Review: NXS Manual Boost Controller for WRX…Hmm

 The NXS, a Cheap Boost Controller…..

Cheap NXS Boost Controler

……if cheap is what you are looking for.


For some time, we’ve been seeing the NXS boost controllers popping up in our search for the best performing manual boost controller.  There seems to be an NXS for every application (but more on that, later).  It ain’t the prettiest thing out there and looks like it is assembled from plumbing parts (because it is).  Still, we’re all about performance and wanted to see if this is worth your money.  As one of the cost leading DIY boost controllers, we wanted to know if it was equal to, or better than, the Dawes Device.  We’ll talk about performance, but first I’m going to say that we found one reason why you should never buy an NXS.  If you want to skip to that part, go right to the end of the article.  Otherwise, read on.



NXS made of pipe fittings

“Cheap”, Definition: 1) costing very little; of low price 2) of small value; shoddy. So which “Cheap” do we have here?


The NXS Boost Controller is a ball and spring type design and should have performance similar to other ball and spring controllers.  It should…….but here is what we found.  First, adjusting the boost is a bitch.  A slight turn of the adjustment screw results in a BIG change in boost pressure on our WRX.  The adjustment is very sensitive.  Like, giver er’ a couple cranks and you might blow your engine, sensitive.  But, in the end we were able to get it adjusted to within .5 psi of what we wanted.  In this respect, the NXS does control boost.  However, we noticed that the boost would rise quickly, to about 8 psi and then it would climb slower to the target 16psi, then overshoot by a couple psi, before coming back down.  At first, we thought we had knocked a hose loose or something.  So, we re-installed the Dawes Devices Hybrid Boost Controller, that we were using previously.  The Dawes Device gave its characteristic fast boost climb, with no hesitation, stopping at a rock solid 17 psi (We had the Dawes set higher, because it is trusted.  But when we test a new boost controller, we always set it a little low until we are confident in it).  We put the NXS back in and it gave the same “meh” performance.  OK, let’s try to figure out why, by looking at the design.



As we noted previously, the NXS is made mostly of plumbing parts and a big screw.  The first thing we did after testing, was a complete tear down.  It’s possible some dirt or something got left in there and was interfering with the ball, or maybe there was an air leak.  Upon dis-assembly, we noticed something odd.  None of the pipe fittings had sealant on the threads.  That is not always a problem, but we thought that maybe a leak was causing the problems.  So, we wrapped pipe tape on and re-installed.  No difference.  We also noticed that the fittings have no chamfer for the ball to sit against.  It’s just a hose nipple/pipe fitting.



The next thing we noticed was that the breather hole was about 5x the size of the one in the Dawes Devices/3 Bar Racing manual boost controller.  Hmmm.  The hole is supposed to release any boost pressure that gets trapped between the closed ball valve and the wastegate.  Without this hole, the boost will rise but once the ball closes, the wastegate will stay open and boost will drop off.  However, if you make the hole too big, it just acts like a bleed.  A slow, lethargic, overboosting bleed.  So, we wrapped electrical tape around the valve and then poked a tiny hole through it with a big pin.   Boost rise was vastly improved  and overboost reduced.  So, problem solved.  Sort of.  There is still a big difference between the Dawes Hybrid and the NXS boost controller, with the NXS falling behind.  The NXS wins on price, but like we said, what kind of “cheap” are you looking for.  Our advice: get on and throw some fittings together.  You can’t do any worse and you can seal up the fittings, drill a smaller hole (This one is like .080 on the NXS.  Try .034″) and use a better spring.  Oh yeah, the spring:



The spring appears to be a cut down version of a longer spring, that has the loose end bent over with a pair of pliers.  Also, it is different at each end, which could mean a problem if you put it in wrong, because one of the two ends is not going to seat properly on the ball.  The other end sits against the adjustment screw (literally a SCREW! ) and is free to migrate around on the surface.  To adjust the NXS, you will need an Allen wrench and a box wrench, should you ever tighten it more than finger tight.  Better keep em in your glovebox. Last, the spring is a very stiff unit (lol, stiff unit!) and short.  So, that explains why it is so hard to adjust (a little bit of compression equals a big change).  Well, that and the coarse adjustment screw.  Now the weird thing is that we bought the NXS on Amazon and we bought the unit specifically for a WRX.  But there is nothing that seems to make it specific to a WRX, or any Subaru.  So, we went to Ebay and ordered an NXS for “DODGE FORD DIESEL TURBO MAX”.  Looks like they are spamming the keywords there, but you would think that the diesel unit would have a stronger spring.  Nope, it is exactly the same as the WRX unit.  Which means, it looks like they are all universal fit units.  That’s why the spring is so heavy; so it can fit different applications.  Apparently the descriptions are just an internet marketing trick to target search keywords.  On the 3 Bar Racing Boost Controllers (aka Dawes Device) the automotive application and diesel applications use different springs.  Nothing wrong with universal fit products, but in this case it is useful to have two ranges of spring pressure, for the two ranges of turbo boost pressure.  This makes the Dawes unit a hell of a lot easier to adjust!


Let’s compare the NXS components to the Dawes:

Dawes Devices Hybrid in broken down to components.

Dawes Devices Hybrid in broken down to components.

Notice how the spring is the same at both ends of the Dawes Hybrid?  So, it doesn’t matter which way you install it.  Also, note the length, which gives a longer range of adjustment.  This light spring is for gasoline applications (generally under 25 psi), but also offers a heavy spring for high boost (i.e. diesel) applications.  The adjustment threads are very fine, which makes it easier to adjust.  Last, there is a captivating ring inside the adjustment knob, that keeps the spring in alignment.  All adjustments can be made and locked down, without an allen wrench or other tools.  Our verdict; you can buy something cheaper, but you can’t buy anything better than the Dawes Devices Hybrid Boost Controller.  But, if you have your mind set on the NXS manual boost controller, read this:

Why You Should Not Buy an NXS Boost Controller:

So in the course of doing this review, we noticed something interesting about the NXS instructions.  Namely, the majority of the information was copied from the Dawes Devices web pages.  We can prove this by using the Internet Archive (wayback machine) and looking at the original website (now  Here is a link to a shot of the Dawes Devices website in Feb 2001:

Take a look at the FAQ and then look at the FAQ in the NXS instructions, below.  Better yet, have a look at the Dawes Devices Super Duty Boost Controller instructions from 2002.

Notice how the pictures and instructions linked on the Dawes site are strikingly similar to the NXS pictures.  Well, if you look again on the Internet Archive ( for, you can see that the site didn’t even exist for another 8 years after Darren Dawes wrote the original instructions.  Conclusion: whoever runs NXS is a douchebag and we are sorry we ever gave him a dollar for his shitty NXS boost controller.  I guess if he has a problem with our review, we can always tell 3 Bar Racing Inc., so they can sue him out of existence.  We recommend you buy something else and not support NXS!



NXS Boost Controller Instructions (plagiarized from Dawes Devices and 3 Bar Racing Inc.)


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