|Once the turbos, exhaust manifolds and turbo piping are mounted to the engine it is ready to go back in the car with the transmission. The radiator, core support and steering shaft are buttoned back up and the massive FMIC is bolted into place. Once the turbo compressor piping is connected to the inlet side of the FMIC and the FMIC outlet joined to the intake piping with 3-inch silicone hose, the front bumper and bumper support brace can be re-installed. APS designed the FMIC to fit with the front bumper support brace, maintaining full OEM front impact protection features. Flexible ducting connects the two cold air intake filters to the turbo intake piping and the supplied brackets ensure that they maintain their intended location underneath the headlights. Finally, the stock transmission cooler is relocated to the front bumper support brace to make room for the passenger side intake.
More air plus more fuel equals more power. In order to compensate for massive amounts of extra air supplied by the twin Garrett turbos, more fuel is required. After removing the upper and lower intake plenum the stock injectors can be easily replaced with the drop-in quad orifice directional pattern injectors supplied in the APS Twin Turbo kit. These injectors flow 500 cc at 4.0 Bar (58 psi) differential fuel pressure and each of these are capable of sustaining 100 horsepower (flywheel) while maintaining a 12.0:1 airfuel ratio. That's enough fuel for 600 flywheel horsepower!
Differential pressure is the critical yardstick when discussing injectors in forced induction applications. As boost pressure increases inside the inlet manifold where the injectors are situated (lower half of the intake manifold the fuel rail pressure must also increase proportionally in order to maintain a constant pressure difference across the injector orifice. This is called a constant differential pressure fuel system. Less sophisticated fuel systems may not employ a constant differential pressure fuel supply. These are called constant fuel pressure systems and were only ever intended for naturally aspirated applications. APS supplies an advanced injector-wiring loom in the upgraded fuel system in order to avoid cutting and soldering of the original injector looms.
The stock fuel pump assembly is located behind the passenger seat and removed for slight modification. In order to ensure precise fuel pressure delivery at high horsepower levels, a 4.0 Bar fuel pressure regulator replaces the stock 3.5 Bar unit. A vacuum line is run from the engine bay to the APS fuel pressure regulator which is vacuum/pressure referenced to the engine's intake manifold. The regulator is then mounted on the outside of the stock fuel pump/sender unit and housed in a custom high flow housing assembly. In this way, fuel pressure across each injector orifice is maintained at a constant level regardless of the turbocharger boost pressure level - a configuration found in the world's best turbocharged production engines. The restriction caused by the stock 3.5 Bar regulator is removed completely and a new custom replacement plug is included to facilitate this. The APS custom high flow regulator housing is safely bracketed on the top of the stock fuel pump/sending unit and therefore no cutting of the stock sheetmetal is required.
If left alone the stock ECU would not know what to do with all the extra air and fuel available to it. In order to put the extra fuel and air to use, APS enlisted Unichip of North America to handle fuel and ignition timing. The Unichip piggyback module is a solid-state computer about the size of an MP3 player that comes pre-programmed with an 8.5 PSI map claimed to be good for 400+ rwhp. By including a plug-and play adaptor to the stock wiring harness, the APS kit eliminates the need or splicing into the stock harness associated with many piggy back engine management solutions.
One item of interest is that the end user cannot tune the Unichip piggy back module and it can only be tuned by a certified Unichip tuner. While this may frustrate the hobby tuners out there, it is undoubtedly safer for the average enthusiast to seek the services of a trained professional tuner when attempting to adjust the fuel and timing maps.
APS 350ZTT DRIVING IMPRESSIONS
Wow. This is what I wanted the 350Z to be from Nissan, a linear improvement on the Z32TT. With a 120 rwhp bump in power and a 122Ib-ft gain in torque, the already torquey VQ35 supplies power on demand throughout the RPM band. At 3500 rpm there are 60lb-ft more torque than stock and 100 more at 4000 RPM.
Unlike the Z32 there is little if any delay in throttle response or "turbo lag", the power is just there whenever you want it! The only downfall with all this new torque is that a heavy foot will produce gobs of wheel spin and smoky burnouts off the line. Even having Volk SF Challenges wrapped with super sticky 275/35YR19 Michelin Pilot Sport PS2s, wheel spin through first, second and into third requires nothing more than a 2500 rpm clutch dump.
From a roll the extra power kicks in quickly and the 350Z really stretches its legs without gasping for air like it did in stock form. I took the car to the drag strip and the APS TT kit paired with Mickey Thompson ET Street Drag Radials produced a 12.44 with bracket-winning consistency at the NOPIX-Box event in Alabama.
There's not much more to say about the APS Twin Turbo kit other than you have to experience the thrill ride yourself!