IO360 EGT Temps seem low

[rogerl]

From what I am gathering, EGT should peak in the vicinity of 1500 (or more).  I am seeing max EGT's of more like 1400, and the absolute max I have seen in flight at about 10,000' is 1435 or so.

Does anyone know if this is normal for the IO360 in a '78 J ?

[Parker_Woodruff]

Quote: rogerl

From what I am gathering, EGT should peak in the vicinity of 1500 (or more).  I am seeing max EGT's of more like 1400, and the absolute max I have seen in flight at about 10,000' is 1435 or so.

Does anyone know if this is normal for the IO360 in a '78 J ?

[carusoam]

Roger,

EGTs are so dependent on instrument and location (compared to CHTs) it would be difficult to compare. 

highest Peak EGTs come with high fuel flows (lower altitudes).

Low Peak EGTs come with lower fuel flows (such as, normally aspirated engine at 10,000' or higher) .  You may notice that it is difficult to heat the cabin in winter at higher altitudes, not enough heat generated.  Heat comes on strong as we descend.

I would expect winter peaks to be slightly lower than summer peaks.  (I never gathered enough apples to apples comparison data.  For comparison to your situation, I see low 1,500s at peak with my continental IO 550G.  My O-360 ships gauge was not calibrated, it did not even have numbers on it (65 M20C).

Quick question, what instrument are you using?  (JPI, EI or ship's gauge?)

Best regards,

-a-

[Cruiser]

High 1400s is normal for me. 1470 - 1490 dF ish.

[ReggieM]

I get about 1450 or slightly less at peak.

-Reg

 

[jlunseth]

If you stick a thermometer in a jet of flame to see how hot the flame is, you are going to get a different temperature for the flame depending on what part of the flame the thermometer is in, or the distance from the flame if the thermometer is not actually sitting in the flame.  That is what is going on with your EGT gauge.  It is installed in the exhaust manifold, but exactly where in the manifold depends on the manifold and what other equipment is around the manifold that needs to be avoided.  Most multi-probe installations will show variations from one cylinder to another just because the probes are at slightly different locations. 

So that is what happens with EGT probes.  There is a jet of flame that comes out of your cylinder every time the exhaust valve opens.  The EGT probe location will have an effect on what the temp. reading is for that flame.  Moreover, the jet that comes from the cyl. is not a constant jet, it is a jet that happens once every rotation of the crankshaft, so the EGT is actually sort of averaging the temp when the flame is on, with the temp when the flame is off. 

Location, location, location.

[rogerl]

Quote: carusoam

Quick question, what instrument are you using?  (JPI, EI or ship's gauge?)

Best regards,

-a-

[Rustler]

Roger--

I'm just up the road from you, a couple thousand feet higher, and generally fly 12,000'-14,000' with EGTs running in the 1425-1475 degree range. Summer/winter? doesn't seem to matter much, but maybe 10-20 degrees lower in the weather we've been having.

 

[Jeff_S]

If you haven't already, I would suggest going to http://www.savvymx.com and going to Mike Busch's past webinars and viewing the one on EGT. It's very enlightening, and covers some of what people have said above. However, the absolutely KEY point he makes is that it is practically useless to measure an exact EGT, rather, it's the relative values that matter.  For what it's worth, I have never seen a peak EGT anywhere near 1500 in my J...generally in the low-mid 14's.