 07:26 AM   #6
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Quote:
Originally Posted by Concentric190 View Post
Nice, looks good. I was just under my D the other day and I was looking at doing something similar as long as I'm still under warranty.

btw two 2 1/2 pipes are not equivalent to a single 6"...

And get some videos up!!!
Thanks

As for the equivalancy, like I said, I wasn't sure if I was remembered correctly; perhaps you know the conversion?
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      11-09-2011, 07:51 AM   #7
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area = pi*r^2
area of two 2.5" pipes = 2*(pi*1.25^2)
=9.82"^2
area of two 2.25" pipes = 2*(pi*1.125^2)
=7.95"^2
area of one 3" pipe = pi*1.5^2
= 7.07"^2

I was a little off. It's more than 3" and less than 6".
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      11-09-2011, 07:59 AM   #8
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That looks awesome! I appreciate the fact that it doesn't interfere with any of the sensors or emissions-related bits that might otherwise go haywire. I live in Maryland so if the price is right I may just end up with this setup under my car.
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      11-09-2011, 09:19 AM   #9
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Nice! Looking forward to the videos.
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      11-09-2011, 09:27 AM   #10
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Quote:
Originally Posted by maswastage View Post
That looks awesome! I appreciate the fact that it doesn't interfere with any of the sensors or emissions-related bits that might otherwise go haywire. I live in Maryland so if the price is right I may just end up with this setup under my car.
+1. I can't see why anyone would want to remove the emissions system. It borders on criminal.
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      11-09-2011, 10:35 AM   #11
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Thanks guys. I will try an get a video up asap, but I'm dropping the car off Monday to have the back bumper replaced. As I described above, the sound improvement is marginal and probably only noticeable to us diesel guys that live with the ultra quiet note each day and I am afraid that a video will not capture the difference sufficiently.
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      11-09-2011, 10:37 AM   #12
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After looking at those pics again, I wonder if I could mount that smaller bmw spare tire up under the car where the mufflers use to be. Hmmmm....
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      11-09-2011, 11:48 AM   #13
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Curious about pricing as well as shipping north of the border. We have some heavy emissions requirements here so I'm glad it doesn't tinker with anything other than making our beast of a car sound better. This and a JBD may very well be my summer upgrades next year.
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      11-09-2011, 12:28 PM   #14
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Quote:
Originally Posted by cssnms View Post
Thanks guys. I will try an get a video up asap, but I'm dropping the car off Monday to have the back bumper replaced. As I described above, the sound improvement is marginal and probably only noticeable to us diesel guys that live with the ultra quiet note each day and I am afraid that a video will not capture the difference sufficiently.
Put the camera close to the exhaust. It'll give us a better determinant, and they can compare to this, if they want:

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      11-10-2011, 08:52 AM   #15
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Quote:
Originally Posted by cssnms View Post
After looking at those pics again, I wonder if I could mount that smaller bmw spare tire up under the car where the mufflers use to be. Hmmmm....
Yeah, that's what I was thinking too. You'd need to retrofit some kind of spare tire "lowering" linkage. My wife's 2005 Chrysler Pacifica has its spare/doughnut tire mounted this way. To lower it, you have to crank a bolt from inside the trunk to lower a steel cable holding the spare. This might be difficult to retrofit as you have the passive DEF tank (I think) mounted under the trunk (and above the stock exhaust).

The first thing to check is whether you have enough room for a spare. You'd need at least 25" in diameter for a 225/45-17 tire. Plus, if you don't have enough distance from the exhaust pipes, you could risk melting your tire. Maybe some extra exhaust shield

Here's some similar DIY threads from other car forums:
http://www.thompdale.com/mini_cooper/add_a_spare.htm
http://www.civicforums.com/forums/17...-car-pics.html
http://www.6speedonline.com/forums/9...-tire-c4s.html
http://www.civicforums.com/forums/17...r-no-pics.html

Let us know if you have any luck taking this to the next step.

Cheers,
-Ted
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      11-10-2011, 09:25 AM   #16
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      11-16-2011, 07:59 AM   #17
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Still no video clip of how it sounds ???
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      11-16-2011, 08:02 AM   #18
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Car is in the shop this week.
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      11-16-2011, 01:08 PM   #19
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Looks fantastic!

I am a bit confused, wasn't whole DEF system connected to the OEM exhaust? How did you leave it untouched? Do you still need to top it off with fluid?
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      11-16-2011, 07:17 PM   #20
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Quote:
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Looks fantastic!

I am a bit confused, wasn't whole DEF system connected to the OEM exhaust? How did you leave it untouched? Do you still need to top it off with fluid?
The DEF injects urea further up the exhaust stream, just past the the DPF. I replaced the exhaust from the mid cat (seen in the pic) back.
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      11-16-2011, 07:29 PM   #21
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I want this system on my car!!!!! Looks great, very high quality.
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      11-16-2011, 11:38 PM   #22
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Just a bit concerned about the airflow without the OEM mufflers ?
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