Grassroots Motorsports
Issue link: http://grassrootsmotorsports.epubxp.com/i/501675
Grassroots Motorsports 107 MEET THE K MIATA, PERHAPS THE BEST ENGINE IN THE BEST CHASSIS When Honda's K20A2 engine hit the market with the 2002 Acura RSX-S, it set a new record for power-per-liter in a mass- produced production car. Its 240 horsepower from just 2.0 liters, all without any forced induction or even direct injection, set the bar high. The new heads flowed like rivers, and variable valve timing as well as sophisticated electronic engine management yielded the fexibility to run lofty compression ratios. Yet this engine could still idle smoothly and putt around town like a grocery getter. The motorsports aftermarket quickly recognized the potential of these K-series engines and upped the ante even more with simple re-tunes and bolt-ons. Suddenly that inline-four could make another 50 horsepower. Honda then gave us a 2.4- liter version of this lightweight, aluminum engine. Along with well-developed aftermarket internal parts, it could achieve a reliable 300 horsepower and 9000 rpm–all on pump fuel. David Calzada is an avid track- day enthusiast who swapped a K-series engine into his Acura Integra in the quest for more speed. It was a dependable and satisfying combination until about a year ago, when he did a few lapping sessions in a friend's Miata. Sure, the Miata didn't make as much power, but that chassis lured him in: On the way home David hatched the idea of blend- ing the best engine with the best chassis. He convinced Adam Jabaay, another friend who is skilled at fabrication, to join him on this quest and a prototype was put together in record time. Proudly chronicling his efforts on a variety of forums netted a lot of interest from folks looking to duplicate the result, so David decided to produce a kit that would clear the major hurdles for these enthusiasts. K Miata was born. The basic package includes an adapter plate and custom flywheel to mate the Honda K-series engine to the Miata transmission. A custom oil pan and pump, along with a replace- ment tubular front subframe, drops the Honda engine into the chassis. An adapter harness makes wiring simpler, while a variety of intake manifold and exhaust solutions are being developed to support a range of power levels. Figure $3750 for the complete conversion kit minus the exhaust header and manifold adaptor. Despite making well in excess of twice the power, the all-alumi- num Honda engine weighs the same as the iron-block Mazda lump, so handling and weight balance are preserved. The frst group buy sold out quickly, and a second run of kits is now in the works. SOURCE K Miata kmiata.com (877) 587-4255 opment. The list never gets completed, but is instead prioritized into sections of "must haves," "known improvements" and "research ideas." Once the "must haves" are ticked off, we can start enjoy- ing the car. Further, and even more important, the list can evolve based on frst-hand experience. Iteration is a much stronger method of development than planning everything out ahead of time. As the saying goes, "You don't even know what you don't know." Our CRX project actually started with a Civic hatchback chassis that we threw a basic suspension and wheel-and-tire package onto based on our autocross experience. The only "must-have" was more motor, so when that was complete we got on track. "More go" quickly led to "more stop" and brakes were upgraded. As speed increased, safety became more of a factor, so a roll bar and race seat and har- ness were added. These had always been on the "improvements" list, but the specifcs became clearer as we ran the car on track. The chassis was later upgraded to a CRX for lighter weight and better aero, the engine got bigger and faster, a splitter and wing were added, and we installed better gearing, full roll cage and so on. Having a running car throughout allowed us to test new technology–especially tires– as it came online. We are following the same course of action with the Miata. We started with a running car with a known history, ordered the engine swap kit, and have now swapped in one of our spare K24 powerplants. Once it's running, we will again draw upon our autocross experience for baseline suspension as well as wheels and tires. However, since the Miata is open top, we can't really start to push it hard on track without some sort of rollover pro- tection. While an off-the-shelf roll bar is the easy button there, with a car this fast we are going to jump straight to a full cage. Besides, cage installation is a fairly intrusive process that also has an impact on suspension due to added chassis rigid- ity and weight, so we might as well go custom. After that we'll add brakes, aero and all the million other little things we hadn't planned for.