We get a lot of emails from readers asking for help with their project cars, and as much as we'd like to make it rain free parts and 24-hour tech support for everyone, for a variety of reasons, there's just no way we could ever make that happen (you know, because we're not billionaire playboys with a staff of race mechanics at our disposal).
But for Ken Wagan, a longtime friend, fellow racer, and now contributor to this glorious publication, the dream of a magazine-supported project car, or at least an engine build, is a reality. Maybe it's because Ken's an ER nurse and he saved my life (or at least kept my health records private), or perhaps it's because we're suckers for a badass-looking FD RX-7 in need of a serious power boost.
Not that Ken's FD is slow-he won the CSCS Super Street RWD Class Championship in 2012 (equivalent to the Limited class under the Super Lap Battle rules) while running the stock twin-turbo engine. But with the competition heating up, we knew he'd need an engine build and single turbo conversion if he had any chance of staying at the front of the pack.
Hi. My name is Ken and I am addicted to rotaries. If you know anything about these Flaming Doritos combustion engines, then you'll understand the importance of beefing up the engine internals before throwing a lot of boost, fuel, and spark at them. To that end, we tore down my spare 13B-REW motor, and after close inspection of the housings, rotors, irons, and rotating assembly by Joe Ferguson at RPM Motorsports (who also built the Renesis engine in Project RX-8) and giving them a clean bill of health, we sent the housings off to Goopy Performance, where they were refurbished. This process removes a tiny bit of material from the housings and gives them a fresh, smooth surface for the 2mm two-piece Goopy seals to mate with.
While the housings were getting reconditioned, we sent out the rotating assembly (rotors, seals, eccentric shaft, rear counterweight, flywheel, and clutch) for balancing. This will provide some added reliability by decreasing stress on the bearings caused by vibrations at high rpm. We also employed Mazdaspeed competition rotor bearings with 0.0005 inch of extra clearance over OE spec and deeper oiling grooves to make sure the rotating assembly is well lubricated during racing conditions. Joe and I also attacked the intake and exhaust ports using Pineapple Racing's medium street porting templates before Joe assembled the short-block using all-new OE Mazda gaskets and seals.
With the engine ready for more boost, we turned to Turbonetics for our turbocharger needs. Turbonetics has been in the forced-induction business since 1978, catering to industrial, military, and motorsports customers. Aside from turbochargers, the company also develops products for heat exchangers and pressure control components and supplies several OE automotive manufacturers. Best of all, all of Turbonetics' products are manufactured in its state-of-the-art facility in Moorpark, California.
For this project we wanted a turbo with quick response and the ability to deliver the goods through a broad powerband. We spoke with Reggie Wynn from Turbonetics, and he suggested its new GT-K 700-series turbocharger with the new HPC billet aluminum compressor wheel. As we learned, the GT-K series has been further developed from the first series of the GT-K turbochargers, the main difference being its use of forged billet wheels with improved compressor vane design.
According to Reggie, "The compressor wheels that are made from forged billet are more robust and able to withstand extreme pressures, and the new blade design increases airflow without increased rotating mass like the standard compressor wheels. This decreases stress on the center housing rotating assembly (CHRA) bearings." Sounds like a win-win situation to us, especially since the GT-K series comes standard with ceramic ball-bearing CHRA for increased response and tolerance to high temperature shutdowns compared with conventional journal bearings, and we all know boosted rotaries make more heat than a Japanese nuclear powerplant (too soon?).
With the turbocharger sorted out, we approached Full-Race for one of its legendary twin-scroll exhaust manifolds. Part of the appeal of the 13B-REW manifold is that it's righthand-drive (RHD) compatible, which is essential for this project given our FD's JDM origin. It's also reassuring to know that Full-Race has been in the game since 2002, with initial efforts in drag racing Hondas having been expanded into a wide range of high-performance vehicles used for everything from blitzing the canyons to attacking time around a racetrack.
The manifold is beautifully crafted from 8ga stainless steel, a thick-walled material strong enough to support our turbocharger without needing any extra bracing, plus we'll never have to worry about it cracking even with the serious EGTs our rotary will throw at it. The flanges are made from the same heavy-duty material to resist warping, and it also features smooth runner radius bends that decrease exhaust gas turbulence and promote efficient flow to the exhaust side of the turbocharger. A thermal coating is available as an option as well, though we chose to leave ours uncoated because we have some other tricks we'll be trying out as far as heat management goes.
But before we get to that, in the next issue, look for us to give the intake side of the engine some attention, as well as sorting out a few other key details. Forcing large amounts of charged air into any engine requires that a serious amount of go-juice be forced in as well, so you can also look forward to a comprehensive fuel system overhaul and a much more sophisticated approach to fuel control. In the end, we think we've cooked up a solid recipe for baking extra spicy Doritos horsepower, but only time (and proper tuning) will tell.