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Thermocouples EGT Sensors and Probes: FAQ


 

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What are some of the benefits to using an Exhaust Gas Thermocouple EGT?

Operation at peak EGT, particularly on long runs like in road racing or circle tracks, will give a fuel savings meaning less pitting for fuel (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. 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.

 


Where is the best place to install the EGT probe?
A general consensus would be 2 inch to 4 inches from the cylinder head. But it's your car so it's your decision.
For turbo engines be sure to CLEAN ALL METAL FILINGS out of the exhaust manifold. Metal filings will damage the turbo impeller if they go through the turbo.
Please keep in mind when installing multiple EGT probes that consistency in distance is important. Plan this out before you start drilling holes!
NOTE: Should there be doubt concerning specific placement of the probe, you should check with the engine manufacturer, your engine builder, or your Tuner.


Should I Install the EGT probe before or after the Turbo?
Many experts suggest installing the EGT probe in the exhaust manifold before the turbo for three reasons:
1) The farther the EGT probe is away from the manifold, the greater the lag time response to dynamic changes in temperature.
2) Exhaust gas will cool as it travels away from the manifold which will result in lower EGT readings. EGT readings can drop over 200 degrees after the turbo.
3) Depending on the balance of your setup, the turbo itself may act as a restriction. Exhaust gas can build up excess heat before the turbo, while post-turbo Exhaust gas temperatures can be lower as a result of faster cooling due to reduced exhaust flow. This can result in higher temperatures between the motor & the turbo, yet temperature readings after the turbo will read cooler.
NOTE 1: Should there be doubt concerning specific placement of the probe, you should check with the engine manufacturer, your engine builder, or your Tuner.
NOTE 2: When installing the EGT probe BE SURE TO CLEAN ALL METAL FILINGS out of the exhaust manifold. Metal filings can cause damage to the turbo impellor if they go through a spinning turbo.


At what depth should I install the EGT probe?
Typically at the center of the exhaust stream.


What makes your probes better than the ones I see from your competition and lower priced overseas thermocouple sensors?
EGT probes are our core business. Our products are manufactured in the USA and constructed from some of the best materials available. The exposed sensing tip MgO insulating material is flame hardened to stop powdering & embrittlement which can lead to failures of the sensing element. The probes' outer sheathing material is made from either Aerospace Alloy Inconel or 316 stainless steel depending on the application. Our EGT probes have water-resistant Teflon insulated wires that will withstand up 500 °F (250°C). The cable's outer jacket is stainless over braided for maximum strength and abrasion resistance. All this adds up to one of the most robust probes on the market.


What is the accuracy of the EGT probe?
Our EGT probes are designated “special limits of error” for +/- 2 degrees F (or +/- 0.4% range) accuracy tolerance.


I only want to purchase and install one EGT probe. If I place only one EGT probe in the collector will I get an average temperature across all of the cylinders?
One EGT probe placed in the collector will measure the leanest (hottest) running cylinder. For a quick test of which one that is you can do the following:
With a running engine, take an EGT probe & touch it to the outside of each pipe. Make sure that you are measuring at the same distance from the header pipe flange or manifold runner. Write down the temperature of each pipe. This will tell you which cylinder is running hottest.


My temperature reading on the meter is going down instead of up. Can you help me?
It sounds like the sensor's wires are hooked up backwards. Please confirm that the sensor's wiring to the meter input terminals is:
YELLOW = + (positive)
RED = - (negative)


When installed, are your EGT probes isolated from or are they common earthed to the exhaust manifold?
All of our EGT probes output wires are isolated (ungrounded) from the probe's outer sheath


 What is the maximum length I can extend the EGT probe's cable?
The maximum length you can extend the EGT probe's cable is about 50 feet.


Can I shorten the EGT probe's cable or will that mess up the accuracy because the ohms of the wire won't be the same?
Reducing the length of the EGT probe's wire by a few feet typically will not affect the operation or accuracy of the probe.


