I was looking at the specs for each year of the first gens. The EPA gas mileage for a 12A jumps from 17/26 in 1980 to 21/30 in 1981. Carburation, Compression, HP, Torque, Gear Ratios and Final Drive all remain the same.

What caused the bump? Was it real or imagined? Did Mazda pay off someone in the EPA?

Herb

 

Thermal reactor = worse gas mileage. Cats = better mileage. Thermal reactors required a rich mixture to keep the fire lit. Cats don't. Simple, really.

 

Has anyone had luck switching a 79 over to a cat?

Herb

 

there is an SAE paper about this, actually.

Mazda improved the apex seals, moved the spark plugs closer to the combustion chamber, revised the spark plugs, and redid the air injection nozzles.

the net effect is that the engine could be run leaner, which let them put a catalytic converter on, instead of the thermal reactor.

so most of us think that the thermal reactor needs a richer mixture, but Mazda's paper states it the opposite way.

if you have an SA, you can use the 81+ spark plugs, and the 81+ apex seals are the only kind Mazda sells anymore, although all the aftermarket ones are the older type.

racing beat used to actually sell the leaner jets for improved mileage, they must have a list somewhere