well i installed a autometer egt. and at idle it sits around 1100 at idle. I was wondering what it should be at idle and whats the max the exhuast temp should reach? thanx
No set maximum. From my days as an aircraft mechanic, with a fixed RPM & power level, EGT increased as the fuel mixture leaned out until it peaked and started to drop off. The highest I remember seeing was 1400-1500 degrees F. If it gets above 1800 degrees F, I would start to be concerned.
Jrichker - your numbers seem high to me - if your aircraft experience was turbine-related, that may not be directly applicable to piston engine applications. Gale Banks recommends staying below 1300F for turbo diesel applications. I found other sources that indicated that the tips of the turbine (turbo) blades started to glow at about 1270F, and that even sustained running in the 1250F range would cause problems before long. I don't think the safe range for gasoline engines is much different since the issue seems to be the metalurgical implications, although I'm having a difficult time coming up with documentation for that. I did find an aircraft piston engine source with the following info: "A reading on an EGT of 1100 to 1200 degrees F should give a nice tan coloured spark plug. Lower readings should give darker colours while higher readings grey/white colours."
One additional thing - VDO offers gauges -- and their maximum reading is 1650F. That seems to support the notion that once you start getting into the 1300F-1400F range, things get a little dicey. And it's my understanding that the damage is cumulative - so even a little time spent much above 1300F can contribute to problems later on.
All of this seems to point in the direction of egt's in the 600F-1200F range depending on load and mixture are normal and relatively safe. If you start going above that for extended periods of time, I'd guess problems will ensue.
In any event - 1100F at idle seems WAY too high to me. With no load on the engine I doubt exhaust temps should be much higher than 500-700F. Not sure what to tell you to do about it though. I'd wonder about the accuracy of the probe/gauge if you're not having drivability or other problems with the engine's operation.
Dont know on a gasser, but my truck idles in the 300-80 range depending on what is running. My box is set to defuel at 1350* to prevent damage to the turbo but again this is a 6.0 psd not an n/a gasser.