Exhaust Gas Temperature (EGT) Sensors for Tuning Internal Combustion Engines,
Installation Information Exhaust Gas Temperature (EGT) Probe placement in the exhaust path requires special attention. If it is closer than 1½ inches to the cylinder head, probe life will be limited, too far away the probe will be less responsive.
Should there be doubt concerning in which exhaust tube or specific placement of the probe, you should check with the engine manufacturer or your engine builder.
There are two basic ways EGT probes are installed in multiple cylinder engines either for monitoring a bank cylinders or individual cylinders.
Monitoring a bank of cylinders will give you averaged information about the over all exhaust gas temperature generated.
For example when installed in a "V8" cylinder engine, two EGT probes can be used by placing them in the exhaust manifold / header collector on each bank just past the point where tubes become common. The probes are connected to high temperature thermocouple wire and a connector and then to either a dual channel meter or two single channel meters for monitoring in the vehicles' cockpit.
One of the considerations of the installation is the distance from the exhaust valve to the probe sensing junction. The farther from the valve the lower the readings will be giving an average of the four cylinders in each bank. This keeps the ability to gather the necessary temperature information simple and less expensive.
If you require more exact temperature readings of each cylinder you may consider installation of probes near each of the combustion chambers (exhaust valve). This maybe be required in situations where you have the ability to individually tune fuel / air ratio for each cylinder. This installation is more complicated and requires the distant of the EGT probes from the exhaust valves to be consistent keeping the variation in temperature to as little as possible. The constancy in probe distance from combustion chamber will insure even and reliable readings.
EGT systems are not complex or expensive to install.
An advantage of the EGT monitoring verses monitoring the cylinder head temperature is a more immediate response to change in temperature. The change in cylinder head take a much longer time since it has a lot more mass to heat.
The peak or point of maximum temperature is the basic reference for performance management. If you have experimented with the exhaust gas temperature sensors at the engine builder’s dyno or engine manufacturers recommended maximum horsepower, you have observed during the tuning process results in the peaking of the exhaust gas temperature via the gradual leaning of fuel and air ratio adjustments.
Tuning for specific atmospheric conditions can be critical on race day.The peak temperature in each cylinder will vary with different power settings, changes in altitude, and ambient temperature. Typically a hand held digital readout like the dual channel or single channel meters The Sensor Connection offers will have the ability to read individual cylinder exhausts or cylinder banks.
Multiple channel data acquisition systems will gather and display data from all exhaust port temperature readings simultaneously. The requirements for precision of the data collection of your application will determine the type of data collection system you will need.
Tuning the fuel to air ratio for peak efficiency with an EGT Probe
From the peak EGT, either increasing or decreasing the fuel to air ratio causes a change in Exhaust gas temperature. Richer EGT cooling occurs because there is excess fuel cooling the exhaust stream via less than optimum burning, and leaner , heating occurs because there is excess air (oxygen) making for a hotter burn. So you must have a base line of where you are starting from regarding cylinder exhaust gas temperatures and a rich or lean condition of the fuel / air delivery system.
Peaking exhaust gas temperature (EGT) with a carbureted engine is frequently a vague point because of less efficient atomization compared to electronic fuel injection to the individual cylinders. As a result, carbureted engines tend to operate smoother at +25 degree +50 degree F on the rich side of peak exhaust gas temperature (EGT).
Fuel injected engines typically provide a more precise peak exhaust gas temperature, therefore the EGT system is likewise a more precise method of performance tuning with fuel injection.
A simple definition of peak EGT is the chemically correct mixture of fuel and air, which gives something close to 100% utilization of all the fuel and all the air delivered to the cylinder.
Benefits of EGT sensors for engine tuning:
Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings translating to lower fuel consumption (increased range) as well as less likelihood of spark plug fouling.
Temperature variations will occur between in between individual cylinders when using a probe for every cylinder and to a lesser degree between banks sine the temperature is averaged.
Typical variations of about 100 degree F between each individual cylinder can be observed with fuel injection systems, and about 200 degree F with conventional carburetion. Carburetion variation is greater because the atomization of the fuel is not as effective when compared with fuel injectors.
In colder air temperatures, the mixture atomization is poorer for both fuel injected and carbureted engines. However, with the carburetor, the fuel/air ration and atomization is less effective resulting in larger temperature variations when comparing individual cylinders.
Advantages and benefits of an exhaust gas temperature (EGT) sensor / probes
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