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.
FAQ
Our EGT probes are designated “special limits of error” for +/- 2 degrees F (or +/- 0.4% range) accuracy tolerance.
EGT probes are our core business. Our products are manufactured in the USA and constructed from high quality materials. 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 FEP 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 affordable yet robust EGT probes available on the market.
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.
A general consensus would be 2 inch to 4 inches from the cylinder head if practical. 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.
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.