How can the EGT Probe or CHT Sensor Cable be Extended?
Some customers will use copper wire to extend the cable, but please note that this can have a negative effect on accuracy of the temperature reading.
We recommend using thermocouple extension wire along with thermocouple connectors. The wire and connectors are made from specific materials that will ensure the best accuracy of the temperature reading.
You can find these products to build your own Extension Cable on our website at the following links…
Extension Wire: http://www.thesensorconnection.net/category/egt-probes/all-egt-probes/accessories/extension-wire
Male Connector: http://www.thesensorconnection.net/egt-probes/connectors/mini-male-plug-connector-type-k
Female Connector: http://www.thesensorconnection.net/egt-probes/connectors/mini-female-jack-connector-type-k


Do these EGT probes come with a calibration sheet or chart?
The EGT probes do not come with a calibration sheet or chart.  They are a standard Type K thermocouple device whose output follows the NIST Type K thermocouple linearization curve. Most modern day instrumentation can read a Type K thermocouple directly.  In some cases, thermocouple amplifiers are required to interface between the thermocouple & the particular measuring instrument.  But if you absolutely must have a calibration sheet then we can send the probe out to an independant agency who will issue us a 5 or 10 point Calibration Test Report that includes data.  There is an additional charge for this service.

Here are some references:
http://archives.sensorsmag.com/articles/1297/sw1297/main.shtml#ref1
http://srdata.nist.gov/its90/main/


Is the EGT probe a thermocouple, RTD, or thermistor? 
Our EGT probes are standard Type K thermocouples. A 2-wire, non-powered device.  Not thermistor or RTD. We can build EGT probes using thermistor or RTD elements upon customer special request


Is the voltage output from the EGT probe linear to the temperature?
The output is a non-linear mV output, conforming to the ITS-90 lookup table.

Here are some references:
http://srdata.nist.gov/its90/download/type_k.tab
http://en.wikipedia.org/wiki/Thermocouple


So how do I linearize the output from the EGT probe so my data logger can read it?
Our Instrumentation page has amplifiers that linearize the EGT probe's output, for example to 1 to 5 VDC or 0 to 5 VDC.


Do you have an 8 channel type K thermocouple amplifier, so I can connect to a data logger?
Currently we have single channel amplifiers available. We are always adding to our product lines so please keep checking back.


My diesel engine runs normally at 720 degrees Celsius. How long do you estimate your sensor will last in this environment?
EGT probes are our core business. We take the quality of construction & materials very seriously. With proper application and respect of the probe, our customers can expect many years of service.  The probes are rated to 1200 degrees Celsius, so 720 degrees Celsius is well within the operating temperature range.


I have a Mercedes turbo diesel and my idea is to monitor both the exhaust temperature and the temperature of the incoming air in the intake manifold. Is there enough range on your EGT probe to measure also lower temperatures (min. about -10 Celsius)?
Yes, our EGT probes are rated to measure -17C to 1200C.
Most of our instrumentation will display temperatures from -20C to +1300C.


What is the largest diameter the muffler clamp will fit?
The range of our standard muffler clamp is 2.5 inches. This can be made to just about any length for custom EGT orders.  We recently added a larger diameter muffler clamp that can be purchased as a spare part that expands to 5.5 inches (140 mm).


I was wondering if you could guide me to where I may find some charts referencing EGT's.
Most race teams and R & D customers closely guard their EGT tables.
There are many factors that affect EGT reading including:
Fuel type, timing, valve size, cam dwell, the fuel delivery system, turbo, and placement of the probe in the manifold. Even environmental issues including track air temperature, barometric pressure and humidity can affect EGT temperature readings.


What is “cold junction compensation”?
Most End-User's shouldn't be concerned with cold junction compensation since most modern day electronics that are used to monitor the EGT probe have this function built in so it is transparent to the End-User.
Thermocouples operate from a principal regarding dissimilar metals forming a junction that can be used to measure temperature.  The primary (or "hot) measuring junction is the tip of the sensor, but secondary junctions are formed when the thermocouple is terminated to your electronics (usually copper wires here).  This is typically referred to as the "cold" junction, since you do not want to measure the temperature at this termination point.
 The temperature at this "cold" junction has to be measured to remove the offset to the measurement at the "hot" end at the tip of the sensor.  If no "cold junction compensation" circuitry is used then your measurement would always be the ambient temperature at the termination to the electronics.  The compensation circuit takes the ambient temperature measurement at this termination point out of the equation.
The Cold Junction is measured at the very end of the long wires (red & yellow leads). This point of measurement is typically done where the thermocouple (or, the Muffler Clamp Probe) connects to the measuring electronics.


How do I return an EGT Thermocouples and or Electronics?
The Sensor Connection warrants that units shipped will be free from defects in material and workmanship for a period of one (1) month from date of shipment. In the event that warranty service is required, The Sensor Connection will, at its discretion, either repair or replace unit(s) or product(s) found to be defective, provided that they are returned prepaid to The Sensor Connection.