How Jonny Energy's E85 Conversion Kits work
What does stoichiometry mean?
The stoichiometry of a fuel refers to the coefficients in the chemical reaction
equation and is expressed as a ratio of the mass of air to the mass of fuel. For
pure octane, the ratio is about 14.7:1, but do you know anyone who burns pure
octane in their car? Gasoline is a mixture of many different compounds, most of
which are usually not octane but various alkelines. Each of these compounds will
have a different stoichiometric ratio and the exact chemical makeup of gasoline
can vary quite a lot from one tankful to the next. The air available can, and does,
change as we drive to different altitudes, the temperature changes, and even from
moment to moment due to wind pressure. It could be terribly complex to compute
the exact mixture needed for each tank of fuel, but a modern ECM will use a fuel
trim system to make the mixture more lean (negative trim) or more rich (positive
trim) to compensate for different operating conditions.
Do Flex-Fuel vehicles trim fuel differently?
The stoichiometry of ethanol requires more fuel for the same amount of air than
does gasoline. As you add small amounts of ethanol to the fuel, like with E10, your
ECM will make positive trim adjustments to correct the fuel to air mixture. As higher
ethanol concentrations are used, higher levels of additional positive trim will be
needed. Non Flex-Fuel vehicles will generally reach their capacity for positive trim
with a concentration of approximately 50% ethanol. A factory Flex-Fuel vehicle will
have an ECM which has the necessary capacity for positive trim to correctly trim
the fuel for high concentrations of ethanol.
How does your converter work?
Our converter works in concert with your vehicle's fuel trim system. Flex-fuel
vehicles have a fuel trim system with more capacity for positive trim than the
positive trim capacity in a non flex-fuel vehicle. By inserting a digital signal
processor and some electronics between the ECM and the injectors, we can add
some positive trim to help the non flex-fuel vehicle reach the amount of positive
trim necessary for correctly using ethanol. This added trim, combined with what the
ECM can provide, allows the ECM to trim the fuel to reach the proper mixture for
E85. Our converter has an internal adjustment which allows it to be tuned to each
vehicle and the range of fuels typically being used. We have found that a setting of
about 60% of the converter's positive trim works very well for the vast majority of
vehicles and ship converters set to this level.
I can't always get E85. With extra trim from converter, can I still use reg gas?
Yes! The vehicle's ECM can also generate significant amounts of negative trim to
lean the mixture. The ECM monitors the oxygen sensors and adjusts the trim to
achieve the proper mix for the fuel being used. For example: When a fuel such as
E10 is being burned, the total positive trim needed would be less than what is
provided by the converter. The ECM's fuel trim would lean the mixture by
generating negative trim. This, combined with the positive trim added by the
converter, results in the correct fuel mixture. A factory adjusted converter won't
add so much positive trim that the ECM would have difficulty trimming for regular
gasoline, so you can easily use petrol when you are unable to find E85.
Do you tap into or modify the signal from any of the sensors?
Absolutely not! We do not modify, disconnect, alter, or otherwise interfere with any
sensor. We also do not interrupt, sample, intercept, reformulate, or otherwise
adulterate the signal from any sensor. Our converter takes a completely hands-off
approach to the sensors, their signals, and the operation of the ECM. We ONLY
modify the injector pulse and leave the sensors completely AS IS. The sensors and
the ability for the ECM to accurately monitor the conditions they are designed to
sense form the heart of a vehicle's emission control system. Any adulteration in the
integrity of the sensor signals would interfere with the ability for the ECM to receive
proper inputs and, in essence, would be an engineering change to the emission
control system with which the vehicle originally certified. Even tapping into a
signal could theoretically cause some unexpected interference. By not messing
with any of the vehicle's sensors, we eliminate the risk of disrupting the ability for
the ECM to get accurate information with which to properly run the emission control
equipment. The on-board diagnostics that have been required since 1996 will
detect if the emission control equipment is not operating within acceptable
parameters. As long as the ECM has unadulterated signals from its sensors, the
emission control equipment will either be operating correctly or a check-engine
condition will occur. For most modern vehicles, the only thing they lack to be able
to use ethanol is a bit of a boost to the amount of positive trim they can produce.
