My Banks(yeah, I know) pyro gauge won't drop under 100 Degrees, even after it's sat overnight. Could it be the gauge, or is it the probe? Any way to test them to find out?

 

I'm also wondering if this has anything to do w/ the fact that I removed a jury rigged piece of wire from the + post that was touching the probe input line (whatever that spiral wrapped poop is called).

 

All thermocouple type instruments have mediocre resolution at temps approaching ambient. Thats why in plants, we usually use RTD's for the lower (250F, down ) ranges. Its probably fine. It anything would or could be wrong, it could only be the gauge. TC's are what they are... they never vary more than a very very small amount. TC's cant and arent calibrated for this reason. The two dissimilar metals joined together at the junction, simply put out a set voltage at a set temperature.... but that voltage is mere millivolts and at low temps its REALLY tiny....



KP

 

I think that was english, could you dumb it down just a tone for me

 

What hes saying is that a pryo may not necessarily go to zero, the indication on the low end isnt really important anyway. This error is mainly due to its construction. Whats more important is how close the thermocouple measures the exhaust temps at operating temperature.

Jeremy, do you have access to an infrared temperature gun?? If not, you could rent one from a rental place and verify your temperature reading when the engine is hot.

 

Yeah, dad's got one. Might use it to verify the pyro gauge's accuracy.
The reason I asked, is because up until a month ago, it would drop to 0 overnight. I even tried thumping it, but it stays at 100 deg. Funny thing is, the little coil of steel wire I found that was grounding out the + post would cause 100 degree drops in temps when you'd thump the gauge.

I have hit 1200 deg. since this started happening, w/ the 100 plate 90% forward and stock injectors, 34Lbs boost, 16.5* timing, and no GSK. Sound about right? I had some RPM's left to go, but let off due to my slipping clutch.

I think I'm just one of those worry-wart perfectionist types.

 

I had that happen...then realized the temp was 100 degrees that morning.
But seriously, hermocouples do not register very accurately down near ambient.
-Del

 

Sorry, here is better explanation of what I said. Our EGT 'probes' are really just devices called thermocouples. There are literally millions of these devices in use in the world at power stations, refineries chemical plants etc. They are made by 'coupling' two different metals together at a junction, which is at the tip of the probe. There are lots of different types of thermocouples (TC's) which use different combinations of metals at the junction. The two different metals, joined together will put out a certain amount of voltage when the tip is heated. The hotter the junction, the more voltage the couple puts out. But this amount is only millivolts, (or about .001 volts at 32F to about .040 Volts at 1,300F). At the lower end, this voltage is extremely small to have to directly move the pointer of a meter or gauge. So the slightest friction in the gauge can cause it to hang a tad and/or be off at the really low ranges. At higher temperatures, and thus voltages, its much better.

As for what I said about the TC never being wrong or needing calibrated, that is because the thermocouple is just a coupling of two different metals. As long as the metals are what they are, then they WILL put out that set voltage at a set temperature. There is no way to 'tweak' or alter the thermocouple itself, only the measuring instrument, be it a gauge or meter etc.


Hope this helps

KP

 

My EGT gauge has never read below 300 - go figure.

 

You forgot there is at least one in almost every home in America, they control your heating, A/C, oven and hot water heater temp.
A thermocouple definitely isn't rocket science.