Last month we made some heat control mods to the RX-8, with the expectation that the secondhand (and no longer in production) Pettit Racing Stage 2 supercharger we picked up on the cheap was going to make our hot-running Renesis even crispier. This month, we learned that buying used parts tends to be a mixed blessing—the discount price is often accompanied by missing parts, no instructions, and no warranty or recourse if things don't work as advertised.
Because we've gone with the high boost pulley, we needed to upgrade the secondary fuel injectors to deliver enough go-juice. We yanked the four factory 450cc (yellow) secondary injectors and replaced them with Injector Dynamics 1,000cc injectors. The blue 11mm adaptors are designed to locate the ID injectors in the correct position in the factory fuel rail, while the included clips had to be soldered on. (Turblown.com sells an injector mini-harness if you don't want to modify your stock harness.)
| Project RX-8 - Getting Ready For Boost: Part 2
| Joe and Dave from RPM Motorsports put in a lot of hours sorting out the wiring and getting the secondhand Pettit Racing Stage 2 supercharger kit installed. This kit is based on a Lysholm twin-screw supercharger and also includes a water-to-air intercooler that’s cleverly integrated with the Pettit upper intake manifold. Since our motor is built with stronger seals, we upgraded to the Stage 3 pulley, good for 12 psi of boost pressure.
We chose Injector Dynamics injectors for a variety of reasons, not least of which is the company's commitment to providing customers with a ton of data and technical information, including dead time compensation values across the entire pressure and voltage range of the injector. This allows you or your ECU tuner to compensate for changing voltage and atmospheric conditions and in the process ensure a stable air/fuel ratio.
We also value the fact that ID tests its injectors across the entire pulse-width range, not just in a wide-open or static position. In fact, Injector Dynamics was the first to introduce this type of "dynamic characterization" (testing injectors in real-world conditions that factor in heat and fuel type as well as the constantly changing fuel delivery needs of an engine operating across its entire rpm range) to the aftermarket/racing industry. The benefits of injectors that are carefully matched based on their dynamic flow include vastly improved cylinder-to-cylinder consistency, even at very low pulse widths, which translates to improved driveability and response at idle, while cruising, and while ripping to redline.
| The guys at Black Halo Racing—who provided their ignition system, drop-in fuel pump kit, and reinforced clutch pedal back when we first began sorting out the RX-8—were kind enough to send us some longer ignition wires. We needed to relocate the coils because the supercharger now lives where the coils normally mount. BHR also sent us its recently released Performance Motor Mounts, designed to replace the failure- prone OE mounts. Constructed from anodized black aluminum and laser-etched with the BHR logo, these mounts come fully assembled and are available with urethane bushings in slightly firmer than stock (red), noticeably firmer than stock and intended for aggressive street and track use (orange), or the track-only black bushings we opted for. BHR wasn’t lying—the black bushings are virtually like hard-mounting the engine. So as much as we like the reduced engine movement, we may wuss out and dial back the NVH with the orange bushings.
In this case, we know the original owner of the supercharger kit, so we were confident it was still in good working condition. Still, you can see the intercooler was allowed to rub on a strut tower brace, but we'll pretty that up later with some powdercoating, along with some other cleanup work the engine bay obviously needs.
With Joe Ferguson and Dave Sibbitt from RPM Motorsports handling the installation for us, we handed them a bin full of used parts and said, "Just make it work." Plus, we handed them a brand-new set of Black Halo Racing engine mounts and longer ignition wires, four 1,000cc Injector Dynamics fuel injectors, a fresh AEM dryflow air filter, and a bunch of other cool parts you'll see next issue.
It may feel like we're dragging out this installation, but trust me, it's been a bit of an ordeal getting it all sorted out and up and running. We just hope all the effort will pay off with some serious horsepower, not to mention the unique soundtrack of a supercharger's whine stacked on top of the high-rpm scream of a rotary engine.
Special thanks to Joe Ferguson (joe_ferg@live.com) and RPM Motorsports.
| The guys at Black Halo Racing—who provided their ignition system, drop-in fuel pump kit, and reinforced clutch pedal back when we first began sorting out the RX-8—were kind enough to send us some longer ignition wires. We needed to relocate the coils because the supercharger now lives where the coils normally mount. BHR also sent us its recently released Performance Motor Mounts, designed to replace the failure- prone OE mounts. Constructed from anodized black aluminum and laser-etched with the BHR logo, these mounts come fully assembled and are available with urethane bushings in slightly firmer than stock (red), noticeably firmer than stock and intended for aggressive street and track use (orange), or the track-only black bushings we opted for. BHR wasn’t lying—the black bushings are virtually like hard-mounting the engine. So as much as we like the reduced engine movement, we may wuss out and dial back the NVH with the orange bushings.
| Project RX-8 - Getting Ready For Boost: Part 2
| Since the original air filter that came with the Mazdaspeed cold air intake had taken a severe beating over the last four or five years of street and track use, we ordered a replacement from AEM. We want our supercharged Renesis to get as much fresh air as possible, and this low-restriction, oil-free Dryflow filter uses a three-dimensional filtering media that enhances airflow capabilities. It’s also extremely durable, thanks to the screen wire structure that houses the filtering media.
| One of the jobs we’ll cover next time is a proper dual catch can setup, because as much as we love beer, these temporary catch cans may not be DOT approved.