EGT Temps at Peak?

I have recently been doing some reading and searching to find what temps you should see at peak EGT. Lycoming never addresses the EGT max temp and says that as long as the engine is running smooth, CHT are lower than 400, and oil temps are in the green you have not over leaned.

In searching the forum the data people have shown typically shows EGTs peaking in the 1400F range. I have talked to several at my airport that say they peek in the mid 1400F. In the Sky Ranch Engineering manual it says normal temps are 1200-1600F. One graph shows temps peeking around 1500-1525F (depending on cylinder). I had always had my peak at about 1510-1520F (I have a IO-360 with a JPI-700). After my recent annual, where I cleaned the injectors with Hopping #9, I now peak around 1550F (consistant with all cylinders).

Questions: What EGT temperture does everyone see at peak? (I know there will be varibility depending on sensor location, sensor type, etc) Any ideas on why my temps went up after cleaning?

Philip,

Lots of variables in addition to calibration errors. The distance the probes are from the exhaust valve makes a large difference as I understand. Power settings will affect it as well as, obviously, mixture. Timing of the spark is a big factor - base timing (as in mags) will run hotter egt's than spark advanced EI will in most conditions, particularly at lower MAP. Just as a data point, mine with dual Lightspeeds run in the mid 1300's to 1400 or so, depending on cruise power setting. When I had mags, they ran mid 1400's. If you shut down one ignition, they will probably go into the high 1400's at cruise settings.

Over-Lean

Just a note about the idea of being "over-lean". If I understand the GAMI experts, as you go leaner than peak, your EGT's come down and in fact that's how you specify LOP - as number of degrees below peak.

Mine: Stock O-360A1A, carb, mags peaks at 1510 +/- depending on OAT, alt., power setting, phase of the moon, etc.

Philip, my engine is carburated, but It will give you some idea as to where mine peak if you look hear. There are some graphs. All over the place is the answer!

If cleaning the injectors means reduced the fuel flow that would be an easy explanation, but I know little of injectors.

Best wishes,

AlexPeterson said:

Philip,

Lots of variables in addition to calibration errors. The distance the probes are from the exhaust valve makes a large difference as I understand. Power settings will affect it as well as, obviously, mixture. Timing of the spark is a big factor - base timing (as in mags) will run hotter egt's than spark advanced EI will in most conditions, particularly at lower MAP. Just as a data point, mine with dual Lightspeeds run in the mid 1300's to 1400 or so, depending on cruise power setting. When I had mags, they ran mid 1400's. If you shut down one ignition, they will probably go into the high 1400's at cruise settings.

Click to expand...

Alex - are you talking about peak EGTs or leaned cruise settings?

On my previous plane (and also specified by Klaus as something to expect) I saw markedly HIGHER EGTs once I installed a Lightspeed. Supposedly this is because the spark is hotter and the fuel burns more completely.

Has anyone else seen LOWER EGTs as a result of installing Electronic Ignition?

breister said:

Has anyone else seen LOWER EGTs as a result of installing Electronic Ignition?

Click to expand...

I am running dual P-mag. They have two standard settings one 5 deg in advance of the other. Both vary the timing depending on MP and RPM.

When I changed from the conservative curve to the more advanced one there was a clear but small increase in CHT and decrease in EGT.

Now that this is not quite what you asked I know, but it is a very similar change since the conservative operation is similar to a conventional mag.

I put this down to more complete combustion occuring inside the cyl since the plug fired earlier, and being converted to work, rather than a fire going down the pipe as the valve opened. I think thats in line with conventional wisdom.

I will say the more data I gather the more confusing this gets! Once you graph the data you realise it is leaping all over the place. (See the link in my previous post.)

Philip,

The EGT temps have a lot to do with the location of probes. Probes that are closer to the valve should read higher than those placed even 1/4" further away.

Runs smooth

I went out and did some leaning this weekend. Temps right around 1550 EGT at peak. Engine still running nice and smooth. Fuel flows down lower then I have seen before by about .4 gal/hour. My best explaination is that I was getting a premature peak on one of the cylinders before I cleaned the injectors. Now they are all peaking closer together and higher giving me better fuel economy.

I have been doing lots of searching and found sources that show peak EGT in the mid 1500 deg. I think the temp is really varible on the location of the probes (along with % power, altitude, etc). No where does it give a max EGT unless you have a turbocharger and then you need to limit the TIT.

another data point

I have been doing some runs to get baseline fuel flows and operating temps at different power settings in my case the set-up is 0-360, dual mags, vetterman exhaust with the probes 2 inches from the flange. Peak EGT at 8500 ft using the Lycoming leaning procedure backed up by the Dynon power and ROP/PK/LOP readout was 1458 on #1 cylinder, CHT's were in the mid 300's.
When you read the stuff available on the web you get a headache as some say EGT is OK up to 1600, other say combination of CHT and EGT should not exceed 1800, other say "it depends". I have been trying to figure out "good practice for engine operation", "economical fuel flow" and "long engine life" and the answers range from a) run at peak as long as you are at 75% power or less to b) run 100 deg ROP for long engine life to c)run 50 deg LOP for fuel economy (can apparently be done with carb setup). It would be nice if it were as simple as "tune for maximum smoke" or tune for XXX fuel flow at YYY rpm