FMU’s Wicked E9x Velocity Stacks

FMU’s Wicked E9x Velocity Stacks

So, after a weekend of waiting, we’ve got a comprehensive photoshoot of our new E90 velocity stack system — and it’s wicked.


Quick addendum: Our E90 stacks are now being featured on Top Gear’s front page! Check it out at the link embedded into this sentence. And check out our Jalopnik coverage, too!



Planning was the name of the game with this stack setup. Just like with Dick Cook’s E46 stacks, we knew we wanted something totally trick, something that immediately grabs the eye and makes you wonder more and more about it. After plenty of designs (and plenty of time spent in AutoCAD), we narrowed ourselves down to a few main ideas — we wanted them in aluminum, we wanted a new catch can design, we wanted water-meth injection (as opposed to nitrous), and we wanted them to look mean. And so we accomplished all four of those ideas in one fell swoop. And so, we made these:



Made entirely from 6061-grade aluminum, this new velocity stack set for the E9x M3 was conceived, designed, cut out and assembled in-house at Fluid MotorUnion. Our system incorporates an Aquamist (care of Howerton Engineering) water-methanol injection system, which runs from the tank in the back to a specially-designed manifold that splits up the 6mm inlet to eight 4mm direct-injection nozzles, which are placed at the ends of the arms that stretch over each individual stack. The tubing from the manifold to the nozzles, just like on the DCM3, are fed through specific channels in the arms themselves. When all’s said and done, it looks like the grim reaper’s put his special touch on this system.



You may notice a couple nozzles are missing. We’re getting them ASAP, but we didn’t want to delay this entire post (and all the picture-taking behind it) just because of a couple small nozzles. If you’ll be at Supercar Saturdays this coming week (and if not, I suggest you come see what it’s all about), we’ll be displaying the final product there, as well.



We’d like to think it turned out well. Only time will tell, however. We still have to mount the AN fittings to the catch can and finish routing that system, too. After we get the nozzles and remainder of the catch can installed, we’re going to try and get some videos of the sound, and perhaps a dyno run or two. It’s all on the way. Thanks again to Jeff at Howerton Engineering for helping us get this done in short order!



  • Derek
    Posted at 13:47h, 27 June

    ¡Boom goes the dyno-mite!

    Looks like amazing just drove up, check please.

  • Frank
    Posted at 17:26h, 27 June

    Amazing. IF that thing performs as good as it looks you have probably the best velocity stack set up I have ever seen on any car in my entire life. Those water meth nozzle arms are what Van Gogh would put on his E90.

  • alex
    Posted at 18:40h, 27 June

    Truly impressive design and I love the integration of the methanol injection! I am actually going to be installing a CF Airbox on my own E46 M3 and I have been contemplating installing my own water/meth kit.

    With a proper tune and feed of a air, I’m sure you guys will gain some good power on the dyno. Please share some dynos when you can! I haven’t seen fabrication and innovation of this high caliber in awhile.

    Great work FMU!

  • evil monkey
    Posted at 19:59h, 27 June


  • M Mathers
    Posted at 16:32h, 29 June

    I apologize if this sounds like a silly question but with this kind of setup, how does one filter the incoming air?

  • fluidmotorunion
    Posted at 16:33h, 29 June

    Not silly at all. We choose to run them without filters. Yes, it’s a bit riskier, but going off our experiences, we’re willing to take the risk for the sake of aesthetics. A life lived without risk is hardly a life at all.

  • Aaron
    Posted at 16:58h, 29 June

    Oh seriously Andrew!! Throw some quotes around that if you’re going to steal it!! Life without risk boyeee!!!

  • MdOGGY
    Posted at 17:46h, 30 June

    wOOP wOOP to the E36 in the background.

  • Frank Falat
    Posted at 18:22h, 30 June

    Is this M3 running naturally aspirated or forced induction? The detail put into the nozzles for the water/meth injection look great, but usually doesn’t result in much bhp gains on NA motors. The velocity stacks look promising, tho. (I worked for Dinan & Roush as a Powertrain Eng’r a few yrs ago.)

  • fluidmotorunion
    Posted at 07:14h, 01 July

    Holla. Just wait ’til you see what we have in store for Burroughs’ engine bay 😀

  • fluidmotorunion
    Posted at 07:19h, 01 July

    It’s all about the knock control. The E9x M3’s adaptive knock control uses an advanced form that measures ionic resistance of the gap in the spark plug inside the cylinder. This system originated with the E60 M5, and when it came out it was the most advanced form of knock control this side of F1.

