One of the dominant “power limiting” factors for the Mazdaspeeds is lack of fuel.
The stock fuel system (with upgraded HPFP internals and pushed to the ragged edge) is sufficient for roughly 380-400 whp; but beyond that, secondary fueling is required. There are no aftermarket injectors available for the platform, and likely never will be due to the complexity of the injector design and high costs of such an approach. Also, as more and more mazdaspeed enthusiasts dabble with higher percentage ethanol blends, the fuel demand only increases for higher air flows. Up until now, methanol injection has been the preferred approach, but it doesn’t come without it’s own hardships. Many meth injections kits lack the reliability and configurability needed for safe and consistent tuning. On top of that, potential faults in the system (be it a slow water/meth drip while the car is parked hydro locking your motor, or a hardware failure while at WOTresulting in detonation) can quickly result in damage to the engine. This isn’t to say there are no high quality meth injection kits out there, cause there are (Aquamist being one of the best), but as expected the higher quality comes with a higher price tag (and necessarily so… as the old adage goes: “you get what you pay for”).
The approach for the PERM Tuning Fifth Port Fuel Kit was a little different. There were 3 main driving factors:
It’s hard to get more reliable than replacing “nozzles” with actual fuel injectors. The Fifth Port kit comes with two, 1000 cc/min, high impedance Bosch injectors. The stock DI injectors are rated at 1700 cc/min at ~1700 psi. In “port injected” terms, this is roughly equivalent to 850 cc/min injectors, so adding an additional 2000 cc/min to the stock 3400 cc/min results in a substantial gain in fuel-ability. To help assure this fuel is delivered from the tank reliably, we recomend an upgraded in tank fuel pump (NOT INCLUDED). From there, fuel is tapped off the low pressure side of theHPFP, and delivered to a custom dual injector boss pipe placed right before the throttle body. Auxiliary injection control is provided by a Split Second fuel controller utilizing their R4software. A provided “true tach” circuit is used to deliver an accurate RPM signal to the SS controller (Now built into the SS controller), along with a voltage from the mass air flow sensor (MAF), giving the SS controller the necessary airflow and rpm information for the use of it’s 2 dimensional fuel table. This results in a very consistent and configurable aux fuel injection amount. When coupled with a proper R4 map (of which Freektune is happy to help you achieve), the necessary ECU tweaks are minimal and predictable