Printable Version of Topic

Posted by: malcolm2 Jan 5 2012, 10:49 PM

I wonder if anyone has ever tried to connect 1 gauge, CHT that is, to 2 cylinders. I can envision the leads coming from the spark-plugs connected to a toggle switch or some type of selector switch and then on to the gauge. Switch to the right, and I get the temp of the right side, switch to the left and I get the left side temp. Could it work? Did I read somewhere that the length of the wire has something to do with the accuracy?

I know there are gauges out there that will show temps on all 4 cylinders, but I do not want to invest that much. Just looking at the VDO CHT gauge.

Any thoughts,

Clark

Posted by: FourBlades Jan 5 2012, 10:59 PM

Thermocouple leads are sensitive to connections. If you put a switch between the thermocouple sensor and the gauge I think your reading could be way off.

There may be a way to do it using connectors made for extending thermocouple leads but I don't know how it would work.

John

Posted by: aircooledtechguy Jan 5 2012, 11:04 PM

Westach makes a kit that can use 4 CHT sensors to hook to one gauge. It hooks all the sensors to a 4 position switch and then goes up to a common gauge. Pretty slick and you don't get any more accurate than a Westach set-up.

Posted by: Rleog Jan 6 2012, 09:30 AM

http://www.tangerineracing.com/engine.htm

Posted by: jaxdream Jan 6 2012, 09:42 AM

QUOTE(malcolm2 @ Jan 5 2012, 08:49 PM)

Posted by: 76-914 Jan 6 2012, 09:59 AM

Here you go, take your pick
http://www.aircraftspruce.com/menus/in/chtgauges.html

Westach is good enough for our cars but it was an entry level gage when I was flying. Our CHT thermocouples only produce about 2Mv so any changes to the original loom will result in some crazy readings. Remove resistance (trimming wires) and the indicated temp will be higher than actual temp. Add in resistance (splitting, soldering additional length's) and the indicated temp will be lower (if it even registers).

Posted by: underthetire Jan 6 2012, 10:21 AM

I agree, the thermocouple wire would be more expensive than an additional gauge. Thermocouples generate a small (millivolt) signal from heat, the gauge amplifies that to a decent signal and gives your reading. Any time you have a "cold joint" in a thermocouple system, you loose some of the millivolt signal. A switch not made for thermocouple would basically render the signal useless.

Its covered here
http://www.omega.com/temperature/Z/pdf/z004.pdf

Omega is generally considered the leaders in temp/force applications.