Stack Swap

20 Dec Stack Swap

Today, we’re going to see whether or not velocity stacks by themselves make any additional power to a motor, specifically the S62.

First off, we at Fluid MotorUnion feel we need to say this right away: This is not marketing material. This is not meant to promote sales of our product. This was not made as an attempt to compare our product to any competitor. This video is merely to open a dialogue with the aftermarket community at large.

That being said, the following video is a one-take shot that’s meant to promote a dialogue as to whether or not the stacks by themselves make power. Often times, our stack systems are incorporated into larger builds with ECU tunes that don’t allow for a way to measure the gains directly from the stacks (sans tune).

Now, power was not our goal when we decided to start investigating different velocity stack designs. Our original goal, one which we believe we’ve achieved, is to give the vehicle a more aggressive and unique sound that’s impossible to replicate on cars without individual throttle bodies (ITBs). Over the years, we’ve played with multiple designs (roughly 8 different ones — short stacks, long Medusa-style stacks, etc.). During our R&D, our engineers have calculated the proper stack length by finding the optimal wavelength to base them upon, and we’ve found that this design we’re currently using is making the most power while still keeping the sound where we want it.

As you can see from the above video, we first did a walk-around of the car to show that there are no laptops or wires running into the car that could apply a different ECU tune to the car while Craig is changing out the velocity stacks. We have purposefully tried to show as much of the room as we can in an effort to remove any potential doubt those viewing the video may have (and trust us, we’ve anticipated a good amount). There’s also a clock on the left of the frame, with a second hand, to show that no editing trickery took place at any point; this is one continuous shot. It would obviously be in one’s benefit to watch this at the highest resolution possible (720p, fullscreen).

While we filmed the dyno room with our Sony Handycam, we also ran CamStudio on our dyno’s computer to record the dyno’s output at the same time, which we synced with the dyno room footage in iMovie (as best as we could, we may be off by a few fractions of a second on the sync). The picture-in-picture doesn’t go away to show that it’s one continuous recording of the dyno output. The small blip of power in the graph of the first stacks-applied run is consistent with the sound and performance of the motor in the dyno room shot, again showing that we’re not trying to pull a fast one on anyone here.

We also are the first to admit that there are drawbacks with running open stacks. The purpose of this video, once again, is not to show our system’s superiority over all closed-airbox designs. Whether or not you choose to run open stacks is up to you. We take as many precautions as we can when running them so as to minimize (but not eradicate) any potential issues.

Regarding the hood being open versus closed, we did later runs with the hood shut, and found no difference in how well the bolted-on stacks performed. It just wasn’t filmed all in one run, so it wasn’t included in this video.

Regarding the vehicle’s initial power output, the only modification to this vehicle is the Fluid MotorUnion axle-back exhaust, which deletes the mufflers in favor of pass-through resonators. The typical term for a motor that puts down stock numbers like this is “factory freak.” The initial power is not indicative of an ECU tune being applied to the motor.

For the sake of consistency in testing, we did this entire run with the MAF sensors unplugged, allowing the vehicle to throw a CEL and enter its alpha-n programming. We did later runs with the MAFs plugged in during the initial runs, and found no difference in average gains. Once again, it wasn’t filmed all in one shot, so it wasn’t included.

And for those of you still worried about a tune being applied to the ECU for this video, the loss of torque and power early on in the powerband should be an indicator that BMW’s stock map was used for this setup. Our stack-specific tune removes this loss of early power while still retaining the power and torque gains at the late end of the powerband. Low end loss can be removed through tweaking the camshaft timing along with a couple other tricks.

Once again, as we did in the beginning of the text, we need to really drive this point home: We are not using this as a shill for our velocity stack products. We are not employing any tricks to get you to believe that you should buy our stuff. We’re merely trying to show that, from our testing, bolting on a set of velocity stacks will produce power, and we want to open a dialogue with those who may not have believed this, as well as those who may still not believe it. If you have any questions or comments, you know our doors are always open for a dialogue. Now enjoy the video!