1.8-Liter DOHC Turbocharged/Intercooled 16-Valve 4-Cylinder Engine
There are many fine engines in the Mazda lineup, but for the core of the MAZDASPEED powerplant there was no need to look any further than the MAZDASPEED MX-5 Miata's own 1.8 liter DOHC inline-4. Though lightweight with a cast aluminum alloy head, the engine has the durability of an iron block. Lightweight components are used throughout - even the oil dipstick has a special lightweight design unique to this engine.
This engine architecture has been with Miata from its very beginning (originally with 1.6 liters), and its smooth, responsive, high-rev-loving character has been loved and praised by owners, reviewers and racers alike throughout its history. Not just a joy to drive, the engine is also a joy to own, as its rock-solid reliability rewrote the book on what it means to own and maintain a sports car.

The combination of high performance and bulletproof reliability is certainly a key factor in the Miata's winning 10 SCCA Showroom Stock National Championships in its 15 years, not to mention countless local wins in Autocross and Solo events. Most of these competitors are, after all, weekend and amateur racers who can't afford periodic engine failure and depend on the reliability of the Miata's 1.8-liter engine to keep their passion affordable.
IHI Turbocharger with Denso Intercooler

The IHI turbocharger reaches a maximum of 8.5 psig boost. Power is further enhanced as the Denso tube-fin air-to-air intercooler, mounted just ahead of the radiator, cools incoming air, increasing its density for more effective combustion. Together with the other modifications, the forced air system bumps the horsepower to 178 @ 6000 rpm, for a 25 percent increase over the normally aspirated engine. That peak also comes at 1,000 fewer rpm and leaves another 500 rpm to go before redline.

The bigger news is the increase in torque, which at its peak is 33 percent higher than on the standard MX-5 Miata. And the torque is more abundant across the rev range. For existing Miata owners who equate increased gas pedal pressure with a downshift, this will be the biggest revelation in driving the MAZDASPEED MX-5 Miata, as the engine is ready to respond to right foot movement with a kick to the rear end at nearly all points across the tach. The level of turbo boost has been calibrated to render turbo lab basically imperceptible.

Full High-Performance Integration

MAZDASPEED engineers went far beyond just bolting on the turbocharger and intercooler and rushing off to the dyno to chart the results. The goal was to have the same perfectly balanced and integrated powertrain system Miatas have always enjoyed, with no single aspect overwhelming anything else.

This balanced, comprehensive approach has another advantage, as the MAZDASPEED MX-5 Miata enjoys the same warranty coverage as every other Mazda. To achieve this balance and integration, further modifications to the MAZDASPEED MX-5 powertrain include:

  • Reshaped pistons and head. The reshaping makes the most of the increased induction flow rate and keeps the effective compression ratio from causing predestination (knocking) by lowering the non-boost compression ratio from 10.0:1 to 9.5:1. The effective compression ratio is still such that 91 octane is the recommended minimum fuel.
  • Increased core radiator volume to compensate for the increased power and heat.
  • Removal of the variable valve system, which is rendered superfluous by the forced induction characteristics and increased torque of the turbocharger.
  • Stiffer bushings for engine and differential mounts to control increased engine block torque motion.
  • Beefier 25 mm axle shafts from the standard limited-slip differential.
Of course, all these refinements and extra power would almost go to waste without a suitably robust exhaust note. So the exhaust system was retuned to filter out unwanted turbo-derived noise while continuing to deliver the rich sports car notes that have so allowed so many MX-5 Miata drivers to shift by ear.
6-Speed Manual Transmission

Naturally, the MAZDASPEED MX-5 Miata would only be available with Mazda's quickest and most driver-involving transmission. Combined with the engine's increased torque, the driver always has about three ratios to choose from to suit their needs of the moment. The Miata shift linkage, which has long been the standard by which all others are judged, is refined even further. The clutch and pressure plates are strengthened, and a shot-peened treatment is given to the gears for increased durability.
Power Plant Frame

The Power Plant Frame is possibly the MAZDASPEED MX-5 Miata's most original yet unseen performance feature. It was invented for the Miata and has also been put into use for the Mazda RX-8. Although unchanged from the standard Miata architecture, the increased torque of the MAZDASPEED engine makes this feature even more significant.
The frame encloses the engine, transmission and differential into a rigid unit. That unit provides structural integrity throughout the entire drivetrain, reducing the twisting and wasted energy that occurs when the drivetrain components are bolted separately to the chassis. The result of this engineering is that every press of the accelerator results in quick and direct power transfer to wheels on the road.