MAF after a curve on an incorrect diameter pipe: a HUGE no-no!
Yikes! Somebody measure their fuel trims with this intake.
The MAF is mounted after
a bend in the pipe which is a HUGE no-no. Actually, it's between bends, which is even worse. Your MAF accuracy is going to be terrible. This intake is producing huge dyno numbers because it is leaning out the air/fuel ratio, plain and simple. While it feel may good, you're screwing yourself in the long run.
In fact, Cobb tuning (respectable company) once tested an intake that put the MAF after a curve. It was an SPT intake, which is to Subaru what Mazdaspeed is to Mazda- an official part. They found that since the MAF was mounted after a curve, it would sometimes report the engine getting less air even as actual air flow ROSE, and vice versa. I'll repeat that: as the engine drew in more air, the MAF sometimes reported a lower
The dynamics of the air within the pipe varied according to velocity (think about the air going to the outside of the bend), and since the MAF only reads air flow in the center, the MAF accuracy went to hell. This is why all OE airboxes use a straight velocity stack (off of a huge airbox) and put the MAF directly after the opening. This is also why companies who actually do R&D, like Custom Performance Engineering, use expensive CNC'd MAF housings and air straighteners to get the fuel trims back to stock.
Strike two is that this intake clearly uses a MAF on tube design, and aluminum tube is not sold (at least not cheaply) in specific enough diameters for this to work. Mazdaspeed may have the diameter close, but air velocity is, I think, something like a 4th power of pipe diameter, so even being off a small amount means the MAF will be off by a lot. In the Mazda6 community, every intake used a 2.75 or 2.5" pipe- since neither matched the stock diameter, every
intake threw a CEL unless it had a fuel tuner to correct the MAF (no exaggeration, every single one ever released). Now, the Mazdaspeeds aren't as quick to set a CEL, but they are every bit as sensitive to pipe changes
, and being DISA turbos, MAF accuracy is even more important
than a naturally aspirated engine.
Mark my words: this intake is a mis-engineered piece of crap. You might wonder why I'm bitter, and it's because Mazda puts their name on these ho-hum aftermarket parts. It's a disgrace. The Mazdaspeed intake for the Mazda6 was just a rebadged AEM
intake that Mazda marked up for more money, and it too threw a CEL.
This intake will work well on a stock car just because they are tuned so incredibly conservative and rich from the factory, but once ECU tuning becomes available, this intake is going to be an Achilles heal. As I said earlier, this intake will dyno high because it leans out the air/fuel ratio- hell, the worse
and intake is in this regard, the higher
it will dyno. These are what I'd call ricer gains, because Mazdaspeed intake owners will not
be able to use Cobb's reflash nor CPE's upcoming piggyback, at least not without paying for custom tuning and dyno time, and MAF corrections are extremely
difficult to do even with a Mustang dyno (which a lot of tuners don't even have).
Those who do run ECU tuners may find their engine detonating or worse, since the MAF, which the ECU relies on for fuel metering, won't know what the hell it's reporting. MAF accuracy becomes incredibly
important when you tune an engine more aggressively. Without a way to produce an accurate air/fuel ratio, you'll be forced to tune the car very conservatively- like old turbo cars. The ECU won't even know the true load the engine is under. The intake combined with an off-the-shelf ECU tune will surely produce a too-lean situation since the ECU tune will lean out the air/fuel ratio a few points beyond what the intake is tuning- it won't be able to tell that your car's MAF is off. It relies on it. Hell, that's why it's there. Ten years ago cars, turbo cars used MAP sensors, and they had to be tuned conservatively because MAP sensors aren't as accurate. The Mazdaspeed3 has both, but with your intake messing up the MAF, you're essentially taking three steps backwards.
Anyway, I know everyone's excited because it's a cheap way to make horsepower, but please understand why
it makes that power and what the long-term consequences are. If you're fine with buying an intake with the engineering pedigree of one of those "eBay resistors" (they make power the same way, throwing off the MAF!), then go ahead. Free market and such. However, I'd strongly recommend owners instead get an intake like Custom Performance Engineering's, since it keeps your MAF accurate while still alleviating the pressure drop
, so it'll be balls-on accurate with piggybacks and ECU reflashes down the road. It's the proper way to tune, with no parts stepping on one another's heels. But perhaps most importantly, you won't have the inconsistent rise of MAF voltage- the CPE intake keeps this sensor linear and reliable. If you don't want CPE's intake, given the current market options, stay stock
and see if another decent design hits the market.