The Blow-Thru Boost Tube is intended for use on Subarus which are using aftermarket turbo chargers that can "outflow" the stock intake system. It replaces a PERRIN front mount intercooler boost tube with one that is larger and accepts the factory MAF sensor, relocating it from the intake system to the the boost tube, allowing the ECU to read more air flow, in turn allowing the tuner to tune beyond 450WHP!
The Blow-Thru Boost Tube has a BigMAF built into it which requires ECU re-calibration in order to run properly on your vehicle. This BigMaf is designed to do two things:
Air leaks such as a disconnected vacuum hose or a loose or popped off boost tube are dangerous as they can cause severe engine damage or leave you stranded on the side of the road. The PERRIN Blow Thru boost tube moves the MAF sensor to only a short distance before the throttle body therefore allowing the ECU to compensate for any leaks in the system saving your engine.
The MAF sensor is very sensitive, and things like fans turning on and blow off valves venting can significantly alter the readings of the MAF sensor. This will cause the car to run erratically at idle and cruise situations. The Blow-Thru boost tube locates the MAF sensor in a smooth straight section of the charge air, making a consistent airflow readings, improving drivability.
The Blow-Thru Boost is designed with a larger pipe diameter right at the MAF housing. With proper tuning, this allows the ECU to read more air entering the engine without maxing out sensor voltage, allowing ECU mapping to 550WHP+. Tuners can start with maps built for the PERRIN BigMAF intake system, easily transitioning from short ram intake to Blow-Thru intercooler. This part does require ECU tuning and will not function correctly when installed on a stock tuned ECU.
The BOV is normally located after the MAF sensor in the boost system. The Blow-Thru boost tube relocates the BOV fitting before the MAF sensor allowing drivers to use vent to atmosphere (VTA) blow off valves (BOV).
Pro tuners now have the option of simply removing the Subaru intake and running a filter directly off the Turbo. No intake system is needed as the MAF sensor is now located within a boost tube.
This PERRIN Performance product features a durable powder coat finish. PERRIN powder coating is available in either red or black and is accented with a wrinkled texture finish.
PERRIN Performance warrants to the original purchaser that all PERRIN products will be free from defects in material and workmanship within a sixty (60) month period from the date of purchase. *Some exclusions apply
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This product is legal in California only for racing vehicles which may never be used upon a highway. Check your local and federal laws prior to installation.
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This product features a 5 year warranty Read Full Warranty
|Tubing||Mandrel bent aluminum tube|
|Finish||Texture powder coating|
|2002-2007 WRX & 2004-2007 STI||Yes, only with PERRIN FMIC (PSP-ITR-400) installed.|
The Blow-Thur Boost Tube has a BigMAF built into it. This is designed to do two things:
1. Allow your ECU to accurately measure airflow above and beyond what the stock intake can measure. This wider range of MAF readings allow for more resolution in the fuel and timing mapping so the engine can be safely tuned for Wheel Horsepower ratings up to 500WHP.
2. It is sized specifically to offset the use of 800cc fuel injectors. When tuning your ECU, this scaling effect will allow other settings to remain the same as though you were using the stock injector size. This lets other internal parameters in the ECU work better so the car runs smoother.
One method of tuning the Blow-Thru Boost tube (w/ BigMAF) is to not change the ECU's injector size to 800cc(or your actual injector size). The increased size of the BigMAF sized housing will offset the larger sized injectors. Leave the scaling and injector size at stock settings with only minor changes to the injector size setting to get the idle and light throttle fuel corrections set. Then start with tuning the MAF curve to hit your AFR Targets. Also keep in mind that this will effect engine load by dropping it down about 25% which means you will need to rescale the timing tables and dynamic advance tables.
The other method involves changing the injector size to 800cc(or your actual injector size), rescaling the entire MAF curve by adding roughly 20% across the whole thing. This is just a starting point and requires lots of time dialing in the entire curve to ensure low RPM drivability is good, as well as full throttle fueling is correct. This method takes longer to dial in, but allows for other timing maps to be left along as the engine load isn't offset.