See Figure 1
On RX-7 models, except those sold in California, a sub-zero starting assist fluid reservoir is located to the right of the engine near the firewall. When the outside temperature is below 0°F (-18°C), a thermoswitch operates a small electric pump in the reservoir which injects a pre-measured squirt of 90% aluminum-compatible antifreeze and 10% water into the carburetor throttle bore or intake manifold while the starter is being cranked. This keeps the fuel from icing and promotes better starting.
Use only ethylene glycol (or other aluminum-compatible antifreeze) and water.
Check the fluid level in the sub-zero starter assist reservoir every two weeks in cold weather. If necessary, unscrew the reservoir cap and refill the reservoir with a 90/10% mixture of ethylene glycol or other suitable antifreeze and water.