That can easily be done by making a small increase in the injector pulse width.
This makes for a very clean conversion and leaves your vehicle's emission control
How does fuel trim work?
Carburetors – Lets first take a quick trip down memory lane and recall some of the
problems with the good old carburetor. If you always drove with the same fuel and
never changed altitude, it was possible to adjust a carburetor so that the fuel to air
mixture was very close to ideal. Unfortunately we often burn fuel from different
vendors, we drive up and down mountains, and even the temperature, wind, and
barometric pressure will affect the fuel to air mixture. Carburetors can be adjusted,
but there is no practical method of making any on-the-fly adjustments as
conditions change. Consequently, when we had a tuneup, rather than making it
ideal for one condition, the mechanic would have to set it to run pretty well for a
variety of conditions. Generally that meant a carbureted engine would be running
a little rich most of the time.
Fuel Injection – The big advantage of fuel injection is that fuel injectors are
controlled by an electronic signal. Changing conditions could be monitored with
sensors. Logic could be added to monitor the sensors and continually adjust the
fuel mixture as needed. The ECM (Electronic Control Module) does this job.
Sometimes a manufacturer will use other terms for the logic center and often we
will call it “the computer”, but an ECM by any other name still keeps the fuel
trimmed. The important part is that it monitors sensors to determine what the
conditions are, has logic to make decisions based upon the sensor readings, and
can control the injectors. Its job is to both keep the fuel to air mixture where it
needs to be and to deliver the amount of power commanded.
What do the oxygen sensors do?
Oxygen sensors allow the ECM to monitor the oxygen content of the exhaust. To
improve fuel economy and reduce pollutants from incomplete combustion, it is
necessary to get the fuel to air mixture just right. The primary oxygen sensors are
located between the exhaust manifold and the catalytic converter. If you have a
split exhaust system and/or the ECM monitors the fuel trim for each side of the
engine as many do, then there will be a primary oxygen sensor for each side. The
primary oxygen sensors allow the ECM to know if the combustion is occurring with
the correct mixture. If there is too little oxygen in the exhaust, this indicates that
there was too much fuel for the available air. Too much oxygen, likewise, indicates
that there was a deficit of fuel. The secondary oxygen sensors will be located after
the catalytic converter. These sensors provide information about the oxygen
content after the exhaust has passed through the catalyst. By doing so, the ECM
can monitor the health and operation of the catalyst and the catalytic converter.
This input is not used for fuel trim but is very important to the vehicle's diagnostic
system. If the ECM detects a problem with catalyst system, it will produce a check-
engine condition. You can see a lot of talk on the web about maintaining the
proper stoichiometric ratios. In theory, if you had good enough sensors to monitor
the fuel chemistry, intake air properties, the engine temperature, etc. then you
could compute out exactly what do to with the fuel. In reality, while this is true, the
fact is that fuel chemistry can vary quite a bit, the combustion air can suddenly
shift characteristics, the oxygen content of the air can change, and even the
sensors are not calibrated that precisely. Why? Because it wouldn't be cost
effective. Sensors that precise would be several hundred times more expensive
and no one could afford the vehicle. Maintenance would also be an issue as the
sensors would have to be re-calibrated frequently.A much more practical approach
is to start by making a good guess at what the fuel to air mixture needs to be, then
monitor the result and make adjustments to correct the guess. The ECM then
enters a mode called closed loop, where it repeats this process to continually
refine the trim and to respond to changing conditions. By taking this approach, the
sensors that monitor the process inputs need not be perfectly accurate and
precisely calibrated in an absolute sense, they only need to be able to report
relative changes with good precision .Because the oxygen sensors examine the
actual results of the combustion, they provide the best indication of whether the
correct fuel to air mixture has actually been achieved.
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