Project Time Attack Part 3 - 1995 Mazda Miata

So what does all this net us? 259wheel-hp and 243ft/lbs of torque at a low break in boost of 7psi. The real story here, though, is the power under the curve. From 3400rpm to redline, we have full boost. Boost response is not like our last Miata--that felt like we were driving a naturally aspirated car. But it's direct enough to make controlling the car on the throttle perfectly possible.

Hot and Fast Unfortunately, the Otto cycle isn't the most efficient power generation process--most of the energy ends up as wasted heat. Now that Project Time Attack will be making three times its stock power, it will probably eat three times as much gas and make even more heat. The stock Miata engine already does a piss-poor job of heat management, so we have an uphill battle to control the monster we've created.

The same lineage that makes this engine take so well to boost also provides its Achilles heel. As a transversely mounted Mazda 323 GTX turbo engine, coolant was routed in one side and out the other. But in the longitudinal configuration for the Miata, Mazda determined the cleanest way to route the coolant was in through the water pump up front and out of the front of the head. Everything on the firewall side of the engine just cooks, since there is minimal circulation.

The best remedy is to plug the original front coolant exit, uncap the heater supply fitting on the back of the head and route the coolant beneath the intake manifold. We did this with a custom pipe fitting (fabricated to hold the stock thermostat), going directly into a newly designed three-core radiator sourced from AWR Racing and Ron Davis Racing. According to AWR, the new radiator core is so massive and efficient that stock fans provide enough flow to control the heat at steady-state loads.

Much of the heat generated by a turbo is carried off by engine oil. While the factory cooling system uses an oil-to-coolant sandwich plate at the oil filter, it's nowhere near capable of dissipating the added thermal load, especially since the coolant is also sucking up heat from the turbo. We ordered a 6x11x2-inch, 18-row core from Mocal along with a Mocal sandwich plate with -10AN fittings and stainless steel lines, since we didn't feel existing Miata oil cooler kits had large enough cores or fittings to avoid unnecessary pressure drops. We placed this core in front of the passenger-side front wheel-well, behind the vents in the Racing Beat Type-2 bumper.

The added cooling and additional 25-percent oil capacity should get the car through hot track days. Larger lines might contribute to a slight pressure drop, so the oil pump has been shimmed with a 1mm spacer on the spring, as a precaution. We're seeing oil pressure of 48psi at idle--right where it should be.

All this thermal transfer efficiency doesn't mean crap if you can't supply air to carry the heat away. Unfortunately, the path of least resistance is around the radiator rather than through it. This is why duct-fed heat exchangers are key, especially for a car that doesn't have to sit in traffic and idle. We just didn't have a chance to finish it at the time of writing. In the meantime, the APR Performance front splitter does give a mild advantage by splitting the oncoming flow and generating a high-pressure region right above it and into the bumper opening.

We also found some radiating heat issues from the turbo at a recent track test. Even with fresh brake fluid in the system, the brake pedal would get soft under mild braking, which meant the brake booster and hydraulic assembly was too close to the turbo and manifold. Boostlogic sent us an asbestos heat blanket to cover the exhaust side of the turbo, which is effective.

Dumb turbo, smart computer As the saying goes, boost is only good when you can manage it. Our previous Project Miata had run two different ECUs. The Link ECU, while superbly supported by Flyin' Miata, was limited in processing power and the ability to provide fine tuning for safe on-the-edge power. We switched to the AEM EMS, which, with its more modern tuning parameters and flexibility, has become a standard in other car communities. Too bad it hasn't been widely adopted by the hairdresser racing community and so has limited support.

As good fortune would have it, there is now an option that combines the strong points from both our previous choices. The Hydra Nemesis ECU is gaining traction in multiple markets (including Subaru and Honda) for its sequential injector and spark control, and multiple features such as water injection, traction, anti-lag, boost control and staged injectors. It also helps that Flyin' Miata is now a supplier of this plug-and-play ECU for Miatas of any vintage, so the support and community for this ECU in this platform could soon be the standard. This is good because while we like the cutting edge, we also appreciate driving our cars more than blowing them up.

Installing Nemesis is straightforward. An adapter harness allows it to plug into the factory wiring with no modification. With a MAP sensor built into its casing, all we had to do was run a vacuum line through the firewall and take out the Mass Air Flow meter. Optional hardware--such as a two-wire knock sensor, intake air temp sensor, and five-wire wideband oxygen sensor--is connected into the pre-made harness adapter. Flyin' Miata also preloaded base maps for our 750cc/min. injectors on this particular engine configuration. The only set-ups required are TPS and wideband oxygen calibrations, which takes five minutes. This is as plug-and-play as it gets. Once the maps are in the ballpark values, the ECU's self-learn fine-tuning takes over and sorts the rest out.

We also ditched our multitude of gauges. It's good to see what's going on, but eyes should be on the track, not the dash. So we've installed an AIM Sports MXL dash to simplify monitoring, not to mention the nightmare wiring of conventional gauges. AIM Sports main market is monitoring and data acquisition equipment for race cars and karts. The MXL dash gives all essential data in one centralized location, in a completely customizable display with warning and shift lights. The best part is that data is pulled directly from the Hydra ECU using a serial cable. AIM Sports has spent a lot of time developing serial interfaces for many popular aftermarket computers such as the AEM, Nemesis, and Motec family, as well as many factory control units. We only had to run three harnesses to the engine bay for aftermarket oil pressure, fuel pressure, and oil temperature senders. Each one is powered and managed by the AIM display, which shows up to six selectable parameters with configurable warning lights for each.

While the Hydra Nemesis will data-log engine activity, it requires a laptop--ruling out the option of logging hot laps. The MXL makes up for this by having 128KB of memory constantly logging all inputs. All this is combined with telemetry data, so we can figure out what the car is doing under track conditions and ultimately make the car faster. With the optional GPS plug-and-play sensor, the MXL can data-log a vehicle's position on-track and display on-the-fly predictive lap times on the dash. This is a serious competitive advantage during time attacks.

Project Time Attack has the main ingredients for being fast. All we have to do is spend some hours at the track, shaking systems down and finding the right balance of grip and boost. It's clear the car is faster even with less than maximum power being applied. We may consider using a scramble boost solenoid to allow high boost for the straights with a more manageable power level in the turns. But for now, we'll focus on getting the suspension, chassis, tire choice, and power output to work together. Next stop: SoCal time attack events.

Other Installments:

Project Time Attack Part 1

Project Time Attack Part 2

Project Time Attack Part 3