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EFIE
versus Electronic Control Circuit
During
the first few years of Hydrogen Boost history we used the EFIE (electronic
fuel injector enhancer) device (oxygen sensor voltage offset device) developed
by Eagle Research, to lean out the air/fuel ratio of the fuel injected
vehicles we worked with. When we
worked on a single wire oxygen sensor it was
easy, and even with a three wire oxygen sensor it was okay, but once we
saw four and five wire oxygen sensors we had trouble identifying the
signal wire, and even determining if we had a lambda sensor or the newer
wide band oxygen sensor (air fuel ratio sensor). Continuing to use the EFIE was just too
difficult and sometimes impossible.
Because of this we researched and developed our own circuit that
so far has been usable on every vehicle with electronic fuel
injection.
When we got around to emissions testing with a
five gas emissions gas analyzer, we discovered other problems with the
EFIE device. To explain the
problems with the EFIE we must first review the web page detailing
Emissions Analysis with Hydrogen Boost at http://www.hydrogen-boost.com/August%202006.html where we see the graph below.
Notice the elevated NOx emissions (blue curve) caused by fuel ratios between 15:1 and 17:1.
This is unacceptable pollution caused by running the engine at a
slightly lean fuel ratio. It is
only when you get to an ultra-lean fuel ratio of 18:1 and beyond, that
the NOx emissions are acceptably low. The reason for this is that the
temperature of combustion is lower with an ultra-lean mixture. This lower combustion temperature is
insufficient to cause the excess oxygen in the combustion air in the
combustion chamber to react with the nitrogen in the that
same combustion air.
What has any of this got to do with the choice of
electronic control circuits? Well,
if an EFIE is used to lean out the mixture, the ECU (engine control unit)
can only lean the mixture to somewhere between 16:1 and 17:1 before the ECU
goes into a perpetual too-rich signal that causes the ECU to continue to
add negative fuel trim until the engine stalls. There is no way to use the EFIE or
other versions of the oxygen sensor voltage offset circuit, to run at
18:1 air to fuel ratio or leaner for more than a few seconds. That means that any use of the EFIE
device will only elevate the NOx emissions. This is unacceptable.
What other problems are there for the EFIE device? It only works on Lambda sensors, oxygen
sensors that have a signal voltage between zero and one volt, with high
voltage indicating too-rich, and low voltage means too-lean. It does not work on wide band oxygen
sensors (sometimes called air-fuel ratio sensors) that have a higher
voltage and opposite indications (low voltage meaning rich and high
voltage meaning lean).
The simple circuit developed by Hydrogen Boost and
copied by many competitors works on every vehicle with fuel injection and
is much more responsive that the EFIE.
When you turn the knob of our circuit you feel the change in
engine performance immediately, not second to minutes later like with the
EFIE. Because of this immediate response
you can tune your mixture to the feel of the engine response.
There
have been a number of ways introduced to address the common complaint
that unplugging the oxygen sensor causes a “check engine” light to
illuminate. We instruct our
customers to simply unplug the oxygen sensor to be able to change the
air/fuel ratio. Others suggest
wrapping aluminum foil around the oxygen (lambda) sensor, and others have
suggested installing a spacer behind the sensor to get it out of the
exhaust flow and make it ineffective.
Some even suggest taking it right out and leave it dangling
there. These suggestions may work
but a simple unplugging of the sensor is our choice. It doesn’t matter which method you use
to disable the oxygen sensor, they are all a violation of EPA rules
against “tampering with the emissions control system of the vehicle.” EPA forbids the use of a cleaner,
ultra-lean air-fuel ratio, that in our case also happens to save fuel,
and reduces all exhaust emissions.
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