| -- look at the design of it. The driver's side throttlebody feeds the passenger bank of cylinders. This means that the driver's turbo is driven by the driver's bank of cylinders, but, the driver's compressor feeds the passenger bank of cylinders. This is done to create a balancing effect. As an example: If the driver's wastegate actuator has more preload than the passenger turbo, it will be more inclined to produce a little more boost pressure than the passenger turbo. However, since the driver's turbo feeds air into the passenger bank of cylinders, that additional pressure is going to make that side of the engine produce a little more power, which in turn, will cause the passenger turbo to spin a little harder and provide additional airflow to the driver's bank of cylinders, thereby balancing the power output of the two banks. A FMIC "crossflows", meaning, the air flows through the intercooler from one side of the vehicle to the other, entering the opposing throttlebody, and returning into the cylinders on the original side. This, in effect, makes the engine operate as if it were two seperate 3-cylinder engines, where each turbo works independently of the other. Dependent on what type of dual intake setup you use, you can run into some serious problems. As an example:
If you have a JWT dual pop, single MAS, the MAS is metering the intake air coming into the driver's bank of cylinders. Given that the passenger side of cylinders is operating completely independently of the driver's bank, this is where the big problem comes into play. If the driver's turbo is generating a little more boost than the passenger side, the ECU is doubling the airflow value for the driver's bank, which is going to cause an overfueling issue for the engine as a whole since the passenger side isn't flowing quite as much air. On the flip side, if teh passenger side is flowing more air, it is going to cause the system to run lean as a whole, potentially melting down your powerplant. I'm not making this a sales pitch, so just bear with my comparison with the AshSPEC XSTream dual intake. If you have the XSTream dual intake, the design of this system is splitting the total amount of airflow in half, putting exactly half of the total airflow through the MAS. If one side is flowing more air than the other, the MAS will still see the average of the two sides. Although this will not correct for extreme differences in turbocharger wastegate actuator balance, it does a much better job at maintaining the A/F between the sides - it simply splits the difference. Another thing about FMICs that crossflow is the fact the cores are very long. The longer the core, the more pressuredrop you will experience as compared to a core of the same height and width. Given that most SMICs have appreciably more height in the core (some also have more width) and significantly less length to them, you are going to see very notable advantages when it comes to pressuredrop - the SMIC cores will beat the long narrow FMICs all day long in a comparison of inlet vs. outlet pressures. FMICs present cooling issues.
FMICs present intake configuration problems.
FMICs present fitment issues. Only thing going for a FMIC setup on a Z32: teh bling, for whatever that's worth.
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