- Replaced water pump, timing belt, hoses, and spark plugs
- Installed remote lock/unlock system
- Replaced stock seats with racing bucket seats
- Installed an aftermarket circuit-spec exhaust
- Installed a roll cage
- New wheels and tires
- LED headlight bulbs
Project Car: 1991 Mazda Miata
In October of 2020, I bought a barely running, 30-year-old Mazda Miata with a bad engine, multiple leaks, and dozens of other problems I would discover throughout the process of restoring it. Knowing almost nothing about cars, I dove in head-first. Over the span of the last few years, I have taken apart and reassembled almost every component of this car and developed a thorough understanding of what it takes to build a reliable, high-performing vehicle.
Basic Upgrades
Engine Replacement
- Original engine had an oil-burning issue due to a malfunctioning PCV valve, causing it to run low on oil and spin a rod bearing
- New engine was a low-mileage engine imported from Japan
- This engine was from an automatic car, so there were some slight difference compared to the original
- Lower compression ratio 9.0:1 instead of 9.4:1
- Different exhaust and intake camshafts, resulting in slightly less horsepower but more low-end torque
- The throttle body on the automatic engine uses a variable throttle position sensor, an improvement over the original two-position throttle position sensor
- Replacing the engine required pulling the engine and transmission together and transferring all the accessories from the original engine onto the new one
- Reused original transmission, alternator, power steering pump, flywheel, clutch, belts, water pump, exhaust manifold, valve cover, and engine mounts
Performance Upgrades and Tuning
Coolant reroute
- The car comes stock with a thermodynamically inefficient coolant system, where coolant both enters and exits the engine at the front, causing the rear cylinders to overheat
- I relocated the thermostat to the rear of the engine and ran the upper radiator hose to it, so now coolant enters at the back and exits at the front, lowering coolant temps
Braking system upgrades
- Replaced all rotors and brake pads
- Replaced rear calipers, which were malfunctioning due to rusted slider pins
- Upgraded to stainless steel braided brake lines, increasing braking power
- Installed a brake master cylinder brace to reduce firewall flex and increase braking power
Transmission upgrades
- New flyhweel, 6-puck ACT clutch, and heavy duty pressure plate
- Replaced all transmission seals and gaskets
- Installed short shifter and a weighted shift knob for faster gear changes
ECU and tuning
- Soldered and assembled a custom ECU based around a V2.2 Microsquirt Module
- Tuned the engine myself by adjusting ignition and fuel tables
- Installed a wideband air-fuel ratio sensor, a manifold air pressure sensor, and a shift light
- The new ECU allowed me to switch from a mass air flow system to a speed density system, which required the installation of an intake air temperature sensor and the fabrication of a custom intake to replace the stock airbox
- Using the variable throttle position sensor from the automatic engine's throttle body, I set up TPSdot acceleration enrichment, which is much more responsive than MAPdot
- Tuned idle using closed-loop PID
- Replaced stock 205cc fuel injectors with 420cc fuel injectors from a Mazda RX8
- Set up launch control and flat-foot shifting