    While our owner/founder was taking his E60 M5 introduction class as part of his factory training, he theorized that the advanced knock control would continue to advance timing and make power, so long as the octane rating was high enough. This was the main reason behind our decision to run water-meth on the N/A S65B40 (which is based off the E60 M5’s S85B50). We feel that as long as the adaptive knock control can keep pushing timing with a higher octane from the water-meth, we’ll keep trying to pull power from that.

    Obviously, risks are inherent. We understand that. On this engine, in previous preliminary testing we’ve seen gains between 20 and 30 hp at the crank.

    BMW’s adaptive knock control works on a per-cylinder basis, but will slowly ease back the other cylinders to keep the engine smooth and safe in the event of the meth system failing in some regard. The advantage of the ionic control in the adaptive knock system is the speed at which the system can react. So, if the system clogs or stalls, not only will the aftermarket Aquamist system pick up on the lack of flow and throw a message, but the E90 itself will also automatically pull timing before any damage is done.

    We’re just taking advantage of this system that’s already been made near-perfect by BMW to make the power we’re looking for.

  • Adam
    Posted at 07:31h, 01 July

    How are you metering the air? Just speed/density? How are you keeping the OEM ECU in the loop?

  • fluidmotorunion
    Posted at 10:40h, 01 July

    We’re going to use our own custom tune, flashed to the stock ECU . All our cars with velocity stack systems feature a custom tune for the stacks (alpha-n if there’s a MAF sensor present in the stock system), given the deletion of the entire intake system up to the throttle bodies. The IAT sensor is also moved to a different location in the engine. The OEM ECU will remain in the loop, it’ll just be flashed with our tune. We won’t tune the car specifically to deal with the water-meth, though; that way, if we run out of solution during a drive, the knock control system will be able to move the timing to match the lack of methanol being injected. With a tune for meth on the car, the timing wouldn’t push itself back, lending to trouble awfully quick. BMW’s adaptive knock control is pretty masterful, and we can’t thank their engineers enough for making this system so lightning fast.

  • Frank Falat
    Posted at 13:58h, 01 July

    I figured there was more to the story than meets the eye. I wonder how large the window of adaptive learning is. Even a few degrees of learned advance will produce some appreciable gains on that motor. Nice work.

  • Marco Zeitler
    Posted at 16:24h, 01 July

    Seriously guys – with this system you have outdone yourself.. great craftmenship, these stacks will give every car fanatic an eyegasm.
    It sucks that you’re over in the states and I am located in Germany, otherwise I’d know where I’d bring my car..

    Kudos for the great work all of you do! Keep it up.

  • fluidmotorunion
    Posted at 19:07h, 01 July

    Thank you, Marco. We appreciate it. Any time you come to the states, you know you’re welcome here!

  • Colin Phelan
    Posted at 11:03h, 02 July

    That is unreal.. You guys continue to amaze me over and over again..

  • nismokid_5
    Posted at 21:13h, 04 July

    Gosh, you guys are SUCH ballers.

  • David
    Posted at 19:21h, 28 July

    That looks awesome!!! I just want to know much to buy the kit? I have a 2008 M3 convertible and this is exactly what I have been waiting for. I have been looking to add a meth kit and Jeff from Howerton told me about you guys.

  • fluidmotorunion
    Posted at 07:07h, 29 July


    E-mail andrew@fluidmotorunion.com and he’ll get you everything you need!


  • chris
    Posted at 20:15h, 05 October

    soundbyte please…

  • fluidmotorunion
    Posted at 06:59h, 06 October

    Check the other posts about our E90 in the Projects subsection — we have plenty of post-stacks video for your enjoyment 🙂

  • BrandoSauce
    Posted at 10:37h, 10 November

    A little late to the game here but a setup as nice as this should at least have SOME filtration. It could be easy though, there are already rain seals at the back and front of the engine bay that the hood lays on. Using that same idea, a filter-media shroud could be made in the bonnet dome with the same style black rubber seal material that comes OEM in the M3 that encircle the velocity stacks. I.E. the air filter would be the size of the whole manifold and would be attached to the hood. When the hood closes, it seals with the rubber gasket that attaches to the engine like an engine cover.

    Even though it wouldn’t be quite as pretty, if done right it would look OEM and protect such a friggin awesome engine from the inevitable road grit that will be tossed in through the hood vents when getting ready to pass a lambo with an aggressive diffuser. Such grit would just make hell on a ring or valve seal if it made it into one of those stacks. Just sayin.

  • Dillon
    Posted at 11:06h, 06 November

    I don’t even know how I ended up here, but I thought this post was great. I do not know who you are but definitely you’re
    going to a famous blogger if you are not already 😉 Cheers!

  • Jerry
    Posted at 08:38h, 30 May

    Very Cool!

    Do you have a V10 version in the works?

    My M6 needs this!

  • fluidmotorunion
    Posted at 09:49h, 23 June

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