Very hot number one cylinder EGT

[bvolcko38]

I have had five flights now with my Aerovee and Aeroinjector. Carb is tuned to the best of my ability, engine runs well, but cyl #1 egt is quite high close to and sometimes over 1400
I removed and replaced left intake manifold. Checked for air leaks, negative. Will need to place a baffle on the front cylinders, they are running too cool with relation to back cylinder,(CHTs)

[tx_swordguy]

try switching EGT probes with the cyl next to it to verify it is accurate. It is an easy check and at least you will know for sure if it is the probe or something happening in the cyl.

[XenosN42]

Hi Bill,

Thanks for using the 'Flight Data Viewer'. Hope it's helping out with diagnosing your problems.

You can label the cylinders by going to 'Options', 'Data Enables' and filling in the cylinder descriptions. For an AeroVee:
#1 Back Left
#2 Front Left
#3 Back Right
#4 Front Right

These labels will be displayed on the CHT & EGT graphs.

IMO, for what it's worth - high EGTs & CHTs usually mean that the engine is running too lean. I've had good luck using this method to tune the AeroInjector:
http://sonex604.com/aerocarb_thoughts.html

-- Michael
Flight Data Viewer http://jasflyer.com/

[sonex1374]

Bill,

You really need to experiment with your probes before chasing too many things. It could simply be a probe indication that is higher than the others. Last year at my annual condition inspection I replaced my #3 EGT probe. That cylinder was reading 200 degrees lower that the others, and I was certain the cylinder was in distress. After replacing the probe, it now reads about 50 degrees higher than the others. Prior to the change the EGT reading tracked well with the other cylinders, and was consistent from flight to flight, but just "too low". Now with the new probe the temps track well with the others, and are consistent, but are "too high".

Here's what I learned from that experience. EGT readings are highly dependent on many variables. Could be a loose or dirty connector, or the probe itself could be simply be the problem. Before chasing the numbers, try to rule out the probe. I suggest swapping probes if that's easy to do, or simply buying a replacement and swapping it out. If the new probe shows no change, keep the old one as a spare and then move on to looking deeper for problems.

Jeff

[bvolcko38]

I will swap one and two. One is hot, two is cool. We will see what happens.

[WesRagle]

Hi Bill,

Just a couple of comments.

I had to deal with thermocouples quite a bit (a lot) during a previous life. Speaking just of the sensor, thermocouples are very simple devices. There were only four states we worried about. Normal, Open, Shorted, and Intermittent.

Normal is just what you would expect. Open was when the weld of the thermocouple failed. Shorted was when there was a fault in the insulation which caused the formation of an unintended junction which was not at the intended sensing point. A failing, but not totally failed, thermocuple was refered to as Intermittent.

The sensing circuitry for cockpit indication we designed/used included a drift circuit which would cause the indication to drift downscale if the thermocouple opened up. I'm not familiar with MGL so I don't know if they did or not. If they did, an open, intermittent, or shorted thermocouple would all cause a low reading.

An easy test is to just apply power to the system, disconnect the suspect thermocouple, and see if the indication for that thermocouple drifts downscale. If it does I doubt that you have a sensor problem.

The above assumes that the T/C amp they used is able to read negative voltages and they are therefor able to indicate temperatures below ambient.

Best of Luck,

Wes

[mike.smith]

Bill:
You didn't say what your CHT's were reading. Those are the numbers that matter most. EGT's are good for relative trends, but ultimately it's the CHT's that matter most. As Michael noted, if you rule out an issue with the EGT probe, and your CHT's are abnormally high, then you are likely running too lean. But remember that during engine break in all the numbers will be higher to start with, so you may need to step climb to keep they cylinders cool during break in. If you do see high CHT's then don't wait too long to start messing with the carb/needle settings. I waited too long, running way too lean, and ended up burning a valve.

If you find you are still running too hot after a few hours of testing, you can check out some of what I did:
http://www.mykitlog.com/users/display_l ... 932&row=11

[lutorm]

The absolute value of the EGT can depend on a bunch of things. The real test is to pull the mixture to lean the engine and see how the EGTs respond. If they all go up and down in concert, I wouldn't worry about the absolute offset. With the stock intake, my bet is you'll find that the rear cylinders are way leaner than the fronts, i.e. they peak earlier when you lean it. (Or they're already running lean of peak and just drop when you start leaning, that's what the rears on our engine did.)

As for a fix that doesn't involve replacing the intake, I don't know...

[bvolcko38]

These are the CHTs from the same flight.
1 and 3 are hot. Probably need to put a little baffle on the front of 2 and 4 to deflect more air to 1 and 3

[mike.smith]

These are the CHTs from the same flight.
1 and 3 are hot. Probably need to put a little baffle on the front of 2 and 4 to deflect more air to 1 and 3

Based on that information I'm pretty sure you're running too lean. You may also need to retard your secondary ignition a bit. I likewise had a couple cylinders that looked "good" and a couple very hot. It doesn't matter so much that you have two that don't look bad. The voice of experience speaking :-)