M-TUNED

Coolant Reroute System

 90-05 Mazda Miata, Roadster, Eunos, MX5

Download Instructions  Engine does not need to be removed to install reroute!

System features

• Allows use of EGR system
• Fits any induction or ignition system
• Extra pre-tapped 1/8 npt port for auxiliary temp sensors or turbo feed
• Optional internal steel coil reinforcement for cut-to-fit main hose can be removed
• High strength CNC 6061 T6 aluminum components
• Clear anodized for corrosion resistance
• Simple, bolt-in installation

Benefits of a coolant reroute for the B series Mazda Miata engine

• Lower and more stable coolant temps - factory ECU runs in standard temp map (not hot enriched) for more power
• Fans will only turn on at idle, cycling on and off on the warm days - less alternator load means more power
• Cooler CHT's raise detonation threshold so timing can be advanced - more power
• Much faster warm up
• On most mildly boosted engines a 55mm radiator is no longer needed, a lighter 37mm is plenty
• Neater appearance at front of motor - front outlet can be removed entirely if you wish

Why the Miata has a built in problem

 The Miata's engine was designed for a front wheel drive car then turned 90* lengthwise in the Miata. To make it fit, Mazda's engineers moved the coolant outlet from the rear of the head where it belongs, to the front of the head. As a result of this backwards flow, only a small portion of the total coolant water flow goes around the 4th cylinder at the rear of the head so it runs hotter that the front of the engine. In addition, not all of the heat the engine generates is being fed to the radiator so a much larger radiator must be used even for mildly tuned engines. Even a bone stock first gen Miata will kick on its cooling fans in steady state hot weather highway cruising with the A/C. As soon as you hit the track or add power the OEM routing becomes a major problem no matter how big the radiator or how much venting/ducting you have.

The M-Tuned system returns the coolant flow path to the correct configuration used before the Miata came along. In addition, the kit retains full functioning of the original system including correct sensor locations for the stock ECU, heater, bypass circuit operation for proper warm-up and cold over-pressure protection.

Attention 01-05 owners: Mazda changed the head gasket design for these years to restrict flow to the #1 cylinder. Not a real fix but it does allow the 01-05 to run a tiny bit cooler than the previous years. Because of this change however, the reroute could cause uneven cylinder head temps, even while improving overall cooling. For this reason, M-Tuned recommends using the 94-00 head gasket (BP26-10-271)if installing the reroute on an 01-05 USDM Miata.

Kit includes everything you need to complete the reroute conversion

• Reroute adapter
• Remote Thermostat housing
• 5/8" hose barb for heater
• 190º thermostat
• Front outlet block off plate- 1.6 has spare 1/8" npt outlet, 1.8 has 2x spare 1/8" npt ports
• 36" coil reinforced silicone transfer hose
• Plugs for spare 1/8" npt ports
• All clamps, fasteners, seals and gaskets needed for installation