The gas price here has been rising up
Gas price past 17 years
Above graph was originally here with the original size.
I have asked the site owner to use it and got a permission. He owns a VW
Golf 3 GTI -16V for many years and I just respect him keeping the car that
long and the way he notes what he does. You can see them here.
Since the gas price is getting higher and to improve the gas mileage means
to help your life. I must say that the current O2 sensor system is a rough
emission control system. It gives too much gas to the cylinders and burns
the remains at the catalytic converter. I am currently doing an experiment to
improve it.
There is a gadget called an O2 sensor enhancer in the European market.
Those are widely used there. The purpose is to use the natural gas instead
of petroleum. Without enhancement, the gas mileage is not very good. I got
some idea from them and decided to do an experiment.
the best matching and the best performance for my cars. Those in the
European market are designed to use for different types of natural gas cars
and you can not expect the best performance on your particular gasoline vehicle. Also it is not easy to obtain here in Japan.
One of my cars which has an engine of 4L eats gas a lot and the higher the
price, the harder is my life to survive. The another car I have does not eat a
lot but it is a Kei - Honda Life which only has an engine of 660cc and the less
power is not OK to run highways but it is small sized and convenient to use
in the city. Sometimes it runs almost 15km/L and the gas mileage is not bad
but I am doing an experiment how much will it be improved using the home
made O2 enhancer.
The 4L car has four O2 sensors and I thought that the experiment would not be
very simple. So I started my experiment to enhance the Honda Life's O2
sensor because it has only one O2 sensor. The way I have tried first was to
add an operational amplifier. The output signal from the O2 sensor varies
between 0V – 0.9V and I tried to give it a bias voltage and some gain
limiting the highest voltage 0.9V.
The circuit using an OP amp was effective but I happened to tried a simple
and an easy way to get a good result with the passive circuit below. The low
voltage regulator can be adjusted between 1.3V to 2.8V.
It consists of a variable voltage regulator and a series resistor with a voltage
limiter. This aims to give some additional voltage to the ECU. When the voltage
from the O2 sensor is low like 0.1V, the circuit gives additional 0.2V and the
ECU considers the total voltage is 0.3V. On the other hand, when the O2
sensor is generating high like 0.9V, the circuit gives only 0.1V. Below is the
graph what I am intending to try. The black line is the original O2 sensor
voltage and the red is the target.
Target voltage graph
The lucky thing is that the impedance of the O2 sensor varies. For examples
when there is no O2 it does not generate any voltage and the impedance is
very high. When there is enough O2, the voltage is high and the impedance is
low. This can be compensated by a simple circuit shown above. Adjusting the
regulator voltage and the series resistance to the O2 sensor, you can obtain
the line shown at the graph. Actually I set the circuit that way and the result I
obtained was 16.56km/L.
The result
With this result, I must try the next step for the bigger cars.
