CHT monitoring all four

[Darick]

I have the MGL Stratomaster E1 EMS which only has four engine temperature inputs, two CHT, two EGT. I'd like to monitor all four CHT simply by flipping a switch (DPDT). So, the two EMS CHT inputs would see either cylinders 1 and 2 or by flipping a switch, cylinders 3 and 4.

The EGT would just be the standard set up unless I find a reason to monitor all four in which case I'd need another DPDT switch.

My first question is if the properties of thermocouples allow you to do this without losing accuracy. My second question is ...can a regular toggle switch do the job or is there some special requirement because this is a thermocouple application?

I vaguely remember someone else doing this same thing.

Thanks for any info and suggestions.

[radfordc]

I did this in my old Sonex. I was using a GRT EIS 2000 but it should work fine for you too.

I used regular small DPDT switches from Radio Shack. After doing it I found that it wasn't very useful. On my engine the two front cylinders were always 20-30 degrees cooler than the rear. I kept the readout on the rear cylinders 99.9% of the time. When I was curious I would switch to the front cylinders but they were always normal.

[Direct C51]

Monitoring all 4 CHTs and EGTs is probably not needed 99.9% of the time, and unfortunately when it is needed, having a switch may not help. The true benefit of monitoring all CHTs/EGTs is getting an immediate alert for any impending engine problems, especially detonation. If you are monitoring the wrong 2 cylinders, you may not notice detonation starting until it has fully developed and caused damage. If you monitor all 4 cylinders you will see the CHT trending upward on 1 cylinder and enriched/reduce power before it fully develops and damages the engine, especially with alerts on. For this reason, I see very little added benefit of having a switch because you will just leave it on the back 2 cylinders since the front 2 will be cooler and operating normal 99.9% of the time. For these reasons, I am an advocate of monitoring all cylinders and will be monitoring all 6 of my Corvair.