How I made my Geo Metro get 66.5 miles per gallon
The car is just like from the factory except;
Economy grind camshaft from 3Tech/Mike Cove
Cylinder head modifications shown here plus exhaust ports
Fuel system modifications;
I made a heat exchanger from hardware store parts to heat the gasoline
from the engine coolant.
It's located first thing in the heater core coolant line so it gets
warm before anything else does when warming up the car.
I installed an EFIE (it adds an adjustable floating voltage to the
output from the oxygen sensor making the car run a leaner air/fuel
Air intake modifications;
I removed most of the housing and plastic tubing of the original air intake path from the front fender.
I installed a K&N air filter made for the car.
I removed the bridge in the throttle body for greater airflow.
I threaded the intake ports in the head.
I polished the exhaust ports in the head. I installed a racing header
from Suzuki Racing Development. I installed an aftermarket replacement
catalytic convertor. I replaced the factory exhaust pipe and muffler
with Thrush glasspack mufflers and shortened the exhaust making it exit
in front the rear wheel.
I replaced the factory spark wires with Magnecor wires. I replaced the
spark plugs with Halo spark plugs.
I replaced the instrument cluster with one from a Metro convertable
which has the tachometer. I adjusted the miles readout to be the same
as the car had at the time of replacement. I added a vacuum gauge.
I covered the vents in the front bumper with lawn edging except where
the radiator goes.
I recently drove the car 55 mph on the Interstate during a
windless, sunny day till it was 648 miles since the previous refueling.
When I filled up with gas it only took 9.75 gallons.