Low EGT, normal CHT on first engine start

[ChiefPilot]

Hi All,

Reviewing the data from my first engine start, I'm puzzled by a low EGT reading on cylinder #1 (first chart). CHTs appear to be ok for the remainder of the cylinders (second chart). My first course of action will be to swap probes between cyls #1 and #3, but I'd like to learn from those who've gone before if something else may be afoot. EGT difference between cyl #1 and the rest is approximately 300 degrees as indicated by the data.

Any input welcome and appreciated!

EGT values:


CHT values:

[Jamie Aust]

Hi Brad,

I would swap probes between cyls #1 and #3 as you said your are going to do.

What engine do you have, also how did you pull the temp data from Efis ?
I have a skyview and dont have that feature just yet

[ChiefPilot]

Originally Posted by Jamie Aust

Hi Brad,

I would swap probes between cyls #1 and #3 as you said your are going to do.

What engine do you have, also how did you pull the temp data from Efis ?
I have a skyview and dont have that feature just yet

This was from an IO-360-B1B built up by Bart at Aerosport Power. I have a Dynon EMS-D10 and configured the data logging to take one second snap shots for the first startup.

Thanks!

[Echo Tango]

swap plugs as well if the probes are inconclusive.

then go to plug wires. im sure you'll find the culprit if you work through it.

[Ironflight]

Are all your probes the same exact distance from the exhaust flanges? Folks sometimes get so wrapped up in figuring out how to make the probes fit under the cowl and around stuff that they put one at a different distance - and it is therefore hotter or cooler than the rest. measure carefully - a fraction of an inch makes a difference.

[ChiefPilot]

Originally Posted by Ironflight

Are all your probes the same exact distance from the exhaust flanges? Folks sometimes get so wrapped up in figuring out how to make the probes fit under the cowl and around stuff that they put one at a different distance - and it is therefore hotter or cooler than the rest. measure carefully - a fraction of an inch makes a difference.

Good question - thanks! Yes, they are all 2.125" from the cylinder flange. The way I measured this was by making a paper template on the bench first, then using that to locate the probe location so that all cyls would be as close as possible.

One thing that is unique about cyl #1 is that it is the only cylinder that has the flange and exhaust header open to the prop blast. Since I was running with the cowl off to check for leaks etc, I wonder if this may have made a difference. I would think it wouldn't be significant, but ???

[PIN 37]

One thing that is unique about cyl #1 is that it is the only cylinder that has the flange and exhaust header open to the prop blast.

No should not make a difference since temp in exhaust stream is much higher than ambient.

[ChiefPilot]

Originally Posted by PIN 37

No should not make a difference since temp in exhaust stream is much higher than ambient.

That makes sense to me - besides, the probe is measuring the temperature of the exhaust stream and not the stainless steel tubing connecting it.

[RV10inOz]

I am with PD on this one, it is either probe position or something about that probe.

Remember there are not hard and fast rules on what is a good or bad EGT. It is only a useful tool as a relative number, either to the norm for your engine or referenced to peak EGT.

I suspect there is nothing to this, subject to more data about how you ran it etc.

At this point you have more to be worried about.

[ChiefPilot]

Quick follow up - I removed probes one and three from the exhaust headers and heated them both with a butane pencil torch. Same heat, same amount of time, and the probe from cyl #1 was telling the EMS. it was 350 degrees cooler than the other one.

Looks like a new probe is in order.

Thanks for all the questions and suggestions!