Opinions, please. EGTs and CHT's

[xftrplt]

Cruising home recently on a short flight in my 231 (with Gami's and intercooler) at 3,500 MSL, 27" MAP, 2460 RPM, and 9.8 GPH, I had the following readings:

CYL EGT CHT

1 1475 318

2 1332 311

3 1418 302

4 1312 317

5 1444 301

6 1447 276

There's no real change from my "normalized" indications, but I'm asking:

-- Is the 153 df spread between 1 and 4 considered excessive? (It seems high to me for a "Gamied" engine.)

-- Is there anything else significant in the numbers?

Thanks in advance,

Dick

[The-sky-captain]

Dick,

For what it's worth when I run my J 100 ROP my EGT differences usually run from 10-30 degrees. When I switch to LOP its a difference of 70-80 generally. My CHT's run a little hotter then yours do at around 330-360. From what I understand the CHT temps are more important then the EGT temps.

[danb35]

Absolute EGT values, including differences between them from cylinder to cylinder, are all but meaningless. They do not represent anything relevant to your operation of the engine. As long as they peak at nearly the same fuel flow (which is where the GAMIs come in), and your TIT isn't too high, nothing to worry about.

[xftrplt]

Thanks, Bodie and Dan.

TIT was <1500.

[garytex]

Unless you have an induction leak, which would show lower numbers on egt if you were lop. Induction leaks eat cylinders. Is this merely a harmless instrument artifact, or is your engine trying to tell you something? Curious that the two anomalous cylinders are side by side. What do they share? Are the probes lower on those two exhaust tubes due to some interference in that area? That would make for lower readings.

Have those two always been different or is this a new development? Happy pondering

Gary

[bd32322]

Unless you have an induction leak, which would show lower numbers on egt if you were lop. Induction leaks eat cylinders. Is this merely a harmless instrument artifact, or is your engine trying to tell you something? Curious that the two anomalous cylinders are side by side. What do they share? Are the probes lower on those two exhaust tubes due to some interference in that area? That would make for lower readings.

Have those two always been different or is this a new development? Happy pondering

Gary

Curious, how do induction leaks eat cylinders. I am a bit concerned because i see a cylinder runiing much cooler CHTs and EGTs. My plan is to swap the richest fuel injector with the leanest and cool running cylinder. If that makes no difference, then probably look at induction leaks. Hopefully that makes sense.

[CAMooneyPilot]

On my 231 the stock temp probe is on the #3 cyclinder. The probe for my engine monitor is mounted in a different location because of the stock probe, and therefore the temps read slightly higher on that cyclinder. Might check that out as a possiblity. Also, your running your engine at a fairly low power setting and you are at a low (for a 231) altitude, and none of your temps are anywere close to maximuns. Try running the engine at 75 to 85% power and climb to altitude (at least 16K ft) and take temperature readings there. You will get a much better indication of engine temp performance if you do.

[garytex]

bd32322:

I think that the primary means is that in ROP climbs the induction leak cyl. can be too lean thence hotter, and in extremis, detonate. All sorts of mischief ensues. If MP doesn't go below 10 " at idle coming down final with the throttle closed, check for induction leaks, especially #2 at the head joint. Evidently that is one of the favored usual suspects as that tube is prone to vibrate and fret the flange. Turned out to be the case in my instance. And thats enough to eat a cyl promptly. Bitter experience speaking. Mine generated sticking coked up rings that made a longitudinal polish on the barrel wall and a crack too big to weld.

Gary

[bd32322]

bd32322:

I think that the primary means is that in ROP climbs the induction leak cyl. can be too lean thence hotter, and in extremis, detonate. All sorts of mischief ensues. If MP doesn't go below 10 " at idle coming down final with the throttle closed, check for induction leaks, especially #2 at the head joint. Evidently that is one of the favored usual suspects as that tube is prone to vibrate and fret the flange. Turned out to be the case in my instance. And thats enough to eat a cyl promptly. Bitter experience speaking. Mine generated sticking coked up rings that made a longitudinal polish on the barrel wall and a crack too big to weld.

Gary

Thanks very much!

[jetdriven]

I dont think WOT well rich operation will harm a cylinder with an induction leak. There isnt a pressure differential in the intake tract to cause it to draw unmetered air. However, pulling the throttle back does create that pressure differential and setting the mixture to 50 ROP puts that leaking cylinder right at peak at high power. That will kill it after a while. LOP operators will discover the leak immediately, as the engine will not run LOP smoothly at all. All these claims of ROP being safer or more conservative arent necessarily so true when you have an engine monitor. Our new engine has new baffles, and is very well balanced. I have spent two full days chasing down air leaks, injector balance, and baffling problems. At 7K runs 385f+ CHT at 80 ROP. Peak is 365f. 25 LOP is 340f.