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  1. #1
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    REVIEW: AR Design catted downpipes / Alpina_B3_Lux

    Hello fellow Bimmerboost members,

    A few of you may know me from "the other forum" and it has been some time since I've been on this one here as well. As I'm not much in favour of the policy (the word comes from "police" I guess...) of E90post and more precisely at its way of handling conflicts (mostly by inflicting bans on members who have posted lots of useful information), I have also decided some time ago to join Bimmerboost.

    Some of you may know the reviews I've written so far, and I would like to make them available to Bimmerboost as well - together with some new ones and updates to the existing reviews. The present article is therefor one among several threads that I will be posting individually (to make them easier to find without having to wade through many posts in one thread).

    Almost all of these are performance oriented, and I will therefor post most of them in the N54 sub-section. @Sticky: If you think one or the other is better placed elsewhere, just move it there please.

    But enough of the preamble, here we go.


    Downpipes (first time round): AR Design catted DPs


    Initially I had only planned to get a flash for the engine and not to do any additional modifications to it that result in an increased power output. Noelle/Evotech officially offered their so-called stage 3 setup for a prohibitive price tag of almost 8000 EUR, which included fitting the OEM downpipes with metal race cats from HJS (which are rather expensive) and an upgraded oil cooler. I know, today these prices sound ridiculous to say the least, but that was the situation back in 2008/2009 - at least in Europe.

    After doing some research, however, it appeared that the increase in power almost exclusively resulted from the modification of the downpipes, as the stock catalysts are made out of ceramic and are rather restrictive, meaning making it harder for air to pass through them and therefore increasing backpressure and thus the workload for the turbos. Furthermore, it seemed that the main function of these primary catalysts (there are further secondary ones just before the mufflers at the end of the exhaust system) consisted in filtering the exhausts during a cold start, and that once the engine warmed up the filtering of the secondary catalysts was largely sufficient to pass emission testing.

    I also learned that there were some tuning companies in the US offering downpipes with high flow metal cats comparable to the HJS ones that Noelle/Evotech are offering, but at a considerably more reasonable price. Another alternative of which I subsequently learned was to remove the primary cats altogether, either by simply cleaning out the ceramic cats from the OEM downpipes or by fixing catless aftermarket downpipes, some of which have a larger diameter than the stock downpipes and therefore further reducing backpressure. The problem with this however would have been that it was unlikely I could pass emission testing with such a setup (which is necessary in Germany in order to be able to drive the car on public roads); furthermore I know of at least one person whose secondary cats burned out due to the higher exhaust temperatures going through the catless downpipes. That could have been avoided by replacing the secondary cats with high flow metal cats as well, but which was too costly for me at that time. I therefore decided to get catted downpipes and combine them with the Evotech stage 3 flash, which was sold at the same price as the stage 2 flash.

    So, which catted downpipes to choose? At the time there was the choice between RissRacing, UR and ar design. After some research it seemed to me that the downpipes from AR design had the most positive user feedback and no fitment issues, which was quite important due to the extremely restricted space in the engine bay where the downpipes are located. Furthermore, they came with 200 cells race cats from Magnaflow, which as far as I could discern have a good reputation.


    I bought the downpipes through a group buy organized in E90post, and got them at quite a fair price from N54Tuning. Payment and shipping was no problem, and I had them installed at my garage alongside the Bastuck quad exhaust (see below). Here's what they look like before the install (photos are taken from ar design's website):
    Click here to enlarge

    Click here to enlarge

    From what my garage told me they fit without any problem, although it's not so easy to install them as there is very little wriggle room. During the several hundred kilometers I had to drive to get my car flashed, no CEL came on and it might be that the Magnaflow cats are enough not to trigger the CEL - but I believe the trip I made is too short to allow for a definite answer in this. The Evotech flash deactivated the O2 sensors, so that I won't have to worry about CEL even should I switch to a catless setup in the future.


    Again, I'm no dyno fetishist and did not have the time to document extensively the power output before and after the install. However, I did notice an increased throttle responsiveness of the engine, and the final dyno run that I did with the downpipes led exactly to the figure advertised by Evotech with their high quality cats. I would therefore figure that the power has indeed increased as claimed by ar design. Furthermore, you can hear the turbos spool up more distinctly, at least if you're driving with the window rolled down. Nice sound!
    It also should not be forgotten that by reducing backpressure the downpipes should contribute to the reliability of the engine and the turbos - at least theoretically, meaning if you don't counteract that by driving like a madman due to the increased power…which IS very tempting!

    Problems / disadvantages?

    The downpipes from ar design are not the cheapest on the market, but then they don't want to be, and quality is not cheap to have - in my opinion they're well worth the money.

    They're not easy to install (due to them being bigger than the OEM downpipes), but the fitment was spot on in my case, so that's no major issue.

    It could be that you don't pass emission testing any more (I haven't had the time to evaluate that), but in any case you change your car's emissions which might be reprehensible in some jurisdictions.

    One thing I noticed is that, in particular in summer and when driving the car hard, but also under more or less normal conditions there is a considerable heat developing in the driver's footwell area (and no, that's not due to the attribute of any female copilot…!), and if you touch the plastic just besides the driver's right shin it's actually rather hot. When asking HP Autowerks about that they told me that this could be a result of the metal cats heating up as they're intended to do, the missing isolation (the OEM cats have two walls instead of just one like the ar design ones) and higher exhaust temperatures due to the tuning. This effect may be lessened by using catless downpipes with ceramic coating that functions like a heat shield.

    Still up to date?


    I have since switched to a setup with catless downpipes (also from AR Design) which are ceramic coated. I think the benefit is there, in particular for cars with upgraded turbos like mine. However, if you intend to stay with stock turbos and worry about emission testing, the catted downpipes are a good alternative.

    Current: Audi R8 V10 2013 S-Tronic, daytona grey, carbon side blades, MTM tune, Michelin PSS tires, Capristo x-pipe
    Gone: Audi R8 V10 2010 manual, ice silver, grey side blades, MTM tune, MTM air filters, Michelin PSS tires
    Gone: BMW 335i Individual (Öhlins, PFC brakes, RB turbos etc.)

    Gone: Alpina B3 E46 3,3

  2. #2
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    Everybody loves these pipes, and rightfully so. Good stuff.

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