ChiefPilot

ChiefPilot

Well Known Member
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:
egt.png


CHT values:
cht.png
 
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 :(
 
Jamie Aust said:
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 :(
Click to expand...

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!
 
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.
 
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.
 
Ironflight said:
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.
Click to expand...

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 ???
 
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.
Click to expand...

No should not make a difference since temp in exhaust stream is much higher than ambient.
 
PIN 37 said:
No should not make a difference since temp in exhaust stream is much higher than ambient.
Click to expand...

That makes sense to me - besides, the probe is measuring the temperature of the exhaust stream and not the stainless steel tubing connecting it.
 
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.
 
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!
 
Is there a quick connect (like a spade terminal) upstream for that probe? Before you order a new one, disconnect and clean and squeeze it and reconnect and see if you get the same results. I swear -- at least with my EIS 4000 -- 90% of the problem problems (EGT) are located there. The CHT probs I had were the probe not being installed far enough.
 
Quite possible you found a dud probe, but remember that an absolute number in EGT means very little.

;)
 
Curve in pipe

Not sure what exhaust you have but at 2" there is a curve in the #1 pipe on my Vetterman crossover. You want the probe the same depth in the pipe as the other probes but you don't get that if you measure your distance along the curve. Larry Vetterman told me to measure along the side of the curve, you kind of need to project the location of the probe in the pipe.

I have not drilled mine yet just thinking based on what Larry told me that your #1 probe may be off just a bit distance wise from the others.

Cheers
 
RVG8tor said:
Not sure what exhaust you have but at 2" there is a curve in the #1 pipe on my Vetterman crossover. You want the probe the same depth in the pipe as the other probes but you don't get that if you measure your distance along the curve. Larry Vetterman told me to measure along the side of the curve, you kind of need to project the location of the probe in the pipe.

I have not drilled mine yet just thinking based on what Larry told me that your #1 probe may be off just a bit distance wise from the others.

Cheers
Click to expand...

Yep, good point. I did this as well.
 
You must log in or register to reply here.